LT3800IFE-TRPBF

LT3800 High-Voltage Synchronous Current Mode Step-Down Controller DESCRIPTIO The LT®3800 is a 200kHz fixed frequency high voltage synchronous current mode step-down switching regulator controller. The IC drives standard gate N-channel power MOSFETs and can operate with input voltages from 4V to 60V. An onboard regulator provides IC power directly from VIN and provides for output-derived power to minimize VIN quiescent current. MOSFET drivers employ an internal dynamic bootstrap feature, maximizing gate-source “ON” voltages during normal operation for improved operating efficiencies. The LT3800 incorporates Burst Mode® operation, which reduces no load quiescent current to under 100µA. Light load efficiencies are also improved through a reverse inductor current inhibit, allowing the controller to support discontinuous operation. Both Burst Mode operation and the reverse-current inhibit features can be disabled if desired. The LT3800 incorporates a programmable soft-start that directly controls the voltage slew rate of the converter output for reduced startup surge currents and overshoot errors. The LT3800 is available in a 16-lead thermally enhanced TSSOP package. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258. FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Wide 4V to 60V Input Voltage Range Output Voltages up to 36V Adaptive Nonoverlap Circuitry Prevents Switch Shoot-Through Reverse Inductor Current Inhibit for Discontinuous Operation Improves Efficiency with Light Loads Output Slew Rate Controlled Soft-Start with Auto-Reset 100µA No Load Quiescent Current Low 10µA Current Shutdown 1% Regulation Accuracy 200kHz Operating Frequency Standard Gate N-Channel Power MOSFETs Current Limit Unaffected by Duty Cycle Reverse Overcurrent Protection 16-Lead Thermally Enhanced TSSOP Package APPLICATIO S ■ ■ ■ ■ 12V and 42V Automotive and Heavy Equipment 48V Telecom Power Supplies Avionics and Industrial Control Systems Distributed Power Converters TYPICAL APPLICATIO VIN 20V TO 55V 12V 75W DC/DC Converter with Reverse Current Inhibit and Input UVLO + 56µF ×2 1M 82.5k 1.5nF SHDN 200k CSS 20k 1% 174k 1% BURST_EN VFB VC 100pF 82.5k 680pF SENSE– VCC BG PGND SENSE+ SGND 1N4148 1µF Si7370DP B160 LT3800 SW 15µH BAS19 1µF ×3 1µF TG Si7850DP 95 90 85 80 LOSS (48V) 75 70 0.1 1 0 VIN = 36V VIN = 60V VIN = 48V 100 VIN = 24V 5 VIN BOOST EFFICIENCY (%) 0.015Ω 10µF + VOUT 12V AT 75W 270µF 3800 TA01a U U U Efficiency and Power Loss 6 POWER LOSS (W) 4 3 2 1 ILOAD (A) 10 3800 TA01b 3800fb 1 LT3800 ABSOLUTE AXI U RATI GS (Note 1) PI CO FIGURATIO TOP VIEW VIN NC SHDN CSS BURST_EN VFB VC SENSE – Supply Voltages Input Supply Pin (VIN) .............................. –0.3V to 65V Boosted Supply Pin (BOOST) ................... –0.3V to 80V Boosted Supply Voltage (BOOST – SW) .. –0.3V to 24V Boosted Supply Reference Pin (SW) ........... –2V to 65V Local Supply Pin (VCC) ............................. –0.3V to 24V Input Voltages SENSE+, SENSE– ...................................... –0.3V to 40V SENSE+ – SENSE– ......................................... –1V to 1V BURST_EN Pin ......................................... –0.3V to 24V Other Inputs (SHDN, CSS, VFB, VC) .......... –0.3V to 5.0V Input Currents SHDN, CSS ............................................... –1mA to 1mA Maximum Temperatures Operating Junction Temperature Range (Note 2) LT3800E (Note 3) ............................. –40°C to 125°C LT3800I ............................................ –40°C to 125°C Storage Temperature Range ................. –65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C 1 2 3 4 5 6 7 8 17 16 BOOST 15 TG 14 SW 13 NC 12 VCC 11 BG 10 PGND 9 SENSE+ FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 40°C/W, θJC = 10°C/W EXPOSED PAD (PIN 17) IS SGND MUST BE SOLDERED TO PCB ORDER I FOR ATIO LEAD FREE FINISH LT3800EFE#PBF LT3800IFE#PBF TAPE AND REEL LT3800EFE#TRPBF LT3800IFE#TRPBF PART MARKING 3800EFE 3800IFE PACKAGE DESCRIPTION 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard 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/ The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, VCC = BOOST = BURST_EN = 10V, SHDN = 2V, SENSE – = SENSE+ = 10V, SGND = PGND = SW = 0V, CTG = CBG = 3300pF, unless otherwise noted. SYMBOL VIN PARAMETER Operating Voltage Range (Note 4) Minimum Start Voltage UVLO Threshold (Falling) UVLO Hysteresis VIN Supply Current VIN Burst Mode Current VIN Shutdown Current Operating Voltage Operating Voltage Range (Note 5) UVLO Threshold (Rising) UVLO Hysteresis VCC > 9V VBURST_EN = 0V, VFB = 1.35V VSHDN = 0V VBOOST – VSW VBOOST – VSW VBOOST – VSW CONDITIONS ● ● ● ELECTRICAL CHARACTERISTICS MIN 4 7.5 3.65 IVIN ● ● ● VBOOST 2 U TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C TYP MAX 60 3.80 670 20 20 8 3.95 UNITS V V V mV µA µA µA V V V V 3800fb U U U U WW W W U 15 75 20 5 0.4 LT3800 The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, VCC = BOOST = BURST_EN = 10V, SHDN = 2V, SENSE – = SENSE+ = 10V, SGND = PGND = SW = 0V, CTG = CBG = 3300pF, unless otherwise noted. SYMBOL IBOOST PARAMETER BOOST Supply Current (Note 6) BOOST Burst Mode Current BOOST Shutdown Current Operating Voltage (Note 5) Output Voltage UVLO Threshold (Rising) UVLO Hysteresis VCC Supply Current (Note 6) VCC Burst Mode Current VCC Shutdown Current Short-Circuit Current Enable Threshold (Rising) Threshold Hysteresis Common Mode Range Current Limit Sense Voltage Reverse Protect Sense Voltage Reverse Current Offset Input Current (ISENSE+ + ISENSE–) Operating Frequency ● ELECTRICAL CHARACTERISTICS CONDITIONS VBURST_EN = 0V VSHDN = 0V ● ● MIN TYP 1.4 0.1 0.1 8.0 6.25 500 3 80 20 –120 1.35 120 150 –150 10 0.8 –20 –0.3 MAX UNITS mA µA µA VCC 20 8.3 V V V mV mA µA µA mA V mV mV mV mV mA µA mA IVCC ● 3.6 VBURST_EN = 0V VSHDN = 0V ● ● ● ● –40 1.30 0 140 VSHDN VSENSE 1.40 36 175 VSENSE+ – VSENSE– VSENSE+ – VSENSE–, VBURST_EN = VCC VBURST_EN = 0V or VBURST_EN = VFB VSENSE(CM) = 0V VSENSE(CM) = 2.75V VSENSE(CM) > 4V ISENSE fO VFB IFB VFB(SS) ICSS gm AV VC IVC VTG,BG tTG,BG tTG(OFF) tTG(ON) tNOL 190 175 1.224 1.215 200 1.231 25 210 220 1.238 1.245 kHz kHz V V nA V mV µA Error Amp Reference Voltage Feedback Input Current Soft-Start Disable Voltage Soft-Start Disable Hysteresis Soft-Start Capacitor Control Current Error Amp Transconductance Error Amp DC Voltage Gain