JAJSHI3C March 2019 – October 2019 TPS23881
COMMAND = 3Ch with 2 Data Byte, (LSByte First, MSByte second), Read Only
|LEGEND: R/W = Read/Write; R = Read only; -n = value after reset|
|13-0||In_13- In_0||R||0||Bit Descriptions: Data conversion result. The I2C data transmission is a 2-byte transfer.
Note that the conversion is done using a TI proprietary multi-slope integrating converter.
14-bit Data conversion result of current for channel n. The update rate is around once per 100 ms in powered state.
The equation defining the current measured is:
I = N × ISTEP
Where ISTEP is defined below as well as the full scale value, according to the operating mode:
|Mode||Full Scale Value||ISTEP|
|Powered and Classification||1.46 A (with 0.200-Ω Rsense)||89.5 µA|
|Note: in any of the following cases, the result through I2C interface is automatically 0000
channel is in OFF mode
channel is OFF while in semiauto mode and detect/class is not enabled
channel is OFF while in semiauto mode and detection result is incorrect
In diagnostic/manual mode, if detect/class has been enabled at least once, the register retains the result of the last measurement
1.46A is the theoretical full scale range of the ADC based on 14bits * Istep. However, due to the 1.25A channel current limit, the channel current will foldback and be disabled when the current exceeds the ILIM-2X threshold (VLIM2X).
For 4-Pair wired ports, these registers still only provide the individual per channel current measurements. The value from both channels need to be added together in order to get the total 4-pair port current reading.
Class Current Reading
Following the completion of any classification measurement on a channel, the measured classification current is reported in these registers until either a port current reading is completed following a port turn on or the port is disabled.
Only the current measurement for the last classification finger is reported. Thus, for a single signature Class 5, 6, 7, and 8 PDs, the reported classification current will report a Class 0, 1, 2, & 3 current level respectively.
The scaling factor for the class current reading is decreased by a factor of 10x to 8.95uA/bit.