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DRV8806: Leakage current

Part Number: DRV8806

Hi Team,

The customer is experiencing below issue and needs your help.

1. How to solve the leakage current during DRV8806 control? For example, when the DRV8806 is powered on but not turned on, D11 and D15 will have weak light. When turned on, the brightness of the light will increase.

2. When multiple groups of DRV8806 are used in cascade, data transmission of D flip-flops one by one. Customer feels inconvenient. Customers use ordinary IO, pulse one by one, and then control the input of each D flip-flop; Is there a more convenient control method? He saw that someone was using SPI pins, but he didn’t know any good way to achieve.

Thanks,

Annie

  • Hi Annie,

    1) What is the part number of the LED?

    The weak light is due to the open load circuitry. This circuit draws current through the resistor/LED.

    Is it possible to add a resistor in parallel with the resistor/diode path? Perhaps a 4.7kOhm would reduce the current enough to turn the LED off.

    2) A SPI interface can be used assuming the number of devices cascaded is an even number.

    This allows the SPI to send 8 bits at once. Please refer to Figure 9 of the datasheet as an example.

  • Hi Rick,

    The LED model is the ordinary 0603 package, or the in-line 3mm LED. Customers have tried parallel resistors. He was using 1KOhm at the time, and there really was no leakage current problem. But the resistor will be very hot. This will have higher requirements on the power of the resistor, and will the open circuit detection of DRV8806 still be useful?

    Thanks,

    Annie

  • Hi Annie,

    A 1k resistor is too low. When the output is low, the resistor power is over 1/2W. Using a 5k reduces the power to ~1/8W and using a 10k reduces the power to ~1/16 W.

    When adding parallel circuits to the outputs, the open load circuit may not operate properly.

    Has the customer measured the voltage at the output when the load is not connected? What is the measured voltage?

    If the output voltage is greater than 1.2V during open load, this is an indication the open load circuit may not work.

  • Hi, Rick:

    When the load output is only connected with resistance and LED, the voltage is about 2.7V;
    If I don't have a 10k resistor on the output, there is no high temperature problem, but I will find that the LED will flicker for about 1 second, and the light is very weak. I retested the 1K resistance, and this phenomenon also exists, which I ignored before;
    If the resistor and LED are removed and the circuit is disconnected, the measured voltage at both ends is 24V;
    Can you help me analyze the reason?
    Thank you.

    Yu

  • Hi Yu,

    Can you provide the information in a table form. An example is

    Load at OUTx Voltage at OUTx (Output off) Voltage at OUTx (Output on) Heat detected (Where)
    No load
    10k + LED only 2.7V
    LED only
    10k + LED with parallel load

    Also what is connected to the 2 Ohm resistor (R103 and R111)?

    When you use the 10k + LED only connected, what is the voltage at the 10k/LED connection point for both the output on and off condition?