LT3570 LINER
Document overview
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Technical content
FEATURES
APPLICATIONS
DESCRIPTION
1.5A Buck Converter, 1.5A Boost Converter and LDO Controller The L T®3570 is a buck and boost converter with internal power switches and LDO controller . Each converter is designed with a 1.5A current limit and an input range from 2.5V to 36V , making the L T3570 ideal for a wide variety of applications. Switching frequencies up to 2MHz are programmed with an external timing resistor and the oscillator can be synchronized to an external clock up to 2.75MHz. The L T3570 features a programmable soft-start function that limits the feedback voltage during start-up helping prevent overshoot and limiting inrush current. The LDO controller is capable of delivering up to 10mA of base current to an external NPN transistor . Effi ciency n 2.5V to 36V Input Voltage Range n Programmable Switching Frequency from 500kHz to 2MHz n Synchronizable Up to 2.75MHz n V OUT(MIN): 0.8V n Independent Soft-Start for Each Converter n Separate V IN Supplies for Each Converter n Duty Cycle Range: 0% to 90% at 1MHz n Available in 24-Lead (4mm × 4mm) QFN and 20-Lead TSSOP Packages n Cable and Satellite Set-Top Boxes n Automotive Systems n Telecom Systems n “Dying Gasp” Systems n TFT LCD Displays VIN1 SHDN1 SHDN2 SHDN3 SHDN1 SHDN2 SHDN3 SW1 FB1 100nF 1nF 10nF 22μF 2.2μF VOUT3 2.5V 100mA 32.4k VOUT2 3.3V 22k 143k VOUT1 12V 275mA VIN 22k 10.0k 10.2k 22.1k 10.2k
3570 TA01a
15.8k 10μF 10μF 1nF 10nF 3.3μH 6.8μH D2 BOOST SW2 FB2 SS2 NPN_DRV FB3 VC2 SS1 VC1 VIN2 VIN3 BIAS RT SYNC L T3570 GND L, L T , L TC and L TM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. IOUT2 (A) EFFICIENCY (%) 100 0.2 0.4 0.6 0.8
3570 TA01b
1.0 fSW = 1.2MHz VIN = 5V VOUT1 = 12V VOUT2 = 3.3V VOUT3 = 2.5V IOUT1 = 275mA IOUT3 = 100mA
SYNC, R (Note 1) Operating Temperature Range (Note 2).. –40°C to 125°C Storage Temperature Range Lead Temperature (Soldering, 10 sec) 24 23 22 21 20 19 7 8 9 TOP VIEW UF PACKAGE 24-LEAD (4mm s 4mm) PLASTIC QFN 10 11 12 18VIN2 VIN2 SW2 SW1 GND GND V SS2 GND R T SYNC SHDN3 BOOST BIAS V IN3 NPN_DRV FB3 FB2 V IN1 SS1 VC1 FB1 SHDN1 SHDN2 TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB FE PACKAGE 20-LEAD PLASTIC TSSOP TOP VIEW FB1 SHDN1 SHDN2 SHDN3 SYNC R T SS2 VC2 FB2 FB3 V SS1 VIN1 GND SW1 SW2 V IN2 BOOST V IN3 NPN_DRV TJMAX = 125°C, θJA = 38°C/W EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB PIN CONFIGURATION ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3570EUF#PBF L T3570EUF#TRPBF 3570 24-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C L T3570IUF#PBF L T3570IUF#TRPBF 3570 24-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C L T3570EFE#PBF L T3570EFE#TRPBF L T3570FE 20-Lead Plastic TSSOP –40°C to 125°C L T3570IFE#PBF L T3570IFE#TRPBF L T3570FE 20-Lead Plastic TSSOP –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container . Consult L TC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/
ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN1,2,3 = 12V , VSHDN1,2,3 = 12V unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operating Voltage (VIN1) (Note 3) l 2.1 2.5 V Minimum Operating Voltage (VIN2) (Note 3) l 2.1 2.5 V Shutdown Current (Note 4) V SHDN1,2,3 = 0V 0 1.5 μA VIN1 Quiescent Current V SHDN1 = 12V , VSHDN2,3 = 0V , VC1 = 0.4V (Not Switching) VSHDN1 = 0V , VSHDN2,3 = 12V 3.2 4.5 150 mA μA VIN2 Quiescent Current V SHDN1,3 = 0V , VSHDN2 = 12V , VC2 = 0.4V (Not Switching) VSHDN1,3 = 12V , VSHDN2 = 0V 3.5 3.5 4.5 4.5 