LT3844IFE-TRPBF

LT3844 High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency DESCRIPTIO The LT®3844 is a DC/DC controller used for medium power, low part count, high efficiency supplies. It offers a wide 4V-60V input range (7.5V minimum startup voltage) and can implement step-down, step-up, inverting and SEPIC topologies. The LT3844 includes Burst Mode operation, which reduces quiescent current below 120μA and maintains high efficiency at light loads. An internal high voltage bias regulator allows for simple biasing. Additional features include current mode control for fast line and load transient response; programmable fixed operating frequency that can be synchronized to an external clock for noise sensitive applications; a gate driver capable of driving large N-channel MOSFETs; a precision undervoltage lockout function; 10μA shutdown current; short-circuit protection and a programmable soft-start function. The LT3844 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 5731694, 6498466, 6611131. FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ High Voltage Operation: Up to 60V Output Voltages up to 36V (Step-Down) Programmable Constant Frequency: 100kHz to 500kHz Synchronizable up to 600kHz Burst Mode® Operation: 120μA Supply Current 10μA Shutdown Supply Current ±1.3% Reference Accuracy Drives N-Channel MOSFET Programmable Soft-Start Programmable Undervoltage Lockout Internal High Voltage Regulator for Gate Drive Thermal Shutdown Current Limit Unaffected by Duty Cycle 16-Pin Thermally Enhanced TSSOP Package APPLICATIO S ■ ■ ■ ■ ■ ■ Industrial Power Distribution 12V and 42V Automotive and Heavy Equipment High Voltage Single Board Systems Distributed Power Systems Avionics Telecom Power TYPICAL APPLICATIO VIN 36V TO 60V High Voltage Step-Down Regulator 48V to 12V, 50W 90 68μF 22μF 1 MEG VIN 1000pF 82.5k SHDN CSS BURST_EN 0.22μF BOOST 88 6 EFFICIENCY 5 4 3 2 1 VIN = 48V 1 LOAD CURRENT (A) 0 10 10Ω SW VCC LT3844 VFB EFFICIENCY (%) TG Si7850DP 1μF PGND SENSE+ SENSE– SGND 10μH PDS5100H 0.02Ω 10k VC VOUT 12V 50W 68μF 33μF 130k 14.7k 680p 120pF SYNC fSET 3844 TA01 R7 49.9k U U U Efficiency and Power Loss vs Load Current 7 86 84 82 80 78 76 0.1 POWER LOSS (W) LOSS 3844 TA01b 3844fa 1 LT3844 ABSOLUTE (Note 1) AXI U RATI GS PI CO FIGURATIO TOP VIEW VIN SHDN CSS BURST_EN VFB VC SYNC fSET 1 2 3 4 5 6 7 8 17 Input Supply Voltage (VIN)......................... 65V to –0.3V Boosted Supply Voltage (BOOST) .............. 80V to –0.3V Switch Voltage (SW) (Note 8) ...................... 65V to –1V Differential Boost Voltage (BOOST to SW) ..................................... 24V to –0.3V Bias Supply Voltage (VCC) ......................... 24V to –0.3V SENSE+ and SENSE– Voltages ................... 40V to –0.3V Differential Sense Voltage (SENSE+ to SENSE–) .................................. 1V to –1V BURST_EN Voltage .................................... 24V to –0.3V SYNC, VC, VFB, CSS, and SHDN Voltages ..... 5V to –0.3V SHDN Pin Currents ................................................. 1mA Operating Junction Temperature Range (Note 2) LT3844E (Note 3) ..............................–40°C to 125°C LT3844I .............................................–40°C to 125°C Storage Temperature .............................–65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 40°C/W, θJC = 10°C/W EXPOSED PAD IS SGND (PIN 17) MUST BE SOLDERED TO PCB ORDER I FOR ATIO LEAD FREE FINISH LT3844EFE#PBF LT3844IFE#PBF TAPE AND REEL LT3844EFE#TRPBF LT3844IFE#TRPBF PART MARKING 3844EFE 3844IFE 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, RSET = 49.9kΩ, SENSE – = SENSE + = 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted. PARAMETER VIN Operating Voltage Range (Note 4) VIN Minimum Start Voltage VIN UVLO Threshold (Falling) VIN UVLO Threshold Hysteresis VIN Supply Current VIN Burst Mode Current VIN Shutdown Current BOOST Operating Voltage Range BOOST Operating Voltage Range (Note 5) BOOST UVLO Threshold (Rising) BOOST UVLO Threshold Hysteresis BOOST Supply Current (Note 6) BOOST Burst Mode Current BOOST Shutdown Current VCC > 9V VBURST_EN = 0V, VFB = 1.35V VSHDN = 0V VBOOST - VSW VBOOST - VSW VBOOST - VSW VBURST_EN = 0V VSHDN = 0V CONDITIONS ● ● ● ELECTRICAL CHARACTERISTICS MIN 4 3.6 ● ● ● 2 U 16 BOOST 15 TG 14 SW 13 VCC 12 PGND 11 SENSE+ 10 SENSE – 9 SGND U U U U WW W W U TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C TYP MAX 60 7.5 4 UNITS V V V mV μA μA μA V V V mV mA μA μA 3844fa 3.8 670 20 20 10 15 75 20 5 400 1.4 0.1 0.1 LT3844 ELECTRICAL CHARACTERISTICS PARAMETER VCC