AFE4300 Electrode Sharing with another device - Impedance Matching

stomp

Other Parts Discussed in Thread: AFE4300

Hi,

So I have an AFE4300 device (actually were using the AFE4300_EVM board). I would like to share the VSense electrodes with another TI AFE device.

However it looks like the AFE4300 has a an input impedance many orders of magnitude lower than the other TI AFE device. When the two are connected together, the second TI AFE input signal is too low for it to function.

The AFE4300_EVM has provision for some additional op-amps in the Vsense path.

Could anyone tell me if the additional op-amps on the AFE4300_EVM are for the purposes of electrode sharing, or is there another way I could overcome this issue.

Thanks

Stomp!

over 8 years ago

0 Praveen Aroul over 8 years ago

TI__Mastermind 49906 points

Hello Stomp,

Safest way would be to have external switches from the electrode pair to each path. That way, the input circuity and connections of either measurement path can be turned off when the other one is being used.

0 stomp over 8 years ago in reply to Praveen Aroul

Genius 4675 points

Thanks Praveen,

We need to take both measurements from both AFE's simultaneously.

Could you please describe the function of the spare op-amp circuits fitted to the AFE4300_EVM?

Thanks.

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AFE4300 Electrode Sharing with another device - Impedance Matching