LM98640QML-SP: voltage divider at input and current leakage impact

Thibaut Deceuleneer

Part Number: LM98640QML-SP

Hello,

In one of our camera application, we would like to use the LM98640. The output sensor voltage is single-ended and supplied with +5V. Therefore, we need to implement a voltage divider with two 100Ohm resistors covered by an amplifier between the sensor and the AFE (see diagram). We are wondering if there would be a problem to connect the AFE input to the divider considering the sample and hold input leakage of the AFE ? Is this current leakage happening during the sample phase ?

Kind regards,

Thibaut

over 3 years ago

0 Thibaut Deceuleneer over 3 years ago

Prodigy 90 points

0 Praveen Aroul over 3 years ago in reply to Thibaut Deceuleneer

TI__Mastermind 49146 points

Hi Thibaut,

Typically the voltage divider method is used frequently in the consumer CCD imaging space to bias the AFE inputs when operating in CDS mode. In these cases the bias impedance is fairly high kOhms compared to the impedance of the signal at the output of the emitter follower on the CCD output signal.

The resistor divider bias is not recommended for S/H mode. In those cases, it is better to use clamping to some voltage (if AC coupled) or even DC coupling for CIS sensor applications where the sensor OS voltage is low enough to be useful directly.

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LM98640QML-SP: voltage divider at input and current leakage impact