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ADS4245-EP

alain PERILHON
Prodigy 160 points
Other Parts Discussed in Thread: ADS4245-EP, ADS4245

Hi sir,

I am using a ADS4245-EP and i have problems... With my 6 first prototypes, 3 are working well and 3 other doesn't work...

First 6 prototypes have AD4245-EP from same batch.

The problem seem to be VCM load at power up.

Remember, in data sheet, it is written VCM output current capability typ. 4mA.

In my schematics, VCM is loaded with arround 1K (0.95mA).

What i have seen;

- If VCM is loaded with 1K at power up, VCM fall and ADC never start.

- If VCM is not loaded at power up and after 1K is load, ADC work.

Can i have a detailed synoptic of VCM circuitry to understand?

Does VCM pin scan something at power up or is there some protections?

Best Regards.

  • 0
    TI__Guru* 91947 points

    Alain,

    We are currently looking into this for you. At power up, is the device clock active? What frequency and amplitude is this clock? Is the device configured for parallel or serial SPI mode? What is the level of the signals on SCLK, SEN, Reset, CTRL1-3 after power up?

    Regards,

    Jim 

  • 0 in reply to jim s
    Prodigy 160 points
    Dear Jim,
    Here are the answers:
    My clock frequency is 60MHz square wave low noise.
    The square wave CLK is 1.6Vpp.
    The square wave clock is connect to CLKP through a 100n capacitor and with 150 ohms series.
    CLK can't be switch off. At power up it can be present at the same time. Clock generation provide from an other module on the same pcb which is powered up and down at the same time.
    VCM is connect to CLKM with 100n decoupling capacitor.
    ADS4245 is supply with two 1.8V LDO. One LDO for AVDD and the other for DRVDD.
    Ctrl2 & Ctrl3 are 0V connected, Ctrl1 is 10K pullup to 3.3V and controlled by CPU.
    At power up, 10K pull up start ADS in Global Power Down. After 200ms, CPU switch Ctrl1 to 0V to initialise ADS in Normal Operation.
    After, a hard reset (pin12) is initiate during 250ns.
    A soft reset via 3.3V SPI is send...
    Please note VCM is connected to differential driver which have a 47k to 2.5V at this pin.
    Best Regards,
    Alain.
  • 0 in reply to alain PERILHON
    TI__Guru* 91947 points

    Alain,

    We need to see the ADC portion of your schematic which shows the connections of all of the pins of ADC, and the input driver as well clock driver circuitry to help us solve this problem for you.

    Regards,

    Jim

  • 0 in reply to jim s
    Prodigy 160 points
    Ok, but the schematics are confidential.
    How to do?
    Regards,
    Alain.
  • 0 in reply to alain PERILHON
    TI__Guru* 91947 points

    Can you just make a reduced copy of the schematic that shows every part that the VCM is connected to? If not, how about a simple block diagram but include device manufacture name.

  • 0 in reply to jim s
    Prodigy 160 points

    Dear Jim,

    Could you send me a Mail address where i can send you my schematics?

    My problem is still relevant, i don't find solution to solve it as it is erratic...!!!...

    Regards.