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TPS4H000-Q1: Circuit to connect LED to OUT

Kaji@PAN
Mastermind 7795 points
Part Number: TPS4H000-Q1

Hi,

I am thinking of using a TPS4H000-Q1 device.
I connected the anode side of four LEDs 1, 2, 3, 4 to the output of TPS4H000-Q1 and connected the current control circuit with a variable current value to the cathode side to select each LED We are designing a circuit that makes only one LED blink with a value.

Q1: About "OPERATING CURRENT (page 6)"
Ilkg(out) Output leakage current in off-state 2uA(MAX) is described.
Is this current flowing from the IC to the load side?
If so, is the maximum leakage current from OUTx to the LED 2 μA?

Q2: About "DIAGNOSTICS (page 7)"
I(ol,off) Off-state output sink current -75uA(MIN) is described.
Is this current flowing from the load side to the IC?
Considering together with the current value of Q1, is the current value of OUTx in the range of -75uA to +2uA depending on the voltage of OUTx?

Q3: About "Figure 30. Open-Load Detection in Off-State (page 21)"
It is recommended to use a 20 kΩ pull-up resistor.
If 20kΩ is connected, current will flow to the LED through the pull-up resistor when it is off, and the LED will emit weak light, so I think it is better not to have a pull-up resistor.
Connecting the LED strings is described in the first page of the data sheet.
Is a pull-up resistor required even when connecting an LED?

Q4: About "Table 2. Fault Table"
I would like to use /FAULT for over-laod detection of the OUT pin when it is on.
Even if the ON-state OUT pin is selected by SEL and SEH, will /FAULT=L be detected when Open load is detected by another OFF-state OUT pin?
At this time, does CS=Vcs(H)?
If so, is there a way around the open load detection that occurs on another off-state OUT pin?

Best regards,

  • 0
    TI__Mastermind 23410 points

    Hi,

    To answer your questions,

    Q1: About "OPERATING CURRENT (page 6)"
    Ilkg(out) Output leakage current in off-state 2uA(MAX) is described.
    Is this current flowing from the IC to the load side? Yes
    If so, is the maximum leakage current from OUTx to the LED 2 μA? Yes

    Q2: About "DIAGNOSTICS (page 7)"
    I(ol,off) Off-state output sink current -75uA(MIN) is described.
    Is this current flowing from the load side to the IC?
    Considering together with the current value of Q1, is the current value of OUTx in the range of -75uA to +2uA depending on the voltage of OUTx?

    This is the output that occurs when the device is in open load and when the device is off but yes, this would be the load side to IC current.

    These would be the currents when the device is switched off.

    Q3: About "Figure 30. Open-Load Detection in Off-State (page 21)"
    It is recommended to use a 20 kΩ pull-up resistor.
    If 20kΩ is connected, current will flow to the LED through the pull-up resistor when it is off, and the LED will emit weak light, so I think it is better not to have a pull-up resistor.
    Connecting the LED strings is described in the first page of the data sheet.
    Is a pull-up resistor required even when connecting an LED?

    The pull-up resistor is recommended to offset the leakage current when an open load is detected. When the device is not in open load, the current will go through the path of least residence and travel through the switch. When disabled, most of the voltage should be dissipated through the pull-up resistor. Note that the first page mentions LED drivers and not LEDs.

    Q4: About "Table 2. Fault Table"
    I would like to use /FAULT for over-laod detection of the OUT pin when it is on.
    Even if the ON-state OUT pin is selected by SEL and SEH, will /FAULT=L be detected when Open load is detected by another OFF-state OUT pin?
    At this time, does CS=Vcs(H)?
    If so, is there a way around the open load detection that occurs on another off-state OUT pin?

    The /FAULT pin is ORed of all the channels faults and when a fault occurs, CS pin will be pulled up to Vcs(H). Individually turning off channels to see when the fault is reported out will help identify where the open-load occurs.