Current-Mode PWM Controllers with an Error Amplifier for Isolated/Nonisolated Power Supplies

The MAX5052/MAX5053 current-mode PWM controllers contain all the control circuitry required for the design of wide-input-voltage isolated and nonisolated power supplies. The MAX5052 is well suited for universal input (rectified 85VAC to 265VAC) or telecom (-36VDC to -72VDC) power supplies. The MAX5053 is well suited for low-input-voltage (10.8VDC to 24VDC) power supplies.

The MAX5052/MAX5053 contain an internal error amplifier that regulates the tertiary winding output voltage. This implements a primary-side regulated, isolated power supply, eliminating the need for an optocoupler. An input undervoltage lockout (UVLO) is provided for programming the input-supply start voltage and to ensure proper operation during brownout conditions. The input-supply start voltage is externally programmable with a voltage-divider. To shutdown the device, the UVLO pin is pulled low. Internal digital soft-start reduces output voltage overshoot. The internal thermal shutdown circuit protects the device in the event the junction temperature exceeds +130°C.

The MAX5052 has an internal bootstrap UVLO with large hysteresis that requires a minimum voltage of 23.6V for startup. The MAX5053 does not have the internal bootstrap UVLO and can be biased directly from a minimum voltage of 10.8V.

The 262kHz switching frequency is internally trimmed to ±12% accuracy; this allows the optimization of the magnetic and filter components resulting in compact, cost-effective power supplies. The MAX5052A/MAX5053A are offered with a 50% maximum duty-cycle limit. The MAX5052B/MAX5053B are offered with a 75% maximum duty-cycle limit. These devices are available in 8-pin µMAX packages and operate over the -40°C to +85°C temperature range.

Applications

* 12V Boost Regulators * 12V SEPIC Regulators * Computer Systems/Servers * Industrial Power Conversion * Isolated Keep-Alive Circuits * Isolated Telecom Power Supplies * Networking Systems * Power Supplies * Universal Input AC

* Available in a Tiny 8-Pin µMAX Package

* Current-Mode Control

* 50W Output Power

* Universal Offline Input Voltage Range

* Rectified 85VAC to 265VAC (MAX5052)

* VIN Directly Driven from 10.8V to 24V Input (MAX5053)

* Digital Soft-Start

* Programmable Input Startup Voltage

* Internal Bootstrap UVLO with Large Hysteresis (MAX5052)

* Internal Error Amplifier with 1% Accurate Reference

* Thermal Shutdown

* 45µA (typ) Startup Supply Current

* 1.4mA (typ) Operating Supply Current

* Fixed Switching Frequency of 262kHz ±12%

* 50% Maximum Duty-Cycle Limit (MAX5052A/MAX5053A)

* 75% Maximum Duty-Cycle Limit (MAX5052B/MAX5053B)

* 60ns Cycle-by-Cycle Current-Limit Response Time