The following application example uses nPM1100 and an nRF5x wireless System on Chip (SoC). Any nRF52 or nRF53 series device with USB can be configured in the same way as this application. When using a device without USB, or for other configurations, see Reference circuitry.

The example application is for a design with the following configuration and features:
  • nPM1100 BUCK regulator supplies the nRF5x device
  • USB current limit negotiation
  • Charging status monitoring using SoC GPIOs
  • ICHG and VTERM configuration
  • NTC thermistor in the battery pack
  • Ship mode
  • Battery monitoring circuit and low battery indication LED (the device must sample the battery voltage)


Figure 1. Application example
Application example

Supplying from BUCK

nRF5x is supplied by nPM1100 VOUTB at 1.8 V. BUCK mode (MODE) is controlled with a GPIO.

An application should not be supplied directly from VBAT because it can disturb the battery charging process and may cause incorrect behavior from the charger. Instead, VOUTB and/or VSYS should be used to supply an application.

USB port negotiation

nRF5x can connect to a USB host.

Port negotiation can be performed after nPM1100 port detection. The nRF5x device and nPM1100 are both connected to USB in the application example. nPM1100 detects SDP or CDP/DCP. If SDP is detected, the USB device can negotiate with the USB host for higher current from VBUS.
  • D+ and D- pins are connected to both nPM1100 and nRF5x. The nRF5x SoC must wait until nPM1100 completes port detection before enabling its USB port. See USB port detection and VBUS current limiting for port detection time after VBUS connection.
  • An nRF5x GPIO is connected to the ISET pin and sets the VBUS current limit after negotiation. If CDP or DCP is detected, then a 500 mA limit is automatically set regardless of ISET state.
  • VBUS is supplied to both nPM1100 and nRF5x to supply nPM1100 SYSREG and the nRF5x VBUS regulator.

See USB port detection and VBUS current limiting for a detailed description.

Charging and error states

Pins CHG and ERR indicate charging and error states. See Charging indication (CHG) and charging error indication (ERR) and Charger error conditions.

Termination voltage and current

For a product using standard VTERM, the termination voltage is configured to 4.2 V. See Termination voltage (VTERMSET). The same configuration would provide 4.35 V for a product using high VTERM.

Charge current is configured to 200 mA (±10%) using a 1.5 kΩ (1%) resistor to ground on the ICHG pin. See Charge current limit (ICHG).

NTC configuration

The NTC pin is connected to an external NTC thermistor which should be placed with thermal coupling to the battery pack. See Battery thermal protection using NTC thermistor (NTC) for more information.

Ship mode

Ship mode is enabled at production time through an off-board circuit with a probe point on the SHIPACT pin.

An external button is in the circuit to exit Ship mode. If another circuit is present instead of a button, any signal that is able to pull the SHIPHLD pin low for the required period can be connected to that net. See Using Ship mode for more information.

Battery monitoring and low battery indication

The battery monitoring circuit allows the battery voltage to be sampled by the nRF5x ADC.

The transistors enable battery voltage sensing through a resistive divider. When not sampling, the transistors prevent current leakage to ground. The circuit is designed to ensure the voltage range on an analog input pin over the battery voltage is within the limits required by the nRF5x GPIO and ADC. A battery voltage of 2.8 V to 4.2 V is scaled down to 360 mV to 540 mV at P0.xx for sampling.

If software on nRF5x determines that the battery on nPM1100 is low, the Low Bat LED can be switched on through GPIO. This circuit sources the LED current from VSYS. VSYS will not be supplied after VBAT drops below VBATBOR because CHARGER will isolate the battery when a brownout reset occurs. See Power-on reset (POR) and brownout reset (BOR).