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Original question:

TIDA-01445: Why is a comparator used for LS current regulation/limitation in dynamic state

TIDA-01445: R36 pull-up on the output of the high side switch

Karol
Prodigy 30 points
Part Number: TIDA-01445
Other Parts Discussed in Thread: TPS2H000-Q1

Hello,

I'd like to ask about the R36 pull-up in the TIDA-01445.

It appears on the schematic in the reference design files (https://www.ti.com/lit/ug/tidud43a/tidud43a.pdf?ts=1695045260458&ref_url=https%253A%252F%252Fwww.google.com%252F, p. 14)

The reference schematic does not consist of such pull-up:
 

I'm confused of this R36 pull-up, because according to the design the static current is done by the Vcc though the D1 and the R6. And the PWM triggers U1 output FET that enables higher voltage from the Vbat to enable dynamic state.

Do the tests in the reference design were performed with this R36 resistor?

Greetings,

Karol

  • 0
    TI__Intellectual 2971 points

    Hello Karol,

    I reviewed the design data and can confirm that the TIDA-01445 was tested with the R36 populated. I am not the author of the design, but I believe this is for the reverse current protection and diagnostics. Please refer to the datasheet of the TPS2H000-Q1

    https://www.ti.com/lit/ds/symlink/tps2h000-q1.pdf

    Chapter 8.3.7.4

    Best regards, Jiri

  • 0
    Prodigy 20 points

    Hi,

    I believe this pull up resistor is meant for open-load detection in off-state. I dont see, how this would work in the configuration of the Interlock reference design, though. The Static state pull-up is much stronger. I dont think this pull-up is necessary in that configuration.

    https://www.ti.com/lit/ds/symlink/tps2h000-q1.pdf

    Chapter 8.3.6.2.2

    "When a channel is off, if a load is connected, the output is pulled down to GND. But if an open load occurs, the
    output voltage is close to the supply voltage (VVS – VOUTx < V(ol,off)), and the fault is reported out.

    There is always a leakage current I(ol,off) present on the output due to internal logic control path or external
    humidity, corrosion, and so forth. Thus, TI recommends an external pullup resistor to offset the leakage current
    when an open load is detected. The recommended pullup resistance is 20 kΩ."

    Best regards