AFE4490SPO2EVM: Relationship between Ambient cancellation Current and LED1 or 2 Ambient

Stephan Scholz

Part Number: AFE4490SPO2EVM
Other Parts Discussed in Thread: AFE4490

Hello all,

i have two little questions about the AFE4490

1: what is the difference between the Ambient cancellation current and the result of the LED1or2 ambient ?

2: question about the working principe of the photodiode in the AFE4490......
i read the FAQ in e2e.ti.com/.../369445 ... but im not sure about the operating principe of the photodiode . the bias is negative. I saw in this Q&A, that the bias for the PD is set by the TIA through negative feedback. For AFE44xx, the TIA sets the PD to a zero differential bias. im not sure what you mean with zero differential bias

thx a lot

over 4 years ago

0 Praveen Aroul over 4 years ago

TI__Mastermind 49906 points

Hi Stephan,

Ambient cancellation current is the current set at the DAC to remove the dc component from the ambient light under high ambient light conditions. This can be estimated by the processor by reading from the led1/led2 ambient registers.

The PD is connected to the AFE in a differential configuration (photovoltaic mode).

The differential TIA sets the same bias at both the anode and cathode pins of the photodiode thus creating the zero differential bias.

0 Stephan Scholz over 4 years ago in reply to Praveen Aroul

Prodigy 120 points

Thank you Praveen,

this solved my problem. Thx a lor

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AFE4490SPO2EVM: Relationship between Ambient cancellation Current and LED1 or 2 Ambient