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some issues on DS90CR287

Ted Xu
Expert 4590 points

1. there are 3 power pins-Vcc, PLLVcc,LVDSVcc. What is the powerup sequency ?

2. In power down mode, what would happen if clock singal excess 85MHz or not is applied to clock in pin?

3. what would happen if the TTL input singal levels exceed the region of  -0.5v to Vcc+0.3V at TxIn input pins? Whether will the chip be  hot?

 

 

  • 0
    TI__Prodigy 515 points

    Please find response to your questions below.

    1. There is no specific power sequence required for proper operation of this device.

    2. In powerdown mode the device PLL is not active, and the rate of the clock signal will have no effect. There will be no output switching - outputs are held in tri-state.

    3. TTL input signal levels exceeding the region of  -0.5v to Vcc+0.3V violate the absolute maximum rating of the device. The safety of the device cannot be guaranteed if operated beyond the absolute maximum ratings.

     

    Best regards,

    Sue

  • 0
    TI__Expert 7395 points

    Hi Hongze Xu,

    1 ) The 287 should power up fine with the following condition:

    1. All supplies (Vcc, PLLVcc, LVDSVcc) at the same time

    2. Vcc before PLLVcc and LVDSVcc

    The only condition that would cause the 287 to not power up correctly would be if PLLVcc is powered before Vcc.

    2 ) When PD Pin = Low, the device is held in a reset state. Applying a clock will not negatively affect the input since the device disabled. It is noted in the datasheet to not enable the part without a clock present.

    3 ) Do not exceed the ABS MAX specs on the LVCMOS inputs, excessive over or undershoot can trigger ESD diodes to turn on and draw excessive current. 

    Dac Tran

    SVA / APPS