Datasheet LTC3858-2 (Analog Devices)

LTC3858-2 Low IQ, Dual 2-Phase Synchronous Step-Down Controller
FEATURES DESCRIPTION
n
Low Operating IQ: 170μA (One Channel On)
The LTC®3858-2 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 LTC3858-2 differs from the LTC3858 by having the overvolt- n Adjustable Output Voltage Soft-Start or Tracking age protection crowbar and short-circuit latchoff disabled. n Power Good Output Voltage Monitor A wide 4V to 38V input supply range encompasses a wide n Low Shutdown IQ: 8μA range of intermediate bus voltages and battery chemistries. n Internal LDO Powers Gate Drive from VIN or EXTVCC n Independent soft-start pins for each controller ramp the No Current Foldback During Start-Up n output voltages during start-up. Current foldback limits 5mm × 5mm QFN Package MOSFET heat dissipation during short-circuit conditions.
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, μModule, PolyPhase, Linear Technology and the Linear logo are registered trademarks and No RSENSE and UltraFast are trademarks of Linear Technology n Automotive Systems Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. n Battery Operated Digital Devices n Distributed DC Power Systems
TYPICAL APPLICATION High Efficiency Dual 8.5V/3.3V Step-Down Converter Efficiency and Power Loss
VIN
vs Load Current
9V TO 38V 22μF 100 10000 4.7μF 50V VIN INTVCC 90 TG1 TG2 80 1000 0.1μF 0.1μF EFFICIENCY POWER LOSS (mW) 3.3μH BOOST1 BOOST2 7.2μH 70 SW1 SW2 60 100 POWER LOSS BG1 BG2 50 LTC3858-2 PGND 40 10 EFFICIENCY (%) SENSE1+ SENSE2+ 30 0.01Ω 20 1 0.007Ω VIN = 12V 10 V V OUT = 3.3V VOUT1 SENSE1– SENSE2– OUT2 FIGURE 13 CIRCUIT 3.3V 8.5V VFB1 VFB2 0 0.1 5A 62.5k I 193k 3.5A 0.0001 0.001 0.01 0.1 1 10 TH1 ITH2 150μF 680pF 680pF SS1 SS2 150μF OUTPUT CURRENT (A) SGND 20k 38582 TA01b 20k 15k 15k 0.1μF 0.1μF 38582 TA01a 38582f 1