Datasheet LTC3868-1 (Analog Devices)

LTC3868-1 Low IQ, Dual 2-Phase Synchronous Step-Down Controller
FEATURES DESCRIPTION
n
Low Operating IQ: 170μA (One Channel On)
The LTC®3868-1 is a high performance dual step-down n
Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 14V
switching regulator controller that drives all N-channel n
Wide VIN Range: 4V to 24V
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 C controller outputs out of phase. OUT n Phase-Lockable Frequency (75kHz to 850kHz) The 170μA no-load quiescent current extends operating n Programmable Fixed Frequency (50kHz to 900kHz) life in battery powered systems. OPTI-LOOP compensation n Selectable Continuous, Pulse-Skipping or allows the transient response to be optimized over a wide Burst Mode® Operation at Light Loads range of output capacitance and ESR values. The LTC3868- n Very Low Dropout Operation: 99% Duty Cycle 1 features a precision 0.8V reference and a power good n Adjustable Output Voltage Soft-Start output indicator. A wide 4V to 24V 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 Independent soft-start pins for each controller ramp the n Low Shutdown IQ: 8μA output voltages during start-up. Current foldback limits n Internal LDO Powers Gate Drive from VIN or EXTVCC MOSFET heat dissipation during short-circuit conditions. n No Current Foldback During Start-Up The output short-circuit latchoff feature further protects n Small 4mm × 5mm QFN and Narrow SSOP Packages the circuit in short-circuit conditions.
APPLICATIONS
For a leadless 32-pin QFN package with the additional fea- n tures of adjustable current limit, clock out, phase modula- Notebook and Palmtop Computers n Portable Instruments tion and two PGOOD outputs, see the LTC3868 data sheet. n Battery Operated Digital Devices L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, μModule, Linear Technology and the Linear logo are registered trademarks and No RSENSE and UltraFast are trademarks of Linear Technology n Distributed DC Power 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.
TYPICAL APPLICATION High Effi ciency Dual 8.5V/3.3V Step-Down Converter
VIN
Effi ciency and Power Loss
9V TO 24V 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 LTC3868-1 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 38681 TA01b 38681 TA01 38681fd 1