LTC1436

Features:

n Maintains Constant Frequency at Low Output Currents
n Dual N-Channel MOSFET Synchronous Drive
n Programmable Fixed Frequency (PLL Lockable)
n Wide V_IN Range: 3.5V to 36V Operation
n Ultrahigh Efficiency
n Very Low Dropout Operation: 99% Duty Cycle
n Low Dropout, 0.5A Linear Regulator for VPP Generation or Low Noise Audio Supply
n Built-In Power-On Reset Timer
n Programmable Soft Start
n Low-Battery Detector
n Remote Output Voltage Sense
n Foldback Current Limiting (Optional)
n Pin Selectable Output Voltage
n Logic Controlled Micropower Shutdown: I_Q < 25A
n Output Voltages from 1.19V to 9V
n Available in 24-Lead Narrow SSOP and 28-Lead SSOP Packages


Application

Notebook and Palmtop Computers, PDAs
Cellular Telephones and Wireless Modems
Portable Instruments
Battery-Operated Devices
DC Power Distribution Systems


Pinout




Specifications

Input Supply Voltage (V_IN).................................................. 36V to 0.3V
Topside Driver Supply Voltage (Boost) ............................... 42V to 0.3V
Switch Voltage (SW)............................................................ V_IN + 5V to 5V
EXTV_CC Voltage .................................................................. 10V to 0.3V
POR, LBO Voltages .............................................................. 12V to 0.3V
AUXFB Voltage .................................................................... 20V to 0.3V
AUXDR Voltage..................................................................... 28V to 0.3V
SENSE⁺, SENSE,V_OSENSE Voltages..................................... INTV_CC + 0.3V to 0.3V
V_PROG Voltage..................................................................... INTV_CC to 0.3V
PLL LPF, I_TH Voltages ......................................................... 2.7V to 0.3V
AUXON, PLLIN, SFB,RUN/SS, LBI Voltages .......................... 10V to 0.3V
Peak Driver Output Current < 10s (TGL, BG)..................... 2A
Peak Driver Output Current < 10s (TGS) .......................... 250mA
INTV_CC Output Current ...................................................... 50mA
Operating Temperature Range
    LTC143XC ...................................................................... 0°C to 70°C
    LTC143XI ....................................................................... 40°C to 85°C
Junction Temperature (Note 1) .......................................... 125°C
Storage Temperature Range ............................................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec)............................... 300°C


Description

The LTC^®1436/LTC1437 are synchronous step-down switching regulator controllers which drive external N-channel power MOSFETs in a phase lockable, fixed frequency architecture. The Adaptive Power^TM output stage selectively drives two N-channel MOSFETs at frequencies up to 400kHz while reducing switching losses to maintain high efficiencies at low output currents.

An auxiliary 0.5A linear regulator of LTC1436/LTC1437 is using an external PNP pass device provides a low noise, low dropout voltage source. A secondary winding feedback control pin (SFB) guarantees regulation regardless of load on the main output by forcing continuous operation.

An additional comparator is available for use as a lowbattery detector. A power-on reset timer (POR) is included which generates a signal delayed by 65536/f_CLK (300ms typically) after the output is within 5% of the regulated output voltage. Internal resistive dividers provide pin selectable output voltages with remote sense capability.

The operating current level of LTC1436/LTC1437  is user-programmable via an external current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum).