00a

Soft-Start Output Voltage and Inductor Current age during this soft-start period depends on the load impedance. If soft-start is not required, capacitor C2 is not used and the current limit setting of the regulator determines the maximum load current during start-up. In order to properly enhance the top MOSFET (Q1), INT VCC is level shifted by charge pumping capacitor C6 to INT VCC minus one diode drop. C6 provides the power to turn Q1 on and off. The INT VCC of the LTC1435 is...

1

UltraFast Transient Response 5V to 3.3V, Figure 220. Transient Response for Low Dropout Regulator 0.2A-5A Output Load Step additional system cost, provides on off control and can provide overvoltage protection or thermal shutdown with the addition of a few simple external components. The LT1575 is available in 8-pin SO or PDIP and the LT1577 is available in 16-pin narrow-body SO. UltraFast 5V to 3.3V Low Dropout Regulator Figure 219 shows the basic regulator control circuit. The...

10

Output Ripple of an LT1533 Switching Regulator Producing 120mA at 12V from a 5V Input Figure 132. Output Ripple of an LT1533 Switching Regulator Producing 120mA at 12V from a 5V Input amplifier reveals the real performance (second trace) peak-to-peak output ripple of the low noise switcher is only 150 iV in a 10kHz to 100MHz bandwidth. The LT1533 is a fixed frequency current mode PWM switching regulator. The output voltage is regulated by controlling the peak switch current on each...

100

Efficiency vs Output Load Current Figure 188. High Efficiency 2.5V Step-Down Converter Single-Cell Li-Ion Operation As shown in Figure 186, a fully charged single-cell Li-Ion battery begins the discharge cycle at either 4.1V or 4.2V (depending upon the manufacturer's charge voltage specifications). During the bulk of the discharge time, the cell produces between 3.5V and 4.0V. Finally, toward the end of discharge, the cell voltage drops fairly quickly below 3V. It is recommended...

100 300

Oscillograph shows output voltage and inductor current as the load current is stepped from 5mA to 55mA, revealing substantial detail about the operation of the LT1307. With a 5mA load, VOUT (top trace) exhibits a ripple voltage of 60mV at 4kHz. The device is in Burst Mode at this output current level. Burst Mode operation enables the converter to maintain high efficiency at light loads by turning off all circuitry inside the LT1307 except the reference and error amplifier. When the LT1307 is...

100 90 80 70 60 50 40 30 20 10

Efficiency Plot for Figure 17'sCircuit Figure 18. Efficiency Plot for Figure 17'sCircuit mal load results in a huge, and most likely unnecessary, design margin. A good understanding of your system requirements can result in substantial savings in the size and cost for the power supply. RIMAX sets current limit to the desired level. Add one-half of the inductor ripple current to the maximum load current to determine the peak switch current. Multiply this current by the maximum...

1000

Efficiency vs Load Current for Figure 67's Circuit (Burst Mode Operation Enabled) supplying 1.5A at a low input voltage. In addition, a sublogic threshold MOSFET is used, since the circuit operates at input voltages as low as 2.7V. The circuit operates at the internally set frequency of 550kHz. A 4.7 i H inductor is chosen so that the inductor's current remains continuous during burst periods at low load current. For low output voltage ripple, a low ESR capacitor (100mQ) is used. The...

10v To 28v

(803) 946-0362 C2 AVX D CASE TPSD107M010R0080 C4, C5 X7R OR COG NPO D1 MOTOROLA MBRS1100 100V, 1A, SMD SCHOTTKY (800) 441-2447 L1 COILCRAFT D03316-104 (847) 639-6400 (803) 946-0362 C2 AVX D CASE TPSD107M010R0080 C4, C5 X7R OR COG NPO D1 MOTOROLA MBRS1100 100V, 1A, SMD SCHOTTKY (800) 441-2447 L1 COILCRAFT D03316-104 (847) 639-6400

13v

Vouti is Output Voltage at 10 iF Capacitor C2 Vout2 is After 4.7Q 1 iF Output Filter. Circuit Supplies 50mA Oscilloscope Bandwidth is 50MHz. Figure 167. A Faster Oscilloscope Shows More High Frequency Content at Both Outputs. Scope Bandwidth is 400MHz. Figure 166. Vouti is Output Voltage at 10 iF Capacitor C2 Vout2 is After 4.7Q 1 iF Output Filter. Circuit Supplies 50mA Oscilloscope Bandwidth is 50MHz. Figure 167. A Faster Oscilloscope Shows More High Frequency Content at Both...

15

Charger Dropout Voltage vs Charge Current Figure 240. Charger Dropout Voltage vs Charge Current The LT1435 Switching Regulator Controller The LTC1435 is a step-down current mode switching regulator controller designed to drive two external N-channel power MOSFETs. Operating from input voltages between 3.5V and 36V, this device includes a programmable switching frequency, synchronous rectification, Burst Mode operation and a 99 maximum duty cycle for low dropout voltage. Additional...

20

Output Regulation for Figure 129's Circuit transformer. This component offers 3750Vrms isolation and full VDE approval at a lower cost than a comparable custom design. Feedback is derived from the primary winding, through D3. R1 acts to filter the leakage-inductance spike at switch turn-off, and C4 smooths the recovered feedback voltage. Note that the transformer is wound 1 1 C4 peak detects a voltage roughly equal to the output. Sizing R1 and C4 is a trade-off between minimum load...

20a

Rent mode operation, external synchronization and low current shutdown mode (12 oA typical). Only a few surface mount components are needed to complete a small, high efficiency DC DC converter. The LT1370 will operate in all the standard switching configurations, including boost, buck, flyback, forward, inverting and SEPIC. Figure 93 shows a typical 5V to 12V boost application. The feedback divider network has been selected to give the desired output voltage. As long as R2 is less than 7k, FB...

