ADS1226 stuck at the power-up

Hi TI Engineers and all,

 

We are using ADS1226 in our flow meter application.

 

Problem:

1. The conversion result is wrong and keeps wrong after power-up(confirmed with the multimeter). if power up and down for 20 times, this would show up once or twice(this possibility is uncertain).

2. After the power-up stage, if the conversion is right, then it keeps right in the following operation.

3. We tried with the MSP430 debugger to see if it is the firmware problem, the program reset can not solve this, only by re-powering. After the start-pin trigger, the data ready interrupt signal is ok, everything is ok, but the data retrieved is wrong. After re-power up, everything is normal again.

 

Condition: 5V for analog, 3.3V for digital, 5Vref by REF5050(TI).

High speed mode.

No input buffer.

Single-trigger.

MCU: TI MSP430F2410TPMR

Comm: Toggle the pin

Speed: about 1MHz

 

the communication time sequence is right. Do you have any experience about this(Power quality? Device initialization?)? Thanks and waiting for your support and solution.

 

1 Reply

  • Jason,


    What conversion results do you get when the device is in error? First, make sure that the input voltage and the reference voltages come up to expected values and compare them with the ADC result. However, it is possible that the repeated power up has cause the digital to come up in a bad state.

    The ADS1226 does a power-on-reset circuit in the device that resets the device as the power is first applied. This works by using an RC circuit that holds the device in reset as power first comes up. As a little time passes, the RC hits a threshold and the reset is released. However, with this type of an RC circuit, the reset might be missed if there is residual charge in the capacitance used in this circuit. This might happen with repeated power-ups where charge doesn't completely leave the circuit.

    Generally we recommend that the supply be returned to 0V when powering down the device before powering it up again. This way, the power-on-reset circuit starts again properly, so that extra charge that has drained away. It may help to reduce decoupling capacitors attached to supplies. You may want to add resistance to drain the charge away when the supply is powered off.

    I would note that our newer devices have better power-on-reset circuits that would do a better job with repeated power-ups. The ADS1220 is similar to the ADS1226 and has a better power-on-reset circuit.


    Joseph Wu