About the Vin voltage at startup for MC34704.

[yuuki]

Dear all,

We monitor VIN and VOUT5 of MC34704.

When the Vin voltage is remained about 0.2V, VOUT5 is output at Vin startup.
However, when the Vin voltage is remained about 0.3V, VOUT5 isn't output even if Vin stands up.

Please see attached file.

I understand that the remains voltage shouldn't exist on Vin at startup.
Is my understanding right?

Is the remains voltage defined?
(Is the allowed remains voltage defined?)

Best Regards,
Yuuki

[reyes · Accepted solution]

Hi yuuki,

Yes, your understanding is correct, there should not exist remain voltage on Vin at Startup.

There should not be any amount of voltage at the system (residual voltages on capacitor for example), voltage should be very close to 0V, otherwise it will may not turn on automatically, so my recommendation would be to add a “discharge circuit” on the part of the system that is keeping the residual voltage.

Unfortunately we do not have this data characterized, so customer would need to do their own tests, but the recommendation it’s to make this voltage as close as possible to 0V.

Have a great day,
Jose Reyes

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reyes