Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- PACKAGE AND ORDERING INFORMATION
- ABSOLUTE MAXIMUM RATINGS
- RECOMMENDED OPERATING CONDITIONS Pull-up resistor value to ROC table for RESET the Pull-up resistor value row in the ROC table
- ELECTRICAL CHARACTERISTICS
- TIMING REQUIREMENTS
- SWITCHING CHARACTERISTICS
- PIN CONFIGURATIONS
- TYPICAL CHARACTERISTICS
- DETAILED DESCRIPTION
- REVISION HISTORY
WDI
WDR
WDT
GND
TPS3813
I/O
GND
Position 1
Position 2
Position 3
Position 5
Position 4
R1
R2
(1)
mC
C
(ext)
V
DD
V
DD
V
DD
0.1 Fm
0.1 Fm
V
DD
V
DD
RESET
RESET
TPS3813J25, TPS3813L30
TPS3813K33, TPS3813I50
SLVS331G –DECEMBER 2000–REVISED OCTOBER 2013
www.ti.com
APPLICATION EXAMPLE
A typical application example (see Figure 8) is used to describe the function of the watchdog in more detail.
To configure the window watchdog function, two pins are provided by the TPS3813. These pins set the window
timeout and ratio.
The window watchdog ratio is a fixed ratio, which determines the lower boundary of the window frame. It can be
configured in two different frame sizes.
If the window watchdog ratio pin (WDR) is set to V
DD
, Position 1 in Figure 8, then the lower window frame is a
value based on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT)
connected to GND, it is a ratio of 1:124.9, for WDT connected to V
DD
, it is a ratio of 1:127.7, and for an external
capacitor connected to WDT, it is a ratio of 1:64.5.
If the window watchdog ratio pin (WDR) is set to GND, Position 2, the lower window frame will be a value based
on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT) connected to GND,
it will be a ratio of 1:31.8, for WDT connected to V
DD
it will be 1:32, and for an external capacitor connected to
WDT it will be 1:25.8.
The watchdog timeout can be set in two fixed timings of 0.25 seconds and 2.5 seconds for the window or can by
programmed by connecting a external capacitor with a low leakage current at WDT.
Example: If the watchdog timeout pin (WDT) is connected to V
DD
, the timeout will be 2.5 seconds. If the window
watchdog ratio pin (WDR) is set in this configuration to a ratio of 1:127.7 by connecting the pin to V
DD
, the lower
boundary is 19.6 ms.
(1) Use this pull-down resistor if a GPIO pin is used to drive the WDI input pin of the TPS3813 to keep the WDI pin from
floating during power-up.
Figure 8. Application Example
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