22

Output Regulation for Figure 129's Circuit Figure 129. 24V 200mA Bulk Supply with 3750VRMS Isolation Figure 129. 24V 200mA Bulk Supply with 3750VRMS Isolation WIDE-INPUT-RANGE, LOW VOLTAGE FLYBACK REGULATOR Many new switching regulators are designed with a specific application or topology in mind. If your requirements happen to fall within these parameters, all is well. Unfortunately, when faced with unusual requirements, the designer is often forced to choose bare-bones, universal...

22V to 16V Converter at 250kHz

The operating envelope has been substantially expanded with the introduction of the new LTC1435A DC DC controller, which has all the outstanding features of the LTC1435 with a reduced minimum on-time of 300ns or less and improved noise immunity at low output voltages. With these improvements, high performance at output voltages down to 1.3V can be achieved with operating frequencies in excess of 250kHz from input supply voltages above 22V. Figure 51 shows the resulting improvement of maximum...

24 Volt To 14 Volt Converter Provides 15 Amps

Efficiency is required, adding a second power MOSFET for synchronous switching will improve efficiency by about 1 . Combining the LTC1435 with a large geometry power MOSFET and good PCB layout allows large currents to be processed easily and efficiently. With the use of a current sense transformer, output voltages greater than 10V can be implemented. The circuit in Figure 15 shows an LTC1435 configured as a conventional buck regulator using a single N-channel MOSFET to control an output voltage...

2Phase Design Example

The circuit shown in Figure 61 is a 2-phase, voltage mode-control, synchronous buck regulator designed for a 5V input and output voltages below 3.3V. It is intended to power large memory arrays, ASICs, FPGAs and the like in server and workstation applications. The output is capable of more than 30 amps continuous at outputs of 2.5V and below, with peak current capability of greater than 40 amps. The design is entirely surface mount and the maximum height above the board is 5.5mm. Overall board...

3

Single-Cell Li-Ion to 3.3V Buck Boost Converter 12V WALL CUBE TO 5V 400mA DC DC CONVERTER IS 85 EFFICIENT The ubiquitous 12V wall cube, power source of countless electronic products, generates an unregulated DC voltage between 8V and 18V, depending on line voltage and load. If you use a linear regulator to drop the voltage to 5V, a 400mA load means the linear regulator must dissipate 5W under worst-case conditions. To deal with this heat, you must provide adequate heat sinking,...

35

Design can be based on the lower current level. Higher currents, while present, are typically not of sufficient duration to significantly heat the power devices. The design does, however, need to be capable of delivering the peak current without entering current limit or resulting in device failures. Keep in mind that the power dissipation in a resistive element, such as a MOSFET, varies as the square of load current. As such, raising the load current from 80 to 100 translates to approximately...

4

UltraFast Transient Response, Low Dropout Regulator with Adjustable Output Voltage Figure 50. UltraFast Transient Response, Low Dropout Regulator with Adjustable Output Voltage NEW DC DC CONTROLLER ENABLES HIGH STEP-DOWN RATIOS The LTC1435 high efficiency synchronous DC DC controller has been extremely popular for notebook computers and other battery-powered equipment due to its low noise, constant-frequency operation and its dual N-channel drive for outstanding high current...

5

Figure 133. 5V to 12V Push-Pull PWM Converter Figure 134. Lowering the Slew Rates of the Power Switches (Trace A) Eliminates High Frequency Ripple at the Output (Traces B and C) voltage (either positive or negative) is compared with an accurate internal 1.25V reference voltage by an error amplifier whose current output, along with loop compensation components tied to the Vq pin, determine the peak switch current required for regulation a comparator turns off the switch when this current level...

50

Single-Cell Converter Efficiency Reaches 77 Figure 208. Single-Cell Converter Efficiency Reaches 77 implemented. Output voltage can be up to 28V in boost mode. Operating quiescent current is 50 iA unloaded grounding the shutdown pin reduces the current to 0.5 uA. The device can generate 3V at 30mA from a single (1V) cell, or 5V at 100mA from two cells (2V). Configured as a Li-Ion cell to 3.3V SEPIC converter, the LT1610 can deliver 100mA. In boost mode, efficiency ranges from 60 at...

5v 084v 5v 084v

Once RPROG and R6 are known, the following equations can be used to determine RPROG and IPROG for lower IBATT currents R6 5 - 10(Ibatt)(Rprog) 0.04 + 10(Ibatt)(Rprog) As with any high frequency switching regulator, layout is important. Switching current paths and heat producing thermal paths should be identified and the printed circuit board designed using good layout practices. Even with efficiency numbers in the mid 90s, under some charging conditions power losses can be as high as 4 watts....

6

FIXED FREQUENCY, 500kHz, 4.5A STEP-DOWN CONVERTER IN AN SO-8 OPERATES FROM A 5V INPUT The LT1506 is a 500kHz monolithic buck mode switching regulator, functionally identical to the LT1374 but optimized for lower input voltage applications. Its high 4.5A switch rating makes this device suitable for use as the primary regulator in small to medium power systems. The small SO-8 footprint and input operating range of 4V to 15V is ideal for local onboard regulators operating from 5V or 12V system...

60

Transient Response with 5mA to 55mA Load Step DC DC Converter Noise Considerations Switching regulator noise is a significant concern in many communications systems. The LT1307 is designed to keep noise energy out of the 455kHz band at all load levels while consuming only 60 iiW-100 iiW at no load. At light load levels, the device is in Burst Mode, causing low frequency ripple to appear at the output. Figure 162 details spectral noise directly at the output of Figure 158's circuit...

7

Intel Mobile Processor VID Power Converter Figure 54 shows the LTC1435A used with an LTC1706-19 to implement an Intel Mobile Pentium II Processor VID power converter. This DC DC converter provides digitally selectable output voltages over the range of 1.3V to 2.0V in 50mV increments at 250kHz and a 7A load current. The selectable output voltage is implemented by replacing the conventional feedback resistor network with the LTC1706-19, which provides the appropriate feedback resistor ratios...

8

Figure 60. 12V 2.2A Adjustable-Output Supply to 5A of load current. Ripple current is 1.8A (36 of full load) and current limit occurs around 6A. Note also that the EXTVcc pin is connected to an external 5V supply. This increases efficiency by drawing the roughly 7mA gate charge current from a supply lower than V N. An efficiency plot of this circuit is shown in Figure 59. An LTC1435 with identical components in the power path is also plotted for comparison. At lower output voltages such as...

