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Microchip – Aux Controller for Secondary Micro Systems – MCP1012

The MCP1012 is used as a primary-side start-up IC for starting an offline auxiliary switching supply working in conjunction with a secondary-side controller. The MCP1012 does not linearly regulate the power converter, but rather a secondary-side controller (digital and/or analog) accurately linear regulates using sophisticated adaptive control schemes that enhance performance and efficiency.

The primary function of the MCP1012 are to provide startup of the flyback converter using an internal open-loop, peak current-mode current regulator.  It does this by accepting PWM commands via an isolation medium (s.a. a pulse transformer, opto, or other) from a secondary-side controller.  It integrates various protection features, including an undervoltage lockout (UVLO) and overvoltage lockout (OVLO) protection, and overtemperature protection (OTP.)  Additionally, the MCP1012 provides peak cycle-by-cycle current limiting both when under control of its internal current regulator or under control of the secondary-side controller.

Additional Features

  • HV Startup Capability (500V Continuous, 700V Transient w/series 10K Resistor)
  • Internal Open-Loop, Peak Current-Mode (PCM) Current Regulator for Start-up (w/Few External Components) w/Integrated Robust Gate Driver
  • Current Regulator (Constant Off Time, 21us)
  • Protection Against Continuous Conduction Mode (CCM) of Operation
  • Programmable Low-Frequency Oscillator (LFO) Period to Set Startup Power
  • Able to Accept External PWM Commands from a Secondary Controller via Isolator (Various)
  • Undervoltage Lockout (UVLO) and Overvoltage Lockout (OVLO) Protections, Cycle-by-Cycle Current Limiting, Overtemperature Protection (Thermal Shutdown)
  • Sleep and Wake-up Commands, w/Low Standby Power (<15 mW)
  • Package: 7-Lead SOIC


Name Value
Minimum Input Voltage (V) 16V (Typical)
Maximum Input Voltage (V) 500V Continuous/700V Transient
Osc Frequency Min (kHz) 37
Osc Frequency Max (kHz) 63
On-Board FET? False
Type of On-Board FET? NA
Rds,on (Max, 25C)? NA
Overcurrent Protection Cycle-Cycle
Other Protections CCM, OVP, UVLO, OTP (Shutdown)
Package 7/SOIC

Evaluation Board: MCP1012 1W Demo Board ( DT100118 )

The DT100118 is a simple evaluation development tool for the MCP1012 that allows functional evaluation.

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