SLVSF02D March 2019 – May 2020 TPS23881
To eliminate the possibility of false detection, the TPS23881 uses a TI proprietary 4-point detection method to determine the signature resistance of the PD device. A false detection of a valid 25-kΩ signature can occur with 2-point detection type PSEs in noisy environments or if the load is highly capacitive.
Detection 1 and Detection 2 are merged into a single detection function which is repeated. Detection 1 applies I1 (160 μA) to a channel, waits approximately 60 ms, then measures the channel voltage (V1) with the integrating ADC. Detection 2 then applies I2 (270 μA) to the channel, waits another approximately 60 ms, then measures the channel voltage again (V2). The process is then repeated a second time to capture a third (V3) and fourth (V4) channel voltage measurements. Multiple comparisons and calculations are performed on all four measurement point combinations to eliminate the effects of a nonlinear or hysteretic PD signature. The resulting channel signature is then sorted into the appropriate category.
The detection resistance measurement result is also available in the Channel Detect Resistance registers (0x44 - 0x47).