8 9

Unregulated Negative Output Voltage with Positive Output Voltage Regulated 12V OUTPUT RIPPLE 0.1V DIV AC COUPLED -12 V OUTPUT RIPPLE 0.1V DIV AC COUPLED Figure 88. Switch Voltage and Current Waveforms 12V OUTPUT RIPPLE 0.1V DIV AC COUPLED -12 V OUTPUT RIPPLE 0.1V DIV AC COUPLED

80

Output Regulation with a Common Load LTC1263 is connected in the usual way to produce a regulated, 12V output, but a 2 diode, 2-capacitor charge pump is added to the C2+ pin. This pin switches between VCC and VOUT, swinging approximately 7VP-P. The result is an outboard charge pump inverter with a -7V output. Schemes like this one often suffer from poor cross regulation. Although the inverting output is not directly regulated, the -7V load does affect the 12V output, thereby...

9

Switch Voltage and Current for Figure 123's Circuit with Outputs of -9V 250mA and -9V 30mA Figure 125. Switch Voltage and Current for Figure 123's Circuit with Outputs of -9V 250mA and -9V 30mA even with one output fully loaded and the other unloaded ( 1.5 with input voltages of 10V-15V). The isolation voltage is ultimately limited only by bobbin selection and transformer construction. Figure 127 implements a 12V to 5V 1A step-down regulator with off-the-shelf magnetics. The circuit...

Battery Charger Application

Figure 83 shows the LT1776 configured as a constant-current constant-voltage battery charger. An LT1620 rail-to-rail current sense amplifier (U2) monitors the differential voltage across current sense resistor R4. As this equals and exceeds the voltage across resistor R5 in the R5 R6 divider, the LT1620 responds by sinking current at its Iout pin. This is connected to the Vq control node of the LT1776 and therefore acts to reduce the amount of power delivered to the load. The overall...

Battery Charger Ic Doubles As Current Sensor

It's always fun to find applications for an IC that its designer never intended. The circuit shown in Figure 264 is such a design. In many cases, a circuit is required to provide a ground-referenced output voltage that is proportional to a measured current. Frequently, the current must be measured with a shunt in the positive rail that may be well above ground and, worse yet, may vary considerably with time. The LT1620 was originally intended as a controller for a synchronous buck regulator in...

Bootstrapped Synchronous Boost Converter Operates At 18v Input

Some applications, such as those powered by batteries or solar cells, see their input voltage decrease as they operate. Many regulators that could operate with high input voltages cease to function as the input voltage decreases. The circuit in Figure 97 maintains the maximum load current as the input voltage drops. The regulator boosts a 2.5V-4.2V input to 5V at a maximum load current of 2A (10W of output power). The circuit is a bootstrapped synchronous boost regulator using an LTC1266...

Burst Mode Application

The minimum component count application demonstrates that power supply efficiency degrades with lower output load current. This is not surprising, as the LT1676 itself represents a fixed power overhead. A possible way to improve light load efficiency is to use Burst Mode operation. Figure 81 shows the LT1676 configured for Burst Mode operation. Output voltage regulation is now provided in a bang-bang digital manner, via comparator U2, an LTC1440. Resistor divider R4 R5 provides a scaled version...

C1

Figure 29. 3.3V to 1.9V 6A Power Supply Figure 29. 3.3V to 1.9V 6A Power Supply THE LT1374 NEW 500kHz, 4.5A MONOLITHIC BUCK CONVERTER The LT1374 is a 4.5A buck converter using an on-chip 80mQ switch. With its 500kHz operating frequency and integral switch, only a few external, surface mount components are required to produce a complete switching regulator. The LT1374's features include current mode control, external synchronization and a low current (typically 20 jA) shutdown mode. Improvements...

C2

Figure 204. 2-Cell to 5V Boost Converter Using the LT1317 mance than its 1-cell predecessor, the LT1307. More gain in the error amplifier results in lower Burst Mode ripple, and an internal preregulator eliminates oscillator variation with input voltage. For comparison, Figure 205 details transient responses of both the LT1307 and the LT1317 generating 5V from a 3V input. The load step is 5mA to 200mA. Output capacitance in both cases is 33 iF. The LT1307 has low frequency ripple of 100mV,...

C5

The LTC1419's High Negative Supply PSRR also Allows the Use of the LT1054 Regulated Charge Pump to Generate -5V without Loss of Performance 106 is an FFT of a typical LTC1419 operating on 5V from a lab supply and converting a full-scale 91kHz sine wave at 800ksps. The noise floor is approximately 114dB below full scale, the second harmonic's amplitude is approximately 90dB below full scale and the SINAD is 80.5dB. Figure 107 shows the FFT of the same LTC1419 operating on a 5V lab...

Charge Pump

LT1516 Charge Pump in Trippler Mode, Discharge Cycle When the battery cells are fully charged (approximately 1.5V per cell, for a nominal 3V VIN), the circuit operates as a voltage doubler to maintain regulation. In doubler mode, only C2 is charged to VIN and discharged onto VOUT when the charge pump is enabled. As the batteries discharge and or the load increases, the circuit will change from doubler mode to tripler mode. Under light load conditions, the part will remain in doubler...

Circuit Operation

The basic design consists of two LTC1430CS8-based synchronous buck regulators connected in parallel and operated 180 out of phase. U4, the CD4047 oscillator, is used to generate the required clock signals and synchro nize the two LTC1430s. Unfortunately, simply connecting two regulators in parallel is a recipe for instant disaster. The output voltages of the two regulators will be slightly different due to normal component tolerances. Therefore, the higher output voltage channel will attempt to...

Cl

< 1k 10k 100k 1M 10M RIPPLE FREQUENCY (Hz) Figure 103. The LTC1419's Positive Supply PSRR of 90dB to 200kHz is a Significant Contributor to this ADC's Wideband Conversion Performance and 80dB SINAD Figure 103. The LTC1419's Positive Supply PSRR of 90dB to 200kHz is a Significant Contributor to this ADC's Wideband Conversion Performance and 80dB SINAD new family of ADCs, here represented by the LTC1419, has excellent PSRR. This family makes it easy to achieve high performance data conversion,...

Combine A Switching Regulator And An Ultrafast Linear Regulator For A High Performance 33v Supply

It is becoming increasingly necessary to provide low voltage power to microprocessor loads at very high current levels. Many processors also exhibit high speed load transients. The Pentium Pro processor from Intel exhibits both of these requirements. This processor requires 3.3V 5 at approximately 14A peak (9A average) and is capable of making the transition from a low power state to full load in several clock cycles. Generally, switching regulators are used to supply such high power devices,...

Cont

Switch-Frequency Modulator Figure 152. Switch-Frequency Modulator Figure 153. Audio Frequencies in Output Noise during Cycle-Skipping Operation Figure 153. Audio Frequencies in Output Noise during Cycle-Skipping Operation Figure 154. Output Noise with Adaptive Power Operation Figure 154. Output Noise with Adaptive Power Operation The Adaptive Power feature of the LTC1436-PLL significantly reduces audio frequency generation, while maintaining good efficiency under very light load...

Cost Effective LTC1437 Switcher Linear Combination with 5V3A and 12V200mA Outputs

The main switcher loop, shown in the schematic in Figure 1, is set to 5V by strapping the VPROG pin high. Other output options include 3.3V (VPROG low) and adjustable (Vprog open). The 12V output in Figure 1's circuit is provided by the auxiliary linear regulator operating in conjunction with a secondary winding feedback loop using the SFB pin. The turns ratio for the transformer is 1 2.2, resulting in a secondary output voltage of approximately 15V. The secondary resistive divider causes the...

Current Sharing Split Input Supplies

Current sharing is accomplished by connecting the VC pins to a common compensation capacitor. The output of the error amplifier is a gm stage, so any number of devices can be connected together. The effective gm of the composite error amplifier is the product of the individual devices. In Figure 44, the compensation capacitor, C4, has been increased by 3x. Tolerances in the reference voltages cause small offset currents to flow between the Vc pins. The overall effect is that the loop regulates...

D1

L1, L2 MURATA LQH3C220 (814) 237-1431 C1, C2 AVX TAJB336M010 (803) 946-0362 C3 AVX1206YC105KAT (CERAMIC, X7R) Figure 113. 5V to -5V DC DC Converter Uses an Inverting Topology and Delivers 200mA. series with both input and output, results in low output noise and also in low reflected noise on the 5V input supply. The output and switch nodes are shown in Figure 114. Output ripple voltage of 40mV is due to the ESR of the tantalum output capacitor C2. Ripple voltage can be reduced substantially by...

Dual Output Sepic Converter

All of the previous applications provide a single positive output voltage. Real world situations often require dual supply voltages. The SEPIC topology (single-ended primary inductance converter) offers a cost-effective way to simultaneously generate a negative voltage with a single piece of magnetics. The circuit in Figure 85 uses an LT1776 to generate both positive and negative 5 V. The two inductors shown are actually just two windings on a standard Coiltronics inductor. Capacitor C3 creates...

Dualoutput Voltage Regulator

The LTC1266-3.3 and LTC1263, as shown in the schematic of Figure 144, are perfect complements for one another. The combination of these two parts provides two regulated outputs of 3.3V 5A and 12V 60mA from an input range of 4.75V to 5.5V. These two outputs are perfect for notebook and palmtop computers with microprocessors that burn several amps of current from a regulated 3.3V supply, flash memories that consume milliamps of current from a regulated 12V supply and interface and logic...

E1

The circuit's 165kHz switching frequency was selected as a compromise between transient response and circuit efficiency. This frequency is determined by the value of C1. Output voltage transient response is shown in Figure 7. The transient response can be adjusted for other applications by changing the values of compensation components R1, C3 and C14. Efficiency curves for different input voltages and load currents up to 3.2 amps are shown in Figure 8. Another feature of the LTC1435 is the...

External Frequency

High Efficiency, Low Noise, Synchronous Step-Down Switching Regulator with Programmable Output and External Synchronization Figure 263. High Efficiency, Low Noise, Synchronous Step-Down Switching Regulator with Programmable Output and External Synchronization Besides the LTC family of 1.19V-referenced DC DC converters, the LTC1706-19 can also be used to program the output voltages of regulators with different onboard references. Figure 264 shows the LTC1706-19 programming the output...

Free Digital Panel Meters From The Oppressive Yoke Of Batteries

Digital panel meters (DPMs) have dropped in price to well under 10 for 3-1 2 digit models, even in single-piece quantities. These make excellent displays for many instruments, but suffer from one major flaw they require a floating power supply, usually in the form of a 9V battery. This renders inexpensive meters useless for most applications because no one wants multiple 9V batteries in their product. The circuit shown in Figure 182 powers up to five meters from a single 1.8V to 6V source. The...

High Isolation Converter Uses Offtheshelf Magnetics

Isolated flyback converters usually evoke thoughts (or bitter memories) of custom transformers, slipped delivery schedules and agency approval problems. Off-the-shelf flyback transformers are available from several vendors, but these carry isolation ratings of only 300V-500V, and, rarely, of up to 1kV. Flyback transformers with isolation ratings of 3750VRMS are impossible to find, and if an application requires this level of isolation, an expensive, custom design is likely the only solution....

Info

Comparison of RUN SHUTDOWN Operation for the LTC1474 and LTC1475 Figure 180. LTC1475 Step-Down Regulator with Push-Button On Off Control divider network connected to the LBI to monitor the input supply voltage level, the voltage at this pin will normally be above the low-battery trip threshold of 1.23V. When this pin is pulled below 0.7V by depressing the switch, the internal flip-flop is reset to invoke shutdown. Figure 181 shows an example of push-button on off control of a...

