Datasheet LTC3708 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Fast 2-Phase, No RSENSE Buck Controller with Output Tracking |
| Pages / Page | 34 / 1 — FEATURES. DESCRIPTION. Very Low Duty Factor Operation (tON(MIN) < … |
| File Format / Size | PDF / 667 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Very Low Duty Factor Operation (tON(MIN) < 85ns). No RSENSE. Option for Maximum Efficiency
Model Line for this Datasheet
Text Version of Document
LTC3708 Fast 2-Phase, No RSENSE Buck Controller with Output Tracking
FEATURES DESCRIPTION
n
Very Low Duty Factor Operation (tON(MIN) < 85ns)
The LTC®3708 is a dual, 2-phase synchronous step-down n
No RSENSE
Option for Maximum Efficiency
switching regulator with output voltage up/down tracking n
Very Fast Transient Response
capability. The IC allows either coincident or ratiometric n
Programmable Output Voltage Up/Down Tracking
tracking. Multiple LTC3708s can be daisy-chained in ap- n
2-Phase Operation Reduces Input Capacitance
plications requiring more than two voltages to be tracked. n 0.6V ±1% Output Voltage Reference Power supply sequencing is accomplished using an ex- n External Frequency Synchronization ternal soft-start timing capacitor. n Monotonic Soft-Start The LTC3708 uses a constant on-time, valley current n Onboard High Current MOSFET Drivers mode control architecture to deliver very low duty factors n Wide VIN Range: Up to 36V without requiring a sense resistor. Operating frequency is n Adjustable Cycle-by-Cycle Current Limit selected by an external resistor and is compensated for n Instant Output Overvoltage Protection variations in input supply voltage. An internal phase-locked n Optional Short-Circuit Shutdown Timer loop allows the IC to be synchronized to an external clock. n Power Good Output with 100µs Masking n Available in 5mm × 5mm QFN Package Fault protection is provided by an output overvoltage comparator and an optional short-circuit shutdown timer.
APPLICATIONS
The regulator current limit level is user programmable. A wide supply range allows voltages as high as 36V to be n Digital Signal Processors stepped down to 0.6V output. n Network Servers L, LT, LTC, LTM, Linear Technology, the Linear logo and PolyPhase are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION High Efficiency Dual Output Step-Down Converter
VOUT1 (0.5V/DIV) VIN 5V 10µF 3.3V TO 28V VOUT2 (0.5V/DIV) 50V 10Ω 1µF 4.7µF 100k ×4 + VCC DRVCC PGOOD M1 TG1 TG2 M2 L1 L2 BOOST1 BOOST2 2ms/DIV 3708 TA01b V 1.4µH 1.2µH OUT1 0.22µF 0.22µF VOUT2 2.5V SW1 SW2 1.8V 15A POSCAP + B340A SENSE1+ SENSE2+ B340A + POSCAP 15A 100 9.0 330µF 470µF 4V M3 BG1 LTC3708 BG2 M4 2.5V ×2 ×2 95 7.5 SENSE1– SENSE2– 12.1k 19.1k PGND1 PGND2 12.1k POWER LOSS (W) 90 6.0 VFB1 VFB2 TRACK2 FCB fIN 1M V 85 4.5 IN ION1 I V ON2 IN 1.5M 20V I IN TO 2.5VOUT TH1 ITH2 5VIN TO 2.5VOUT INTLPF EXTLPF EFFICIENCY (%) 80 3.0 20VIN TO 1.8VOUT RUN/SS TRACK1 5VIN TO 1.8VOUT 6.04k 6.04k 33k 10k 1k 33k 6.04k SGND VRNG1 VRNG2 75 1.5 100k 0.01µF 0.01µF 0.1µF 0.01µF 180pF 25k 70 0 0.1µF 180pF 5V 0.01 0.1 1 10 LOAD CURRENT (A) 3708 TA01 L1: PANASONIC ETQP3HIR4BF M1, M2: RENESAS HAT2168 3708 TA01c L2: PANASONIC ETQP2HIR2BF M3, M4: RENESAS HAT2165 3708fc For more information www.linear.com/LTC3708 1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Operation Applications Information Package Description Typical Application Related Parts
