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TLV3701-Q1: Power Up and Signal input timing

cafain
Mastermind 6425 points
Part Number: TLV3701-Q1
Other Parts Discussed in Thread: TLV7031, TLV7011, TLV7032, TLV1805-Q1

Hi Staff,

Let me ask a question in TLV3701-Q1

The signal also rises at the same time as the Vcc power supply rises (0 → 3.3V).
※IN+(0→1.8V), IN-(0→2.45V)

As a result, 3.3V High-Level is output to the OUT pin at the same time as the power is turned on and the signal is applied.
High-Level is output and transitions to Low-Level after about 2.5ms.
* There is no load connection.
* Since IN+ < IN-, I was expecting Out=Low, but I would like to know the reason why High is output for 2.5ms.

Question
1.If the power is turned on and a signal is applied at the same time, will the Out pin be output for about 2.5ms?

2.Is there anything wrong with starting up the power and applying the signal at the same time?

best regards
cafain

  • 0
    TI__Guru 52396 points

    Hello Cafain,

    Most devices have a start-up time - they do not turn on immediately. The internal bias generator needs time to start-up and provide proper biasing.

    Since this is a micropower device, it will take longer to start up due to lower internal biasing currents charging up internal capacitance - so that may take a few milliseconds to get everything charged-up and going. During this time - the output is indeterminate since internal biasing is not stable. So the output may not correctly respond to the input conditions during this time.

    So, yes, there may be a "glich" at first power-on.

    To avoid this issue, we have introduced the TLV7011 and TLV7031 family of comparators that have a POR circuit built-in. The output will be in a known state until the supply voltage rises above 1.6V, and 200us after that. This should give the input voltages time to stabilize and allow a correct output state.

    The open drain output versions will be high-impedance (High) during power-up. The push-pull outputs will be low during power-on.

    I would recommend looking at the TLV7032, which is the push-pull micropower version that would be similar to the TLV3701-Q1.

    If you need the Q1 automotive version, see the TLV1805-Q1. It also has the POR circuit.