It

(803) 946-0362 C2 AVX TPSD476M016R0065 L1 MURATA LQN6C-1R5M04 (814) 237-1431 (803) 946-0362 C2 AVX TPSD476M016R0065 L1 MURATA LQN6C-1R5M04 (814) 237-1431 Figure 72. 2.5V 1.5A Converter with Improved Transient Response (310) 322-3331 R2 DALE, 0.25W (605) 665-9301 Figure 72. 2.5V 1.5A Converter with Improved Transient Response OUTPUT VOLTAGE (AC COUPLED) 0.1v div OUTPUT VOLTAGE (AC COUPLED) 0.1v div Figure 73. Transient Response with Burst Mode Operation Enabled Load Step 50mA to 1.2A OUTPUT...

J T

A bootstrap winding on the output inductor, L1. When input voltage is first applied, R1 begins charging C1. As C1 charges, Q1 is held on by R2, shorting R3. R4 and R5 form a voltage divider that holds the RUN SHDN pin below its 1.25V threshold until the 12VIN pin reaches approximately 14V. Once out of standby, Q1 is turned off by Q2, reducing the run threshold to approximately 9V and allowing C1 time to discharge slightly before the overwinding on L1 takes over. The only remaining issue is...

L 63v

C1 PANASONIC HFQ (2C1) 348-2552 C2 AVX D CASE TPSD1C7MC1CRCC8C (8C3) 946-C362) C4, C5 X7R OR COG NPO D1 MOTOROLA 1CCV, 1A, SMD SCHOTTKY (8CC) 441-2447 COILCRAFT DO3316-224 (847) 639-64CC Figure 81. Burst Mode Operation Configuration C1 PANASONIC HFQ (2C1) 348-2552 C2 AVX D CASE TPSD1C7MC1CRCC8C (8C3) 946-C362) C4, C5 X7R OR COG NPO D1 MOTOROLA 1CCV, 1A, SMD SCHOTTKY (8CC) 441-2447 COILCRAFT DO3316-224 (847) 639-64CC Figure 81. Burst Mode Operation Configuration

Low Cost 33v To 1xv 6 Amp Power Supply

As voltage requirements for microprocessors drop, the need for high power DC DC conversion from a 3.xV supply to a lower voltage keeps growing. The LTC1430 is a very attractive choice for such DC DC applications, due to its low cost, high efficiency and high output power capability. However, there are two problems first, 3.xV does not provide enough gate drive to ensure low RDs(oN) using external logic-level FETs and second, the LTC1430 has a 4V minimum input requirement. These obstacles are...

Low Dropout Regulator Driver Handles Fast Load Transients And Operates On A Single 3v10v Input

The LT1573 is designed to provide a low cost solution to applications requiring high current, low dropout and fast transient response. When combined with an external PNP power transistor, this device provides up to 5A of load current with dropout voltages as low as 0.35V. The LT1573's circuitry is designed for extremely fast transient response. This greatly reduces the bulk storage capacitance required when the regulator is used in applications with fast, high current load transients....

Low Noise 33v Varactor Bias Supply

Wideband tuning circuits, such as those used in cable television systems, require a power supply for driving a varactor. This bias supply is usually at a voltage higher than the system supply voltage, allowing a large tuning range. The supply must have very little noise voltage ripple, for example, can appear as sidebands on a local oscillator. This circuit takes advantage of the fixed operating frequency of the LT1317B boost regulator to generate a low noise 33V bias voltage.

Ltc

SINGLE-CELL Li-Ion BATTERY SUPERVISOR Recently introduced precision products from Linear Technology allow designers to implement high precision applications at supermicropower levels. Among these devices are the LT1496 quad precision input rail-to-rail output op amp and the LT1634 precision shunt voltage reference, which operate at only 1.5 uA and 10 iA, respectively. Even at such low power levels, precision performance is not compromised. The LT1496 features 475 iV maximum input offset voltage...

Making 5v 14bit Quiet

Many high performance data acquisition systems reap multiple benefits when using 5V supplies rather than a single 5V supply. These benefits include the ability to handle larger signal magnitudes than is possible with a single 5V supply. This increases a system's dynamic range and helps improve the signal-to-noise ratio. Operating on 5V also increases headroom, which is important for signal conditioning. Compared to operating on 5V, conditioning circuitry operating on 5V has twice the headroom,...

Mbrd340

Type found in most notebook computers and other portable equipment. The power management system in Figure 253 shows the LTC1473 driving two sets of back-to-back N-channel MOSFET switches connecting the two batteries to the system DC DC regulator. Each of the switches is controlled by a TTL CMOS compatible input that interfaces directly with a power management system microprocessor. An internal boost regulator provides the voltage to fully enhance the logic-level N-channel MOSFET switches....

Minimum PC Board Area Application

The previous application example used the LT1676 to demonstrate simultaneously the maximum input voltage and output current capability. As such, the input bypass capacitor choice was a high frequency aluminum electrolytic type, rated to 63V. Also, the 100kHz switching rate of the LT1676 requires an inductor of about 220 iH. The DO3316 device size was chosen to support the output current requirements. However, both of these components are physically large. The application example in Figure 79...

Motorola Mmbd914lt1 Avx Taj156m010 Sanyo 35cv33gx Murata Lqh3c220

This Circuit Generates a Low Noise Bais Supply for Varactor-Based Tuning Circuits The circuit (Figure 213) is a simple boost regulator with its output voltage doubled by diodes D2 and D3 and capacitor C3. With this doubler, the circuit can generate an output voltage greater than the voltage rating of the LT1317B's internal power switch. This supply can deliver 10mA at 33V from a 3V to 6V input, allowing operation from either 3.3V or 5V logic rails. The high operating frequency...

Negativetopositive Telecommunication Supply

Many telecommunication circuits require a positive supply voltage derived from a -48V input. The traditional approach to negative-to-positive conversion has been to use a buck-boost converter (see Figure 109). Unfortunately, this topology suffers drawbacks as the power level and input-to-output voltage difference increases. A more appropriate solution for -48V to 5V conversion is shown in Figure 110. The LT1680 is used to implement a forward converter with its output referenced to the input...

