UCPD TCPP01-M12 Hardware Design Question

Jason927 · ‎2025-08-26

I'm using tcpp01-m12 and stm32u5 borad to develop a UCPD sink application.

The UCPD module seems works fine, and I can request selected voltage from source.

But when I closed the MOS which controlled by tcpp(mcu set tcpp ctrl pin high), the vcc output voltage still have about 500mV.

Is this a Characteristics of MOS tube, or any hardware design suggestion?

Peter BENSCH · ‎2025-08-27

Well, the gate threshold voltage of the STL100N10F7 is between 2.5V and 4.5V, meaning that an unfavourable specimen may not be able to conduct (see data sheet, fig. 8, Transfer characteristics).

Instead of the STL100N10F7, you could use a low gate threshold MOSFET (known as a logic level types), e.g. the STL160N6LF7, whose threshold voltage is between 1.2V and 2.5V and which typically reaches its maximum current at 3.8V (see data sheet, fig. 6, typical transfer characteristics).

However, I also noticed that you are apparently connecting the voltage divider R30/R31 with its impedance of 180k||20k = 18k directly to the ADC input of the MCU. Please note that this only makes sense for the STM32U5 at resolutions of max. 8 bits; for higher resolutions, an impedance converter or lower-impedance resistors are strongly recommended (see data sheet, search term ‘input impedance’).

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

View solution in original post

Peter BENSCH · ‎2025-08-27

Well, the gate threshold voltage of the STL100N10F7 is between 2.5V and 4.5V, meaning that an unfavourable specimen may not be able to conduct (see data sheet, fig. 8, Transfer characteristics).

Instead of the STL100N10F7, you could use a low gate threshold MOSFET (known as a logic level types), e.g. the STL160N6LF7, whose threshold voltage is between 1.2V and 2.5V and which typically reaches its maximum current at 3.8V (see data sheet, fig. 6, typical transfer characteristics).

However, I also noticed that you are apparently connecting the voltage divider R30/R31 with its impedance of 180k||20k = 18k directly to the ADC input of the MCU. Please note that this only makes sense for the STM32U5 at resolutions of max. 8 bits; for higher resolutions, an impedance converter or lower-impedance resistors are strongly recommended (see data sheet, search term ‘input impedance’).

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.