LM5067EVAL: No output when Vin= -40v

Hi Mia,

Thanks for reaching out to us. We'll get back to you tomorrow.

Hi Mia,

Please could you measure the values of R1, R2, and R3 resistors in the EVM using a multi-meter. Because, the values of voltages at UVLO and OVLO pins presented in the above screenshot are not correct. With R1= 95.3 kΩ, R2=4.64 kΩ, & R3=3.32 kΩ, and VEE at -40 V, voltages at UVLO and OVLO pins with respect to GND should be -36.74 V and -38.52 V respectively. We suspect that because of violation in UVLO pin voltage, the controller is not starting up. However, this can confirmed after measuring the actual values of R1, R2, and R3 in the EVM, what customer is using now.

Hi Avishek，

Acutually we have confirmed the R1.R2 and R3 resistor value already.

1. if solder LM5057 on the EVM:

R1=86K, R2=3K,R3=150R

2. if remove LM5067 out of EVM

R1=95.3K,R2=4.64 kΩ, & R3=3.32 kΩ

So if it's because the LM5067 already damage or wrong?

Thanks

Best regards

Mia Ma

Hi Mia,

Thanks for sharing the update. Please could you populate another one samples of LM5067 and measure the values of R1, R2, and R3. 

Hi Avishek,

Actually we only have one EVM but no lm5067 samples at present.

So from your view, you think the IC is not normal already?

any other condition we need to confirm or not?

Thanks

From Mia

Hi Mia,

Please make the JMP1 completely open by removing the shorting jumper from it and see whether startup is happening or not. By removing this jumper, the UVLO and OVLO features are disabled. 

Hi Avishek,

Removing JMP1 already, this couldn't work either.

Thanks

From Mia