LT8610A/LT8610AB Series 42V, 3.5A Synchronous Step-Down Regulator with 2.5µA Quiescent Current FEATURES DESCRIPTION LT8610 Feature Set, Plus: 3.5A Maximum Output Current Fast 30ns Minimum Switch-On Time Improved Burst Mode Efficiency (LT8610AB Only) Improved EMI n Wide Input Voltage Range: 3.4V to 42V n Ultralow Quiescent Current Burst Mode® Operation: 2.5μA IQ Regulating 12VIN to 3.3VOUT n Fixed Output Voltages: 3.3V, 5V n Output Ripple < 10mV P-P (LT8610A Only) n High Efficiency Synchronous Operation: 95% Efficiency at 1A, 5VOUT from 12VIN 93% Efficiency at 1A, 3.3VOUT from 12VIN n Low Dropout Under All Conditions: 200mV at 1A n Safely Tolerates Inductor Saturation in Overload n Adjustable and Synchronizable Frequency: 200kHz to 2.2MHz n Accurate 1V Enable Pin Threshold n Output Soft-Start and Tracking n Small Thermally Enhanced 16-Lead MSOP Package The LT®8610A/LT8610AB series are compact, high efficiency, high speed synchronous monolithic step-down switching regulators that consume only 2.5µA of quiescent current. Compared to the LT8610, they have higher maximum output currents of 3.5A and a faster minimum switch-on time of 30ns. The LT8610A has the same low ripple burst mode performance of the LT8610, while the LT8610AB has even higher light load efficiency. n APPLICATIONS The other features of the LT8610 remain unchanged in the LT8610A/LT8610AB series. A SYNC pin allows synchronization to an external clock. The EN/UV pin has an accurate 1V threshold for VIN undervoltage lockout or shut down. A capacitor on the TR/SS pin programs the output voltage ramp rate during startup. The PG flag signals when VOUT is within ±9% of the programmed output voltage as well as fault conditions. OUTPUT CURRENT MINIMUM ON TIME 1mA LOAD EFFICIENCY** LT8610* 2.5A 50ns 82% LT8610A 3.5A 30ns 82% LT8610AB 3.5A 30ns 91% *See LT8610 data sheet. **VIN = 12V, VOUT = 3.3V, L = 4.7µH Automotive and Industrial Supplies GSM Power Supplies n L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n TYPICAL APPLICATION LT8610AB Efficiency at 5VOUT 5V 3.5A Step-Down Converter 4.7µF 10nF 1µF VIN BST EN/UV LT8610AB-5 SW PG SYNC BIAS TR/SS VOUT INTVCC RT 0.1µF 4.7µH 90 VOUT 5V 47µF 3.5A ×2 80 EFFICIENCY (%) VIN 5.5V TO 42V 100 70 60 50 GND VIN = 12V VIN = 24V VIN = 36V 40 60.4k fSW = 700kHz 30 0.1 8610ab TA01a 1 10 100 1000 LOAD CURRENT (mA) 8610ab TA01b 8610abfa For more information www.linear.com/LT8610A 1 LT8610A/LT8610AB Series ABSOLUTE MAXIMUM RATINGS (Note 1) VIN, EN/UV, PG...........................................................42V BIAS...........................................................................30V BST Pin Above SW Pin................................................4V FB, TR/SS, RT, INTVCC ................................................4V VOUT, SYNC Voltage ....................................................6V Operating Junction Temperature Range (Note 2) LT8610AE/LT8610ABE............................ –40 to 125°C LT8610AI/LT8610ABI.............................. –40 to 125°C LT8610AH/LT8610ABH........................... –40 to 150°C Storage Temperature Range.......................–65 to 150°C PIN CONFIGURATION LT8610A, LT8610AB LT8610A-3.3, LT8610A-5, LT8610AB-3.3, LT8610AB-5 TOP VIEW SYNC TR/SS RT EN/UV VIN VIN NC GND 1 2 3 4 5 6 7 8 17 GND TOP VIEW 16 15 14 13 12 11 10 9 FB PG BIAS INTVCC BST SW SW SW SYNC TR/SS RT EN/UV VIN VIN NC GND MSE PACKAGE 16-LEAD PLASTIC MSOP θJA = 40°C/W, θJC(PAD) = 10°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB 1 2 3 4 5 6 7 8 17 GND 16 15 14 13 12 11 10 9 VOUT PG BIAS INTVCC BST SW SW SW MSE PACKAGE 16-LEAD PLASTIC MSOP θJA = 40°C/W, θJC(PAD) = 10°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8610AEMSE#PBF LT8610AEMSE#TRPBF 8610A 16-Lead Plastic MSOP –40°C to 125°C LT8610AEMSE-3.3#PBF LT8610AEMSE-3.3#TRPBF 610A33 16-Lead Plastic MSOP –40°C to 125°C LT8610AEMSE-5#PBF LT8610AEMSE-5#TRPBF 8610A5 16-Lead Plastic MSOP –40°C to 125°C LT8610AIMSE#PBF LT8610AIMSE#TRPBF 8610A 16-Lead Plastic MSOP –40°C to 125°C LT8610AIMSE-3.3#PBF LT8610AIMSE-3.3#TRPBF 610A33 16-Lead Plastic MSOP –40°C to 125°C LT8610AIMSE-5#PBF LT8610AIMSE-5#TRPBF 8610A5 16-Lead Plastic MSOP –40°C to 125°C LT8610AHMSE#PBF LT8610AHMSE#TRPBF 8610A 16-Lead Plastic MSOP –40°C to 150°C LT8610AHMSE-3.3#PBF LT8610AHMSE-3.3#TRPBF 610A33 16-Lead Plastic MSOP –40°C to 150°C LT8610AHMSE-5#PBF LT8610AHMSE-5#TRPBF 8610A5 16-Lead Plastic MSOP –40°C to 150°C LT8610ABEMSE#PBF LT8610ABEMSE#TRPBF 8610AB 16-Lead Plastic MSOP –40°C to 125°C LT8610ABEMSE-3.3#PBF LT8610ABEMSE-3.3#TRPBF 10AB33 16-Lead Plastic MSOP –40°C to 125°C LT8610ABEMSE-5#PBF LT8610ABEMSE-5#TRPBF 610AB5 16-Lead Plastic MSOP –40°C to 125°C LT8610ABIMSE#PBF LT8610ABIMSE#TRPBF 8610AB 16-Lead Plastic MSOP –40°C to 125°C LT8610ABIMSE-3.3#PBF LT8610ABIMSE-3.3#TRPBF 10AB33 16-Lead Plastic MSOP –40°C to 125°C LT8610ABIMSE-5#PBF LT8610ABIMSE-5#TRPBF 610AB5 16-Lead Plastic MSOP –40°C to 125°C LT8610ABHMSE#PBF LT8610ABHMSE#TRPBF 8610AB 16-Lead Plastic MSOP –40°C to 150°C LT8610ABHMSE-3.3#PBF LT8610ABHMSE-3.3#TRPBF 10AB33 16-Lead Plastic MSOP –40°C to 150°C LT8610ABHMSE-5#PBF LT8610ABHMSE-5#TRPBF 610AB5 16-Lead Plastic MSOP –40°C to 150°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 8610abfa 2 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Minimum Input Voltage (Note 4) VIN Quiescent Current VEN/UV = 0V MIN TYP MAX l 2.9 3.4 V l 1.0 1.0 3 8 µA µA l 1.7 1.7 4 10 µA µA VEN/UV = 2V, Not Switching, VSYNC = 0V VEN/UV = 2V, Not Switching, VSYNC = 2V UNITS 0.26 0.5 mA VIN Current in Regulation VOUT = 0.97V, VIN = 6V, Output Load = 100µA (LT8610A) VOUT = 0.97V, VIN = 6V, Output Load = 1mA (LT8610A) VOUT = 0.97V, VIN = 6V, Output Load = 100µA (LT8610AB) VOUT = 0.97V, VIN = 6V, Output Load = 1mA (LT8610AB) l l l l 24 210 24 210 50 350 50 350 µA µA µA µA VIN Current in Regulation VOUT = 3.3V, VIN = 8V, Output Load = 100µA (LT8610A-3.3) VOUT = 3.3V, VIN = 8V, Output Load = 1mA (LT8610A-3.3) VOUT = 3.3V, VIN = 8V, Output Load = 100µA (LT8610AB-3.3) VOUT = 3.3V, VIN = 8V, Output Load = 1mA (LT8610AB-3.3) VOUT = 5V, VIN = 8V, Output Load = 100µA (LT8610A-5) VOUT = 5V, VIN = 8V, Output Load = 1mA (LT8610A-5) VOUT = 5V, VIN = 8V, Output Load = 100µA (LT8610AB-5) VOUT = 5V, VIN = 8V, Output Load = 1mA (LT8610AB-5) l l l l l l l l 60 540 55 500 100 790 80 730 120 900 100 800 180 1200 150 1100 µA µA µA µA µA µA µA µA Feedback Reference Voltage (LT8610A/LT8610AB) VIN = 6V, ILOAD = 0.5A VIN = 6V, ILOAD = 0.5A l 0.964 0.958 0.970 0.970 0.976 0.982 V V Output Voltage (LT8610A-3.3/LT8610AB-3.3) VIN = 8V, ILOAD = 0.5A VIN = 8V, ILOAD = 0.5A l 3.28 3.26 3.30 3.30 3.32 3.34 V V Output Voltage (LT8610A-5/LT8610AB-5) VIN = 8V, ILOAD = 0.5A VIN = 8V, ILOAD = 0.5A l 4.97 4.94 5.00 5.00 5.03 5.06 V V Feedback Voltage Line Regulation (LT8610A/LT8610AB) VIN = 4V to 42V, ILOAD = 1A l 0.004 0.02 %/V Voltage Line Regulation (LT8610A-3.3/LT8610AB-3.3) VIN = 4V to 42V, ILOAD = 1A l 0.004 0.02 %/V Voltage Line Regulation (LT8610A-5/LT8610AB-5) VIN = 6V to 42V, ILOAD = 1A l 0.004 0.02 %/V Feedback Pin Input Current (LT8610A/LT8610AB) VFB = 1V 20 nA –20 Internal Feedback Resistor Divider (LT8610A-3.3/LT8610AB-3.3) 14.3 MΩ Internal Feedback Resistor Divider (LT8610A-5/LT8610AB-5) 12.5 MΩ INTVCC Voltage ILOAD = 0mA, VBIAS = 0V ILOAD = 0mA, VBIAS = 3.3V INTVCC Undervoltage Lockout BIAS Pin Current Consumption VBIAS = 3.3V, ILOAD = 1A, 2MHz Minimum On-Time ILOAD = 1A, SYNC = 0V ILOAD = 1A, SYNC = 3.3V Minimum Off-Time 3.23 3.25 3.4 3.29 3.57 3.35 2.5 2.6 2.7 9 l l 15 15 V V V mA 30 30 45 45 ns ns 95 125 ns 8610abfa For more information www.linear.com/LT8610A 3 LT8610A/LT8610AB Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Oscillator Frequency RT = 221k, ILOAD = 1A RT = 60.4k, ILOAD = 1A RT = 18.2k, ILOAD = 1A Top Power NMOS On-Resistance ISW = 1A Top Power NMOS Current Limit LT8610A LT8610AB l l l MIN TYP MAX UNITS 