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TLC59208F: About VDD of TLC59208F

taichi
Expert 1395 points
Part Number: TLC59208F

Hello,

My customer have two questions about TLC59208F below.

1. When the power supply is turned on, the voltage of VDD drops from 3.3 V to 2.5 V, is there a problem with IC?

　Voltage drop time is about 20 to 30 ns.

2. About I2C Fast Mode(400kHz),

    Fall time is state as min 20nS + 1Cb in the datasheet.

   Its time will be 6 ns on their system. Should it be better to adjust to 20 ns or more with buffers?

Regards,

Taichi Nakamura

  • 0
    TI__Genius 14295 points
    Hi, Taichi,

    Vdd should not drop and where is this Vdd from? Any capacitors in parallel?

    The minimum requirement for tf in fast mode is 20ns + 0.1Cb to make sure the communications is correct.

    6 ns is a little less and it's better to adjust it to 20ns but don't exceed 300ns.

    Thanks.
    Regards,
    Kenneth
  • 0 in reply to Kenneth Du
    Expert 1395 points
    Hello, Kenneth-san,

    Thank you for your quick reply.

    There is no capacitor on the input side. They will try to put it in.
    I will let them adjust the I2C time with buffers.

    Regards,
    Taichi Nakamura
  • 0 in reply to Kenneth Du
    Expert 1395 points
    Hello, Kenneth-san,

    Please let me ask you a little more.

    ①Vdd should not drop and where is this Vdd from? Any capacitors in parallel?
    ⇒They are not using capacitors at the moment, but are there any problems if Vcc falls below 3V?
    I understand that it is out of warranty, but does it have an operational effect such as being reset?

    ②he minimum requirement for tf in fast mode is 20ns + 0.1Cb to make sure the communications is correct.
    6 ns is a little less and it's better to adjust it to 20ns but don't exceed 300ns.
    ⇒When they evaluated I2C at the falling time at 6 nS, there seemed to be no communication obstruction.
    In TLC59208F, only Fast Mode has a time specification of min value,
    but what kind of thing can be thought about if communication is performed in a shorter time?

    Regards,
    Taichi Nakamura
  • 0 in reply to taichi
    TI__Genius 14295 points
    Hi, Taichi-san,

    Vcc falls below 3V may reset the device.

    This is a standard requirement for I2C communication. The falling time beyond the required range may not be recognized and cause communication issue.

    Thanks.
    Regards,
    Kenneth