On

Start-Up Response of LED Circuit. Many Switching Cycles Elapse before Current Flows in LEDs Because of C1 Charging L1 MURATA-ERIE LQH3C100K04 D1 MOTOROLA MBR0520L , C2 CERAMIC D2, D3 LUMEX SSL-X100133SRC 4 MEGA-BRITE RED LED OR PANASONIC LNG992CF9 HIGH BRIGHTNESS BLUE LED Figure 169. Start-Up Response of LED Circuit. Many Switching Cycles Elapse before Current Flows in LEDs Because of C1 Charging Figure 168. Single-Cell LED Driver Supplies 25mA to LED String. Two Red LEDs Can Be...

Output C3

Current Sensor Schematic 100V, 2A, CONSTANT-VOLTAGE CONSTANT-CURRENT BENCH SUPPLY Most engineering labs are well stocked with low voltage, moderate current power supplies, but higher voltage supplies capable of several amperes of output current are hard to find. We solved this problem in our lab by building the supply shown in Figure 267. The circuit is based on U1, an LT1270 high efficiency switching regulator configured in a SEPIC topology, which allows the output to be adjusted...

P

Power Magagement 134-141 LTC1479 PowerPath Controller 3-Diode Mode 136 Block Digram 134 PowerPath Switch Driver LTC1623, Controls P-Channel Switch 140 LTC1623, Controls Two High-Side Switches 140 LTC1710, Switches Two Peripherals 141 LTC1710, Switches Two Peripherals with Different Voltages 141 System Dual Li-Ion Battery 134 VID Controlled LT1575 LTC1706, LDO with Adjustable Output Voltage 144 Power Supply. See Regulators Linear Regulators Switching Regulators Switching (Micropower)

Positiveto Negative Converter

The previous example used a dual inductor to create a pair of output voltages, one positive and the other negative. The positive-to-negative converter topology illustrated in Figure 86 generates a single negative output voltage from a positive input voltage, using just an ordinary inductor. The topology is somewhat similar to the original step-down arrangement, but the inductor is grounded and the LT1776 ground is now referred to the negative output voltage. Note that the integrated circuit...

Positivetonegative Converter Powers 48v Telecom Circuits

If you're designing a system that interfaces to telecom equipment, chances are you'll need a -48V supply. The circuit in Figure 111 supplies up to 6W at -48V and scales to more than 12W with higher power components. Based on the inverting topology, the converter exhibits excellent efficiency over a wide range of loading conditions (see Figure 112).

Power Management

LTC1479 PowerPath Controller Simplifies Portable Power Management The LTC1473 Dual PowerPath Switch Driver Simplifies Portable Power Management Design 137 Short-Circuit-Proof Isolated High-Side Tiny MSOP Dual Switch Driver is SMBus LTC1710 Two 0.4Q Switches with SMBus Control Fit into Tiny MSOP-8

R15 470w2

(847) 843-7500 C13, C14 NICHICON, UPL1E471MHH6 D1, D3, D6 MOTOROLA, MBRS0540 (800) 441-2447 D4 MOTOROLA MBR2045 WITH THERMALLOY 7020 HEAT SINK Q3 INTERNATIONAL RECTIFIER, IRL3803 (310) 322-3331 WITH THERMALLOY 6299 HEAT SINK (972) 243-4321 L1 CORE MAGNETICS, 55930-AZ (800) 245-3984 WINDING 8T 14 BIFILAR T1 CORE MAGNETICS W-41406-TC WINDING PRI 1T 18 SEC 100T 32

R2 R3

VREF 1.19V USE APPROXIMATELY 100kQ FOR R3 Iprog is a current from the PROG pin to ground that is used to program the maximum charging current. Iprog can be derived from a resistor to ground, from the output of a DAC or by other methods. This program current is generated using resistors and the 5V Vcc available from the LTC1435. Refer to the simplified diagram of the constant-current control loop shown in Figure 242. The DC voltage across CAVG is proportional to the average charge current. This...

Rectification

The LT1339 is the buck boost converter that needs no steroids. As a full-featured switching controller, the LT1339 incorporates the features needed for system-level solutions. The LT1339 has an innovative slope-compensation function that allows the circuit designer freedom in controlling both the slope and offset of the slope-compensation ramp. Additionally, the LT1339 has an average current limit loop that yields a constant output current limit, regardless of input and or output voltage. The...

Shortcircuitproof Isolated Highside Switch

Figure 255 shows a MOSFET switch, driven by the LTC1177-5 2.5kVRMs isolator. This device allows a logic signal to control a power MOSFET and provides complete galvanic isolation. The device includes an internal current limiting circuit, but at higher voltages limiting the current is just not enough for effective protection of the MOSFET. Foldback (shown on the LTC1177 data sheet) helps, but the part has trouble starting certain types of loads when foldback current limiting is used. The circuit...

Shutdown

C N AVX TPSC226M016R0375 COUT SANYO 16CV100GX * OPTIONAL DELETE TO DISABLE SOFT START ** OPTIONAL DELETE TO DISABLE CURRENT LIMIT C N AVX TPSC226M016R0375 COUT SANYO 16CV100GX * OPTIONAL DELETE TO DISABLE SOFT START ** OPTIONAL DELETE TO DISABLE CURRENT LIMIT Figure 33. Minimum Parts-Count 5V-3.3V Converter

Murata Lqh3c220

C1 MURATA GRM235Y5V106Z01 D1 MBR0520 D2 BAT54S (DUAL DIODE) C2 AVX TAJB33M6010 C3 AVX TAJA156MO1O C4, C5 CERAMIC Figure 206. This SIngle Li-Ion Cell to 4V DC DC Converter Has a Maximum Height of 2mm C1 MURATA GRM235Y5V106Z01 D1 MBR0520 D2 BAT54S (DUAL DIODE) C2 AVX TAJB33M6010 C3 AVX TAJA156MO1O C4, C5 CERAMIC Figure 206. This SIngle Li-Ion Cell to 4V DC DC Converter Has a Maximum Height of 2mm LT1610 MICROPOWER STEP-UP DC DC CONVERTER RUNS AT 1.7MHZ The LT1610, a micropower DC DC converter IC,...

