Reset time of TL7700

Takahiro,

For this device, we only provide the typical delay. Things like operating conditions and capacitor tolerance will have slight impact on delay accuracy.

Typical delay is given in section 8.3.3 Output Pulse-Duration Setting of the datasheet.

tpo = Ct × 10^5 seconds
where Ct is the timing capacitor in farads.

Please refer to Figure 6 and let me know if you have additional questions. Thank you!

-Michael

Thank you for your answer!

We understand that reset time is calculated by the following formula.
tpo = Ct × 10^5 seconds

We think this formula is typical value.
Do you have the data about the variation?
For example, ±%
Is it difficult to check the variation of reset time?


Best regards,


Takahiro Nishizawa

Takahiro,

Unfortunately since this device was created in 1999, not much data exists on this device. We have newer Wide Vin devices that have been better characterized. For TL7700, all we have are the typical curves to suggest an approximate delay. Factors such as operating temperature, capacitor tolerance, parasitic capacitance on the reset pins will degrade delay accuracy. From the Output Pulse Duration spec in table 6.6 which specs the delay with CT = 0.01uF, we see that the accuracy can vary up to +/- 50% absolute worst case. We often times see the delay accuracy to be better than +/- 50% but it is not something we have enough data to make a guarantee. The best thing to do is test the device in your specific application to see if the performance will meet your needs. Also, use accurate capacitors to minimize error.

Please let me know if you need additional support with this. Thanks!

-Michael

Thank you for your answer!

Variation of reset time is +/- 50% absolute worst case.
Is this understanding correct?

Best regards,

Takahiro Nishizawa

Takahiro,

Yes that is correct.

-Michael

Thank you for your answer!


We have new questions.
We don't use the external capacitor of CT pin.

Question.1
Is the reset time 10µS(typ) when we don't use the external capacitor of CT pin?

Question 2.
Reset time is 15µS(max) and 5µS(min) when reset time(typ) is 10µS.
Because variation of reset time is about ±50%.
Is this correct?

Question 3.
Please tell us the terminal processing of CT pin when we don't use the external capacitor of CT pin.
Open? connect to the GND?


Best regards,


Takahiro Nishizawa

Thank you for your answer!


How is your situation?
We hope earlier answer!


Best regards,


Takahiro Nishizawa

Thank you for your support!

In datasheet p.3 CT pin,
even if CT is set to 0, response speeds remain at approximately 5 to 10 µs.

And you said "we see that the accuracy can vary up to +/- 50% absolute worst case."


When Ct=0

min=5µS
typ=10µS
max=15µS

Is this correct?

And please tell us the terminal processing of to set forrlowing conditon.
even if CT is set to 0, response speeds remain at approximately 5 to 10 µs.

Open or Connected to GND and so on.

We hope earlier answer!


Best regards,


Takahiro Nishizawa