180 665 1.85 210 700 2.00 240 735 2.15 kHz kHz MHz 120 l l 5 5 Bottom Power NMOS On-Resistance VINTVCC = 3.4V, ISW = 1A 8 8 65 Bottom Power NMOS Current Limit VINTVCC = 3.4V 3.4 SW Leakage Current VIN = 42V, VSW = 0V, 42V –1.5 EN/UV Pin Threshold EN/UV Rising l 0.94 EN/UV Pin Hysteresis 4.3 1.0 VEN/UV = 2V –20 PG Upper Threshold Offset from VFB VFB Falling l 6 PG Lower Threshold Offset from VFB VFB Rising l –12 PG Hysteresis A A mΩ 5.4 A 1.5 µA 1.06 40 EN/UV Pin Current V mV 20 nA 9.0 12 % –9.0 –6 % 40 nA 680 2000 Ω 1.1 2.0 1.4 2.4 V V 40 nA 2.0 3.2 µA 1.3 PG Leakage VPG = 3.3V PG Pull-Down Resistance VPG = 0.1V SYNC Threshold SYNC Falling SYNC Rising SYNC Pin Current VSYNC = 6V –40 l 0.8 1.6 –40 TR/SS Source Current TR/SS Pull-Down Resistance 6.7 6.7 mΩ l Fault Condition, TR/SS = 0.1V 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 LT8610AE/LT8610ABE is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT8610AI/LT8610ABI is guaranteed over the full –40°C to 125°C operating junction temperature range. The LT8610AH is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125°C. 1.0 % 230 Ω Note 3: This IC includes overtemperature protection that is intended to protect the device during overload conditions. Junction temperature will exceed 150°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature will reduce lifetime. Note 4: For fixed output voltage versions, minimum input voltage will be limited by output voltage. 8610abfa 4 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series TYPICAL PERFORMANCE CHARACTERISTICS LT8610AB Efficiency at 5VOUT 100 95 90 fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 70 65 70 fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 60 50 VIN = 12V VIN = 24V VIN = 36V 55 0 0.5 1.5 2 2.5 1 LOAD CURRENT (A) 3 20 0.01 3.5 0.1 1 10 100 LOAD CURRENT (mA) LT8610AB Efficiency at 3.3VOUT 100 65 60 50 1000 50 EFFICIENCY (%) 80 fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 40 LT8610A Efficiency at 5VOUT 20 0.01 0.1 1 10 100 LOAD CURRENT (mA) 100 80 75 fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 70 65 50 100 100 90 0 0.5 1.5 2 2.5 1 LOAD CURRENT (A) 3 65 VIN = 12V VIN = 24V VIN = 36V 55 0 0.5 1.5 2 2.5 1 LOAD CURRENT (A) 3 3.5 8610ab G44 VIN = 12V VIN = 24V VIN = 36V 0.1 1 10 100 LOAD CURRENT (mA) 100 VOUT = 3.3V 95 L = IHLP-2020BZ-01, 4.7µH 90 70 60 50 85 80 75 70 VIN = 12V VIN = 24V VIN = 36V 30 20 0.01 1000 LT8610A/LT8610AB Efficiency vs Frequency at 1A LT8610A Efficiency at 3.3VOUT 40 60 50 8610ab G43 EFFICIENCY (%) 70 EFFICIENCY (%) fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 60 20 0.01 3.5 80 75 70 30 fSW = 700kHz 90 L = IHLP-2020BZ-01, 4.7µH 95 3.5 LT8610A Efficiency at 5VOUT 8610ab G42 LT8610A Efficiency at 3.3VOUT 3 40 VIN = 12V VIN = 24V VIN = 36V 8610ab G04 80 1.5 2 2.5 1 LOAD CURRENT (A) 80 85 55 1000 85 0.5 90 60 VIN = 12V VIN = 24V VIN = 36V 30 0 8610ab G02 90 60 VIN = 12V VIN = 24V VIN = 36V 55 95 70 fSW = 700kHz L = IHLP-2020BZ-01, 4.7µH 70 8610ab G03 90 EFFICIENCY (%) 75 VIN = 12V VIN = 24V VIN = 36V 30 8610ab G01 EFFICIENCY (%) 80 40 60 50 85 EFFICIENCY (%) 75 EFFICIENCY (%) EFFICIENCY (%) 80 LT8610AB Efficiency at 3.3VOUT 95 80 85 100 100 90 90 50 LT8610AB Efficiency at 5VOUT EFFICIENCY (%) 100 0.1 1 10 100 LOAD CURRENT (mA) 1000 8610ab G45 65 VIN = 12V VIN = 24V 60 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 SWITCHING FREQUENCY (MHz) 8610ab G05 8610abfa For more information www.linear.com/LT8610A 5 LT8610A/LT8610AB Series TYPICAL PERFORMANCE CHARACTERISTICS Reference Voltage LT8610A-3.3 Output Voltage 0.979 OUTPUT VOLTAGE (V) 0.976 0.973 0.970 0.967 0.964 0.961 5.100 3.345 5.075 3.330 5.050 3.315 3.300 3.285 3.270 3.255 0.958 0.955 –55 65 35 5 95 TEMPERATURE (°C) –25 125 65 35 5 95 TEMPERATURE (°C) –25 8610ab G06 EN Pin Thresholds 125 155 4.900 –55 0.98 0.97 EN FALLING 0.96 0.95 –55 –25 5 35 65 95 TEMPERATURE (°C) 125 155 0.05 0 –0.05 –0.10 0 –0.03 –0.06 –0.20 –0.12 0 0.5 1.5 2 2.5 1 LOAD CURRENT (A) 3 3.5 –0.15 5.0 TESTED IN REGULATION 8610AB: VOUT = 3.3V 4.5 INPUT CURRENT (µA) 8610A 2.5 8610A-5 2.0 8610A-3.3 1.5 20 3.5 3.0 1.5 0.5 0.5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 8610ab G10 8610AB-5 2.0 1.0 5 8610AB 2.5 1.0 0 15 20 25 30 35 INPUT VOLTAGE (V) 0 40 45 No Load Supply Current 25 4.0 3.0 10 8610ab G09 LT8610AB No Load Supply Current 4.0 3.5 5 0 8610ab G08 TESTED IN REGULATION 8610A: VOUT = 3.3V 4.5 0.03 –0.09 8610ab G07 5.0 0.06 –0.15 LT8610A No Load Supply Current 155 0.09 0.10 –0.25 125 VOUT = 3.3V ILOAD = 0.5A 0.12 CHANGE IN VOUT (%) CHANGE IN VOUT (%) 0.99 35 5 65 95 TEMPERATURE (°C) Line Regulation 0.15 0.15 EN RISING –25 8610ab G47 VOUT = 3.3V VIN = 12V 0.20 1.00 EN THRESHOLD (V) 4.950 Load Regulation 0.25 1.01 INPUT CURRENT (µA) 4.975 8610ab G46 1.02 0 5.000 4.925 3.240 –55 155 5.025 INPUT CURRENT (µA) REFERENCE VOLTAGE (V) 0.982 LT8610AB-3.3 Output Voltage 3.360 OUTPUT VOLTAGE (V) 0.985 8610AB-3.3 VOUT = 3.3V VIN = 12V IN REGULATION 15 10 5 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 8610ab G48 0 –55 –25 65 5 95 35 TEMPERATURE (°C) 125 155 8610ab G11 8610abfa 6 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series TYPICAL PERFORMANCE CHARACTERISTICS Top FET Current Limit 5.50 7.5 6.75 5.25 7.0 6.50 6.5 6.25 5.5 5.0 4.5 5.00 30% DC CURRENT LIMIT (A) 6.0 6.00 5.75 5.50 5.25 4.50 4.25 4.00 3.75 5.00 3.50 3.5 4.75 3.25 0.4 0.6 DUTY CYCLE 0.8 4.50 –55 1.0 –25 5 35 65 TEMPERATURE (°C) –55 Switch Drop SWITCH DROP (mV) 200 150 TOP SW BOT SW 65 5 95 35 TEMPERATURE (°C) 125 400 ILOAD = 1.5A 43 VSYNC = 0V 350 41 300 250 TOP SW 200 BOT SW 150 0 155 110 105 100 95 90 85 0 0.5 1 1.5 2 SWITCH CURRENT (A) 31 25 –55 3 2.5 125 155 8610ab G18 VOUT = 3.3V VOUT = 0.97V –25 5 65 95 35 TEMPERATURE (°C) 155 Switching Frequency 740 700 730 600 500 400 300 200 0 125 8610ab G17 800 RT = 60.4k 720 710 700 690 680 670 100 80 95 65 35 TEMPERATURE (°C) 33 27 SWITCHING FREQUENCY (kHz) DROPOUT VOLTAGE (V) 115 5 35 Dropout Voltage VOUT = 3.3V ILOAD = 0.5A 75 –50 –25 37 8610ab G41 Minimum Off-Time 120 39 29 8610ab G40 125 155 Minimum On-Time 50 –25 125 45 100 50 0 –55 95 5 35 65 TEMPERATURE (°C) –25 8610ab G15 450 SWITCH CURRENT = 1A 100 3.00 125 8610ab G14 Switch Drop 250 95 MINIMUM ON-TIME (ns) 0.2 0 8610ab G13 MINIMUM OFF-TIME (ns) 4.75 4.0 3.0 SWITCH DROP (mV) Bottom FET Current Limit 7.00 CURRENT LIMIT (A) CURRENT LIMIT (A) Top FET Current Limit vs Duty Cycle 8.0 0 0.5 1.5 2 2.5 1 LOAD CURRENT (A) 3 3.5 8610ab G19 660 –55 –25 95 65 35 TEMPERATURE (°C) 5 125 155 8610ab G20 8610abfa For more information www.linear.com/LT8610A 7 LT8610A/LT8610AB Series TYPICAL PERFORMANCE CHARACTERISTICS Minimum Load to Full Frequency 700 70 600 LT8610A 500 LT8610AB 400 300 200 VIN = 12V VOUT = 3.3V L = 4.7µH 100 0 0 VOUT = 3.3V fSW = 700kHz PULSE-SKIPPING MODE 60 50 40 30 20 10 0 100 200 300 400 500 600 700 800 LOAD CURRENT (mA) 5 10 20 15 25 30 INPUT VOLTAGE (V) SS PIN CURRENT (µA) FB VOLTAGE (V) 1.0 0.6 0.4 0.2 1.2 VSS = 0.5V 2.2 2.1 2.0 1.9 1.8 1.6 –50 –25 1.4 250 –7.5 225 –8.0 200 95 65 35 TEMPERATURE (°C) 5 125 –10.0 FB FALLING –10.5 9.5 125 155 8610ab G26 FB FALLING 9.0 8.5 8.0 7.5 65 35 5 95 TEMPERATURE (°C) –25 75 0 0.2 125 155 8610ab G25 3.2 100 25 65 35 5 95 TEMPERATURE (°C) FB RISING 10.0 3.4 125 –11.5 –25 10.5 VIN UVLO 150 50 –12.0 –55 11.0 3.6 175 –11.0 1 11.5 7.0 –55 155 INPUT VOLTAGE (V) RT PIN RESISTOR (kΩ) PG THRESHOLD OFFSET FROM VREF (%) –7.0 0.8 8610ab G22 RT Programmed Switching Frequency FB RISING 0.4 0.6 FB VOLTAGE (V) 8610ab G24 PG Low Thresholds –8.5 0.2 0 PG High Thresholds 8610ab G23 –9.5 200 12.0 1.7 –9.0 300 0 40 35 2.3 1.0 0.4 0.6 0.8 TR/SS VOLTAGE (V) 400 Soft-Start Current 2.4 0.2 500 100 PG THRESHOLD OFFSET FROM VREF (%) Soft-Start Tracking 0 600 8610ab G39 1.2 0.8 VOUT = 3.3V VIN = 12V VSYNC = 0V RT = 60.4k 700 8610ab G21 0 Frequency Foldback 800 SWITCHING FREQUENCY (kHz) 80 LOAD CURRENT (mA) SWITCHING FREQUENCY (kHz) Burst Frequency 800 3.0 2.8 2.6 2.4 2.2 0.6 1.4 1.8 1 SWITCHING FREQUENCY (MHz) 2.2 8610ab G27 2.0 –55 –25 95 65 35 TEMPERATURE (°C) 5 125 155 8610ab G28 8610abfa 8 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series TYPICAL PERFORMANCE CHARACTERISTICS Bias Pin Current 6.5 VBIAS = 5V VOUT = 5V ILOAD = 1A fSW = 700kHz 5.5 5.0 4.5 4.0 3.5 IL 1A/DIV 8 VSW 5V/DIV 6 4 500ns/DIV 12VIN TO 5VOUT AT 1A 2 3.0 2.5 Switching Waveforms VBIAS = 5V VOUT = 5V VIN = 12V ILOAD = 1A 10 BIAS PIN CURRENT (mA) 6.0 BIAS PIN CURRENT (mA) Bias Pin Current 12 5 10 15 20 25 30 35 INPUT VOLTAGE (V) 40 45 0 0 2.5 0.5 1 1.5 2 SWITCHING FREQUENCY (MHz) 8610ab G30 8610ab G29 Switching Waveforms LT8610A/LT8610AB Transient Response Switching Waveforms IL 200mA/DIV IL 1A/DIV VOUT 200mV/DIV VSW 10V/DIV VSW 5V/DIV 500µs/DIV 12VIN TO 5VOUT AT 10mA VSYNC = 0V (LT8610A) LT8610A/LT8610AB Transient Response 50µs/DIV 1.5A TO 3.5A TRANSIENT 12VIN, 3.3VOUT COUT = 47µF 8610ab G33 Start-Up Dropout Performance VIN 2V/DIV VOUT 2V/DIV IL 2A/DIV 50µs/DIV 30mA TO 2A TRANSIENT 12VIN, 3.3VOUT COUT = 47µF IL 2A/DIV 500ns/DIV 36VIN TO 5VOUT AT 1A 8610ab G32 VOUT 200mV/DIV 8610ab G35 8610ab G31 VIN 100ms/DIV 2.5Ω LOAD (2A IN REGULATION) Start-Up Dropout Performance VIN 2V/DIV VOUT VOUT 2V/DIV 8610ab G37 8610ab G34 VIN VOUT 100ms/DIV 20Ω LOAD (250mA IN REGULATION) 8610ab G38 8610abfa For more information www.linear.com/LT8610A 9 LT8610A/LT8610AB Series PIN FUNCTIONS SYNC (Pin 1): External Clock Synchronization Input. Ground this pin for low ripple Burst Mode operation at low output loads. Tie to a clock source for synchronization to an external frequency. Apply a DC voltage of 3V or higher or tie to INTVCC for pulse-skipping mode. When in pulseskipping mode, the IQ will increase to several hundred µA. Do not float this pin. TR/SS (Pin 2): Output Tracking and Soft-Start Pin. This pin allows user control of output voltage ramp rate during start-up. A TR/SS voltage below 0.97V forces the LT8610A/LT8610AB to regulate the FB pin to equal the TR/SS pin voltage. When TR/SS is above 0.97V, the tracking function is disabled and the internal reference resumes control of the error amplifier. An internal 2.2μA pull-up current from INTVCC on this pin allows a capacitor to program output voltage slew rate. This pin is pulled to ground with an internal 230Ω MOSFET during shutdown and fault conditions; use a series resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not needed. RT (Pin 3): A resistor is tied between RT and ground to set the switching frequency. EN/UV (Pin 4): The LT8610A/LT8610AB is shut down when this pin is low and active when this pin is high. The hysteretic threshold voltage is 1.00V going up and 0.96V going down. Tie to VIN if the shutdown feature is not used. An external resistor divider from VIN can be used to program a VIN threshold below which the LT8610A/ LT8610AB will shut down. VIN (Pins 5, 6): The VIN pins supply current to the LT8610A/ LT8610AB internal circuitry and to the internal topside power switch. These pins must be tied together and be locally bypassed. Be sure to place the positive terminal of the input capacitor as close as possible to the VIN pins, and the negative capacitor terminal as close as possible to the GND pins. NC (Pin 7): No Connect. This pin is not connected to internal circuitry. SW (Pins 9, 10, 11): The SW pins are the outputs of the internal power switches. Tie these pins together and connect them to the inductor and boost capacitor. This node should be kept small on the PCB for good performance. BST (Pin 12): This pin is used to provide a drive voltage, higher than the input voltage, to the topside power switch. Place a 0.1µF boost capacitor as close as possible to the IC. INTVCC (Pin 13): Internal 3.4V Regulator Bypass Pin. The internal power drivers and control circuits are powered from this voltage. INTVCC maximum output current is 20mA. Do not load the INTVCC pin with external circuitry. INTVCC current will be supplied from BIAS if VBIAS > 3.1V, otherwise current will be drawn from VIN. Voltage on INTVCC will vary between 2.8V and 3.4V when VBIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor placed close to the IC. BIAS (Pin 14): The internal regulator will draw current from BIAS instead of VIN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V and above this pin should be tied to VOUT. If this pin is tied to a supply other than VOUT use a 1µF local bypass capacitor on this pin. PG (Pin 15): The PG pin is the open-drain output of an internal comparator. PG remains low until the FB pin is within ±9% of the final regulation voltage, and there are no fault conditions. PG is valid when VIN is above 3.4V, regardless of EN/UV pin state. FB (Pin 16, LT8610A/LT8610AB Only): The LT8610A/ LT8610AB regulates the FB pin to 0.970V. Connect the feedback resistor divider tap to this pin. Also, connect a phase lead capacitor between FB and VOUT. Typically, this capacitor is 4.7pF to 10pF. VOUT (Pin 16, LT8610A-3.3/LT8610A-5/LT8610AB-3.3/ LT8610AB-5 Only): The LT8610A-3.3 and LT8610AB-3.3 regulate the VOUT pin to 3.3V. This pin connects to a 14.3MΩ internal feedback divider that programs the fixed output. The LT8610A-5 and LT8610AB-5 regulate the VOUT pin to 5V. This pin connects to a 12.5MΩ internal feedback divider that programs the fixed output. GND (Pin 8, Exposed Pad Pin 17): Ground. These pins are the return path of the internal bottom-side switch and must be tied together. Place the negative terminal of the input capacitor as close to the GND pin and exposed pad as possible. The exposed pad must be soldered to the PCB in order to lower the thermal resistance. 8610abfa 10 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series BLOCK DIAGRAM VIN VIN 5, 6 CIN R3 OPT 4 R4 OPT 15 EN/UV PG 1V + – SHDN ±9% + + – R1 R2 16 FB SHDN TSD INTVCC UVLO VIN UVLO 16 INTVCC OSCILLATOR 200kHz TO 2.2MHz VC BST BURST DETECT SWITCH LOGIC AND ANTISHOOT THROUGH 2.2µA VOUT 14 13 CVCC 12 CBST M1 L SW 9-11 VOUT COUT M2 GND SHDN TSD VIN UVLO LT8610A/LT8610AB ONLY VOUT BIAS 3.4V REG SLOPE COMP ERROR AMP VOUT C1 – + INTERNAL 0.97V REF 8 C1 R1 LT8610A-3.3/LT8610A-5 LT8610AB-3.3/LT8610AB-5 ONLY R2 2 TR/SS CSS OPT 3 RT 1 SYNC GND 17 8610ab BD RT 8610abfa For more information www.linear.com/LT8610A 11 LT8610A/LT8610AB Series OPERATION The LT8610A/LT8610AB is a monolithic, constant frequency, current mode step-down DC/DC converter. An oscillator, with frequency set using a resistor on the RT pin, turns on the internal top power switch at the beginning of each clock cycle. Current in the inductor then increases until the top switch current comparator trips and turns off the top power switch. The peak inductor current at which the top switch turns off is controlled by the voltage on the internal VC node. The error amplifier servos the VC node by comparing the voltage on the VFB pin with an internal 0.97V reference. When the load current increases it causes a reduction in the feedback voltage relative to the reference leading the error amplifier to raise the VC voltage until the average inductor current matches the new load current. When the top power switch turns off, the synchronous power switch turns on until the next clock cycle begins or inductor current falls to zero. If overload conditions result in more than 3.3A flowing through the bottom switch, the next clock cycle will be delayed until switch current returns to a safe level. If the EN/UV pin is low, the LT8610A/LT8610AB is shut down and draws 1µA from the input. When the EN/UV pin is above 1V, the switching regulator will become active. To optimize efficiency at light loads, the LT8610A/ LT8610AB operates in Burst Mode operation in light load situations. Between bursts, all circuitry associated with controlling the output switch is shut down, reducing the input