Current-Mode PWM Controllers for Isolated Power Supplies

 

Part Number	Replacement	Explanation

Description

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The MAX5021/MAX5022 current-mode PWM controllers contain all the control circuitry required for the design of wide input voltage range isolated power supplies. These devices are well suited for use in universal input (85VAC to 265VAC) off-line or telecom (-36VDC to -72VDC) power supplies.

An undervoltage lockout (UVLO) circuit with large hysteresis coupled with low startup and operating current reduce power dissipation in the startup resistor and allow use of ceramic bypass capacitors. 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 MAX5021 with 50% maximum duty cycle and MAX5022 with 75% maximum duty cycle are recommended for forward converters and flyback converters, respectively. The MAX5021/MAX5022 are available in 6-pin SOT23, 8-pin µMAX, and 8-pin DIP packages and are rated for operation over the -40‹C to +85‹C temperature range.

MAX5021, MAX5022: Typical Operating Circuit Enlarge+

Key Features

• Available in a Tiny 6-Pin SOT23 Package
• 50µA Typical Startup Current
• 1.2mA Typical Operating Current
• Large UVLO Hysteresis of 14V
• Fixed Switching Frequency of 262kHz ±12%
• 50% Maximum Duty Cycle Limit (MAX5021)
• 75% Maximum Duty Cycle Limit (MAX5022)
• 60ns Cycle-by-Cycle Current-Limit Response Time

Applications/Uses

• Isolated Power Supplies
• Low-Power Telecom Power Supplies
• Mobile Phone Chargers
• Standby Power Supplies
• Universal Offline Power Supplies