Operating Voltage Range (Note 5) VCC Output Voltage VCC UVLO Threshold (Rising) VCC UVLO Threshold Hysteresis VCC Supply Current (Note 6) VCC Burst Mode Current VCC Shutdown Current VCC Current Limit Error Amp Reference Voltage VFB Pin Input Current SHDN Enable Threshold (Rising) SHDN Threshold Hysteresis Sense Pins Common Mode Range Current Limit Sense Voltage Input Current (ISENSE+ + ISENSE–) Operating Frequency 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, RSET = 49.9kΩ, SENSE – = SENSE + = 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted. CONDITIONS Over Full Line and Load Range ● ● MIN TYP 8 6.25 500 1.7 95 20 –120 1.231 25 MAX 20 8.3 UNITS V V V mV mA μA μA mA V V nA V mV V mV μA μA μA ● 2.1 VBURST_EN = 0V VSHDN = 0V ● –40 1.224 1.215 1.3 0 90 Measured at VFB Pin ● 1.238 1.245 1.4 36 115 VFB = 1.231V ● ● ● 1.35 120 100 350 –25 –170 VSENSE+ – VSENSE– VSENSE(CM) = 0V VSENSE(CM) = 2V VSENSE(CM) > 4V ● 290 270 500 100 300 310 330 100 600 kHz kHz kHz kHz kHz kΩ V μA μS dB μA V V ns Minimum Programmable Frequency Maximum Programmable Frequency External Sync Frequency Range SYNC Input Resistance SYNC Voltage Threshold Soft-Start Capacitor Control Current Error Amp Transconductance Error Amp DC Voltage Gain Error Amp Sink/Source Current TG Drive On Voltage (Note 7) TG Drive Off Voltage TG Drive Rise/Fall Time Minimum TG Off Time Minimum TG On Time 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 LT3844 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 LT3844E 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 LT3844I is guaranteed CLOAD = 2200pF CLOAD = 2200pF 10% to 90% or 90% to 10%, CLOAD = 2200pF ● ● ● ● ● 40 1.4 2 270 340 62 ±30 9.8 0.1 40 ● ● 2 410 350 250 500 350 ns ns 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 the VCC is externally driven above 6.5V. Note 5: Operating range is dictated by MOSFET absolute maximum VGS. 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. Note 8: The –1V absolute maximum on the SW pin is a transient condition. It is guaranteed by design and not subject to test. 3844fa 3 LT3844 TYPICAL PERFOR A CE CHARACTERISTICS Shutdown Threshold (Rising) vs Temperature 1.38 1.26 SHUTDOWN THRESHOLD, FALLING (V) SHUTDOWN THRESHOLD, RISING (V) 1.37 1.36 1.35 1.34 1.33 1.32 –50 –25 1.23 1.22 1.21 1.20 –50 –25 VCC (V) 0 50 25 75 TEMPERATURE (°C) VCC vs ICC(LOAD) 8.05 TA = 25°C 9 8 8.00 7 ICC CURRENT LIMIT (mA) VCC (V) 7.95 VCC (V) 7.90 4 7.85 3 0 5 10 15 20 25 ICC(LOAD) (mA) 30 VCC UVLO Threshold (Rising) vs Temperature 6.5 25 ERROR AMP TRANSCONDUCTANCE (μS) VCC UVLO THRESHOLD, RISING (V) 6.4 ICC (μA) 6.3 6.2 6.1 6.0 –50 –25 0 25 50 75 TEMPERATURE (°C) 4 UW 100 3844 G01 Shutdown Threshold (Falling) vs Temperature 8.2 8.1 8.0 1.24 7.9 7.8 7.7 7.6 VCC vs Temperature ICC = 20mA 1.25 125 0 50 25 75 TEMPERATURE (°C) 100 125 7.5 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3844 G02 3844 G03 VCC vs VIN 200 ICC = 20mA TA = 25°C 175 150 125 100 75 ICC Current Limit vs Temperature 6 5 35 40 4 5 6 7 8 VIN (V) 9 10 11 12 50 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3844 G04 3844 G05 3844 G06 ICC vs VCC (SHDN = 0V) TA = 25°C 350 345 340 335 330 325 Error Amp Transconductance vs Temperature 20 15 10 5 100 125 0 0 2 4 6 8 10 12 14 16 18 20 VCC (V) 3844 G08 320 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 3844 G07 3844 G09 3844fa LT3844 TYPICAL PERFOR A CE CHARACTERISTICS I(SENSE+ + SENSE–) vs VSENSE (CM) 400 TA = 2 5° C OPERATING FREQUENCY (kHz) I(SENSE+ + SENSE –) (μA) 304 302 300 298 296 294 292 ERROR AMP REFERENCE (V) 300 200 100 0 –100 –200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VSENSE (CM) (V) 3844 G10 Maximum Current Sense Threshold vs Temperature 106 CURRENT SENSE THRESHOLD (mV) 104 102 100 98 96 94 –50 –25 VIN UVLO THRESHOLD, RISING (V) 4.52 4.50 4.48 4.46 4.44 4.42 4.40 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 50 25 75 0 TEMPERATURE (°C) 100 125 VIN UVLO THRESHOLD, FALLING (V) PI FU CTIO S VIN (Pin 1): The VIN pin is the main supply pin and should be decoupled to SGND with a low ESR capacitor located close to the pin. SHDN (Pin 2): The SHDN pin has a precision IC enable threshold of 1.35V (rising) with 120mV of hysteresis. It is used to implement an undervoltage lockout (UVLO) circuit. See Application Information section for implementing a UVLO function. When the SHDN pin is pulled below a transistor VBE (0.7V), a low current shutdown mode is entered, all internal circuitry is disabled and the VIN supply current is reduced to approximately 9μA. Typical pin input bias current is