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TL7700: Reset output pluse duration

Hisao Uchikoshi
Genius 14220 points
Part Number: TL7700
Other Parts Discussed in Thread: TLV840

Hi Experts,

My customer is evaluating TL7700. The reset pulse duration is not expected one. Below is the schematics.

10uF is connected at CT pin so the expected reset duration is around 1sec from below figure.

Below is the actual waveform at customer.

C1 : Vin(5V)

C2 : Voltage at CT pin

C3 : please ignore

C4 : RESET of TL7700

The reset pulse duration(C4) is about 700ms while the expected one is 1 sec. It looks that Reset pin is going high when CT pin voltage is 1.2V. Customer is gessing this 1.2V threshold makes the reset pulse shorten. According to the datasheet, TL7700 uses 1.5V internal reference so the threashold should be around 1.5V.

Could you please invesitage why this differece happens? Customer just wants to know the fact.

Regards,

Uchikoshi

  • +1
    TI__Genius 14770 points

    Hello Uchikoshi,

    Thank you for your question, since this is an older device, the timing is Tpo (1+/-50%). Stipulated from section 6.6 Tpo with CT=.01uf as example. Do you know the test environment for the customer and the tolerance of the CT capacitor?

    Also, has the costumer considered using a newer device such as a TLV840?

    Jesse