https://community.nxp.com/t5/Power-Management/NEX81801-Vcc-not-getting-charged/m-p/2162063#M4654 <P>Hello!</P><P>I'm using the NEX81801 SR-FET controller for the first time, and I'm facing an issue. I'm using the Low-side implementation and I was planning to use it for a 5V output. According to the datasheet, the VCC capacitor should be charged by VD in my case, because HV would be just 5V. I'm getting pulses in my winding and therefore in the VD pin, captured in the image below:&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_0-1756802791916.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355159i653BC0F7A9CA0C10/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_0-1756802791916.png" alt="NonoSerranoVP_0-1756802791916.png" /></span></P><P>Based on these pulses, shouldn't the VCC be charged to 6V? I just implemented the following circuitry from the datasheet for now, but I see no voltage in VCC and there's no short and VCC is high-impedance.&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_1-1756802978092.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355161i8287BD1A7879A548/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_1-1756802978092.png" alt="NonoSerranoVP_1-1756802978092.png" /></span></P><P>Apart from that, the SR-FET driving voltage has the same offset as the VD rail:&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_0-1756806606604.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355180i39A46AEDFC040073/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_0-1756806606604.png" alt="NonoSerranoVP_0-1756806606604.png" /></span></P><P>Any clue what could be happening?</P><P>Thanks a lot in advance for your time!&nbsp;</P><P>Best regards,</P><P>Nono</P><P>&nbsp;</P><P>&nbsp;</P> Tue, 02 Sep 2025 10:03:31 GMT NonoSerranoVP 2025-09-02T10:03:31Z https://community.nxp.com/t5/Power-Management/NEX81801-Vcc-not-getting-charged/m-p/2162063#M4654 <P>Hello!</P><P>I'm using the NEX81801 SR-FET controller for the first time, and I'm facing an issue. I'm using the Low-side implementation and I was planning to use it for a 5V output. According to the datasheet, the VCC capacitor should be charged by VD in my case, because HV would be just 5V. I'm getting pulses in my winding and therefore in the VD pin, captured in the image below:&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_0-1756802791916.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355159i653BC0F7A9CA0C10/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_0-1756802791916.png" alt="NonoSerranoVP_0-1756802791916.png" /></span></P><P>Based on these pulses, shouldn't the VCC be charged to 6V? I just implemented the following circuitry from the datasheet for now, but I see no voltage in VCC and there's no short and VCC is high-impedance.&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_1-1756802978092.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355161i8287BD1A7879A548/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_1-1756802978092.png" alt="NonoSerranoVP_1-1756802978092.png" /></span></P><P>Apart from that, the SR-FET driving voltage has the same offset as the VD rail:&nbsp;</P><P><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="NonoSerranoVP_0-1756806606604.png" style="width: 400px;"><img src="https://community.nxp.com/t5/image/serverpage/image-id/355180i39A46AEDFC040073/image-size/medium?v=v2&amp;px=400" role="button" title="NonoSerranoVP_0-1756806606604.png" alt="NonoSerranoVP_0-1756806606604.png" /></span></P><P>Any clue what could be happening?</P><P>Thanks a lot in advance for your time!&nbsp;</P><P>Best regards,</P><P>Nono</P><P>&nbsp;</P><P>&nbsp;</P> Tue, 02 Sep 2025 10:03:31 GMT https://community.nxp.com/t5/Power-Management/NEX81801-Vcc-not-getting-charged/m-p/2162063#M4654 NonoSerranoVP 2025-09-02T10:03:31Z https://community.nxp.com/t5/Power-Management/NEX81801-Vcc-not-getting-charged/m-p/2162122#M4657 <P>Hello,</P> <P>For inquiries related to Nexperia products such as the NEX81801, I recommend reaching out directly to Nexperia's support team for the most accurate assistance.</P> <P>BRs, Tomas</P> Tue, 02 Sep 2025 11:23:42 GMT https://community.nxp.com/t5/Power-Management/NEX81801-Vcc-not-getting-charged/m-p/2162122#M4657 TomasVaverka 2025-09-02T11:23:42Z