MP3429 – Output voltage present when EN = 0 V (Shutdown mode)

DC-DC Power Converters
1

Hello,

I am using the MP3429 in a boost configuration with the following conditions:

  • Input supply: 2S Li-Ion battery pack

  • VIN during measurement: approx. 6.5 V

  • Target VOUT: 12 V

  • MODE tied to VDD (FCCM mode)

  • Standard boost topology per datasheet

The converter regulates properly to 12 V when EN is tied high.

However, when I pull EN to 0 V, I still measure a voltage present at the output:

  • EN = 0 V (measured directly at the IC pin)

  • VIN ≈ 6.5 V

  • VOUT ≈ 5.5–6 V

The device is not switching, but the output node does not fall to 0 V.

There is no external bias applied to VOUT. The output is connected only to the output capacitors and the downstream circuitry.

I am attaching a schematic screenshot for reference.

Could you please clarify:

  1. Is it expected that VOUT remains near VIN when EN = 0 V?

  2. Does MP3429 provide true output disconnect in shutdown mode?

  3. Are there specific design considerations required to fully discharge or isolate VOUT when the device is disabled?

Thank you in advance for your clarification.

schem
schem1643×1144 217 KB

2

Hello @majek89

Thank you for posting your question in the MPS Technical Forum.

To answer your questions, the MP3429 does not provide a true output disconnect from input. The High-Side MOSFET (Q2) body-diode from SW to VOUT will lead to the seen output voltage even when EN is low. Here is an image which can be found in the MP3429 datasheet, page 14.

image
image1248×429 33.1 KB

Nevertheless, the MP3428A is an alternative boost converter that you can consider for your application. This part can drive one additional MOSFET which can be used to disconnect Output Voltage from Input.

I hope this is helpful!

Regards,
Edgar

3

Ok, got it, thanks a lot!