3.1 Power Supply

The following are the power supply sources to power the WFI32-IoT board; see the following figure:
  • PKOB4 Micro-B USB (Debug USB) (J200)
  • Battery Header (J101)
Figure 3-2. WFI32-IoT Board Power Supply Block Diagram

PKOB4 Micro-B USB (Debug USB) (J200)

The Debug USB (J200) supplies power to the WFI32-IoT board from the host PC using Type-A male to Micro-B USB cable.

Note: The maximum available current from the Debug USB (J200) is limited to 500 mA. The current is shared between charging the external battery (if connected) and the target application section.

Battery Header (J101)

Connect a 4.2V Li-ion/Li-Po battery to the battery header (J101).

Note:
  1. The 4.2V Li-ion/Li-Po battery is not a part of the EV36W50A kit.
  2. The minimum recommended battery capacity is 400 mAh with a battery charge voltage of 4.2V.
  3. Uses a standard battery connector, which is a 2 pin, 2 mm pitch and right angle male battery header.

Li-ion/Li-Po Battery Charger (U101)

The WFI32-IoT board features an on-board MCP73871 Li-ion/Li-Po battery charger. The battery management circuit automatically handles the selection between the USB power supply and battery supply. The current is shared between charging the battery (if connected) and the target application section. For more details on the MCP73871 Li-ion/Li-Po battery charger, refer to the Stand-Alone System Load Sharing and Li-Ion/Li-Polymer Battery Charge Management Controller Data Sheet (DS20002090).

Note: The charger is configured to limit the charge current to 100 mA to prevent the overcharging of small capacity batteries.
Warning: The MCP73871 has a battery charge voltage of 4.2V and ensures that the battery has the same charge voltage.

Voltage Regulators (U102 and U104)

The following are the two on-board MCP1727 voltage regulators on the WFI32-IoT board that generate +3.3V power supply:
  • U102 – Generates +3.3V that powers the WFI32E01PC module along with the associated circuits

  • U104 – Generates +3.3V that powers the USB hub IC (U201), PKOB4 micro controller (U300), along with the associated circuits that connect the PKOB4 debugger to a host PC

For more details on the U102 and U104 voltage regulators, refer to the MCP1727 1.5A, Low Voltage, Low Quiescent Current LDO Regulator Data Sheet (DS21999).

Power Measurement Header (J400)

The current measurement header (J400) measures the total current consumed by the WFI32E01PC module using a multimeter. To measure the total current consumption of the WFI32E01PC module, remove the jumper (JP401) from the J400 header and connect a voltmeter across its pins. A 1Ω resistor option available on-board across the jumper gives a 1:1 relationship between the voltage drop and current consumption.

For the direct current measurement, use a jumper wire to short the J400 pin 1-2 and connect a current clamp probe, for example, the TEKTRONIX TCP0030A current probe. The normal probes with long wires may add a load to the current path and introduce a voltage drop, which leads to incorrect readings.

For the current measurement in terms of voltage, mount the R400 with 0.1Ω resistor for Active mode and 1Ω resistor for Sleep mode current consumption using a voltage probe or multimeter.