LTC7821 (REV A) - Analog Devices

1 LTC7821 . Hybrid Step-Down Synchronous Controller FEATURES DESCRIPTION. nn Wide VIN Range: 10V to 72V (80V ABS Max) The LTC 7821 uses a proprietary architecture that merges nn Soft Switching for Low Noise Operation a soft switching charge pump topology with a synchro- nn Phase-Lockable Fixed Frequency 200kHz to nous step-down converter to provide superior efficiency nn 1% Output Voltage Accuracy and EMI performance compared to traditional switching nn R. SENSE or DCR Current Sensing architectures. nn Programmable CCM, DCM, or Burst Mode Operation In a typical 48V to 12V application, efficiency of greater nn CLKOUT Pin for multiphase Operation than 97% is attainable with the LTC7821 switching at nn Short Circuit Protected 500kHz.

2 The same efficiency can only be achieved with a nn EXTV. CC Input for Improved Efficiency traditional controller switching at one-third the frequency. nn Monotonic Output Voltage Start-Up Higher switching frequencies allow the use of smaller in- nn Optional External Reference ductances that yield faster transient response and smaller nn 32-Pin (5mm 5mm) QFN. solution size. APPLICATIONS The LTC7821 can be easily paralleled to provide higher nn Intermediate Bus Converters output currents with its accurate current sharing capability nn High Current Distributed Power Systems and frequency synchronization function.

3 Nn Telecom, Datacom, and Storage Systems All registered trademarks and trademarks are the property of their respective owners. Protected by patents, Including 9484799. nn Automotive Applications TYPICAL APPLICATION. 100 Efficiency at Various VIN for 1 F. VIN VOUT = 12V. 36V TO 72V. + CIN F 100. VIN_SENSE VIN. 100 F 6. TG1 M1. CB1, F 99. IOUT = 10A. BOOST1. 98. SW1 IOUT = 20A. EFFICIENCY (%). TIMER D1. LTC7821 97. BG1 M2 96. CFLY. FREQ. BOOST2 10 F. CB2 8 95. F. MID fSW = 500 KHz MID_SENSE. 94 VOUT = 12V. INTVCC EXT_REF. D2 1k CMID. CCM. 10k 10k 10 F. F 93. 8 30 40 50 60 70 80. TG2 M3. FAULT FAULT.

4 INPUT VOLTAGE (V). PGOOD PGOOD BOOST3 7821 TA01b CB3. D3 1 F 2 H VOUT. PINS NOT SHOWN IN THIS CIRCUIT: SW3 12V. CLKOUT ITH 20A. TEMP INTVCC. F. RUN M4 10 F. BG2. HYS_PRGM 2. MODE/PLLIN INTVCC. F + COUT. TRACK/SS 150 F. PGND 2. 8V EXTVCC ISNS+. VFB ISNS M1: BSZ070N08 LSS. M2, M3: BSC032N04LS. 7821 TA01a M4: BSC014N04 LSI. Rev A. Document Feedback For more information 1. LTC7821 . ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION. (Note 1). TOP VIEW. Input Supply Voltage (VIN, VIN_SENSE).. to 80V. MID_SENSE. VIN_SENSE. BOOST1. Top Side Driver Voltages SW1. MID. TG1. VIN. to 86V. NC. 32 31 30 29 28 27 26 25.

5 BOOST2, to 46V MODE/PLLIN 1 24 BG1. Switch Voltages CLKOUT 2 23 BOOST2. 0V to 80V RUN 3 22 BOOST3. to 40V FAULT 4. 33. 21 TG2. MID, to 40V PGOOD 5 SGND 20 SW3. (BOOST1-SW1), (BOOST2-MID), TIMER 6 19 INTVCC. TRACK/SS 7 18 BG2. (BOOST3-SW3).. to 6V EXT_REF 8 17 PGND. ISNS+, ISNS .. to 40V 9 10 11 12 13 14 15 16. (ISNS+ ISNS ).. HYS_PRGM. ITH. FREQ. TEMP. VFB. ISNS . ISNS+. EXTVCC. to 40V. TEMP, FREQ, EXT_REF, to INTVCC. HYS_PRGM, ITH, RUN, to INTVCC UH PACKAGE. 32-LEAD (5mm 5mm) PLASTIC QFN. FAULT, to 80V TJMAX = 125 C, JA = 44 C/W, JC = C/W. EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB. TIMER, to INTVCC.