FEATURES DESCRIPTION
n
Very Low Duty Factor Operation (tON(MIN) < 85ns)
The LTC®3708 is a dual, 2-phase synchronous step-down n
No RSENSE
Option for Maximum Efficiency
switching regulator with output voltage up/down tracking n
Very Fast Transient Response
capability. The IC allows either coincident or ratiometric n
Programmable Output Voltage Up/Down Tracking
tracking. Multiple LTC3708s can be daisy-chained in ap- n
2-Phase Operation Reduces Input Capacitance
plications requiring more than two voltages to be tracked. n 0.6V ±1% Output Voltage Reference Power supply sequencing is accomplished using an ex- n External Frequency Synchronization ternal soft-start timing capacitor. n Monotonic Soft-Start The LTC3708 uses a constant on-time, valley current n Onboard High Current MOSFET Drivers mode control architecture to deliver very low duty factors n Wide VIN Range: Up to 36V without requiring a sense resistor. Operating frequency is n Adjustable Cycle-by-Cycle Current Limit selected by an external resistor and is compensated for n Instant Output Overvoltage Protection variations in input supply voltage. An internal phase-locked n Optional Short-Circuit Shutdown Timer loop allows the IC to be synchronized to an external clock. n Power Good Output with 100µs Masking n Available in 5mm × 5mm QFN Package Fault protection is provided by an output overvoltage comparator and an optional short-circuit shutdown timer.
APPLICATIONS
The regulator current limit level is user programmable. A wide supply range allows voltages as high as 36V to be n Digital Signal Processors stepped down to 0.6V output. n Network Servers L, LT, LTC, LTM, Linear Technology, the Linear logo and PolyPhase are registered trademarks and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION High Efficiency Dual Output Step-Down Converter
VOUT1 (0.5V/DIV) VIN 5V 10µF 3.3V TO 28V VOUT2 (0.5V/DIV) 50V 10Ω 1µF 4.7µF 100k ×4 + VCC DRVCC PGOOD M1 TG1 TG2 M2 L1 L2 BOOST1 BOOST2 2ms/DIV 3708 TA01b V 1.4µH 1.2µH OUT1 0.22µF 0.22µF VOUT2 2.5V SW1 SW2 1.8V 15A POSCAP + B340A SENSE1+ SENSE2+ B340A + POSCAP 15A 100 9.0 330µF 470µF 4V M3 BG1 LTC3708 BG2 M4 2.5V ×2 ×2 95 7.5 SENSE1– SENSE2– 12.1k 19.1k PGND1 PGND2 12.1k POWER LOSS (W) 90 6.0 VFB1 VFB2 TRACK2 FCB fIN 1M V 85 4.5 IN ION1 I V ON2 IN 1.5M 20V I IN TO 2.5VOUT TH1 ITH2 5VIN TO 2.5VOUT INTLPF EXTLPF EFFICIENCY (%) 80 3.0 20VIN TO 1.8VOUT RUN/SS TRACK1 5VIN TO 1.8VOUT 6.04k 6.04k 33k 10k 1k 33k 6.04k SGND VRNG1 VRNG2 75 1.5 100k 0.01µF 0.01µF 0.1µF 0.01µF 180pF 25k 70 0 0.1µF 180pF 5V 0.01 0.1 1 10 LOAD CURRENT (A) 3708 TA01 L1: PANASONIC ETQP3HIR4BF M1, M2: RENESAS HAT2168 3708 TA01c L2: PANASONIC ETQP2HIR2BF M3, M4: RENESAS HAT2165 3708fc For more information www.linear.com/LTC3708 1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Operation Applications Information Package Description Typical Application Related Parts
