The NRES pin drives the reset of the primary system MCU or DSP. This pin must keep the primary MCU or DSP and peripheral devices in a defined state during power up and power down when the supply voltages are out of range
or a critical failure is detected. Therefore, the NRES pin is always held at a low level when the NRES pin is asserted even if the VIN supply decreases to less than the NPOR voltage threshold (VIN_POR_F) or if the device is in
the OFF state. The NRES pin is an open-drain output with an internal pullup resistor. The NRES pin is driven low when any of the NRES conditions are met. These conditions are defined
as follows:
NPOR event
The device power-on reset occurs with each device power-up from the OFF state. It is the master reset source that initializes the complete device.
Device is in OFF state
Any time the device enters the OFF state.
Device is in RESET state
Any time the device enters the RESET state.
BUCK1 undervoltage event
This event occurs when the BUCK1 output voltage is less than its UV-threshold level.
BUCK2 undervoltage event
This event occurs when the BUCK2 output voltage is less than its UV-threshold level. The BUCK2 UV event must be enabled as a global RESET state event.
BOOST undervoltage event
This event occurs when the BOOST output voltage is less than its UV-threshold level. The BOOST UV event must be enabled as a global RESET state event.
External VMON1 and VMON2 undervoltage event
This event occurs when the monitored voltage of the external VMON1 or VMON2 is less than its UV-threshold level. The external VMON1 UV event and the external VMON2 UV event must be enabled as a global RESET state event.
BUCK1 overvoltage event
This event occurs when the BUCK1 output voltage is greater than its OV-threshold level. The BUCK1 OV event must be enabled as a global RESET state event.
BUCK2 overvoltage event
This event occurs when the BUCK2 output voltage is greater than its OV-threshold level. The BUCK2 OV event must be enabled as a global RESET state event.
BOOST overvoltage event
This event occurs when the BOOST output voltage is greater than its OV-threshold level. The BOOST OV event must be enabled as a global RESET state event.
External VMON1 and VMON2 overvoltage event
This event occurs when the monitored voltage of the external VMON1 or VMON2 is greater than its OV-threshold level. The external VMON1 OV event and the external VMON2 OV event must be enabled as a global RESET state event.
MCU watchdog reset
This event occurs when the WD failure counter is greater than the RESET state threshold value of the programmed WD-failure counter while WD reset is enabled.
MCU ESM error reset
This event occurs when the MCU ESM failure counter is greater than the RESET state threshold value of the programmed MCU ESM failure counter while MCU ESM reset is enabled.
MCU SW reset request
This event occurs when the MCU sends a SPI SW reset command.
MCU warm reset
This event occurs when the NRES pin driven low by the external MCU (the nRES_IN bit is set to 0b, the nRES_OUT bit is set to 1b, and the NRES_ERR_RST_EN bit is set to 1b).
The TPS65313-Q1 device keeps the NRES pin low for the
programmed delay time (the RESET extension time) after all reset conditions are removed. The NRES_EXT[1:0] bits in DEV_CFG4 configuration register set the programmable reset-extension time.
The error detection circuit for NRES driver compares the external logic level on the output of NRES pin input buffer (nRES_IN) against the logic level on the input of the NRES pin output
buffer (nRES_OUT). If a mismatch between the output of the NRES pin input buffer (nRES_IN) and the input of the NRES pin output buffer (nRES_OUT) logic levels is detected, the NRES_ERR status bit in the SAFETY_ERR_STAT1 register is
set. The result of a detected mismatch is configured by the NRES_ERR_RST_EN bit and NRES_ERR_SAFE_EN bit in the SAFETY_CFG2 register.
In the DIAGNOSTIC state, the system MCU can run the diagnostics on the error detection circuit for the NRES driver if the system MCU can externally control the NRES pin interconnect.
Note:
The system MCU can only externally control the NRES pin interconnect if the system MCU has a single bi-direction pin used as power-on reset input and warm reset output.
The sequence to perform diagnostics on the error detection circuit for the NRES driver is as follows:
- Force the NRES pin low externally and confirm that the NRES_ERR status bit is set while the device stays in the DIAGNOSTIC state, and when both the NRES_ERR_RST_EN and NRES_ERR_SAFE_EN bits are cleared.
- Force the NRES pin low externally and confirm that the NRES_ERR status bit is set while the device goes into the SAFE state, when the NRES_ERR_RST_EN is cleared, and while the NRES_ERR_SAFE_EN bit is set.