TPS3610U18 Datasheet, PDF (10/26 Pages) Texas Instruments – BATTERY-BACKUP SUPERVISORS FOR RAM RETENTION

TPS3610U18, TPS3610T50
BATTERYĆBACKUP SUPERVISORS FOR RAM RETENTION
SLVS327B – DECEMBER 2000 – REVISED DECEMBER 2002
detailed description (continued)
manual switchover (MSWITCH)
While operating in the normal mode from V_DD, the device can be forced manually to operate in battery-backup
mode by connecting MSWITCH to V_DD. Refer to Table 1 for different switchover modes.
Table 1. Switchover Modes
VDD mode
Battery-backup mode
MSWITCH
GND
VDD
GND
VDD
STATUS
VDD mode
Switch to battery-backup mode
Battery-backup mode
Battery-backup mode
If the manual switchover feature is not used, MSWITCH must be connected to ground.
watchdog
In a microprocessor- or DSP-based system, it is important not only to supervise the supply voltage, but also to
ensure correct program execution. The task of a watchdog is to ensure that the program is not stalled in an
indefinite loop. The microprocessor, microcontroller or DSP has to toggle the watchdog input within typically
0.8 s to avoid the occurence of a time-out. Either a low-to-high or a high-to-low transition resets the internal
watchdog timer. If the input is unconnected, the watchdog is disabled and is retriggered internally.
saving current while using the watchdog
The watchdog input is internally driven low during the first 7/8 of the watchdog time-out period, then the input
momentarily pulses high, resetting the watchdog counter. For minimum watchdog input current (minimum
overall power consumption), WDI should be left low for the majority of the watchdog time-out period, and pulsed
low-high-low once within 7/8 of the watchdog time-out period to reset the watchdog timer. If instead WDI is
externally driven high for the majority of the timeout period, a current of, e.g., 5 V/40 kΩ ≈ 125 µA, can flow into
WDI.
VOUT
VIT
WDI
t(tout)
RESET
td
td
td
Undefined
Figure 5. Watchdog Timing
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