Smart Plug Reference Design

February 06, 2020 by Paul Shepard

Nowadays everything is connected. So why not also connect the wall plugs? Monolithic Power Systems presents a reference design with the MP161 part that will allow customers to join the IoT market. This is a two boards design, one for the dc-dc converter and the relay and the other for the Wi-Fi module. The configuration is designed to fit into a wall-plug.

This reference design is based on the MP161 which includes a 700V switching regulator, a low-dropout linear regulator and two channel relay drivers. The design includes Wi-Fi 802.11 b/g/n (HT20) protocol and 35.4mW active input power under stand-by operation.

The MP161 also has a special standby mode to minimize standby power.  The MP161 is designed for home automation, industrial automation, and any other applications that adopt relays and MCUs.

Smart plug block diagram.

The relay driver in the MP161 includes 2Ω on-state resistance, rail voltage up to 30V, integrated freewheeling diode, and a nominal off driver. The integrated LDO handles up to 30V input voltage; it delivers a fixed output of either 3.3V or 5V and includes over-temperature protection

Summary of MP161 Features

  • Integrated 700V MOSFET and current source
  • Constant voltage regulation with internal loop compensation
  • Optimized light-load efficiency by frequency modulation
  • Standby mode
  • Anti-audible noise operation by peak current modulation
  • Adjustable or fixed 12V Output
  • Low operating current
  • Integrated protection functions
    • Over-Temperature Protection (OTP)
    • Short-Circuit Protection (SCP)
    • Over-Load Protection (OLP)
    • Over-Voltage Protection (OVP)