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TPS717-Q1: Adding 10ms delay for enable signal

Charles (KAT) Zhang
Intellectual 1035 points
Part Number: TPS717-Q1

Hi All,

My customer is trying to do sequence control of TPS717-Q1, but there is no MCU to control the EN pin, so they want to use RC delay to control the EN signal.

When checking the datasheet, the EN high level is 1.2V, EN low level is 0.4V, so

  • Does EN pin have requirement for the slew rate?
  • what's the status of the device when EN signal is between 0.4~1.2V?
  • Is it possible to add 10ms time delay by adding RC filter at the EN pin? If yes, Which threshold should customer use to calculate the RC filter parameter

Best Regards

Charles Zhang

  • 0
    TI__Genius 10200 points

    Hi Charles,

    • The EN pin can tolerate high slew rates as it is meant to handle digital signals. If the slew rate is limited it is typically mentioned in the datasheet. 
    • The EN high level specification is the logic high specification for the EN pin. It is the EN pin voltage at which all TPS717-Q1 devices are ensured to be regulating the output. The actual threshold where the regulator changes from disabled to enabled will vary between 0.4 V and 1.2 V depending on the device. As a result, if EN is between 0.4 V and 1.2 V, the state of an individual device is indeterminate - it could be regulating or disabled depending on the device's specific threshold.
    • It is possible to add a delay using an RC filter before the EN pin. However, because the exact enable thresholds will vary, the exact turn-on delay will be inconsistent. If this is not a problem for your customer's application, they should design the filter around the 1.2 V EN high level threshold. If the application requires precision timing, a supervisor can be placed between the filter and the EN pin. The supervisor would apply at least 1.2 V to the EN pin after a 10 ms delay controlled by the RC filter, ensuring consistent turn-on delays across all TPS717-Q1 devices. TI has a wide selection of supervisors here:

    Thanks,

    Gerard