mA mA VIN3 Quiescent Current V SHDN1,2 = 0V , VSHDN3 = 12V VSHDN1,2 = 12V , VSHDN3 = 0V 700 950 1.5 μA μA Bias Quiescent Current V BIAS = 2.5V 2.3 3.1 mA VSHDN1,2,3 Pin Threshold I VIN2 > 100μA 0.3 1.4 V VSHDN1,2,3 Pin UVLO l 1.1 1.25 1.4 V VSHDNX Pin Current V SHDNX = 12V , VSHDNY,Z = 0V (Note 5) VSHDN1,2,3 = 0V 0.1 1.5 μA μA Switching Frequency R T = 44.2k RT = 7.87k 450 1900 500 2100 550 2300 kHz kHz Maximum Duty Cycle R T = 44.2k RT = 7.87k Synchronous Frequency Threshold 0.3 1.5 V Synchronous Frequency Ratio, fSYN/fOSC RT = 44.2k RT = 7.87k 1.3 1.3 Synchronous Frequency Minimum On/Off Time 50 ns FB1,2,3 Pin Voltage l 772 788 804 mV FB1,2,3 Pin Voltage Line Regulation V VIN1,2,3 = 2.5V to 40V , VC1,2 = 1V 0.01 %/V FB1,2 Pin Bias Current V FB1,2 = 800mV , VC1,2 = 1V (Note 6) 30 200 nA FB3 Pin Bias Current V FB3 = 800mV (Note 6) 30 200 nA SS1,2 Pin Source Current V SS1,2 = 500mV 4.5 μA VC1,2 Pin Source Current V FB1,2 = 600mV 12 μA VC1,2 Pin Sink Current V FB1,2 = 1V 12 μA SW1 Error Amplifi er 1 T ransconductance 190 μMho Error Amplifi er 1 Voltage Gain 100 V/V V C1 Pin Switching Threshold 750 mV VC1 to SW1 Current Gain 5.9 A/V SW1 Current Limit (Note 7) 1.5 2.4 3.1 A SW1 V CESAT ISW1 = 1A (Note 7) 240 mV SW1 Leakage Current SW1 = 40V , V SHDN1 = 0V 0.2 5 μA
PARAMETER CONDITIONS MIN TYP MAX UNITS SW2 Error Amplifi er 2 T ransconductance 195 μMho Error Amplifi er 2 Voltage Gain 100 V/V VC2 Pin Switching Threshold 700 mV VC2 to SW2 Current Gain 5.4 A/V SW2 Current Limit (Note 7) 1.5 2.4 3.1 A SW2 V CESAT ISW2 = 1A (Note 7) 240 mV SW2 Leakage Current SW2 = 0V , V IN2 = 40V , VSHDN2 = 0V 0.2 5 μA BOOST Pin Current I SW2 = 0.5A ISW2 = 1.5A mA mA LDO LDO Maximum Output Current V FB3 = 600mV 10 20 mA ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN1,2,3 = 12V , VSHDN1,2,3 = 12V unless otherwise noted. Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The L T3570E is guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The L T3570I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note 3: V IN2 supplies power for the part. VIN1 supplies power only to the boost converter . VIN3 supplies power only to the LDO Controller . Note 4: Shutdown current is for each individual input current. Note 5: Current fl ows into the pin. Note 6: Current fl ows out of the pin. Note 7: Switch current limit and switch VCESAT guaranteed by design and/or correlation to static test. Note 8: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating junction temperature range when overtemperature protection is active. Continuous operation above the specifi ed maximum operating junction temperature may impair device reliability. TYPICAL PERFORMANCE CHARACTERISTICS Feedback Voltage vs Temperature Frequency vs Temperature Soft-Start Current vs Temperature TEMPERATURE (°C) –50
0.770 VOLTAGE (V)
0.775 0.780 0.785 0.790 05 0 100 150
3570 G01
0.795 0.800 –25 25 75 125 TEMPERATURE (°C) –50 FREQUENCY (kHz) 1500 2000 2500 25 75 150
3570 G02
–25 0 50 100 125 RT = 7.87k RT = 20k RT = 44.2k TEMPERATURE (°C) –50 CURRENT (μA) 4.4 4.6 4.8 25 50 75 100 125
3570 G03
4.2 4.0 –25 0 150 3.8 3.6 5.0
TYPICAL PERFORMANCE CHARACTERISTICS VIN1 Quiescent Current vs Temperature VIN2 Quiescent Current vs Temperature VIN3 Quiescent Current vs Temperature Bias Pin Current vs Temperature SHDN Pin UVLO vs Temperature SHDN Pin Current vs Voltage SW1 Current Limit vs Duty Cycle SW1 Saturation Voltage vs SW1 Current TEMPERATURE (°C) –50 CURRENT (mA) 2.0 2.5 3.0 25 50 75 100 125
3570 G04
1.5 1.0 –25 0 150 0.5 3.5 TEMPERATURE (°C) –50 CURRENT (mA) 2.0 3.0 150