Single LiIon Step Down Converter

The circuit in Figure 57 is intended for input voltages below 4.5V, making it ideal for single Li-Ion battery applications. Diodes D1 and D2 and capacitors C1 and C2 comprise the bootstrapped charge pump to realize a negative supply at the VDR pin, the return pin for the top P-channel MOSFET driver. This allows Figure 57's circuit to maintain low switch RDs(oN) all the way down to the UVLO trip voltage.

Sink Source Capability Improves SCSI Terminators and Supply Splitters

Figure 35 shows an adjustable-output LTC1504 connected as a 2.85V regulator for use as a SCSI terminator. The ability of the LTC1504 circuit to sink current makes it ideal for use in terminator applications, where the load is just as likely to be putting current into the regulator as taking it out. The synchronous-buck architecture of the LTC1504 allows it to shift cleanly between sourcing and sinking current, making it ideal for such applications. The small number of tiny external components...

Slave

Phase Relations Between the Switching Nodes of the Two Regulators Figure 20. Phase Relations Between the Switching Nodes of the Two Regulators to run at approximately 300kHz (a 130k resistor from FSET to ground) the slave can be left to run at its natural frequency of 200kHz. The slave frequency will be forced up to that of the master. The sync function on the LTC1430 works as follows when the shutdown pin is pulled low, the high-side switch turns off normal duty factor control...

Ss Comp

COUT TAJC476M016R Lext SUMIDA CDRH73-470 (LOWER RIPPLE HIGHER EFFICIENCY) *CDRH73-220 (FASTER TRANSIENT RESPONSE) COUT TAJC476M016R Lext SUMIDA CDRH73-470 (LOWER RIPPLE HIGHER EFFICIENCY) *CDRH73-220 (FASTER TRANSIENT RESPONSE) Substituting a different set of feedback resistors (Figure 35) creates a 5V supply splitter, which creates a 2.5V ground to allow analog circuitry to operate from split supplies. Op amp circuits and data converters like to operate from dual supplies, and the sink source...

Swb

LTC1479 PowerPath Controller in 3-Diode Mode Figure 252. LTC1479 PowerPath Controller in 3-Diode Mode critical decisions can be made by the microprocessor without the inherent delays associated with bus protocols and the like. These delays are acceptable in certain portions of the power management system, but it is vital that the power path switching control be made through a direct connection to the power management microprocessor. The remainder of the power management system can...

Synchronizable Triple Output Low Dropout Supply

The LTC1439-based supply shown in Figure 2 is an example of how three logic supply voltages, 5V, 3.3V and 2.9V, can be easily derived using only two simple inductors. The two main DC DC controller loops are used to supply 5V 3A and 3.3V 5.5A. Up to 2.5A of the 3.3V output current is then used to supply a 2.9V output using the adjustable capability of the auxiliary linear regulator. The 2.9V output also illustrates the use of an external NPN pass transistor with the auxiliary regulator. Because...

Synchronized Ripple Currents

A ring counter generates three synchronization signals at 600kHz, 33 duty cycle, phased 120 apart. The sync input will operate over a wide range of duty cycles, so no further pulse conditioning is needed. At full load, each device's input ripple current is a 4A trapezoidal wave at 600kHz, as shown in Figure 45. Summing these waveforms gives the effective input ripple for the complete system. The resultant waveform, shown at the bottom of Figure 45, remains at 4A but its frequency has increased...

Table Of Contents

New LTC 1435-LTC1439 DC DC Controllers Feature Value and The LTC1266 Operates From > 12V and Provides 3.3V Out at The New LTC1435 Makes a Great Microprocessor Core Voltage LTC1433 LTC1434 High Efficiency, Constant-Frequency Monolithic Buck 24 Volt to 14 Volt Converter Provides 15 LTC1553 Synchronous Regulator Controller Powers Pentium Pro and Other Big Synchronizing LTC1430s for Reduced Combine a Switching Regulator and an UltraFast Linear Regulator for a High Performance 3.3V Supply 18 The...

Tantalum

* RIPPLE CURRENT RATING > IOUT 2 ** L1 COILTRONICS UP2-4R7 (561) 241-7876 INCREASE L1 TO 10 i H FOR LOAD CURRENTS ABOVE 3.5A AND TO 20 H ABOVE 4A 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 LOAD CURRENT (A) Figure 32. Efficiency of Figure 31's Circuit 10V In, 5V Out The loop compensation capacitor, Cc, produces a pole in the frequency response at 240Hz. Unity-gain phase margin can be further improved with the addition of a resistor, typically 2k, in series with Cc, adding a zero to the frequency response....

Technology

LT1575, 5V to 3.3V with Current Limit 110 LT1575, 5V to 3.3V 5A 109 Microprocessor Supply LT1573, 3.3V 5A 108 LT1577, Dual Regulator for Split-Plane Systems 110 Multioutput LT1577, Dual Regulator for Split-Plane Systems 110 Regulators Switching. See also Regulators Switching (Micropower) Boost 51-53 LT1339, 5V In, 28V 6A Out Synchronous 28 LT1370, 5V In, 12V 2A Out 53 LT1377, 4V-10V In, 12V 100mA Out 51, 52 LT1533, 3.3V to 5V 350mA Boost Converter 72 LTC1266, 2.5V-4.2V In, 5V 2A Out 55 LTC1624,...

The Lt1425 Isolated Flyback Controller

Low voltage circuitry, such as local area networks (LAN), isolation amplifiers and telephone interfaces, frequently requires isolated power supplies. The flyback converter is often the choice for these low power supplies because of its simplicity, size and low parts count. Unfortunately, designers are forced to add optocouplers and references in order to achieve the desired output regulation and transient response. The LT1425 provides a one-chip solution for these and other applications. The...

