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TLV3202: Schematic Review

TI-CSC
Genius 16060 points

Part Number: TLV3202
Other Parts Discussed in Thread: LM393, LM393LV

Hello E2E Experts,

I am either using LM393ADR or TLV3202 and ST's TS3121(optional) comparator

Can you please check my schematic, is there need anything more filtering or anything?

SCHEMATIC 04 v2_9.pdf 

Regards,

TICSC

  • 0
    TI__Guru 68006 points

    Hello,

    The threshold is close to the VCC-2V limit, but it should be ok.

    Note that the LM393 is bipolar, and there is 3-26nA (depending on die rev) flowing OUT of the input pin towards ground.

    You have a fairly large pull-up (4.7M) on the diode. When the diode is not conducting (dark), the ~3-26nA bias current could pull-up against the diode "dark current" leakage and float the input to some voltage dependent on the diode leakage.

    I would use the LM393LV, which has CMOS inputs and the bias current should not be an issue.

    Are you trying to use the RX diode in voltage mode or current mode? You may need to decrease the 4.7M resistor to get cleaner input signals.

    How fast is the interruption? A 40ns device may be overkill and may oscillate with such a large input impedance. The 4.7M and the diode capacitance will set a maximum time constant.

    If the rep rate is slow-ish, you may need to add positive feedback to prevent "chatter" on the edges. I would put a place for a resistor between the output and the positive input to be able to add positive feedback in case it does chatter.