OPA2374: How important is the buffer in this circuit?

Lucas Schulte9

Part Number: OPA2374
Other Parts Discussed in Thread: BOOSTXL-DRV8301, LM7705

This is the external current sense circuit from the BOOSTXL-DRV8301. How important is the buffer for the 1.5V coming off of the voltage divider? Mainly I would like to see if a single channel op amp could be used rather than the dual channel.

over 4 years ago

0 Lucas Schulte9 over 4 years ago

TI__Expert 6955 points

Correction : 1.65V from the voltage divider.

0 Michael Steffes over 4 years ago in reply to Lucas Schulte9

Guru 48205 points

If you look at the divider from that DC output, it is probably trying to hold the output of the diff stage above ground as no op amp can swing to ground completley - if so, your other option is to use the LM7705 as a negative supply (can be shared among multiple channels) and get rid of the DC level shift positive through that buffer.

0 Former Member over 4 years ago in reply to Lucas Schulte9

Hello Lucas,

The buffer prevents the input non-inverting input of the amplifier from seeing the equivalent resistance of the voltage divider. The voltage divider and buffer look to be setting the DC offset.

Also, 2.2uF at the output of the buffer is quite significant. Given that their is no stability compensation here, this may very well cause stability issues for the buffer.

Regards,

Daniel

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OPA2374: How important is the buffer in this circuit?