Analog Coprocessor Use PGA component as inverted PGA

[MiNe_85951]

Hi,

We would like to use the PGA component of analog coprocessor as an inverted PGA.

With the above configuration, no error occurs in build.

(1)

Is this usage possible?

(2)

If it is usable, it is necessary to know the internal resistance value in order to know the input impedance.

I confirm for the data sheet and TRM, but the resistance is not listed.

Is it possible to tell us the resistance value?

(3)

I think the frequency characteristics will deteriorate depending on the resistance value.
Are there any other concerns about using it as an inverted PGA?

Regards,

[Vasanth · Accepted solution]

Hello Masashi san,

1)This is not an advisable configuration due the obvious set backs. As the input is connected to the resistor divider input resistance will be less. With the reference connected the output swing is also limited with the opamp connected.

2) Rin can vary approximately from 192kohm to 6 kohm (not guaranteed) .

Best Regards,
Vasanth

[MiNe_85951]

Vasanth-san,

Thank you for your reply.

We don't use it as an inverting PGA.

Regards,

[Vasanth]

Hello Masashi san,

Additional to the previous answer, routing resistance from pin to PGA will affect accuracy. Regarding third question GBW is unaffected.

Best Regards,
Vasanth R S

[MiNe_85951]

Vasanth-san,

Vref(Negative input) of PGA is connected to amplifier output.
For Vin(positive input) of PGA, input a reference voltage divided by an external resistor.

We are considering the above configuration.
Do you think this configuration can be used without any problems?

Regards,

[Vasanth]

Hello Masashi san,

This configuration should be work as expected. Again the routing resistance from pin to PGA will affect accuracy as mentioned earlier.

Best Regards,
Vasanth