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Using the TL7733B to monitor 3.3V supply

BobW
Intellectual 280 points
Other Parts Discussed in Thread: TL7733B

For the TL7733B supply voltage supervisor, it is apparent from the datasheet that the recommended operating supply (VCC) voltage is 3.6 to 18 V. 

However, the application information Figure 8 (of the datasheet) shows an example where the system supply (VCC) is the same voltage being monitored at the SENSE input. 

If the system supply is 3.3 V, does this imply that the 3.3V supervisor cannot be used in the configuration of Figure 8 since 3.3 V is below the recommended operating voltage? 

If so, how might the IC be used to monitor 3.3V? 

Is there a reference design where the TL773B is used to monitor 3.3V?

  • 0
    TI__Mastermind 40100 points

    Hi Robert,

    An answer will be posted when the appropriate apps engineer looks into this. Thanks!

    Regards,

    Darwin

  • 0
    TI__Mastermind 21285 points

    Hello Robert,

    TL7733B does not support VCC operation at 3.3V.  To use this device, you would need to provide a separate voltage rail of >3.6V.

    You could always look at a device such as TLV803S or TPS3839G33 which support VCC operation at 3.3V.

    Let me know what you think.

  • 0 in reply to Michael S
    Intellectual 280 points

    Thanks, Michael.

    I have an option (which I know intend to use) for VCC to be supplied by 5V. However, this makes the datasheet a little confusing in that the Application Information figure (page 9 of the current datasheet) shows the SENSE and VCC tied together. So I will assume this figure is not applicable to the 7733 version of the part.

    However, in the case where the 7733 part is used to sense a 3.3V supply, and the 7733's VCC is powered by 5V, now it seems that the low-true RESET output would be pulled up to 3.3V and the high-true RESET output being driven to nearly VCC (+5V). So I am curious... are there any reference designs where the 7733 is used in this fashion?

    Thanks again,

    Bob W.

  • 0 in reply to BobW
    TI__Mastermind 21285 points

    Hi Bob,

    I've not seen any references that use this part in a similar manner.  You could add a 20k to ground on the high-true RESET line (in the example) to bring the actual RESET signal to 3.3V.