JAJSC25I March 2014 – July 2019 TPS23861
PRODUCTION DATA.
Command = 6Eh with 2 Data Byte (LSByte first, MSByte second), Read
LSB: 6Eh
BITS | D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |
---|---|---|---|---|---|---|---|---|
BIT NAME | Port 4 Voltage Difference [7:0] | |||||||
RESET or POR VALUE | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
MSB: 6Fh
BITS | D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |
---|---|---|---|---|---|---|---|---|
BIT NAME | VDS4[3:0] | Port 4 Voltage Difference [11:8] | ||||||
RESET or POR VALUE | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
This register is used to determine the presence of a legacy PD by measuring the PD input capacitance on the PI. A charge is injected into the PI, and the resulting Δv is reported. The Δv value shown is useable only if VDSn[3:0] = 0001.
The I2C data transmission is a 2-byte transfer.
Bit Descriptions
Port n Voltage Difference[11:0]: 12-bit data conversion result of the difference in voltage on the port as a result of a fixed charge injected into the port. The equation defining the resistance measured is:
where
NOTE
The expression for port capacitance ignores the effect of any conductance in parallel with the capacitance being measured. The effect of parallel conductance is to give a higher value than the actual value of any capacitance present.
USEABLE CAPACITANCE RANGE | VOLTAGE DIFFERENCE LSB VALUE |
---|---|
10 to 100 µF | 4.884 mV |
VDSn[3:0]: Most recent detect voltage difference result status on Port n. If “0001” state, the 12-bit Δv value is useable.
This measurement is made on a port if legacy detect is enabled using the Legacy Detect Mode Register.
VDSn is set to the Power-On Reset State (0000b) when legacy detection is enabled until a Δv measurement is made.
The detection result is maintained in the register in any operating mode following the measurement.
The selection is as following:
VDSn[3:0] | VOLTAGE-DIFFERENCE MEASUREMENT STATUS |
---|---|
0000 | Power-on reset |
0001 | Valid measurement |
0010 | Unable to discharge PD input capacitance to 2.4 V before timeout |
0011 | Unable to achieve 0.4V to take first measurement before timeout |
0100 | First measurement exceeds VDet-clamp (min) |
0101 | Second measurement exceeds VDet-clamp (min) |
0110 | ΔV < 0.5 V (insufficient signal) |