supply current to 1.7μA. In a typical application, 2.5μA will be consumed from the input supply when regulating with no load. The SYNC pin is tied low to use Burst Mode operation and can be tied to a logic high to use pulseskipping mode. If a clock is applied to the SYNC pin the part will synchronize to an external clock frequency and operate in pulse-skipping mode. While in pulse-skipping mode the oscillator operates continuously and positive SW transitions are aligned to the clock. During light loads, switch pulses are skipped to regulate the output and the quiescent current will be several hundred µA. To improve efficiency across all loads, supply current to internal circuitry can be sourced from the BIAS pin when biased at 3.3V or above. Else, the internal circuitry will draw current from VIN. The BIAS pin should be connected to VOUT if the LT8610A/LT8610AB output is programmed at 3.3V or above. Comparators monitoring the FB pin voltage (or VOUT pin voltages for fixed output versions) will pull the PG pin low if the output voltage varies more than ±9% (typical) from the set point, or if a fault condition is present. The oscillator reduces the LT8610A/LT8610AB’s operating frequency when the voltage at the FB pin (or VOUT pin for fixed output versions) is low. This frequency foldback helps to control the inductor current when the output voltage is lower than the programmed value which occurs during start-up or overcurrent conditions. When a clock is applied to the SYNC pin or the SYNC pin is held DC high, the frequency foldback is disabled and the switching frequency will slow down only during overcurrent conditions. The LT8610AB differs from the LT8610A in that it has improved efficiency during Burst Mode operation. This comes with the trade-off of increased output voltage ripple, which can be proportionally decreased with an increase in output capacitance. The other trade-off is that the LT8610AB will not reach the full switching frequency programmed by the RT pin resistor until a higher load compared to the LT8610A. 8610abfa 12 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series APPLICATIONS INFORMATION Achieving Ultralow Quiescent Current To enhance efficiency at light loads, the LT8610A/LT8610AB operates in low ripple Burst Mode operation, which keeps the output capacitor charged to the desired output voltage while minimizing the input quiescent current and minimizing output voltage ripple. In Burst Mode operation the LT8610A/LT8610AB delivers single pulses of current to the output capacitor followed by sleep periods where the output power is supplied by the output capacitor. While in sleep mode the LT8610A/LT8610AB consumes 1.7μA. As the output load decreases, the frequency of single current pulses decreases (see Figure 1a) and the percentage of time the LT8610A/LT8610AB is in sleep mode increases, Burst Frequency SWITCHING FREQUENCY (kHz) 800 700 600 LT8610A 500 LT8610AB 400 300 200 VIN = 12V VOUT = 3.3V L = 4.7µH 100 0 100 200 300 400 500 600 700 800 LOAD CURRENT (mA) 0 (1a) LT8610A IL 200mA/DIV VOUT 10mV/DIV VOUT = 3.3V fSW = 700kHz PULSE-SKIPPING MODE 70 LOAD CURRENT (mA) While in Burst Mode operation the current limit of the top switch is approximately 400mA for the LT8610A resulting in output voltage ripple shown in Figure 2a. The LT8610AB has a 1A current limit in Burst Mode operation, which increases the efficiency but also the output voltage ripple compared to the the LT8610A (Figure 2b). However, increasing the output capacitance will decrease the output ripple proportionally (Table 1). As load ramps upward from zero the switching frequency will increase but only up to the switching frequency programmed by the resistor at the RT pin as shown in Figure 1a. The output load at 8610ab F01a Minimum Load to Full Frequency 80 resulting in much higher light load efficiency than for typical converters. By maximizing the time between pulses, the converter quiescent current approaches 2.5µA for a typical application when there is no output load. Therefore, to optimize the quiescent current performance at light loads, the current in the feedback resistor divider must be minimized as it appears to the output as load current. The fixed output versions of the LT8610A/LT8610AB series have larger internal feedback resistors than can practically be used externally, so are a good choice for optimizing quiescent current performance. VSYNC = 0V COUT = 47µF L = 4.7µH 5µs/DIV 8610ab F02a VSYNC = 0V COUT = 47µF L = 4.7µH 20µs/DIV 8610ab F02b (2a) 60 50 LT8610AB 40 VSW 5V/DIV 30 IL 500mA/DIV 20 10 0 5 10 20 15 25 30 INPUT VOLTAGE (V) (1b) 35 40 8610ab F01b Figure 1. SW Frequency vs Load Information in Burst Mode Operation (1a) and Pulse-Skipping Mode (1b) VOUT 20mV/DIV (2b) Figure 2. Burst Mode Operation of LT8610A (2a) and LT8610AB (2b) For more information www.linear.com/LT8610A 8610abfa 13 LT8610A/LT8610AB Series APPLICATIONS INFORMATION which the LT8610A/LT8610AB reaches the programmed frequency varies based on input voltage, output voltage, and inductor choice. However, the output load required to reach full frequency will be higher for the LT8610AB as compared to the LT8610A (Figure 1a). Inductor value has a very strong effect on Burst Mode efficiency. Larger value inductors allow more charge to be transferred to the output per pulse, which increases both efficiency and output voltage ripple. This dependence on inductance is stronger for the LT8610AB than it is for the LT8610A. If higher efficiency is needed in a Burst Mode application, increasing inductor value can be a quick solution. Table 1. Output Voltage Ripple vs Output Capacitance for LT8610AB when VIN = 12V, VOUT = 3.3V, and L = 4.7µH OUTPUT CAPACITANCE OUTPUT RIPPLE 47µF 40mV 47µF ×2 20mV 47µF ×4 10mV V V 1 IQ = 1.7µA + OUT OUT R1+R2 VIN n (2) where 1.7µA is the quiescent current of the LT8610A/ LT8610AB and the second term is the current in the feedback divider reflected to the input of the buck operating at its light load efficiency n. For a 3.3V application with R1 = 1M and R2 = 412k, the feedback divider draws 2.3µA. With VIN = 12V and n = 80%, this adds 0.8µA to the 1.7µA quiescent current resulting in 2.5µA no-load current from the 12V supply. Note that this equation implies that the no-load current is a function of VIN; this is plotted in the Typical Performance Characteristics section. Setting the Switching Frequency FB Resistor Network The output voltage is programmed with a resistor divider between the output and the FB pin. Choose the resistor values according to: (1) Reference designators refer to the Block Diagram. 1% resistors are recommended to maintain output voltage accuracy. 14 The fixed output versions of the LT8610A/LT8610AB series have the feedback resistor network and phase lead capacitor integrated within the part. The FB pin is replaced with a VOUT pin for these regulators. The VOUT pin can be connected directly to the inductor and output capacitor. The 3.3V fixed output products (LT8610A-3.3/ LT8610AB-3.3) have a total of 14.3M of internal feedback divider resistance from the VOUT pin to ground. The 5V fixed output products (LT8610A-5/LT8610AB-5) have a total of 12.5M of internal feedback divider resistance from the VOUT pin to ground. If low input quiescent current and good light-load efficiency are desired, use large resistor values for the FB resistor divider. The current flowing in the divider acts as a load current, and will increase the no-load input current to the converter, which is approximately: For some applications it is desirable for the LT8610A/ LT8610AB to operate in pulse-skipping mode, offering two major differences from Burst Mode operation. First is the clock stays awake at all times and all switching cycles are aligned to the clock. In this mode much of the internal circuitry is awake at all times, increasing