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TPA5050 IO consideration

na na78
Guru 16770 points
Other Parts Discussed in Thread: TPA5050, SN74LV4051A

Hi

We have following considerations. Would you advise us?

1.

BCLK, LRCLK, DATA is 5V tolerant inputs according to datasheet.

Are there any problem when Vcc=0V and input = 5V?

2. 

If voltage is applied to output side (DATA_OUT) before VCC, current flows to VCC and IC is damaged?

BestRegards

  • 0
    TI__Mastermind 34665 points

    Hello Na,

    5V tolerant is with respect to a min VCC of 3V. If VCC is 0V and the I/O pin is 5V the protection clamps will turn-on and large enough currents to flow that can cause damage to device. If you have such a case it would best to add series 50-100 ohms resistor to help limit the current and prevent damage to the device. Also the resistor value should be selected to maintain good signal integrity of the I2S signals BCLK, LRCLK and DATA going to TPA5050.

  • 0 in reply to Damian Lewis
    Guru 16770 points

    Hi Damian

    Thank you for your reply.

    Sorry, we still can't understand why input=5V and Vcc=0v condition are not supported even if BCLK, LRCLK, DATA has 5V tolerant.

    We can see the following description on the datasheet and think DATA, LRCLK, BCLK, SCL, SDA can accept 5V input, independent on VCC.

    Is that error?


    How about output pin?

    BestRegards

  • 0 in reply to na na78
    TI__Mastermind 34665 points

    Hi Na,

    Sorry for your confusion. In normal operation with VDD set to 3-3.6V and internal logic running off VDD, the 5V tolerant pins can accept voltages ranging from 0V to 5V. There's circuitry on the input that level shifts signals above the VIH threshold (VIH to 5V) to VDD. 5V signals are shifted down to VDD. This is in normal operation. As part of the ESD protection the 5V tolerant pins have clamps to VDD and GND that turns on depending on the polarity and magnitude of the voltage applied to the pin.

    Therefore if VDD = 0V and BCLK/LRCLK/DATA/SCL/SDA = 5V, the ESD clamp will turn on and conduct current to VDD. Depending on the magnitude of the current it can damage the device. Adding a series resistor can help limit the current and prevent damage. Don't use a large resistor, since it will compromise the signal integrity.

  • 0 in reply to Damian Lewis
    Guru 16770 points
    Hi Damian

    Thank you for your reply.

    I hope you don't mind me asking it, but could you show us functional block diagram for 5V tolerant in this device?

    BestRegards
  • 0 in reply to na na78
    Guru 16770 points

    Hi Damian

    We found a following site which shows input tolerant function.

    [Tell me about the input tolerant function]

    We can understand ESD clamp turns on and conducts current to VCC when VDD=0V and BCLK/LRCLK/DATA/SCL/SDA=5V if ESD clamp exists at the input of IC, but is that 5V tolerant?

    For TPA5050, we believe the input function is like following figure because it has 5V tolerant input.

    If our understanding is not correct, please tell us.

    BestRegards

  • 0 in reply to na na78
    TI__Mastermind 34665 points

    Hello,

    The TPA5050 IO is different. The IO has 4 series diode connection to VDD, even with the protection circuits referenced to GND. The IO will start to conduct current when the pin voltage is ~one diode voltage above VDD. The current will increase with increasing voltage above VDD.

    I answered your question previously that the IO will conduct current, if VDD = 0V and IO = 5V and a series resistor should be used to limit the current. This condition should be avoided. I would recommend keeping IO voltage at or below VDD.

  • 0 in reply to Damian Lewis
    Guru 16770 points

    Hi Damian

    Thank you for your reply.

    We understand TPA5050 IO  has diode connection to VDD, including BCLK/LRCLK/DATA/SCL/SDA.

    So, we may need the absolute maximum rating of the input current value which we should limit.

    Do you have information?

    And we think the usage of keeping IO voltage at or below VDD indicates that we should use BCLK/LRCLK/DATA/SCL/SDA like ADD[2:0] pins. 

    So, we think it would be better that the absolute maximum rating of the input voltage is changed to be the same description.

    Bestregards

  • 0 in reply to na na78
    Guru 16770 points
    Hi

    Let me add supplementary note.

    We can see other ICs which have diode internally for ESD protection, indicating
    input clamp current, I/O diode current in datasheet.

    For example SN74LV4051A has diode internally, and it indicates input clamp current as absolute
    maximum ratings which should be limited not to flow into the device.

    So, we suspected that TPA5050 would also have the maximum
    input clamp current which should be limited.

    Bestregards
  • 0 in reply to na na78
    TI__Mastermind 34665 points

    Hello,

    Sorry for the delayed response. I don't have a firm number of the max current. The least you can allow is best. 10mA or less will not damage the diode. The concern with your condition VDD=0V and IO = 5V the current is being conducted through body diode to substrate, which there's a risk of latching up the device.