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. 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.

2 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. 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. INPUT VOLTAGE (V). PGOOD PGOOD BOOST3 7821 TA01b CB3. D3 1 F 2 H VOUT. PINS NOT SHOWN IN THIS CIRCUIT: SW3 12V.

3 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. 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.

4 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. 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. 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).

5 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. 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.

6 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. 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).

7 VIN = VIN_SENSE = 48V, VRUN = 5V, EXTVCC = 9V, EXT_REF = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. INTVCC Linear Regulator VINTVCC Internal VCC Regulator 10V < VIN < 72V, VEXTVCC = 0V V. VLDOINT INTVCC Load Regulation ICC = 1mA to 50mA, VIN = 12V, VEXTVCC = 0V 2 %. VEXTVCC EXTVCC Switchover Voltage EXTVCC Ramping Positive, ICC = 1mA 7 V. VEXTVCC_HYS EXTVCC Switchover Voltage Hysteresis 200 mV. VLDOEXT EXTVCC Load Regulation VEXTVCC = 12V, ICC = 1mA to 50mA 2 %. Oscillator and Phase Lock Loop fNOM Nominal Frequency RFREQ = 68k 440 490 550 kHz fLOW Lowest Frequency VFREQ = 0V 20 50 100 kHz fHIGH Highest Frequency VFREQ = INTVCC 1400 1700 2000 kHz fSYNC_LOW Lowest Synchronizing Frequency 200 kHz fSYNC_HIGH Highest Synchronizing Frequency 1500 KHz IFREQ Frequency Setting Current VFREQ = 0V l 9 10 11 A. RMODE/PLLIN MODE/PLLIN Resistance 250 k . CLKOUTHIGH CLKOUT High Amplitude V. CLKOUTLOW CLKOUT Low Amplitude 0 V. PGOOD Output VPG1 PGOOD 1st Trip Level (with Delay) VFB with Respect to Regulated Voltage VFB Ramping Up (Overvoltage 1st Level) 6 11 %.

8 VFB Ramping down (Undervoltage 1st %. Level). VPG1_HYST PGOOD 1st Trip Level Hysteresis (with Delay) 15 mV. VPG2 PGOOD 2nd Trip Level VFB with Respect to Regulated Voltage VFB Ramping Up (Overvoltage 2nd Level) 15 %. VFB Ramping down (Undervoltage 2nd 25 %. Level). VPG2_HYST PGOOD 2nd Trip Level Hysteresis 15 mV. VPGL PGOOD Voltage Low IPGOOD = V. IPGOOD PGOOD Leakage Current VPGOOD = 80V 1 A. Capacitor Balancing VTIMER_LOW Voltage At TIMER Pin To Start Capacitor V. Balancing VTIMER_HIGH Voltage At TIMER Pin To Stop Capacitor V. Balancing ITIMER TIMER Pin Charge Current VTIMER = l 6 7 8 A. VTIMER = l 3 4 A. VHYS_PRGM Capacitor Balancing Window Comparator VHYS_PRGM = 0V V. Threshold VHYS_PRGM = V. VHYS_PRGM = INTVCC V. IHYS_PRGM HYS_PRGM Pin Current VHYS_PRGM = 0V l 9 10 11 A. VFAULT FAULT Pin Voltage Low IFAULT = V. IFAULT FAULT Leakage Current VFAULT = 80V 1 A. Rev A. 4 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).

9 VIN = VIN_SENSE = 48V, VRUN = 5V, EXTVCC = 9V, EXT_REF = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. IFLYSRC1 Current Out of SW1 During Capacitor (VSW1 VSW3) < VIN/2, VSW3 = 12V 40 mA. Balancing IFLYSNK1 Current into SW1 During Capacitor Balancing (VSW1 VSW3) > VIN/2, VSW3 = 12V 6 mA. IFLYSNK3 Current into SW3 During Capacitor Balancing (VSW1 VSW3) < VIN/2, VSW3 = 12V 40 mA. IFLYSRC3 Current Out of SW3 During Capacitor (VSW1 VSW3) < VIN/2, VSW3 = 12V 6 mA. Balancing IMID_SRC Current Out of MID During Capacitor VMID < VIN/2, VMID = VMID_SENSE = 20V 60 mA. Balancing VSW1 36V, VSW3 = 12V. IMID_SNK Current into MID During Capacitor Balancing VMID > VIN/2, VMID = VMID_SENSE = 28V 40 mA. VSW1 36V, VSW3 = 12V. Gate Driver TG1,2 Pull-Up ON Resistance 2 . Pull- down ON Resistance 1 . BG1, 2 Pull-Up ON Resistance 2 . Pull- down ON Resistance 1 . TG1,2 tr TG1, TG2 Transition Time: (Note 7). TG1,2 tf Rise Time 4 ns Fall Time 4 ns BG1,2 tr BG1, BG2 Transition Time: (Note 7).

10 BG1,2 tf Rise Time 4 ns Fall Time 4 ns T1D TG1 Off to BG1 On 45 ns T2D TG2 Off to BG2 On 20 ns T3D TG1 Off to TG2 Off 25 ns T4D BG1 Off to TG1 On 40 ns T5D BG2 Off to TG2 On 20 ns T6D BG1 Off to BG2 Off 20 ns ton(MIN) Minimum On-Time (Note 8) 210 ns Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 5: The LTC7821 is tested in a feedback loop that servos VITH to a may cause permanent damage to the device. Exposure to any Absolute specified voltage and measures the resultant VFB. Maximum Rating condition for extended periods may affect device Note 6: Dynamic supply current is higher due to the gate charge being reliability and lifetime. delivered at the switching frequency. See Applications Information. Note 2: The LTC7821E is guaranteed to meet performance specifications Note 7: Rise and fall times are measured using 10% and 90% levels. Delay from 0 C to 85 C. Specifications over the 40 C to 125 C operating times are measured using 50% levels.