3570 G05
1.0 0 50 100–25 25 75 125 4.0 1.5 2.5 0.5 3.5 TEMPERATURE (°C) –50 CURRENT (μA) 500 600 700 150
3570 G06
0 50 100–25 25 75 125 200 100 900 800 TEMPERATURE (°C) –50 CURRENT (mA) 0.5 1.0 1.5 2.0 05 0 100 150
3570 G07
2.5 3.0 –25 25 75 125 TEMPERATURE (°C) –50 SHDN PIN VOLTAGE (V) 0.25 0.50 0.75 1.00 05 0 100 150
3570 G08
1.25 1.50 –25 25 75 125 VOLTAGE (V) CURRENT (μA) 15 25 40
3570 G09
DUTY CYCLE (%) CURRENT (A) 1.0 2.0 3.0 0.5 1.5 2.5 20 40 60 80
3570 G10
TJ = 125°C TJ = 25°C TJ = –40°C CURRENT (A) VOLTAGE (mV) 150 200 250 350 0.1 0.5 0.7
3570 G11
TJ = 125°C TJ = 25°C TJ = –40°C
TYPICAL PERFORMANCE CHARACTERISTICS SW2 Saturation Voltage vs SW2 Current BOOST Pin Current vs Switch Current NPN_DRV Output Current vs VIN3 SW2 Current Limit vs Duty Cycle DUTY CYCLE (%) CURRENT (A) 1.0 2.0 3.0 0.5 1.5 2.5 20 40 60 80
3570 G12
TJ = 125°C TJ = 25°C TJ = –40°C CURRENT (A) VOLTAGE (mV) 150 200 250 350 0.1 0.5 0.7
3570 G13
TJ = 125°C TJ = 25°C TJ = –40°C VOLTAGE (V) CURRENT (mA)
3570 G15
TJ = 25°C TJ = 125°C TJ = –40°C CURRENT (A) CURRENT (mA) 0.2 0.4 0.6 0.8
3570 G14
1.0 TJ = –40°C TJ = 125°C TJ = 25°C
PIN FUNCTIONS (QFN/TSSOP) VIN2 (Pins 1,2/Pin 14): Input Voltage for the Buck Regulator . This pin also supplies the current to the internal circuitry of the L T3570. This pin must be locally bypassed with a capacitor . SW2 (Pin 3/Pin15): Switch Node. This pin connects to the emitter of an internal NPN power switch. Connect a diode, inductor and boost capacitor to this pin to form the buck regulator SW1 (Pin 4/Pin16): Switch Node. This pin connects to the collector of an internal NPN power switch. Connect a diode and inductor to this pin to form the boost regulator GND (Pins 5, 6, 16, 25/Pins 17, 21): Ground. The Exposed Pad of the package provides both electrical contact to ground and good thermal contact to the printed circuit board. The Exposed Pad must be soldered to the circuit board for proper operation. V IN1 (Pin 7/Pin18): Input Voltage for the Boost Regulator . This pin supplies current to drive the boost NPN transistor of the L T3570. This pin must be locally bypassed with a capacitor . SS1 (Pin 8/Pin 19): Soft-Start Pin. Place a soft-start capacitor here. Upon start-up, a current charges the capacitor to 2V . This pin ramps the reference voltage of the boost switcher . V C1 (Pin 9/Pin 20): Control Voltage and Compensation Pin for the Internal Error Amplifi er . Connect a series RC from this pin to ground to compensate the switching regulator loop for the boost regulator . FB1 (Pin 10/Pin 1): Feedback Pin. The L T3570 regulates this pin to 788mV . Connect the feedback resistors to this pin to set the output voltage for the boost switching regulator . SHDN1 (Pin 11/Pin 2): Shutdown Pin. Tie to 1.5V or more to enable the boost switcher . Ground to shutdown the part. SHDN2 (Pin 12/Pin 3): Shutdown Pin. Tie to 1.5V or more to enable the buck switcher . Ground to shutdown the part. SHDN3 (Pin13/Pin 4): Shutdown Pin. Tie to 1.5V or more to enable the NPN LDO. Ground to shut down the part. SYNC (Pin 14/Pin 5): Synchronization Pin. The SYNC pin is used to synchronize the internal oscillator to an exter- nal signal. The synchronizing range is equal to the initial operating frequency set by the R T pin up to 1.3 times the initial operating frequency. RT (Pin 15/Pin 6): Frequency Set Pin. Place a resistor to GND to set the internal frequency. The range of oscillation is 500kHz to 2MHz. SS2 (Pin 17/Pin 7): Soft-Start Pin. Place a soft-start capacitor here. Upon start-up, a current charges the capacitor to 2V . This pin ramps the reference voltage of the buck switcher . V C2 (Pin 18/Pin 8): Control Voltage and Compensation Pin for the Internal Error Amplifi er . Connect a series RC from this pin to ground to compensate the switching regulator loop for the buck regulator . FB2 (Pin 19/Pin 9): Feedback Pin. The L T3570 regulates this pin to 788mV . Connect the feedback resistors to this pin to set the output voltage for the buck switching regulator . FB3 (Pin 20/Pin 10): Feedback Pin. The L T3570 regulates this pin to 788mV . Connect the feedback resistors to this pin to set the output voltage for the LDO controller . NPN_DRIVE (Pin 21/Pin 11): Base Drive for the External NPN. This pin provides a bias current to drive the base of the NPN. This base current is driven from the IN3 supply voltage. V IN3 (Pin 22/Pin 12): Input Voltage for the NPN LDO. This pin supplies current to drive the base of the NPN. This pin must be locally bypassed with a capacitor . BIAS (Pin 23): QFN Package Only. This pin supplies current to the internal circuitry of the L T3570 if greater than 2.5V . This pin must be locally bypassed with a capacitor . BOOST (Pin 24/Pin 13): Bias for the Base Drive of the NPN Switch for the Buck Regulator . This pin provides a bias voltage higher than V IN2. The voltage on this pin is charged up through an external Schottky diode.
Figure 1. Block Diagram
The L T3570 is a constant frequency, current mode, buck converter and boost converter with an NPN LDO regula- tor . Operation can be best understood by referring to the Block Diagram. If all of the SHDN pins are held low, the L T3570 is shut down and draws zero quiescent current. When any of the pins exceed 1.4V the internal bias circuits turn on. Each regulator will only begin regulating when its corresponding SHDN pin is pulled high. Each switching regulator controls the output voltage in a similar manner . The operation of the switchers can be understood by looking at the boost regulator . A pulse from the oscillator sets the RS fl ip-fl op A4 and turns on the internal NPN bipolar power switch Q1. Current in Q1 and the external inductor L1 begins to increase. When this current exceeds a level determined by the voltage at V C1, comparator A3 resets A4, turning off Q1. The current in L1 fl ows through the external Schottky diode D1 and begins to decrease. The cycle begins again at the next pulse from the oscillator . In this way, the voltage on the V C1 pin controls the current through the inductor to the output. The internal error amplifi er A1 regulates the output voltage by continually adjusting the VC1 pin voltage. The threshold for switching on the V C1 pin is approximately 750mV and an active clamp of 1.15V limits the output current. The soft-start capacitor C6A allows the part to slowly start up by ramping the internal reference. The driver for the buck regulator can operate from either V IN2 or from the BOOST pin. An external capacitor and diode are used to generate a voltage at the BOOST pin that is higher than the input supply. This allows the driver to saturate the internal bipolar NPN power switch for effi cient operation. The driver for the boost regulator is operated from V IN1. The BIAS pin allows the internal circuitry to draw its current from a lower voltage supply than the input. This reduces power dissipation and increases effi ciency. If the voltage on the BIAS pin falls below 2.5V , then the L T3570 quiescent current will fl ow from V IN2.
