TPS3606-33 Datasheet, PDF (6/18 Pages) Texas Instruments – BATTERY-BACKUP SUPERVISOR FOR LOW-POWER PROCESSORS

TPS3606Ć33
BATTERYĆBACKUP SUPERVISOR FOR LOWĆPOWER PROCESSORS
SLVS335C − DECEMBER 2000 − REVISED JANUARY 2007
detailed description (continued)
manual switchover (MSWITCH)
While operating in the normal mode from V_DD, the device can be manually forced to operate in the
battery-backup mode by connecting MSWITCH to V_DD. The table below shows the different 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 not only important to supervise the supply voltage, it is also
important to ensure the 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 the DSP has to toggle the watchdog input
within typically 0.8 s to avoid a time-out from occurring. 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 momentarily
pulses high, resetting the watchdog counter. For minimum watchdog input current (minimum overall power
consumption), leave WDI low for the majority of the watchdog time-out period, pulsing it 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 time-out 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 1. Watchdog Timing
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