SLUSFQ1A December 2024 – December 2024 BQ41Z90
ADVANCE INFORMATION
Refer to the PDF data sheet for device specific package drawings
The BQ41Z90 device can be reset through several hardware methods including a Power-On-Reset (POR), Windowed Watchdog timer (WWDT) initiated reset, optional FLASH DED initiated reset, security violation initiated reset and CPU initiated reset. The device can also be triggered to MCU reset or Power-On-Reset through an external pin assertion (see the description in the next section). Through communications from the host the device can also be configured into reset if the application firmware on the device is programmed to allow this and is operational, for example: the use of a ManufacturerAccess( ) command to trigger an MCU power cycle.
| Reset Type | Blocks Reset | ||||||
|---|---|---|---|---|---|---|---|
| CPU | MCU DieDigital | RAM | Communications | Diagnostics Registers on MCU (2) | Diagnostics Registers on AFE(3) | AFE | |
| POR | X | X | X | X | X | X | X |
| MCU | X | X | X | X | |||
| WWDT | X | ||||||
| Communications(1) | X | X | X | X | X | X | |
The AFE enters power-on reset when the voltage at VREG18 falls below VREG18POR– which is typically triggered by voltage at both BAT and VCC pins being removed. The device exits reset when VREG18 rises above VREG18POR– + VHYS for tRST time.
In the event of a power-cycle, the BQ41Z90 AFE will hold its internal RESET output pin high for tRST_POR duration to allow its on-chip trim to load and the integrated 1.8 V LDO, 1.35 V LDO and LFO to stabilize before releasing the MCU die from its reset.
When the MCU die is released from reset it will power up and perform some limited trim loading and then enable the CPU. The time from when power is applied until this stage is tRST_ROM.
Once the CPU boots up and the ROM initialization code has run then the flash code can begin to execute. The time from when power is applied until this stage is tRST_EXE.
The MCU Reset can be triggered by the WWDT, CPU, Security violation or optional Flash DED
This is on the MCU and doesn't influence the AFE. This resets everything related to the CPU.
This is on the MCU and doesn't influence the AFE. This resets everything in the MCU other than the RESET_REASON register which indicates that the WWDT triggered the RESET and the USER_DATA register.
The MCU of the BQ41Z90 can be reset through a command to the AFE. If activated then the AFE will cycle power to the MCU by disabling and then enabling the REG135 regulator output of the AFE.