quiescent current to several hundred µA. Second is that full switching frequency is reached at lower output load than in Burst Mode operation (see Figure 1b). To enable pulse-skipping mode, the SYNC pin is tied high either to a logic output or to the INTVCC pin. When a clock is applied to the SYNC pin the LT8610A/LT8610AB will also operate in pulse-skipping mode. V R1= R2 OUT – 1 0.970V When using large FB resistors, a 4.7pF to 10pF phase-lead capacitor should be connected from VOUT to FB. The LT8610A/LT8610AB uses a constant frequency PWM architecture that can be programmed to switch from 200kHz to 2.2MHz by using a resistor tied from the RT pin to ground. A table showing the necessary RT value for a desired switching frequency is in Table 1. The RT resistor required for a desired switching frequency can be calculated using: RT = 46.5 – 5.2 fSW For more information www.linear.com/LT8610A (3) 8610abfa LT8610A/LT8610AB Series APPLICATIONS INFORMATION where RT is in kΩ and fSW is the desired switching frequency in MHz. Table 1. SW Frequency vs RT Value fSW (MHz) RT (kΩ) 0.2 232 0.3 150 0.4 110 0.5 88.7 0.6 71.5 0.7 60.4 0.8 52.3 1.0 41.2 1.2 33.2 14 28.0 1.6 23.7 1.8 20.5 2.0 18.2 2.2 15.8 For applications that cannot allow deviation from the programmed switching frequency at low VIN/VOUT ratios use the following formula to set switching frequency: VIN(MIN) = Selection of the operating frequency is a trade-off between efficiency, component size, and input voltage range. The advantage of high frequency operation is that smaller inductor and capacitor values may be used. The disadvantages are lower efficiency and a smaller input voltage range. The highest switching frequency (fSW(MAX)) for a given application can be calculated as follows: fSW(MAX) = ( tON(MIN) VIN – VSW(TOP) + VSW(BOT) VOUT + VSW(BOT) 1– fSW • tOFF(MIN) – VSW(BOT) + VSW(TOP) (5) where VIN(MIN) is the minimum input voltage without skipped cycles, VOUT is the output voltage, VSW(TOP) and VSW(BOT) are the internal switch drops (~0.42V, ~0.21V, respectively at maximum load), fSW is the switching frequency (set by RT), and tOFF(MIN) is the minimum switch off-time. Note that higher switching frequency will increase the minimum input voltage below which cycles will be dropped to achieve higher duty cycle. Operating Frequency Selection and Trade-Offs VOUT + VSW(BOT) The LT8610A/LT8610AB is capable of a maximum duty cycle of greater than 99%, and the VIN-to-VOUT dropout is limited by the RDS(ON) of the top switch. In this mode the LT8610A/LT8610AB skips switch cycles, resulting in a lower switching frequency than programmed by RT. ) Inductor Selection and Maximum Output Current The LT8610A/LT8610AB is designed to minimize solution size by allowing the inductor to be chosen based on the output load requirements of the application. During overload or short-circuit conditions the LT8610A/LT8610AB safely tolerates operation with a saturated inductor through the use of a high speed peak-current mode architecture. A good first choice for the inductor value is: (4) where VIN is the typical input voltage, VOUT is the output voltage, VSW(TOP) and VSW(BOT) are the internal switch drops (~0.42V, ~0.21V, respectively at maximum load) and tON(MIN) is the minimum top switch on-time (see the Electrical Characteristics). This equation shows that a slower switching frequency is necessary to accommodate a high VIN/VOUT ratio. For transient operation, VIN may go as high as the absolute maximum rating of 42V regardless of the RT value, however the LT8610A/LT8610AB will reduce switching frequency as necessary to maintain control of inductor current to assure safe operation. L= VOUT + VSW(BOT) fSW (6) where fSW is the switching frequency in MHz, VOUT is the output voltage, VSW(BOT) is the bottom switch drop (~0.21V) and L is the inductor value in μH. To avoid overheating and poor efficiency, an inductor must be chosen with an RMS current rating that is greater than the maximum expected output load of the application. In addition, the saturation current (typically labeled ISAT) rating of the inductor must be higher than the load current plus 1/2 of in inductor ripple current: 1 IL(PEAK) =ILOAD(MAX) + ∆IL 2 (7) 8610abfa For more information www.linear.com/LT8610A 15 LT8610A/LT8610AB Series APPLICATIONS INFORMATION where ∆IL is the inductor ripple current as calculated in Equation 9 and ILOAD(MAX) is the maximum output load for a given application. As a quick example, an application requiring 1A output should use an inductor with an RMS rating of greater than 1A and an ISAT of greater than 1.3A. During long duration overload or short-circuit conditons, the inductor RMS routing requirement is greater to avoid overheating of the inductor. To keep the efficiency high, the series resistance (DCR) should be less than 0.04Ω, and the core material should be intended for high frequency applications. The LT8610A/LT8610AB limits the peak switch current in order to protect the switches and the system from overload faults. The top switch current limit (ILIM) is at least 6A at low duty cycles and decreases linearly to 5A at DC = 0.8. The inductor value must then be sufficient to supply the desired maximum output current (IOUT(MAX)), which is a function of the switch current limit (ILIM) and the ripple current. IOUT(MAX) =ILIM – ∆IL 2 (8) The peak-to-peak ripple current in the inductor can be calculated as follows: ∆IL = VOUT L • fSW V • 1– OUT VIN(MAX) (9) where fSW is the switching frequency of the LT8610A/ LT8610AB, and L is the value of the inductor. Therefore, the maximum output current that the LT8610A/LT8610AB will deliver depends on the switch current limit, the inductor value, and the input and output voltages. The inductor value may have to be increased if the inductor ripple current does not allow sufficient maximum output current (IOUT(MAX)) given the switching frequency, and maximum input voltage used in the desired application. The optimum inductor for a given application may differ from the one indicated by this design guide. A larger value inductor provides a higher maximum load current and reduces the output voltage ripple. For applications requiring smaller load currents, the value of the inductor may be lower and the LT8610A/LT8610AB may operate with higher ripple current. This allows use of a physically smaller inductor, or one with a lower DCR resulting in higher efficiency. Be aware that low inductance may result in discontinuous mode operation, which further reduces maximum load current. Inductor value has a very strong effect on Burst Mode efficiency. Larger value inductors allow more charge to be transferred to the output per pulse, which increases both efficiency and output voltage ripple. This dependence on inductance is stronger for the LT8610AB than it is for the LT8610A. If higher efficiency is needed in a Burst Mode application, increasing inductor value can be a quick solution. For more information about maximum output current and discontinuous operation, see Linear Technology’s Application Note 44. Finally, for duty cycles greater than 50% (VOUT/VIN > 0.5), a minimum inductance is required to avoid sub-harmonic oscillation. See Application Note 19. Input Capacitor Bypass the input of the LT8610A/LT8610AB circuit with a ceramic capacitor of X7R or X5R type placed as close as possible to the VIN and PGND pins. Y5V types have poor performance over temperature and applied voltage, and should not be used. A 4.7μF to 10μF ceramic capacitor is adequate to bypass the LT8610A/LT8610AB and will easily handle the ripple current. Note that larger input capacitance is required when a lower switching frequency is used. If the input power source has high impedance, or there is significant inductance due to long wires or cables, additional bulk capacitance may be necessary. This can be provided