LTC1437A Series

High Efficiency Low Noise Synchronous Step-Down Switching Regulators

Catalog

High Efficiency Low Noise Synchronous Step-Down Switching Regulators

Part	Mounting Type	Operating Temperature [Max]	Operating Temperature [Min]	Output Type	Duty Cycle (Max) [Max]	Supplier Device Package	Output Phases	Topology	Voltage - Supply (Vcc/Vdd) [Min]	Voltage - Supply (Vcc/Vdd) [Max]	Control Features	Number of Outputs	Synchronous Rectifier	Package / Case [custom]	Package / Case	Package / Case [custom]	Function	Clock Sync	Frequency - Switching [Max]	Output Configuration
Analog Devices LTC1437CG#TRPBF	Surface Mount	70 °C	0 °C	Transistor Driver	99 %	28-SSOP	1	Buck	3.5 V	30 V	Enable Power on Reset Soft Start	1		0.209 in	28-SSOP	5.3 mm	Step-Down		400 kHz	Positive
Analog Devices LTC1437AIG#PBF	Surface Mount	85 °C	-40 °C	Transistor Driver	99 %	28-SSOP	1	Buck	3.5 V	30 V	Enable Power on Reset Soft Start	1		0.209 in	28-SSOP	5.3 mm	Step-Down		400 kHz	Positive

Catalog

High Efficiency Low Noise Synchronous Step-Down Switching Regulators

Key Features

• Maintains Constant Frequency at Low Output Currents

• Programmable Fixed Frequency (PLL Lockable)

• Wide VINRange: 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< 25µA

• Output Voltages from 1.19V to 9V

• Available in 24-Lead Narrow SSOP and 28-Lead SSOP Packages

Description

The LTC1436A/LTC1437A are synchronous step-down switching regulator controllers that drive external N-channel power MOSFETs in a phase lockable, fixed frequency architecture. The Adaptive Power™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 external current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum).ApplicationsNotebook and Palmtop Computers, PDAsCellular Telephones and Wireless ModemsPortable InstrumentsBattery-Operated DevicesDC Power Distribution Systems