Hi Sir,
My customer has a question that when he adds pull-up resistor EN for 300 kohm (pull up to 3.3V), EN pin voltage will become 3.9V. when pull-up resistor changes to 10 kohm, EN pin voltage will become 3.3V. I duplicated this situation and found that it really has a higher voltage than pull-up voltage when the pull-up resistor is higher than 10 kohm. The schematic and test result are shown below. could you please kindly tell us the reason of it? thank you so much.
I changed R4 value for 300k, 200k, 100k, 10k and 1kohm and NI R2, R3 and C20.
R4 value |
EN voltage |
Pull up voltage |
300kohm |
3.778V |
3.2351V |
200kohm |
3.596V |
3.2351V |
100kohm |
3.415V |
3.2351V |
10kohm |
3.249V |
3.2351V |
1kohm |
3,2388V |
3.2351V |
Best regards,
Ann Lien