with a low performance electrolytic capacitor. Step-down regulators draw current from the input supply in pulses with very fast rise and fall times. The input capacitor is required to reduce the resulting voltage ripple at the LT8610A/LT8610AB and to force this very high frequency switching current into a tight local loop, minimizing EMI. A 4.7μF capacitor is capable of this task, but only if it is placed close to the LT8610A/LT8610AB (see the PCB Layout section). A second precaution regarding the ceramic input capacitor concerns the maximum input voltage rating of the LT8610A/LT8610AB. A ceramic input capacitor combined 8610abfa 16 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series APPLICATIONS INFORMATION with trace or cable inductance forms a high quality (under damped) tank circuit. If the LT8610A/LT8610AB circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT8610A/ LT8610AB’s voltage rating. This situation is easily avoided (see Linear Technology Application Note 88). Output Capacitor and Output Ripple The output capacitor has two essential functions. Along with the inductor, it filters the square wave generated by the LT8610A/LT8610AB to produce the DC output. In this role it determines the output ripple, thus low impedance at the switching frequency is important. The second function is to store energy in order to satisfy transient loads and stabilize the LT8610A/LT8610AB’s control loop. Ceramic capacitors have very low equivalent series resistance (ESR) and provide the best ripple performance. For good starting values, see the Typical Applications section. Use X5R or X7R types. This choice will provide low output ripple and good transient response. Transient performance can be improved with a higher value output capacitor and the addition of a feedforward capacitor placed between VOUT and FB. Increasing the output capacitance will also decrease the output voltage ripple. A lower value of output capacitor can be used to save space and cost but transient performance will suffer and may cause loop instability. See the Typical Applications in this data sheet for suggested capacitor values. When choosing a capacitor, special attention should be given to the data sheet to calculate the effective capacitance under the relevant operating conditions of voltage bias and temperature. A physically larger capacitor or one with a higher voltage rating may be required. Ceramic Capacitors Ceramic capacitors are small, robust and have very low ESR. However, ceramic capacitors can cause problems when used with the LT8610A/LT8610AB due to their piezoelectric nature. When in Burst Mode operation, the LT8610A/LT8610AB’s switching frequency depends on the load current, and at very light loads the LT8610A/ LT8610AB can excite the ceramic capacitor at audio fre- quencies, generating audible noise. Since the LT8610A/ LT8610AB operates at a lower current limit during Burst Mode operation, the noise is typically very quiet to a casual ear. If this is unacceptable, use a high performance tantalum or electrolytic capacitor at the output. Low noise ceramic capacitors are also available. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LT8610A/LT8610AB. As previously mentioned, a ceramic input capacitor combined with trace or cable inductance forms a high quality (underdamped) tank circuit. If the LT8610A/LT8610AB circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT8610A/ LT8610AB’s rating. This situation is easily avoided (see Linear Technology Application Note 88). Enable Pin The LT8610A/LT8610AB is in shutdown when the EN pin is low and active when the pin is high. The rising threshold of the EN comparator is 1.0V, with 40mV of hysteresis. The EN pin can be tied to VIN if the shutdown feature is not used, or tied to a logic level if shutdown control is required. Adding a resistor divider from VIN to EN programs the LT8610A/LT8610AB to regulate the output only when VIN is above a desired voltage (see the Block Diagram). Typically, this threshold, VIN(EN), is used in situations where the input supply is current limited, or has a relatively high source resistance. A switching regulator draws constant power from the source, so source current increases as source voltage drops. This looks like a negative resistance load to the source and can cause the source to current limit or latch low under low source voltage conditions. The VIN(EN) threshold prevents the regulator from operating at source voltages where the problems might occur. This threshold can be adjusted by setting the values R3 and R4 such that they satisfy the following equation: R3 VIN(EN) = +1 •1.0V R4 (10) where the LT8610A/LT8610AB will remain off until VIN is above VIN(EN). Due to the comparator’s hysteresis, switching will not stop until the input falls slightly below VIN(EN). 8610abfa For more information www.linear.com/LT8610A 17 LT8610A/LT8610AB Series APPLICATIONS INFORMATION When operating in Burst Mode operation for light load currents, the current through the VIN(EN) resistor network can easily be greater than the supply current consumed by the LT8610A/LT8610AB. Therefore, the VIN(EN) resistors should be large to minimize their effect on efficiency at low loads. voltage 3.4 times that of the TR/SS pin, while the 5V output options will track to a voltage 5.15 times that of the TR/SS pin. When TR/SS is above 0.97V, tracking is disabled and the feedback voltage will regulate to the internal reference voltage. The TR/SS pin may be left floating if the function is not needed. INTVCC Regulator An active pull-down circuit is connected to the TR/SS pin which will discharge the external soft-start capacitor in the case of fault conditions and restart the ramp when the faults are cleared. Fault conditions that clear the soft-start capacitor are the EN/UV pin transitioning low, VIN voltage falling too low, or thermal shutdown. An internal low dropout (LDO) regulator produces the 3.4V supply from VIN that powers the drivers and the internal bias circuitry. The INTVCC can supply enough current for the LT8610A/LT8610AB’s circuitry and must be bypassed to ground with a minimum of 1μF ceramic capacitor. Good bypassing is necessary to supply the high transient currents required by the power MOSFET gate drivers. To improve efficiency the internal LDO can also draw current from the BIAS pin when the BIAS pin is at 3.1V or higher. Typically the BIAS pin can be tied to the output of the LT8610A/ LT8610AB, or can be tied to an external supply of 3.3V or above. If BIAS is connected to a supply other than VOUT, be sure to bypass with a local ceramic capacitor. If the BIAS pin is below 3.0V, the internal LDO will consume current from VIN. Applications with high input voltage and high switching frequency where the internal LDO pulls current from VIN will increase die temperature because of the higher power dissipation across the LDO. Do not connect an external load to the INTVCC pin. Output Voltage Tracking and Soft-Start The LT8610A/LT8610AB allows the user to program its output voltage ramp rate by means of the TR/SS pin. An internal 2.2μA pulls up the TR/SS pin to INTVCC. Putting an external capacitor on TR/SS enables soft starting the output to prevent current surge on the input supply. During the softstart ramp the output voltage will proportionally track the TR/SS pin voltage. For output tracking applications, TR/SS can be externally driven by another voltage source. From 0V to 0.97V, the TR/SS voltage will override the internal 0.97V reference input to the error amplifier, thus regulating the FB pin voltage to that of TR/SS pin. In the fixed output voltage options the output voltage will track the TR/SS pin voltage based on a factor set by the internal feedback resistor divider. The 3.3V output options will track to a Output Power Good When the LT8610A/LT8610AB’s output