Error Amp Output Range Error Amp Sink/Source Current Gate Drive Output On Voltage (Note 7) Gate Drive Output Off Voltage Gate Drive Rise/Fall Time Minimum Off Time Minimum On Time Gate Drive Nonoverlap Time Measured at VFB Pin ● VFB Rising 1.185 300 2 ● 275 350 62 1.2 ± 30 9.8 0.1 400 µmhos dB V µA V V ns ns Zero Current to Current Limit 10% to 90% or 90% to 10% ● 50 450 300 200 150 500 ns ns ns TG Fall to BG Rise BG Fall to TG Rise 3800fb 3 LT3800 ELECTRICAL CHARACTERISTICS 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: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 3: The LT3800E 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 LT3800I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note 4: VIN voltages below the start-up threshold (7.5V) are only supported when VCC is externally driven above 6.5V. Note 5: Operating range dictated by MOSFET absolute maximum gatesource voltage ratings. Note 6: Supply current specification does not include switch drive currents. Actual supply currents will be higher. Note 7: DC measurement of gate drive output “ON” voltage is typically 8.6V. Internal dynamic bootstrap operation yields typical gate “ON” voltages of 9.8V during standard switching operation. Standard operation gate “ON” voltage is not tested but guaranteed by design. TYPICAL PERFOR A CE CHARACTERISTICS Shutdown Threshold (Rising) vs Temperature 1.37 SHUTDOWN THRESHOLD, FALLING (V) SHUTDOWN THRESHOLD, RISING (V) 1.36 1.35 1.230 VCC (V) 1.34 1.33 –50 –25 0 25 50 75 TEMPERATURE (°C) VCC vs ICC(LOAD) 8.05 TA = 25°C 8 8.00 6 ICC CURRENT LIMIT (mA) VCC (V) VCC (V) 7.95 7.90 7.85 0 5 10 15 20 25 ICC(LOAD) (mA) 30 4 UW 100 3800 G01 Shutdown Threshold (Falling) vs Temperature 1.240 VCC vs Temperature 8.1 1.235 ICC = 0mA 8.0 ICC = 20mA 7.9 1.225 125 1.220 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 7.8 –50 –25 0 50 75 25 TEMPERATURE (°C) 100 125 3800 G02 3800 G03 VCC vs VIN ICC = 20mA TA = 25°C ICC Current Limit vs Temperature 200 175 150 125 100 75 50 –50 7 5 4 3 35 40 4 5 6 7 8 VIN (V) 3800 G04 3800 G05 9 10 11 12 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3800 G06 3800fb LT3800 TYPICAL PERFOR A CE CHARACTERISTICS VCC UVLO Threshold (Rising) vs Temperature 6.30 25 20 6.25 ERROR AMP TRANSCONDUCTANCE (µmho) 6 8 10 12 14 16 18 20 VCC (V) 3800 G12 VCC UVLO THRESHOLD, RISING (V) ICC (µA) 6.20 5 6.15 –50 –25 0 25 50 75 TEMPERATURE (°C) I(SENSE+ + SENSE–) vs VSENSE(CM) 800 600 I(SENSE+ + SENSE–) (µA) OPERATING FREQUENCY (kHz) 210 400 200 0 –200 –400 ERROR AMP REFERENCE (V) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VSENSE(CM) (V) 3800 G09 PI FU CTIO S VIN (Pin 1): Converter Input Supply. NC (Pin 2): No Connection. SHDN (Pin 3): Precision Shutdown Pin. Enable threshold is 1.35V (rising) with 120mV of input hysteresis. When in shutdown mode, all internal IC functions are disabled. The precision threshold allows use of the SHDN pin to incorporate UVLO functions. If the SHDN pin is pulled below 0.7V, the IC enters a low current shutdown mode with IVIN < 10µA. In low-current shutdown, the IC will sink 20µA from the VCC pin until that local supply has collapsed. Typical pin input bias current is