Features

• Synchronizable/Programmable Fixed Frequency
• OPTI-LOOP™ Compensation Minimizes C_OUT
• ±1% Output Voltage Accuracy
• Dual N-Channel MOSFET Synchronous Drive
• Wide V_IN Range: 4V to 36V Operation
• V_OUT Range: 0.8V to 6V
• Internal Current Foldback
• Output Overvoltage Crowbar Protection
• Latched Short-Circuit Shutdown Timer with Defeat Option
• Very Low Dropout Operation: 99% Duty Cycle
• Forced Continuous Control Pin
• Optional Programmable Soft-Start
• Remote Output Voltage Sense
• Power Good Output (LTC1735F Only)
• Logic Controlled Micropower Shutdown: I_Q < 25µA
• LTC1435 Pin Compatible with Minor Component Changes
• Available in 16-Lead Narrow SSOP, SO Packages and 20-Lead TSSOP Package (LTC1735F Only)

Typical Application

Description

The LTC1735 is a synchronous step-down switching regulator controller that drives external N-channel power MOSFETs using a fixed frequency architecture. Burst Mode operation provides high efficiency at low load currents. The precision 0.8V reference is compatible with future generation microprocessors. 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) is set by an external capacitor allowing maximum flexibility in optimizing efficiency. A forced continuous control pin reduces noise and RF interference and can assist secondary winding regulation by disabling Burst Mode operation when the main output is lightly loaded.

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 is user-programmable via an external current sense resistor. Wide input supply range allows operation from 4V to 30V (36V maximum).