LM74670-SQEVM: Is this usage any issue

Hello,

Let me look into this and get back soon today or tomorrow.

Regards,
Kari.

Hello Toshihiro,

When you say the EVM is broken, the MOSFET is damaged or the IC is broken.

Could you let us know what is the frequency of 15V AC input applied?


Regards,
Kari.

Karl-san,

MOSFET or IC is unknown. I will check the frequency.

Does this mean you don't see any issue for the usage?

Best regards,

Toshihiro Watanabe

Hi Toshihiro Watanabe,

IC is not exected to damage, but if the MOSFET sees lot of AC current then it can get damaged.
Could you tell us what it frequency of the AC input and also the AC RMS is 15V and not more than that?


Regards,
Kari.

Hello Karl-san,

The frequency is 50Hz. The amplitude is AC15Vrms.

Best regards,

Toshihiro Watanabe

Hi Toshihiro,

We don't expect the IC or the MOSFET to get damaged in the operating condition.

Let us know if you were able to check whether the MOSFET is damaged or IC is damaged or both?

Regards,
Kari.

Hello Karl-san,

We expected the broken device would be LM74670 expecting Gate drive signal is not generating. MOSFET function is to do as a diode.

Best regards,

Toshihiro Watanabe

Hello Toshihiro,

LM74670-Q1 turns off the MOSFET when the Iac current reverses to 1.75A.
This is because reverse turnoff threshold of LM74670-Q1 is -7mV (across Anode to cathode) and MOSFET has 4mohm RdsON.
So reverse current threshold is -7mV/4mohm = 1.75A. So the IC is working fine, no issues.

However, after the MOSFET is turned off, we could see that Vds is going very high and it can exceed 42V abs maximum value.
This peak value is not clear from waveforms.

If the Vds exceeds 40V, the MOSFET will gate damaged as its Vds is rated to 40V.
If the Vds exceeds 42V, the IC also will get damaged as its cathode-anode is rated to 42V abs maximum.

Otherwise we don’t see any issue.

Regards,
Kari.