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Questions about ADS1240

ttd
Mastermind 8590 points
Other Parts Discussed in Thread: ADS1240

Dear Technical Support Team,

 

I have a question about ADS1240.

 

①/PDWN

Datasheet Page5 shows following about /PDWN, but it doesn't describe the detail.

Dose it keep the resister value?

How is the behavior of pins such as clock generator(XOUT), Serial Interface and so on.

 

----------------

Active LOW, Power Down. The power down function

shuts down the analog and digital circuits.

----------------

 

②

These are customer's settings.

 

AVDD=3.3V

Vref=2.5V

RANGE bit=0

 

Datasheet says that differences of Vref between AVDD and RANGE.

 

----------------

For AVDD = 5.0V and RANGE = 0 in the ACR, the differential

VREF must not exceed 2.5V.

For AVDD = 5.0V and RANGE = 1 in the ACR, the differential

VREF must not exceed 5V.

For AVDD = 3.0V and RANGE = 0 in the ACR, the differential

VREF must not exceed 1.25V.

For AVDD = 3.0V and RANGE = 1 in the ACR, the differential

VREF must not exceed 2.5V.

----------------

 

In AVDD=3.3V(customer's situation), is it AVDD=3.0V condition above?

Does it have threshold voltage whether 3V or 5V condition?

I think Range bit should be "1", when AVDD=3V and Vref=2.5V.

 

Best Regards,

y.i

  • 0
    TI__Guru* 97585 points

    y.i,


    The /PDWN is functionally the same as a device shutdown. After the power is restored, it might retain some of the original registers, but do not count on it. As for the clock generator, I'm not sure, but I wouldn't count on it functioning during a device shutdown.

    If you are interested in conserving power, use the SLEEP and WAKEUP commands, which will retain the register settings.

    With AVDD=3.3V, VREF=2.5V, I would set the RANGE=1. I'm not entirely sure why these conditions are set on the VREF voltage and the RANGE bit, but it may be related to reference sampling limitations in the ADC.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Mastermind 8590 points

    Hi Joseph-san,

    Thank you for your reply.

    Should we set all registers for correct operation after /PDWN ?

    If /PWDN is enable, /DRDY pin is hold. Is it stop converting?  Dose it operate correct conversion after disabling /PWDN?

    This device has /RESET pin.
    What is the difference between /RESET and /PWDN ?

    Best Regards,
    y.i

  • 0 in reply to ttd
    TI__Guru* 97585 points
    y.i.,


    A /PDWN shuts down the device. It is really a power down where the power is removed. Since this is the case, you should set the registers for correct operation after /PDWN.

    With /PDWN enabled, the /DRDY won't do anything and the device will not be converting. When /PDWN is disabled, the device may resume converting. However, since the registers may be wrong, I would re-write the registers to the operation that you want before you resume reading from the device.

    The /RESET will put the device back to it's default state when enabled. During this time the device will still remained powered up, but it is not converting and the digital section is held in this state. When the device is released from the reset state, it will resume it's operation with the default settings in its register.


    Joseph Wu