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SGLS273B – OCTOBER 2004 – REVISED MARCH 2009
MICROPROCESSOR SUPERVISOR WITH WATCHDOG TIMER
1
FEATURES
Qualified for Automotive Applications
Fully Programmable Reset Threshold
Fully Programmable Reset Period
Fully Programmable Watchdog Period
•
•
•
•
2% Accurate Reset Threshold
Input Voltage Down to 2 V
Input 18-µA Maximum Input Current
Reset Valid Down to 1 V
•
•
•
•
DESCRIPTION
The UCC2946 is designed to provide accurate microprocessor supervision, including reset and watchdog
functions. During power up, the device asserts a reset signal RES with VDD as low as 1 V. The reset signal
remains asserted until the VDD voltage rises and remains above the reset threshold for the reset period. Both
reset threshold and reset period are programmable by the user.
The UCC2946 is also resistant to glitches on the VDD line. Once RES has been deasserted, any drops below
the threshold voltage need to be of certain time duration and voltage magnitude to generate a reset signal.
These values are shown in
An I/O line of the microprocessor may be tied to the watchdog input (WDI)
for watchdog functions. If the I/O line is not toggled within a set watchdog period, programmable by the user,
WDO is asserted. The watchdog function is disabled during reset conditions.
The UCC2946 is available in 8-pin TSSOP (PW) package to optimize board space.
VDD
8
400 nA
RP
4
+
1.235 V
+
RTH 2
WP
6
+
100 mV
+
WATCHDOG
TIMING
WDI
7
EDGE DETECT
POWER TO
CIRCUITRY
+
S
R
Q
POWER ON RESET
Q
Q
Q
400 nA
+
S
R
8−BIT
COUNTER
A3
A2
CLR A1
A0
CLK
S
R
Q
5 WDO
Q
3 RES
1.235 V
+
1 GND
UDG−02192
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004–2009, Texas Instruments Incorporated
TI [ TEXAS INSTRUMENTS ]