voltage is within the ±9% window of the regulation point, which is a VFB voltage in the range of 0.883V to 1.057V (typical), the output voltage is considered good and the open-drain PG pin goes high impedance and is typically pulled high with an external resistor. Otherwise, the internal pull-down device will pull the PG pin low. To prevent glitching both the upper and lower thresholds include 1.3% of hysteresis. This ±9% power good window around the regulation point is the same for the fixed output options, which for the 3.3V output version corresponds to a 3.003V to 3.597V range (typical) and for the 5V output version corresponds to a 4.55V to 5.45V range (typical). The PG pin is also actively pulled low during several fault conditions: EN/UV pin is below 1V, INTVCC has fallen too low, VIN is too low, or thermal shutdown. Synchronization To select low ripple Burst Mode operation, tie the SYNC pin below 0.4V (this can be ground or a logic low output). To synchronize the LT8610A/LT8610AB oscillator to an external frequency connect a square wave (with 20% to 80% duty cycle) to the SYNC pin. The square wave amplitude should have valleys that are below 0.4V and peaks above 2.4V (up to 6V). The LT8610A/LT8610AB will not enter Burst Mode operation at low output loads while synchronized to an external clock, but instead will pulse skip to maintain regulation. The LT8610A/LT8610AB may be synchronized over a 200kHz 8610abfa 18 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series APPLICATIONS INFORMATION to 2.2MHz range. The RT resistor should be chosen to set the LT8610A/LT8610AB switching frequency equal to or below the lowest synchronization input. For example, if the synchronization signal will be 500kHz and higher, the RT should be selected for 500kHz. The slope compensation is set by the RT value, while the minimum slope compensation required to avoid subharmonic oscillations is established by the inductor size, input voltage, and output voltage. Since the synchronization frequency will not change the slopes of the inductor current waveform, if the inductor is large enough to avoid subharmonic oscillations at the frequency set by RT, then the slope compensation will be sufficient for all synchronization frequencies. For some applications it is desirable for the LT8610A/ LT8610AB to operate in pulse-skipping mode, offering two major differences from Burst Mode operation. First is the clock stays awake at all times and all switching cycles are aligned to the clock. Second is that full switching frequency is reached at lower output load than in Burst Mode operation. These two differences come at the expense of increased quiescent current. To enable pulse-skipping mode, the SYNC pin is tied high either to a logic output or to the INTVCC pin. There is another situation to consider in systems where the output will be held high when the input to the LT8610A/ LT8610AB is absent. This may occur in battery charging applications or in battery-backup systems where a battery or some other supply is diode ORed with the LT8610A/ LT8610AB’s output. If the VIN pin is allowed to float and the EN pin is held high (either by a logic signal or because it is tied to VIN), then the LT8610A/LT8610AB’s internal circuitry will pull its quiescent current through its SW pin. This is acceptable if the system can tolerate several μA in this state. If the EN pin is grounded the SW pin current will drop to near 1µA. However, if the VIN pin is grounded while the output is held high, regardless of EN, parasitic body diodes inside the LT8610A/LT8610AB can pull current from the output through the SW pin and the VIN pin. Figure 3 shows a connection of the VIN and EN/UV pins that will allow the LT8610A/LT8610AB to run only when the input voltage is present and that protects against a shorted or reversed input. D1 VIN The LT8610A/LT8610AB does not operate in forced continuous mode regardless of SYNC signal. Never leave the SYNC pin floating. VIN LT8610A/ LT8610AB EN/UV GND 8610ab F03 Figure 3. Reverse VIN Protection Shorted and Reversed Input Protection PCB Layout The LT8610A/LT8610AB will tolerate a shorted output. Several features are used for protection during output short-circuit and brownout conditions. The first is the switching frequency will be folded back while the output is lower than the set point to maintain inductor current control. Second, the bottom switch current is monitored such that if inductor current is beyond safe levels switching of the top switch will be delayed until such time as the inductor current falls to safe levels. For proper operation and minimum EMI, care must be taken during printed circuit board layout. Figure 4 shows the recommended component placement with trace, ground plane and via locations. Note that large, switched currents flow in the LT8610A/LT8610AB’s VIN pins, GND pins, and the input capacitor (C1). The loop formed by the input capacitor should be as small as possible by placing the capacitor adjacent to the VIN and GND pins. When using a physically large input capacitor the resulting loop may become too large in which case using a small case/value capacitor placed close to the VIN and GND pins plus a larger capacitor further away is preferred. These components, along with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections should be made on that layer. Place a local, unbroken ground plane under the application circuit on Frequency foldback behavior depends on the state of the SYNC pin: If the SYNC pin is low the switching frequency will slow while the output voltage is lower than the programmed level. If the SYNC pin is connected to a clock source or tied high, the LT8610A/LT8610AB will stay at the programmed frequency without foldback and only slow switching if the inductor current exceeds safe levels. 8610abfa For more information www.linear.com/LT8610A 19 LT8610A/LT8610AB Series APPLICATIONS INFORMATION can be left unconnected to help meet PCB clearance and creepage requirements between the VIN and GND traces. GND High Temperature Considerations 16 TR/SS 2 15 RT 3 14 BIAS 4 13 INTVCC 5 12 6 11 7 10 8 9 EN/UV VIN FB PG BST SW GND VOUT VOUT LINE TO BIAS VIAS TO GROUND PLANE 8610ab F04 OUTLINE OF LOCAL GROUND PLANE Figure 4. Recommended PCB Layout for the LT8610A/LT8610AB the layer closest to the surface layer. The SW and BOOST nodes should be as small as possible. Finally, keep the FB and RT nodes small so that the ground traces will shield them from the SW and BOOST nodes. The exposed pad on the bottom of the package must be soldered to ground so that the pad is connected to ground electrically and also acts as a heat sink thermally. To keep thermal resistance low, extend the ground plane as much as possible, and add thermal vias under and near the LT8610A/LT8610AB to additional ground planes within the circuit board and on the bottom side. Unlike the LT8610, the LT8610A/LT8610AB has pin 7 as an NC (no connect) pin. This pin can be soldered to GND to have an LT8610 compatible PCB layout. Alternatively, pin 7 For higher ambient temperatures, care should be taken in the layout of the PCB to ensure good heat sinking of the LT8610A/LT8610AB. The exposed pad on the bottom of the package must be soldered to a ground plane. This ground should be tied to large copper layers below with thermal vias; these layers will spread heat dissipated by the LT8610A/LT8610AB. Placing additional vias can reduce thermal resistance further. The maximum load current should be derated as the ambient temperature approaches the maximum junction rating. Power dissipation within the LT8610A/LT8610AB can be estimated by calculating the total power loss from an efficiency measurement and subtracting the inductor loss. The die temperature is calculated by multiplying the LT8610A/LT8610AB power dissipation by the thermal resistance