Current-Mode PWM Controllers for Isolated Power Supplies

SOT23 Universal Off-Line Power Supply Controller

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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 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


  • Isolated Power Supplies
  • Low-Power Telecom Power Supplies
  • Mobile Phone Chargers
  • Standby Power Supplies
  • Universal Offline Power Supplies
Part NumberApplication (VIN)VIN
Duty Cycle
Gate Drive Current
Oper. Temp.
minmaxmaxmaxmaxmaxSee Notes
Networking (48V)
Power Over Ethernet (32-58V)
Telecom (36-72V)
Universal Off-line (90-240VAC)
241000Single-Ended ForwardOpto262500.0852.430.25-40 to +85
$0.50 @1k
MAX5022 Flyback75
$0.73 @1k
See All Isolated Power Supplies (25)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX5022EVKIT: Evaluation Kit for the MAX5022

Technical Documents

App Note 4033 Programmable Fan Controllers
App Note 1062 Designing Compact Telecom Power Supplies
Tutorial 967 How to Minimize Power Dissipation in Li+ Linear Chargers

Quality and Environmental Data

Request Reliability Report for: MAX5021 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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