LM74610-Q1 /Vg drops after start up

Kuramochi Tadahiko

Guru 28715 points

Hi,

My customer is evaluating the LM74610.

However the Vg drops after start up.

Is it correct operation?

Please refer the following file.

LM74610.pptx

Best Regards,

Kuramochi

over 9 years ago

0 Alex Triano over 9 years ago

TI__Genius 12621 points

Hi Kuramochi-san,

I have contacted the team who supports this device. They will follow up with you on this forum thread.

Thanks,
Alex

0 Kaisar Ali over 9 years ago

TI__Intellectual 2010 points

Kuramochi-san,
This is not typical behavior. Datasheet FIg 13 shows a typical start up operation. In your scope plot, the gate is still held high because there is no diode drop on the output.
The gate voltage in LM74610 doesn't stay at one constant value when ON. It depends on the charge pump cap value. The gate voltage gradually decreases as the Vcap voltage goes towards a lower threshold. Finally the Gate turns OFF. However, we never saw gate voltage bump like this during our evaluation. What MOSFET are they using?

0 Kuramochi Tadahiko over 9 years ago in reply to Kaisar Ali

Guru 28715 points

Ali-san,

Thank you for your help.

The FET is IPD90N04S4L-04.

Best Regards,
Kuramochi

0 Kuramochi Tadahiko over 9 years ago in reply to Kuramochi Tadahiko

Guru 28715 points

Ali-san,

This problem is solved.
This phenomenon is by the too low load current and charging current to capacitor at the cathode side.

Best Regards,
Kuramochi

0 Kaisar Ali over 9 years ago in reply to Kuramochi Tadahiko

TI__Intellectual 2010 points

Kuramochi-san

Thank you for sharing that information. LM74610 is designed for typically higher current applications. For current's in mA range, the Gate might not even activate at higher temps.

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LM74610-Q1 /Vg drops after start up