Table 1. Inductors the inductor value and the input and output voltages.
to 1.2A at DC2 = 0.8. The maximum output current is a function of the chosen inductor value: IOUT2(MAX) =ILIM2 – ΔIL2 Choosing an inductor value so that the ripple current is small will allow a maximum output current near the switch current limit. One approach to choosing the inductor is to start with the simple rule given above, look at the available inductors and choose one to meet cost or space goals. Then use these equations to check that the L T3570 will be able to deliver the required output current. Note again that these equations assume that the inductor current is continu- ous. Discontinuous operation occurs when I OUT2 is less than ΔIL2/2. Boost Inductor Selection For most applications the inductor will fall in the range of 2.2μH to 22μH. Lower values are chosen to reduce physical size of the inductor . Higher values allow more output current because they reduce peak current seen by the power switch, which has a 1.5A current limit. Higher values also reduce input ripple voltage and reduce core loss. The following procedure is suggested as a way of choosing a more optimum inductor . Assume that the average inductor current for a boost converter is equal to the load current times V OUT1/VIN1 and decide whether or not the inductor must withstand continuous overload conditions. If average inductor cur- rent at maximum load current is 0.5A, for instance, a 0.5A inductor may not survive a continuous 1.5A overload condition. Also be aware that boost converters are not short-circuit protected, and that under short conditions, inductor current is limited only by the available current of the input supply Calculate peak inductor current at full load current to en- sure that the inductor will not saturate. Peak current can be signifi cantly higher than output current, especially with smaller inductors and lighter loads, so don’t omit this step. Powdered iron cores are forgiving because they saturate softly, whereas ferrite cores saturate abruptly. Other core materials fall somewhere in between. The following formula assumes continuous mode operation but it errs only slightly on the high side for discontinuous mode, so it can be used for all conditions. IPEAK1 = IOUT1 VOUT1 VIN1 + VIN1 VOUT1 –V IN1() 2fLV OUT1 Make sure that IPEAK1 is less than the switch current ILIM1. ILIM1 is at least 1.5A at low duty cycles and decreases linearly to 1.2A at DC1 = 0.8. The maximum switch current limit can be calculated by the following formula: I where DC1 is the duty cycle and is defi ned as: DC1= 1– VIN1 VOUT1 Remember also that inductance can drop signifi cantly with DC current and manufacturing tolerance. Consideration should also be given to the DC resistance of the inductor as this contributes directly to the effi ciency losses in the overall converter . Table 1 lists several inductor vendors and types that are suitable. Buck Output Capacitor Selection For 5V and 3.3V outputs, a 10μF , 6.3V ceramic capacitor (X5R or X7R) at the output results in very low output volt- age ripple and good transient response. For lower voltages, 10μF is adequate for ripple requirements but increasing C OUT will improve transient performance. Other types and values will also work; the following discusses tradeoffs in output ripple and transient performance. The output capacitor fi lters the inductor current to gener ate an output with low voltage ripple. It also stores energy in order to satisfy transient loads and stabilize the L T3570’s control loop. Because the L T3570 operates at a high frequency, minimal output capacitance is necessary. In addition, the control loop operates well with or without the presence of output capacitor series resistance (ESR). Ceramic capacitors, which achieve very low output ripple APPLICATIONS INFORMATION
Table 2. Low ESR Surface Mount Capacitors maximum that the output current ripple can be is ~0.75A. Table 2 lists several capacitor vendors.
and is largest when V IN2 = 2 • V OUT2 (50% duty cycle). ripple current will always be less than 0.75A. of the same value. Use X5R and X7R types. ceramic capacitor . For details, see Application Note 88. will then increase to the typical peak switch current. Peak reverse voltage is equal to the regulator input volt age. Table 3. Schottky Diodes
3.3V , use a small Schottky diode (such as the BAT-54). the BOOST and SW2 pins is less than 25V . present a load to the switcher that will allow it to start. to achieve low output ripple and small circuit size.
