Power supply¶

Power input connectors¶

The COM Express 7 Baseboard supports two power supply scenarios:

• DC locking connector (J6) which accepts a 2-wire Molex Nano-Fit plug.

  This is the easiest and most recommended solution for starters. You can use an off-the-shelf Nano-Fit Cable assembly (Molex/451300203) or build a custom one from a Nano-Fit receptacle (Molex/1053071202) and pre-crimped wires (Molex/797582130). The COM Express 7 Baseboard can be powered with a benchtop PSU or AC/DC wall adapter providing 12V DC with at least 60W. If you are using a DC locking connector - please observe the polarity marked in the render below.

• Backplane PCB-edge connector (J16) is designed to interface with Samtec HSEC8 2x20 HSEC8-120-01-S-D-EM2 female connector. This connector has the same electrical requirements as the DC locking connector, since they are directly connected with each other on the baseboard. See the Pinouts section for the connector pinout.

These inputs are protected with a 12A fuse and 15V TVS diode. The nominal supply voltage is 12V. When LX2160A is used, absolute maximum is 15V and it requires 50W full system.

Auto startup¶

J7 jumper determines if auto startup is on/off.

When auto startup is enabled, all power rails of the COM Express 7 Baseboard turn on automatically after power is provided to the baseboard, and the SoM boots.

If auto startup is off, only the always on (AON) rails turn on after power is provided to the baseboard. Then to continue the power up, power button SW1 needs to be pressed.

Power sequence¶

graph LR
V_IN --> +12V_AON --> +5V_AON --> +3V3_AON --> Power_button/auto_startup -->  +12V --> +5V --> +3V3 --> +1V8 --> +1V0 -->|120ms| PWR_OK

• When 12V is supplied to the baseboard, LED D18 glows red, indicating that power is connected

• After all power supplies start-up correctly, 1V0 rail will trigger PWR_OK line to set to high state after 120ms (the delay is created by U20). This will result in (D18) changing color from red to green, which signals successful power supply section startup.

• There is a combinational logic circuit which pulls the PSON net low, if the COM Express module is NOT type 7. It is determined by the state of !TYPE0, !TYPE1 and !TYPE2 signals, which come from the connected COM Express module (pins C54, C57 and D57 of J12). This will prevent the baseboard from powering up, if wrong type of COM Express module is connected.

Power indicator LEDs¶

There are power indicator LEDs for every power rail (D26, D27, D28, D30, D31, D32, D33 and D34) as shown on the render below.

Supply monitoring¶

• Three INA219AIDCNR ICs are used to monitor voltage and current draw on 12V input, 3V3 and 5V rails. They are connected to I2C bus 1 of the SoM. Their I2C addresses and corresponding power rails are listed below:

  Address	Description
  0x40	12V rail
  0x41	3V3 rail
  0x42	5V rail

• ADT7476AARQZ IC is used to monitor voltage of 1V0, 1V8, 3V3, 5V0 and 12V rails. It is also connected to I2C bus 1 of the SoM, and its address is 0x2D. The voltage readings can be accessed through the following register addresses:

  Register	Description
  0x20	1V0 reading
  0x21	1V8 reading
  0x22	3V3 reading
  0x23	5V reading
  0x24	12V reading