TPL0102 interface problems

Swanagan Ray

Other Parts Discussed in Thread: INA111

I am trying to use the TPL0102 digital potentiometer as the Rg input to the INA111 instrumentation amplifier to control its gain. The INA111 works well on its own with an external resistor but does not work with the TPL0102. It acts like there is no input. The TPL0102 does output a multimeter measurable resistance but the INA111 does not seem to recognize it as such. What am I doing wrong?

Thanks!

over 9 years ago

0 Joseph Wu over 9 years ago

TI__Guru* 94285 points

Swanigan,

I'm moving this post to the I2C forum. I had to search for it, but there have been other questions of this device posted to this forum.

Joseph Wu

0 Swanagan Ray over 9 years ago

Prodigy 100 points

Also, there is no problem with the I2C bus. I have verified connection and it works fine. I am supplying the INA111 with +-9 V and the TPL0102 with a single supply 5 V.

0 Rajan Arora over 9 years ago in reply to Swanagan Ray

TI__Intellectual 2175 points

Can you post your schematic on how you use TPL0102?

0 Swanagan Ray over 9 years ago in reply to Rajan Arora

Prodigy 100 points

Sure! Sorry for the wait.

Thanks!

0 Rajan Arora over 9 years ago in reply to Swanagan Ray

TI__Intellectual 2175 points

Thanks for the schematic. Are you able to acknowledge from the I2C bus?
Also, what value are you trying to set for the resistor from the table on page 16?

Thanks,
Rajan

0 Swanagan Ray over 9 years ago in reply to Rajan Arora

Prodigy 100 points

I am able to communicate via I2C.
There is no problem getting the device ID or writing to the chip from the microcontroller.
I was setting it for a value of Rhw = 50 kΩ or 0x80 which I could verify using a multimeter.
There was also no problem setting it for other values.
Thanks!
Swanagan

0 Rajan Arora over 9 years ago in reply to Swanagan Ray

TI__Intellectual 2175 points

I do not see any issue with your schematic. Are you setting the registers correctly? Make sure the SHDN bit in ACR register is set to 1. Also the ACR register address is 0x10. In the description on page 10 it is incorrectly mentioned as 0x00.

0 Swanagan Ray over 9 years ago in reply to Rajan Arora

Prodigy 100 points

Thanks for checking! Yes, I am able to do that. Even if it was set to 0 would it give us the problem that we have?

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TPL0102 interface problems