Datasheet LTC3858-1 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Low IQ, Dual 2-Phase Synchronous Step-Down Controller |
| Pages / Page | 38 / 1 — FEATURES. DESCRIPTION. Low Operating IQ: 170μA (One Channel On). Wide … |
| File Format / Size | PDF / 439 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Low Operating IQ: 170μA (One Channel On). Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
Model Line for this Datasheet
Text Version of Document
LTC3858-1 Low IQ, Dual 2-Phase Synchronous Step-Down Controller
FEATURES DESCRIPTION
n
Low Operating IQ: 170μA (One Channel On)
The LTC®3858-1 is a high performance dual step-down n
Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
switching regulator controller that drives all N-channel n
Wide VIN Range: 4V to 38V
synchronous power MOSFET stages. A constant frequency n
RSENSE or DCR Current Sensing
current mode architecture allows a phase-lockable fre- n Out-of-Phase Controllers Reduce Required Input quency of up to 850kHz. Power loss and noise due to the Capacitance and Power Supply Induced Noise input capacitor ESR are minimized by operating the two n OPTI-LOOP® Compensation Minimizes COUT controller outputs out of phase. n Phase-Lockable Frequency (75kHz-850kHz) The 170μA no-load quiescent current extends operating n Programmable Fixed Frequency (50kHz-900kHz) life in battery powered systems. OPTI-LOOP compensa- n Selectable Continuous, Pulse-Skipping or tion allows the transient response to be optimized over Burst Mode® Operation at Light Loads a wide range of output capacitance and ESR values. The n Very Low Dropout Operation: 99% Duty Cycle LTC3858-1 features a precision 0.8V reference and a power n Adjustable Output Voltage Soft-Start good output indicator. A wide 4V to 38V input supply range n Power Good Output Voltage Monitor encompasses a wide range of intermediate bus voltages n Output Overvoltage Protection and battery chemistries. n Output Latchoff Protection During Short Circuit n Low Shutdown I Independent soft-start pins for each controller ramp the Q: 8μA n Internal LDO Powers Gate Drive from V output voltages during start-up. The output Latchoff feature IN or EXTVCC n No Current Foldback During Start-Up protects the circuit in short-circuit conditions. n Tiny 4mm × 5mm QFN and Narrow SSOP Packages For a leadless 32-pin QFN package with the additional fea-
APPLICATIONS
tures of adjustable current limit, clock out, phase modula- tion and two PGOOD outputs, see the LTC3858 data sheet. n Automotive Systems L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, μModule, Linear Technology and the Linear logo n Battery Operated Digital Devices are registered trademarks and No RSENSE and UltraFast are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. n Distributed DC Power Systems Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
TYPICAL APPLICATION High Effi ciency Dual 8.5V/3.3V Step-Down Converter
VIN
Effi ciency and Power Loss
9V TO 38V 22μF
vs Load Current
4.7μF 50V VIN INTVCC 100 10000 TG1 TG2 90 0.1μF 0.1μF 3.3μH BOOST1 BOOST2 7.2μH 80 1000 SW1 SW2 POWER LOSS (mW) 70 EFFICIENCY BG1 BG2 60 100 LTC3858-1 PGND 50 POWER LOSS SENSE1+ SENSE2+ 40 10 EFFICIENCY (%) 0.007Ω 0.01Ω 30 20 1 V V OUT1 SENSE1– SENSE2– OUT2 VIN = 12V 3.3V 8.5V VFB1 VFB2 10 VOUT = 3.3V 5A 62.5k I 193k 3.5A TH1 ITH2 FIGURE 12 CIRCUIT 0 0.1 150μF 680pF 680pF SS1 SS2 150μF SGND 20k 0.0001 0.001 0.01 0.1 1 10 20k 15k 15k OUTPUT CURRENT (A) 0.1μF 0.1μF 38581 TA01b 38581 TA01 38581fd 1
FEATURES DESCRIPTION
n
Low Operating IQ: 170μA (One Channel On)
The LTC®3858-1 is a high performance dual step-down n
Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
switching regulator controller that drives all N-channel n
Wide VIN Range: 4V to 38V
synchronous power MOSFET stages. A constant frequency n
RSENSE or DCR Current Sensing
current mode architecture allows a phase-lockable fre- n Out-of-Phase Controllers Reduce Required Input quency of up to 850kHz. Power loss and noise due to the Capacitance and Power Supply Induced Noise input capacitor ESR are minimized by operating the two n OPTI-LOOP® Compensation Minimizes COUT controller outputs out of phase. n Phase-Lockable Frequency (75kHz-850kHz) The 170μA no-load quiescent current extends operating n Programmable Fixed Frequency (50kHz-900kHz) life in battery powered systems. OPTI-LOOP compensa- n Selectable Continuous, Pulse-Skipping or tion allows the transient response to be optimized over Burst Mode® Operation at Light Loads a wide range of output capacitance and ESR values. The n Very Low Dropout Operation: 99% Duty Cycle LTC3858-1 features a precision 0.8V reference and a power n Adjustable Output Voltage Soft-Start good output indicator. A wide 4V to 38V input supply range n Power Good Output Voltage Monitor encompasses a wide range of intermediate bus voltages n Output Overvoltage Protection and battery chemistries. n Output Latchoff Protection During Short Circuit n Low Shutdown I Independent soft-start pins for each controller ramp the Q: 8μA n Internal LDO Powers Gate Drive from V output voltages during start-up. The output Latchoff feature IN or EXTVCC n No Current Foldback During Start-Up protects the circuit in short-circuit conditions. n Tiny 4mm × 5mm QFN and Narrow SSOP Packages For a leadless 32-pin QFN package with the additional fea-
APPLICATIONS
tures of adjustable current limit, clock out, phase modula- tion and two PGOOD outputs, see the LTC3858 data sheet. n Automotive Systems L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, μModule, Linear Technology and the Linear logo n Battery Operated Digital Devices are registered trademarks and No RSENSE and UltraFast are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. n Distributed DC Power Systems Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
TYPICAL APPLICATION High Effi ciency Dual 8.5V/3.3V Step-Down Converter
VIN
Effi ciency and Power Loss
9V TO 38V 22μF
vs Load Current
4.7μF 50V VIN INTVCC 100 10000 TG1 TG2 90 0.1μF 0.1μF 3.3μH BOOST1 BOOST2 7.2μH 80 1000 SW1 SW2 POWER LOSS (mW) 70 EFFICIENCY BG1 BG2 60 100 LTC3858-1 PGND 50 POWER LOSS SENSE1+ SENSE2+ 40 10 EFFICIENCY (%) 0.007Ω 0.01Ω 30 20 1 V V OUT1 SENSE1– SENSE2– OUT2 VIN = 12V 3.3V 8.5V VFB1 VFB2 10 VOUT = 3.3V 5A 62.5k I 193k 3.5A TH1 ITH2 FIGURE 12 CIRCUIT 0 0.1 150μF 680pF 680pF SS1 SS2 150μF SGND 20k 0.0001 0.001 0.01 0.1 1 10 20k 15k 15k OUTPUT CURRENT (A) 0.1μF 0.1μF 38581 TA01b 38581 TA01 38581fd 1
