JAJSMF5B september 2022 – june 2023 TPS25990
PRODUCTION DATA
VIN_UV_FLT is a standard PMBus® command for configuring or reading an 8-bit threshold for the input undervoltage fault detection. This command uses the PMBus® DIRECT format. When reading and writing to this register, use the coefficients shown in Table 8-67, Equation 19, and Equation 20 to convert between the real world units and hexadecimal values.
This command uses the PMBus® read or write word protocol.
Contents of this register are compared to the VIN ADC telemetry value. Once the input voltage has fallen below the undervoltage fault threshold, the output is turned off, and the VIN_UV_FLT flags are set in the respective registers. The SMBA# signal is asserted. 250 mV (typical) of hysteresis is added to the value in this register. This is to provide the rising threshold the input voltage must rise above for this fault to clear. Once the input voltage rises above the rising threshold, the output is turned back on. However, the fault flags and alerts remain until cleared by the host by sending the CLEAR_FAULTS command.
Bit | Name | Description | Minimum Value | Maximum Value | Default Value | Access |
---|---|---|---|---|---|---|
15:0 | VIN_UV_FLT | Input undervoltage fault threshold | 0x0000 (0 V) | 0x00FF (19.42 V) | 0x008Dh (10.74 V) | Read/Write |
When an input undervoltage fault is detected, the device:
sets the FET_OFF, VIN_UV_FLT, and NONE_OF_THE_ABOVE/UNKNOWN bits in the STATUS_BYTE register
sets the OUT_STATUS, INPUT_STATUS, PGOODB, and NONE_OF_THE_ABOVE/UNKNOWN bits in the upper byte of the STATUS_WORD register
sets the VOUT_UV_WARN bit in the STATUS_OUT register
sets the VIN_UV_FLT bit in the STATUS_INPUT register
sets the PGOODB bit in the STATUS_MFR_SPECIFIC_2 register
notifies the host by asserting SMBA#, if it is not masked setting the STATUS_IN, PGOODB, and STATUS_OUT bits in the ALERT_MASK register and the GPIO4 pin is configured as SMBA# Output in the GPIO_CONFIG_34 register
deasserts the external PGOOD signal, if the GPIO1 pin is configured as PGOOD output in the GPIO_CONFIG_12 register
A write command to this register should be preceded by the MFR_WRITE_PROTECT command to unlock the device first to prevent accidental accidental/spurious writes.