3570 F02
Figure 2. Boost Pin Confi gurations
compensation resistor , RC, is usually in the range of 5k to 50k. A good technique to compensate a new application is to use a 50k potentiometer in place of R C, and use a 1nF capacitor for CC. By adjusting the potentiometer while observing the transient response, the optimum value for R C can be found. Figures 3a to 3c illustrate this process for the circuit of Figure 1 with load current stepped from 100mA to 500mA for the buck converter . Figure 3a shows the transient response with R C equal to 1.6k. The phase margin is poor as evidenced by the excessive ringing in the output voltage and inductor current. In Figure 3b, the value of R C is increased to 5.75k, which results in a more damped response. Figure 3c shows the result when R C is increased further to 25k. The transient response is nicely damped and the compensation procedure is complete. The same procedure is used to compensate the boost converter . Soft-Start The Soft-start time is programmed with an external capaci- tor to ground on SS. An internal current source charges it with a nominal 4.5μA. The voltage on the soft-start pin is used to control the feedback voltage. The soft-start time is determined by the equation: t SS = 0.2 • CSS where CSS is in nF and t SS is in ms. In the event of a commanded shutdown, ULVO on the input or a thermal shutdown, the capacitor is discharged automatically. The soft-start will remain low and only charge back up after the fault goes away and the voltage on SS is less than approximately 100mV . Figure 3a. T ransient Response Shows Excessive Ringing Figure 3b. T ransient Response is Better Figure 3c. T ransient Response Well Damped IOUT 500mA/DIV VOUT 200μs/DIV
3570 F03a
200μs/DIV
3570 F03b
200μs/DIV
3570 F03c
Figure 4. Frequency vs RT Resistance inductor current will increase, exceeding the current limit. the input voltage or load current must decrease.
3570 F04
2000 FREQUENCY (kHz)
3570 F05
Figure 5. Minimum Duty Cycle vs Frequency
will be enabled again going through a soft-start cycle. temperature may result in device degradation or failure. Figure 6. Buck High Speed Switching Path Figure 7. Boost High Speed Switching Path DC1106A demonstration board. with as much area as possible. loop compensation, and stability testing. Figure 8. Suggested Layout
3570 F06
3750 F07
“Dying Gasp” System VIN1 SHDN1 SHDN2 SHDN3 SHDN1 SHDN2 SHDN3 SW1 FB1 100nF 1nF 10nF 22μF 2.2μF V OUT3 3.3V 500mA 118k VOUT2 25k 105k V OUT1 250mA VIN 8V TO 28V 25k 11.5k 22.1k 34.0k 10.7k
3570 TA02
20.0k 10μF 10μF C6 1nF 10nF 10μHL1 4.7μH BOOST SW2 FB2 SS2 NPN_DRV FB3 V SS1 VC1 VIN2 VIN3 BIAS RT SYNC L T3570 GND VIN1 SHDN1 SHDN2 SHDN3 SW1 FB1 100nF 1nF 10nF 22μF 2.2μF V OUT3 2.5V 200mA 205k VOUT2 3.3V 200mA 51k 442k V OUT1 34V VIN 12V 20k 10.5k 64.9k 137k 64.9k
3570 TA03
44.2k 10μF C10 0.1μF 10μF 1nFC4 10nF 22μHL1 47μH BOOST SW2 FB2 SS2 NPN_DRV FB3 V SS1 VC1 VIN2 VIN3 BIAS RT SYNC L T3570 GND
