Datasheet LTC7821 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Hybrid Step-Down Synchronous Controller |
| Pages / Page | 36 / 1 — FEATURES. DESCRIPTION. Wide VIN Range: 10V to 72V (80V ABS Max). Soft … |
| Revision | A |
| File Format / Size | PDF / 1.6 Mb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide VIN Range: 10V to 72V (80V ABS Max). Soft Switching for Low Noise Operation. APPLICATIONS
Model Line for this Datasheet
Text Version of Document
LTC7821 Hybrid Step-Down Synchronous Controller
FEATURES DESCRIPTION
n
Wide VIN Range: 10V to 72V (80V ABS Max)
The LTC®7821 uses a proprietary architecture that merges n
Soft Switching for Low Noise Operation
a soft switching charge pump topology with a synchro- n Phase-Lockable Fixed Frequency 200kHz to 1.5MHz nous step-down converter to provide superior efficiency n ±1% Output Voltage Accuracy and EMI performance compared to traditional switching n RSENSE or DCR Current Sensing architectures. n Programmable CCM, DCM, or Burst Mode® Operation In a typical 48V to 12V application, efficiency of greater n CLKOUT Pin for Multiphase Operation than 97% is attainable with the LTC7821 switching at n Short Circuit Protected 500kHz. The same efficiency can only be achieved with a n EXTVCC Input for Improved Efficiency traditional controller switching at one-third the frequency. n Monotonic Output Voltage Start-Up Higher switching frequencies allow the use of smaller in- n Optional External Reference ductances that yield faster transient response and smaller n 32-Pin (5mm × 5mm) QFN solution size.
APPLICATIONS
The LTC7821 can be easily paralleled to provide higher output currents with its accurate current sharing capability n Intermediate Bus Converters and frequency synchronization function. n High Current Distributed Power Systems n All registered trademarks and trademarks are the property of their respective owners. Protected Telecom, Datacom, and Storage Systems by U.S. patents, Including 9484799. n Automotive Applications
TYPICAL APPLICATION
100Ω
Efficiency at Various VIN for
VIN
VOUT = 12V
1µF 36V TO 72V + CIN V 2.2µF 100 IN_SENSE VIN 100µF ×6 TG1 M1 CB1, 0.22µF 99 I BOOST1 OUT = 10A 98 I TIMER SW1 OUT = 20A D1 LTC7821 97 BG1 M2 C 96 FLY FREQ 10µF BOOST2 EFFICIENCY (%) CB2 ×8 95 0.47µF MID fSW = 500KHz 94 INTVCC EXT_REF MID_SENSE V D2 OUT = 12V 1k CMID CCM 10k 10k 0.1µF 10µF 93 ×8 TG2 M3 30 40 50 60 70 80 FAULT FAULT INPUT VOLTAGE (V) PGOOD PGOOD BOOST3 7821 TA01b CB3 1µF 2µH D3 VOUT PINS NOT SHOWN IN THIS CIRCUIT: SW3 12V CLKOUT ITH 20A TEMP INTVCC 0.22µF RUN BG2 M4 10µF 6.81k ×2 HYS_PRGM 4.7µF + C MODE/PLLIN OUT INTVCC 150µF TRACK/SS ×2 PGND 8V EXTVCC I 4.32k SNS+ VFB ISNS– M1: BSZ070N08LSS M2, M3: BSC032N04LS 60.4k 7821 TA01a M4: BSC014N04LSI Rev A Document Feedback For more information www.analog.com 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Related Parts
FEATURES DESCRIPTION
n
Wide VIN Range: 10V to 72V (80V ABS Max)
The LTC®7821 uses a proprietary architecture that merges n
Soft Switching for Low Noise Operation
a soft switching charge pump topology with a synchro- n Phase-Lockable Fixed Frequency 200kHz to 1.5MHz nous step-down converter to provide superior efficiency n ±1% Output Voltage Accuracy and EMI performance compared to traditional switching n RSENSE or DCR Current Sensing architectures. n Programmable CCM, DCM, or Burst Mode® Operation In a typical 48V to 12V application, efficiency of greater n CLKOUT Pin for Multiphase Operation than 97% is attainable with the LTC7821 switching at n Short Circuit Protected 500kHz. The same efficiency can only be achieved with a n EXTVCC Input for Improved Efficiency traditional controller switching at one-third the frequency. n Monotonic Output Voltage Start-Up Higher switching frequencies allow the use of smaller in- n Optional External Reference ductances that yield faster transient response and smaller n 32-Pin (5mm × 5mm) QFN solution size.
APPLICATIONS
The LTC7821 can be easily paralleled to provide higher output currents with its accurate current sharing capability n Intermediate Bus Converters and frequency synchronization function. n High Current Distributed Power Systems n All registered trademarks and trademarks are the property of their respective owners. Protected Telecom, Datacom, and Storage Systems by U.S. patents, Including 9484799. n Automotive Applications
TYPICAL APPLICATION
100Ω
Efficiency at Various VIN for
VIN
VOUT = 12V
1µF 36V TO 72V + CIN V 2.2µF 100 IN_SENSE VIN 100µF ×6 TG1 M1 CB1, 0.22µF 99 I BOOST1 OUT = 10A 98 I TIMER SW1 OUT = 20A D1 LTC7821 97 BG1 M2 C 96 FLY FREQ 10µF BOOST2 EFFICIENCY (%) CB2 ×8 95 0.47µF MID fSW = 500KHz 94 INTVCC EXT_REF MID_SENSE V D2 OUT = 12V 1k CMID CCM 10k 10k 0.1µF 10µF 93 ×8 TG2 M3 30 40 50 60 70 80 FAULT FAULT INPUT VOLTAGE (V) PGOOD PGOOD BOOST3 7821 TA01b CB3 1µF 2µH D3 VOUT PINS NOT SHOWN IN THIS CIRCUIT: SW3 12V CLKOUT ITH 20A TEMP INTVCC 0.22µF RUN BG2 M4 10µF 6.81k ×2 HYS_PRGM 4.7µF + C MODE/PLLIN OUT INTVCC 150µF TRACK/SS ×2 PGND 8V EXTVCC I 4.32k SNS+ VFB ISNS– M1: BSZ070N08LSS M2, M3: BSC032N04LS 60.4k 7821 TA01a M4: BSC014N04LSI Rev A Document Feedback For more information www.analog.com 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Related Parts