from junction to ambient. The LT8610A/LT8610AB will stop switching and indicate a fault condition if safe junction temperature is exceeded. Temperature rise of the LT8610A/LT8610AB is worst when operating at high load, high VIN, and high switching frequency. If the case temperature is too high for a given application, then either VIN, switching frequency, or load current can be decreased to reduce the temperature to an acceptable level. Figure 5 shows an example of how case temperature can be managed by reducing VIN, switching frequency, or load. 140 CASE TEMPERATURE RISE (°C) 1 SYNC VOUT TA = 25°C 120 fSW = 2MHz ILOAD = 3.5A 100 80 60 40 20 0 fSW = 2MHz ILOAD = 2.5A 8 12 fSW = 1MHz ILOAD = 3.5A 20 16 24 28 INPUT VOLTAGE (V) 32 36 8610ab F05 Figure 5. LT8610AB Case Temperature Rise 8610abfa 20 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series TYPICAL APPLICATIONS 5V 2MHz Step-Down Converter VIN 5.5V TO 42V 4.7µF VIN BST 0.1µF 2.2µH EN/UV LT8610A/ SW LT8610AB BIAS SYNC 10nF 100k 1µF TR/SS INTVCC RT PG 1M FB VOUT 5V 3.5A 47µF* 1210 X7R POWER GOOD 4.7pF GND 18.2k 243k fSW = 2MHz 8610ab TA02 L: XAL 5030 12V Step-Down Converter VIN 12.5V TO 42V 4.7µF VIN BST 0.1µF 10µH EN/UV LT8610A/ SW LT8610AB BIAS SYNC 10nF 100k 1µF TR/SS INTVCC RT PG 1M FB VOUT 12V 3.5A 47µF* 1210 X7R POWER GOOD 10pF GND 41.2k 88.7k fSW = 1MHz 8610ab TA09 L: IHLP-2525CZ-01 5V Step-Down Converter VIN 3.8V TO 42V 4.7µF 10nF VIN BST EN/UV LT8610A-5 0.1µF 10µH SW SYNC BIAS TR/SS VOUT 100µF 1210 X5R 1µF VOUT 12V 3.5A 100k INTVCC RT PG POWER GOOD GND 110k fSW = 400kHz 8610ab TA03 L: IHLP-2525CZ-01 *Consider doubling output capacitance for LT8610AB if application requires low output voltage ripple in Burst Mode operation. 8610abfa For more information www.linear.com/LT8610A 21 LT8610A/LT8610AB Series TYPICAL APPLICATIONS 1.8V 2MHz Step-Down Converter VIN 3.4V TO 15V (42V TRANSIENT) VIN 4.7µF BST 0.1µF 1µH EN/UV LT8610A/ PG SW LT8610AB BIAS SYNC 100µF* 1210 X5R 10nF TR/SS 1µF INTVCC RT VOUT 1.8V 3.5A 866k FB 4.7pF GND 18.2k 1M fSW = 2MHz 8610ab TA06 L: IHLP-2020BZ-01 3.3V 2MHz Step-Down Converter VIN 3.8V TO 27V (42V TRANSIENT) VIN 4.7µF BST 0.1µF 2.2µH EN/UV LT8610A/ PG SW LT8610AB BIAS SYNC 47µF* 1210 X7R 10nF TR/SS 1µF INTVCC RT VOUT 3.3V 3.5A 1M FB 4.7pF GND 18.2k 412k fSW = 2MHz 8610ab TA04 L: XAL 5030 1.8V Step-Down Converter VIN 3.4V TO 42V 4.7µF VIN BST EN/UV LT8610A/ PG SW LT8610AB BIAS SYNC 0.1µF 4.7µH 47µF* ×3 1210 X7R 10nF 1µF TR/SS INTVCC RT 110k fSW = 400kHz FB VOUT 1.8V 3.5A 866k 4.7pF GND 1M 8610ab TA07 L: IHLP-2020BZ-01 *Consider doubling output capacitance for LT8610AB if application requires low output voltage ripple in Burst Mode operation. 8610abfa 22 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series TYPICAL APPLICATIONS 3.3V Step-Down Converter VIN 3.8V TO 42V 4.7µF 10nF 1µF VIN BST 0.1µF 8.2µH EN/UV LT8610A-3.3 SW PG SYNC BIAS TR/SS VOUT INTVCC RT VOUT 3.3V 100µF 3.5A 1210 X5R GND 110k fSW = 400kHz 8610ab TA05 L: IHLP-2525BD-01 Ultralow EMI 5V 2.5A Step-Down Converter VIN 5.5V TO 42V FB1 BEAD 4.7µF 4.7µH 4.7µF 4.7µF 10nF 1µF VIN BST EN/UV LT8610A/ SW PG LT8610AB SYNC BIAS TR/SS FB 0.1µF 4.7µH 1M 47µF* 1210 X7R VOUT 5V 3.5A 10pF INTVCC RT GND 52.3k fSW = 800kHz 243k 8610ab TA11 FB1: TDK MPZ2012S101A L: IHLP-2020BZ-01 *Consider doubling output capacitance for LT8610AB if application requires low output voltage ripple in Burst Mode operation. 8610abfa For more information www.linear.com/LT8610A 23 LT8610A/LT8610AB Series PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 16-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1667 Rev F) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 5.10 (.201) MIN 2.845 ±0.102 (.112 ±.004) 0.889 ±0.127 (.035 ±.005) 8 1 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 3.20 – 3.45 (.065 ±.004) (.126 – .136) 0.305 ±0.038 (.0120 ±.0015) TYP 16 0.50 (.0197) BSC 4.039 ±0.102 (.159 ±.004) (NOTE 3) RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 0.35 REF 0.12 REF DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY 9 NO MEASUREMENT PURPOSE 0.280 ±0.076 (.011 ±.003) REF 16151413121110 9 DETAIL “A” 0° – 6° TYP 3.00 ±0.102 (.118 ±.004) (NOTE 4) 4.90 ±0.152 (.193 ±.006) GAUGE PLANE 0.53 ±0.152 (.021 ±.006) DETAIL “A” 1.10 (.043) MAX 0.18 (.007) SEATING PLANE 0.17 – 0.27 (.007 – .011) TYP 1234567 8 0.50 (.0197) BSC NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.86 (.034) REF 0.1016 ±0.0508 (.004 ±.002) MSOP (MSE16) 0213 REV F 8610abfa 24 For more information www.linear.com/LT8610A LT8610A/LT8610AB Series REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 08/14 Added fixed output options. 1 - 4, 10, 12, 13 Clarified Applications Information. 14, 18 8610abfa 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. For more information www.linear.com/LT8610A 25 LT8610A/LT8610AB Series TYPICAL APPLICATION 3.3V and 1.8V with Ratio Tracking VIN 3.8V TO 42V 4.7µF VIN BST EN/UV LT8610A/ PG LT8610AB SYNC VIN 3.8V TO 27V 0.1µF 5.6µH SW 47µF* 1210 X7R 10nF 1µF BIAS TR/SS INTVCC RT FB Ultralow IQ 2.5V, 3.3V Step-Down with LDO VIN 4.7µF VOUT1 3.3V 3.5A PG 232k BIAS TR/SS INTVCC RT GND VOUT GND 18.2k fSW = 500kHz fSW = 2MHz L: IHLP-2020BZ-01 4.7µF 24.3k VIN BST EN/UV LT8610A/ PG LT8610AB SYNC SW BIAS TR/SS 10k 1µF INTVCC RT FB 0.1µF 3.3µH VOUT1 3.3V 3.5A 47µF ×2 1210 X7R LT8610AB-3.3 1µF 97.6k 0.1µF 2.2µH SW SYNC 10nF 4.7pF 88.7k BST EN/UV IN OUT LT3008-2.5 VOUT2 2.5V 2.2µF 20mA SHDN SENSE 8610ab TA10 VOUT2 1.8V 100µF* 3.5A 1210 X5R 80.6k 4.7pF GND 88.7k fSW = 500kHz 93.1k 8610ab TA08 L: IHLP-2020CZ-01, 5.6µH L: IHLP-2020CZ-01, 3.3µH *Consider doubling output capacitance for LT8610AB if application requires low output voltage ripple in Burst Mode operation. RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT8610 42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous Micropower Step-Down DC/DC Converter with IQ = 2.5µA VIN: 3.4V to 42V, VOUT(MIN) = 0.97V, IQ = 2.5µA, ISD < 1µA, MSOP-16E Package LT8614 42V, 2.5A with 4A, 96% Efficiency, 2.2MHz Synchronous Micropower Step-Down DC/DC Converter with IQ = 2.5µA VIN: 3.4V to 42V, VOUT(MIN) = 0.97V, IQ = 2.5µA, ISD < 1µA, 3mm × 6mm QFN-28 Package LT8611 42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous Micropower Step-Down DC/DC Converter with IQ = 2.5µA and Input/Output Current Limit/Monitor VIN: 3.4V to 42V, VOUT(MIN) = 0.97V, IQ = 2.5µA, ISD < 1µA, 3mm × 5mm QFN-24 Package LT3690 36V with 60V Transient Protection, 4A, 92% Efficiency, 1.5MHz Synchronous Micropower Step-Down DC/DC Converter with IQ = 70µA VIN: 3.9V to 36V, VOUT(MIN) = 0.985V, IQ = 70µA, ISD < 1µA, 4mm × 6mm QFN-26 Package LT3971 38V, 1.2A, 2.2MHz High Efficiency Micropower Step-Down DC/DC Converter with IQ = 2.8µA VIN: 4.2V to 38V, VOUT(MIN) = 1.21V, IQ = 2.8µA, ISD < 1µA, 3mm × 3mm DFN-10 and MSOP-10E Packages LT3970 40V, 350mA, 2.2MHz High Efficiency Micropower Step-Down DC/DC Converter with IQ = 2.5µA VIN: 4.2V to 40V, VOUT(MIN) = 1.21V, IQ = 2.5µA, ISD < 1µA, 3mm × 2mm DFN-10 and MSOP-10 Packages LT3990 62V, 350mA, 2.2MHz High Efficiency MicroPower Step-Down DC/DC Converter with IQ = 2.5µA VIN: 4.2V to 62V, VOUT(MIN) = 1.21V, IQ = 2.5µA, ISD < 1µA, 3mm × 3mm DFN-10 and MSOP-6E Packages LT3480 36V with Transient Protection to 60V, 2A (IOUT), 2.4MHz, High Efficiency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 36V, Transient to 60V, VOUT(MIN) = 0.78V, IQ = 70µA, ISD < 1µA, 3mm × 3mm DFN-10 and MSOP-10E Packages LT3980 58V with Transient Protection to 80V, 2A (IOUT), 2.4MHz, High Efficiency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 58V, Transient to 80V, VOUT(MIN) = 0.78V, IQ = 85µA, ISD < 1µA, 3mm × 4mm DFN-16 and MSOP-16E Packages 8610abfa 26 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LT8610A (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT8610A LT 0814 REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2013