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However , no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. 24-Lead Plastic QFN (4mm × 4mm) (Reference L TC DWG # 05-08-1697) PACKAGE DESCRIPTION 20-Lead Plastic TSSOP (4.4mm) (Reference L TC DWG # 05-08-1663) Exposed Pad Variation CB 4.00 ± 0.10 (4 SIDES) NOTE: 1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-X)—TO BE APPROVED 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE, IF PRESENT 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE PIN 1 TOP MARK (NOTE 6) 0.40 ± 0.10 2423 BOTTOM VIEW—EXPOSED PAD 2.45 ± 0.10 (4-SIDES) 0.75 ± 0.05 R = 0.115 TYP 0.25 ± 0.05
0.50 BSC
0.200 REF
0.00 – 0.05 (UF24) QFN 0105 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 0.70 ±0.05 0.25 ±0.05 2.45 ± 0.05 (4 SIDES)3.10 ± 0.05 4.50 ± 0.05 PACKAGE OUTLINE PIN 1 NOTCH R = 0.20 TYP OR 0.35 × 45° CHAMFER FE20 (CB) TSSOP 0204 0.09 – 0.20 (.0035 – .0079) 0° – 8° 0.25 REF RECOMMENDED SOLDER PAD LAYOUT 0.50 – 0.75 (.020 – .030) 4.30 – 4.50* (.169 – .177) 13 4 5 6 7 89 1 0 111214 13 6.40 – 6.60* (.252 – .260) 3.86 (.152) 2.74 (.108) 20 1918 17 16 15 1.20 (.047) MAX 0.05 – 0.15 (.002 – .006) 0.65 (.0256) BSC 0.195 – 0.30 (.0077 – .0118) TYP 2.74 (.108) 0.45 ±0.05
0.65 BSC
4.50 ±0.10 6.60 ±0.10 1.05 ±0.10 3.86 (.152) MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE SEE NOTE 4 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT 6.40 (.252) BSC
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008 LT 1108 REV A • PRINTED IN USA RELATED PARTS TYPICAL APPLICATION PDA Core PART NUMBER DESCRIPTION COMMENTS L T1767 1.5A, 1.25MHz Step-Down Switching Regulator 3V to 25V Input, V REF = 1.2V , Synchronizable up to 2MHz, L T1930/L T1930A 1A (I SW), 1.2MHz/2.2MHz, High Effi ciency Step-Up DC/DC Converter VIN: 2.6V to 16V , VOUT(MAX) = 34V , IQ = 4.2mA/5.5mA, ISD < 1μA, ThinSOT TM Package L T1939 25V , 2.4MHz Step-Down DC/DC Converter and LDO Controller V IN: 3V to 40V , VOUT(MIN) = 0.8V , IQ = 2mA, ISD < 1μA, 3mm × 3mm DFN L T1943 Quad Output, 2.6A Buck, 2.6A Boost, 0.3A Boost, 0.4A Inverter 1.2MHz TFT DC/DC Converter VIN: 4.5V to 22V , VOUT(MAX) = 40V , IQ = 10mA, ISD < 35μA, L T1945 Dual Output Pos/Neg 350mA (I SW), Constant Off-Time, High Effi ciency Step-Up DC/DC Converter VIN: 1.2V to 15V , VOUT(MAX) = ±34V , IQ = 20μA, ISD < 1μA, 10-Pin MS Package L T3463 Dual Output Pos/Neg 250mA (I SW), Constant Off-Time, High Effi ciency Step-Up DC/DC Converter with Integrated Schottkys VIN: 2.4V to 15V , VOUT(MAX) = ±40V , IQ = 40μA, ISD < 1μA, 3mm × 3mm DFN10 Package L T3467 1.1A, 1.3MHz Step Up DC/DC Converter with Integrated Soft-Start V IN: 2.4V to 16V , VOUT(MAX) = 40V , ISD < 1 μA, Low profi le (1mm) SOT-23 Package L T3500 40V , 2A, 2.4MHz Step-Down DC/DC Converter and LDO Controller V IN: 3V to 40V , VOUT(MIN) = 0.8V , IQ = 2mA, ISD < 1μA, 3mm × 3mm DFN L T3507 36V , 2.5MHz T riple (2.4A, 1.5A, 1.5A) Step-Down DC/DC Converter and LDO Controller VIN: 4V to 36V , VOUT(MIN) = 0.8V , IQ = 7mA, ISD < 1μA, 5mm × 7mm QFN38 Package ThinSOT is a trademark of Linear Technology Corporation. VIN1 SHDN1 SHDN2 SHDN3 SHDN1 SHDN2 SHDN3 SW1 FB1 100nF 1nF 10nF 22μF 4.7μF V OUT3 1.8V 500mA 34k VOUT2 3.3V 500mA 25k 191k V OUT1 15V 200mA VIN 4V TO 12V 25k 10.7k 10.7k 13.7k 10.7k
3570 TA04
10μF 10μF C6 1nFC4 10nF 8.2μHL1 12μH BOOST SW2 FB2 SS2 NPN_DRV FB3 V SS1 VC1 VIN2 VIN3 BIAS RT SYNC L T3570 GND