LTC1436A-PLL| Datasheet

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LTC1436A LTC1436A-PLL/LTC1437A High Efficiency Low Noise Synchronous Step-Down Switching Regulators DESCRIPTIO
The LTC 1436A/LTC1437A are synchronous step-down switching regulator controllers that drive external N-channel power MOSFETs in a phase lockable, fixed frequency architecture. The Adaptive PowerTM 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 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 the 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/fCLK (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 is user-programmable via an e
xternal current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum).
, LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive Power is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6304066, 5929620, 6580258, 5705919, 5731731

FEATURES

Maintains Constant Frequency at Low Output Currents Programmable Fixed Frequency (PLL Lockable) Wide VIN Range: 3.5V to 36V Operation Low Minimum On-Time ( 300ns) for High Frequency, Low Duty Cycle Applications Dual N-Channel MOSFET Synchronous Drive Very Low Dropout Operation: 99% Duty Cycle Low Dropout, 0.5A Linear Regulator for CPU I/O or Low Noise Audio Supplies Built-In Power-On Reset Timer Programmable Soft Start Low-Battery Detector Remote Output Voltage Sense Foldback Current Limiting (Optional) Pin Selectable Output Voltage Logic Controlled Micropower Shutdown: IQ < 25uA Output Voltages from 1.19V to 9V Available in 24-Lead Narrow SSOP and 28-Lead SSOP Packages

APPLICATIO S

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

TYPICAL APPLICATIO
COSC 43pF CSS 0.1uF RC 10k COSC RUN/SS

VIN 4.5V TO 22V VIN TGL TGS ITH CC 510pF SGND 100pF VPROG VOSENSE SENSE 1000pF
1436 F01

M3 IRLML2803 DB CMDSH-3

M1 Si4412DY

SW LTC1436A INTVCC BOOST BG PGND SENSE +

CB 0.1uF

L1 4.7uH

+

4.7uF

M2 Si4412DY

D1 MBRS140T3

Figure 1. High Efficiency Step-Down Converter
14367afb

U
+

U

U

CIN 22uF 35V 2 RSENSE 0.02 VOUT 1.6V 5A R1 35.7k R2 102k

+

COUT 100uF 6.3V 2

1

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LTC1436A-PLL DATASHEET