LTC1735-1

Features:

Dual N-Channel MOSFET Synchronous Drive
Programmable/Synchronizable Fixed Frequency
V_OUT Range: 0.8V to 7V
Wide VIN Range: 3.5V to 36V Operation
Very Low Dropout Operation: 99% Duty Cycle
OPTI-LOOPTM Compensation Minimizes COUT
±1% Output Voltage Accuracy
Power Good Output Voltage Monitor
Internal Current Foldback
Output Overvoltage Crowbar Protection
Latched Short-Circuit Shutdown Timer with Defeat Option
Optional Programmable Soft-Start
Remote Output Voltage Sense
Logic Controlled Micropower Shutdown: IQ < 25mA
Available in 16-Lead Narrow SSOP and SO Packages 


Application

Notebook and Palmtop Computers, PDAs
Power Supply for Mobile Pentium® III Processor with SpeedStepTM Technology
Cellular Telephones and Wireless Modems


Specifications

Input Supply Voltage (VIN)............................ 36V to 0.3V
Topside Driver Supply Voltage (BOOST)......... 42V to 0.3V
Switch Voltage (SW) ........................................ 36V to 5V
INTVCC, EXTVCC (BOOST, SW) Voltages ......... 7V to 0.3V
SENSE+, SENSE,
PGOOD Voltages.................... 1.1(INTVCC + 0.3V) to 0.3V
ITH, VOSENSE, COSC Voltages ......................2.7V to 0.3V
RUN/SS Voltage ...........................(INTVCC + 0.3V) to 0.3V
Peak Driver Output Current <10ms (TG, BG) .............. ....3A
INTVCC Output Current ............................................. 50mA
Operating Ambient Temperature Range
LTC1735C-1 ................................................... ...0 to 85
LTC1735I-1 ................................................... 40 to 85
Junction Temperature (Note 2) .................................. 125
Storage Temperature Range ....................... 65 to 150
Lead Temperature (Soldering, 10 sec)........................ 300 


Description

The LTC®1735-1 is a synchronous step-down switching regulator controller optimized for CPU power. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values.

The operating frequency (synchronizable up to 500kHz) of LTC1735-1 is set by an external capacitor allowing maximum flexibility in optimizing efficiency. The output voltage is monitored by a power good window comparator that indicates when the output is within 7.5% of its programmed value, conforming to Intel Mobile CPU Specifications.

Protection features include internal foldback current limiting, output overvoltage crowbar and optional shortcircuit shutdown. Soft-start is provided by an external capacitor that can be used to properly sequence supplies.

The operating current level of LTC1735-1 is user-programmable via an external current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum).

Pin defeatable Burst ModeTM operation provides high efficiency at low load currents while 99% duty cycle provides low dropout operation.