The Lt1533 Heralds A New Class Of Low Noise Switching Regulators

Introducing the LT1533 Low Noise Switcher The LT1533 is a switching regulator that provides a solution to EMI problems through two flexible approaches. First, the slew rates of both the current through the power switch and the voltage on it are easily programmed with external resistors. Limiting these slew rates will remove the highest harmonics from the switching waveforms. Second, the LT1533, with two 1A power switches, is designed to operate in push-pull circuits. Such circuits, with their...

The New Ltc1435 Makes A Great Microprocessor Core Voltage Regulator

Current microprocessor architectures require different voltages for the core and the I O ring. For portable computer applications, the microprocessor core voltage is reduced for lower power consumption. Three high current regulated voltages, 5V, 3.3V and 2.9V, are commonly required. Several IC manufacturers offer two-output controllers, like the LTC1438, which are normally used for 5V and 3.3V. Another controller is required to generate the 2.9V. Figure 6 shows a simple circuit using the...

Url

* Logic Devices formerly manufactured by by Motorola are now manufactured by ON Semiconductor there have been no changes in part numbers as of January 2000 * Logic Devices formerly manufactured by by Motorola are now manufactured by ON Semiconductor there have been no changes in part numbers as of January 2000

V

Efficiency versus load current is detailed in Figure 121. Note that for the range of 4mA to 80mA, 70 efficiency or greater is achieved. Figure 122 shows input current versus output power. Less than 80 A quiescent current flows when the converter supplies 0.5mW over the 36V-72V range. Figure 119. Switch Voltage and Current Waveforms Figure 119. Switch Voltage and Current Waveforms

Vid Voltage Programmer For Intel Mobile Processors

Figure 47 shows a VID-programmed DC DC converter for an Intel mobile processor that uses the LTC1435A and LTC1706-19 to deliver 7A of output current with a programmable VOUT of 1.3V to 2.0V from a VIN of 4.5V to 22V. Simply connecting the LTC1706-19's FB and SENSE pins to the LTC1435A's VOSENSE and SENSE- pins, respectively, closes the loop between the output voltage sense and the feedback inputs of the LTC1435A regulator with the appropriate resistive divider network, which is controlled by...

Why Stop at

If two channels are good, aren't more channels better In a word, yes. In principle, there is no limit to the number of parallel channels that can be added. As the number of channels, n, increases, the ripple frequency increases to n times the single-channel frequency. Input and output RMS ripple currents continue to decrease. Diminishing returns are reached as nrises above three. At three stages, the ripple reductions are very substantial and dynamic performance is excellent. Adding more...

X

LT1579 Basic Application LBO2, BACKUP and DROPOUT) are open-collector outputs that require an external pull-up resistor. They are capable of sinking 20 iA at a maximum output voltage of 0.32V, which is useful for driving both CMOS and TTL logic families. For driving LED's, all logic outputs can sink 5mA at a maximum output voltage of 1.2V. Figure 224 is the timing diagram for the basic circuit. No time scale is shown for the timing diagram because actual discharge rates are a...

Battery Charger Ic Can Also Serve As Main Stepdown Converter

Using a power adapter with the highest feasible output voltage is attractive to portable system designers for a couple of reasons. Lower current is required to maintain the same system power, which translates into a smaller cable and input connector. If the adapter output voltage is considerably higher than the battery voltage, the adapter output voltage does not need to be regulated or well filtered, resulting in lower adapter cost. A portable system with a high output-voltage adapter,...

Switcher Generates Two Bias Voltages Without Transformer

LCD displays and CCD imaging circuits in today's portable products require several bias voltages of 10V to 20V at a few mA. When symmetric bipolar bias supplies are needed, the negative supply can be generated with a discrete charge pump operating from the power switch of the boost regulator that generates the positive supply. However, an asymmetric bipolar supply is typically required for example 20V and -10V for LCD displays or 15V and -7.5V for CCDs. One possible solution is to add a linear...

Inductor Current

Vco Ckt Dig

Simplified Digram of Constant-Current Control Loop Figure 242. Simplified Digram of Constant-Current Control Loop current programming limitations previously mentioned, to produce a high current, high performance constant-voltage constant-current battery charger for lithium-ion and other battery types. To understand how the two parts work together, a brief review of the LTC1435 operation is necessary. See Figure 241. During each cycle of operation, the series MOSFET switch Q1 is...

Zetex Ztx849

CENTRAL SEMICONDUCTOR (516) 435-1110 Figure 2. High Efficiency, Constant-Frequency, Triple-Output Supply Features 200mV Dropout case in Figure 1, the regulator automatically configures itself for fixed 12V operation using an internal AUX FB resistive divider. When AUX DR is less than 8.5V, the internal divider is removed and the user can adjust the output voltage via an external divider referenced to 1.19V. The external auxiliary regulator PNP pass transistor is sized for the desired output...

New Ic Features Reduce Emi From Switching Regulator Circuits

One disadvantage of using a switching regulator is that it generates electronic noise, known as EMI (electromagnetic interference). This noise can be conducted or radiated, and it can affect other circuits in your product or interfere with the operation of nearby products. The LTC1436-PLL, LTC1437, LTC1439 and LTC1539 have features that can be used to suppress this interference. Frequently, EMI problems don't show up until the integration phase of product development. By using this EMI...

The Ltc1516 Converts Two Cells To 5v With High Efficiency At Extremely Light Loads

Many battery-powered applications require very small amounts of load current from the regulated supply over long periods of time, followed by moderate load currents for short periods of time. In these types of applications (for example, remote data-acquisition systems, hand-held remote controls, and the like), the discharge rate of the battery is dominated by the overall current demands under low load conditions. In such low load systems, a primary source of battery drain is the DC DC converter...

Pushbutton Reset

This solution requires low-battery detection, necessitates battery access and invites inadvertent battery removal. The LTC1558 battery backup controller eliminates these problems by permitting the use of a single, low cost 1.2V rechargeable Nickel-Cadmium (NiCd) cell. The LTC1558 has a built-in fast- trickle-mode charger that charges the NiCd cell when main power is present. FROM n P -4 OPEN DRAIN SOFT RESET