LTC1628

Features:

Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
OPTI-LOOP^TM Compensation Minimizes COUT
Dual N-Channel MOSFET Synchronous Drive
±1% Output Voltage Accuracy
Power Good Output Voltage Monitor (LTC1628-PG)
DC Programmed Fixed Frequency 150kHz to 300kHz
Wide VIN Range: 3.5V to 36V Operation
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Soft-Start Current Ramping
Foldback Output Current Limiting
Latched Short-Circuit Shutdown with Defeat Option
Output Overvoltage Protection
Remote Output Voltage Sense
Low Shutdown I_Q: 20A
5V and 3.3V Standby Regulators
Small 28-Lead SSOP Package
Selectable Constant Frequency or Burst Mode^TM Operation



Application

Notebook and Palmtop Computers, PDAs
Battery Chargers
Portable Instruments
Battery-Operated Digital Devices
DC Power Distribution Systems


Specifications

Input Supply Voltage (VIN).........................36V to 0.3V
Top Side Driver Voltages
(BOOST1, BOOST2) ...................................42V to 0.3V
Switch Voltage (SW1, SW2) .........................36V to 5V
INTV_CC, EXTV_CC, RUN/SS1, RUN/SS2, (BOOST1-SW1),
(BOOST2-SW2), PGOOD .............................7V to 0.3V
SENSE1+, SENSE2 +, SENSE1,
SENSE2 Voltages ........................ (1.1)INTVCC to 0.3V
FREQSET, STBYMD, FCB,
FLTCPL Voltage ................................... INTVCC to 0.3V
I_TH1, I_TH2, V_OSENSE1, V_OSENSE2 Voltages ...2.7V to 0.3V
Peak Output Current <10ms (TG1, TG2, BG1, BG2) ... 3A
INTVCC Peak Output Current ................................ 50mA
Operating Temperature Range
LTC1628C/LTC1628C-PG ........................ 0 to 85
LTC1628I/LTC1628I-PG ..................... 40 to 85
Junction Temperature (Note 2) ............................. 125
Storage Temperature Range ................. 65 to 150
Lead Temperature (Soldering, 10 sec).................. 300 


Description

The LTC®1628/LTC1628-PG are high performance dual step-down switching regulator controllers that drive all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows adjustment of the frequency up to 300kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase.

OPTI-LOOP compensation of LTC1628/LTC1628-PG  allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 3.5V to 30V (36V maximum) input supply range encompasses all battery chemistries.

A RUN/SS pin for each controller provides both soft-start and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC1628-PG includes a power good output pin that replaces the FLTCPL, fault coupling control pin of the LTC1628.