6 INTVCC Peak Output Operating Junction Temperature Range (Notes 2, 3, 9).. 40 C to 125 C. Storage Temperature 65 C to 150 C. ORDER INFORMATION #orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE. LTC7821 EUH#PBF LTC7821 EUH#TRPBF 7821 32-Lead (5mm 5mm) Plastic QFN 40 C to 125 C. LTC7821 IUH#PBF LTC7821 IUH#TRPBF 7821 32-Lead (5mm 5mm) Plastic QFN 40 C to 125 C. Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.

7 Rev A. 2 For more information LTC7821 . ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25 C (Note 2). VIN = VIN_SENSE = 48V, VRUN = 5V, EXTVCC = 9V, EXT_REF = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. Main Control Loops VIN Input Voltage Range 10 72 V. Output Voltage Range (Note 4) VIN V. 2. VFB Regulated Feedback Voltage ITH Voltage (Note 5) l V. IFB Feedback Current (Note 5) 10 50 nA. VREFLNREG Reference Voltage Line Regulation VIN = 36V to 72V (Note 5) %/V.

8 VLOADREG Output Voltage Load Regulation (Note 5). ITH Voltage = to l %. ITH Voltage = to l %. gm Transconductance Amplifier gm ITH = ; Sink/Source 5 A (Note 5) 2 mmho IVIN Input DC Supply Current (Note 6). Normal Mode mA. Shutdown VRUN = 0V, EXTVCC = 0V 240 A. Precharging Phase VIN = 20V, VMID = VMID_SENSE = 9V, 40 mA. VSW1 = 15V, VSW3 = 10V. VIN = 48V, VMID = VMID_SENSE = 20V, 84 mA. VSW1 36V, VSW3 = 12V. IVIN_SENSE Input DC Supply Current (Note 6). Normal Mode 1 mA. Shutdown VRUN = 0V 45 A. IEXTVCC Input DC Supply Current (Note 6) mA. IMID MID Pin Current 45 A. IMID_SENSE MID_SENSE Pin Current 4 A.

9 VUVLO VIN Undervoltage Lockout VIN Ramping Up l V. VUVLO_HYST UVLO Hysteresis V. VSENSE Current Sense Threshold VISNS = 0V l 45 50 55 mV. ISNS+/- ISNS+ and ISNS Pin Current VISNS+ = VISNS = 12V l A. ITRACK/SS Soft-Start Charge Current VTRACK/SS = 0V 9 10 11 A. VRUN_ON RUN Pin On Threshold VRUN Rising l V. IRUN RUN Pin Current VRUN = 0V 1 A. VRUN_HYST RUN Pin Hysteresis V. VEXT_REF_UC EXT_REF Upper Clamp Limit (Note 5) l V. VEXT_REF_LC EXT_REF Lower Clamp Limit (Note 5) l V. VSEL_EXT_REF EXT_REF De-Select Threshold (Ramping Up) V. IEXT_REF EXT_REF Pin Current VEXT_REF = 150 nA. VTEMP_TRIP TEMP Pin Trip Point, Rising l V.

10 VTEMP_TRIP_HYST TEMP Pin Trip Point Hysteresis 100 mV. ITEMP TEMP Pin Current VTEMP = 1V 1 nA. VBSTUVLO Undervoltage Lockout of (BOOST1-SW1), Difference Voltage, Rising V. (BOOST2- VMID) and (BOOST3-SW3). VBSTUVLO_HYST Bootstrap Undervoltage Lockout Hysteresis V. TOUT TEMP Trip TimeOut 100 ms Rev A. For more information 3. LTC7821 . ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25 C (Note 2). VIN = VIN_SENSE = 48V, VRUN = 5V, EXTVCC = 9V, EXT_REF = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS.