nPM1300 MIKROE Click – VOUT1 and VOUT2 not turning OFF after entering ship mode

RE: nPM1300 MIKROE Click – VOUT1 and VOUT2 not turning OFF after entering ship mode

Michal — Fri, 19 Dec 2025 16:43:30 GMT

From ship mode documentation:

When entering Ship mode, BUCK can be configured to discharge by enabling their pull downs, see BUCKCTRL0.

You should try that. First enable pull downs, then turn off bucks.

Best regards,

Michal

RE: nPM1300 MIKROE Click – VOUT1 and VOUT2 not turning OFF after entering ship mode

mhni — Thu, 18 Dec 2025 11:50:05 GMT

Hello,

Even after disabling BUCK1 and BUCK2 before ship mode, I still measure:

VOUT1 ≈ 1.8 V
VOUT2 ≈ 2.4 V

Code used:

void vDisableAllBuck()
{
  // Disable BUCK1
  vWriteRegister(NPM1300_ADDR, 0x00000400, 0x01, 0x01);
  delay(2);

  // Disable BUCK2
  vWriteRegister(NPM1300_ADDR, 0x00000400, 0x03, 0x01);
  delay(2);
}

void vShipMode()
{
  stopCharging();
  delay(10);

  vDisableAllBuck();
  delay(10);

  // Enter ship mode
  vWriteRegister(NPM1300_ADDR, 0x00000B00, 0x02, 0x01);
}

Setup details:

VOUT1 = 1.8 V
VOUT2 = 3.3 V
USB-C disconnected before ship mode

Observation:

VOUT1/VOUT2 are not fully OFF after ship mode
Voltages look like back-powered rails, not regulated outputs

According to the nPM1300 datasheet (Ship Mode section), outputs are left high-impedance in ship mode unless discharged beforehand. This suggests:

BUCKs may need explicit discharge and event wait before ship mode
ESP32 GPIO / VDDIO / I2C lines may be back-powering the rails

Questions:

Is there a recommended register sequence to fully discharge BUCKs before ship mode?
Any hardware recommendations to avoid back-powering (GPIO isolation, resistors, load switch)?

Thanks for your guidance.

RE: nPM1300 MIKROE Click – VOUT1 and VOUT2 not turning OFF after entering ship mode

Michal — Wed, 17 Dec 2025 18:12:27 GMT

Hello,

[quote user=""]I am using nPM1300 MIKROE Click with ESP32 over I2C and enter ship mode by writing the required I2C registers from ESP32.[/quote]

So what do you exactly send to the I2C registers? Do you do anything more than just sending the ship mode command?

Have you read this page of nPM1300 datasheet? https://docs.nordicsemi.com/bundle/ps_npm1300/page/chapters/core_components/ship/doc/ship-mode.html

It says for example about waiting for a few events before going into ship mode

[quote user=""]

VOUT1 is not fully OFF

VOUT2 is not fully OFF

~2.4 V is still present on VOUT2

[/quote]

What is the voltage set by you on VOUT1 and VOUT2? Is it 2.4V or something else?

[quote user=""]Is it expected behavior that VOUT1/VOUT2 are not fully OFF in ship mode?[/quote][quote user=""]Are there any additional registers required to disable VOUTs before ship mode?[/quote]

Please look at the page I have linked almost at the top. It should say all about the events, how to properly discharge bucks, etc.

[quote user=""]Could back-powering from ESP32 (I2C / GPIO / VDDIO) prevent full shutdown?[/quote]

I2C shouldn't, but I don't know how do you connect the rest, especially with those USB-C cables.

Have you disconnected the USB-C cable from the PMIC before going into ship mode?

Best regards,

Michal