5-7
TELCOM SEMICONDUCTOR, INC.
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6
5
4
3
1
2
8
TC70/71
MICROMASTER – SYSTEM SUPERVISOR WITH POWER SUPPLY
MONITOR, WATCHDOG AND BATTERY BACKUP
VCC
VCCO
VBATT
TC70/71
CEI
(TC70)
V
DETECTOR
WATCHDOG
TIMER
WDD
(TC70)
CEO
(TC70)
TDO
(TC71)
VREF1
VREF2
VREF3
PF
(TC71)
TDI
(TC71)
RS
BATTERY
BACK-UP
CONTROL
DELAY
TIMER
GND
PIN CONFIGURATIONS
(DIP and SOIC)
1
8
2
7
3
6
4
5
TC70
1
8
2
7
3
6
4
5
TC71
CEO
VCCO
GND
CEI
VCC
VCCO
GND
TDI
VCC
WDD
VBATT
RS
TDO
PF
VBATT
RS
ORDERING INFORMATION
Part No.
Package
Temp. Range
T
C70COA
TC70CPA
TC70EOA
TC70EPA
T
C71COA
TC71CPA
TC71EOA
TC71EPA
8-Pin SOIC
8-Pin Plastic DIP
8-Pin SOIC
8-Pin Plastic DIP
8-Pin SOIC
8-Pin Plastic DIP
8-Pin SOIC
8-Pin Plastic DIP
0
°
C to +70
°
C
0
°
C to +70
°
C
– 40
°
C to +85
°
C
– 40
°
C to +85
°
C
0
°
C to +70
°
C
0
°
C to +70
°
C
– 40
°
C to +85
°
C
– 40
°
C to +85
°
C
FUNCTIONAL BLOCK DIAGRAM
FEATURES
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Maximum Functional Integration: Precision Power
Supply Monitor, Watchdog Timer, External RESET
Override, Threshold Detector and Battery Backup
Controller in an 8-Pin Package
Generates Power-on RESET and Guards Against
Unstable Processor Operation Resulting from
Power "Brown-out"
Automatically Halts and Restarts an Out-of-
Control Microprocessor
Output Can be Wire-ORed, or Hooked to Manual
RESET Pushbutton Switch
Watchdog Disable Pin for Easier Prototyping
(TC70)
Voltage Monitor for Power Fail or Low Battery
Warning (TC71)
Available in 8-Pin Plastic DIP or 8-Pin SOIC
Packages
Cost Effective
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TYPICAL APPLICATIONS
I
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I
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All Microprocessor-based Systems
Test Equipment
Instrumentation
Set-Top Boxes
GENERAL DESCRIPTION
The TC70/71 is a fully-integrated power supply monitor,
watchdog and battery backup circuit in a space-saving
8-pin package.
When power is initially applied, the TC70/71 holds the
processor in its reset state for a minimum of 500msec after
V
CC
is in tolerance to ensure stable system start-up. After
start-up, processor sanity is monitored by the on-board
watchdog circuit. The processor must provide periodic high-
to-low level transitions to the TC70/71 to verify proper
execution. Should the processor fail to supply this signal
within the specified timeout period, an out-of-control proces-
sor is indicated and the TC70/71 issues a momentary
processor reset as a result. The TC70 also features a
watchdog disable pin to facilitate system test and debug.
The output of the TC70/71 can be wire-ORed to a push-
button switch (or electronic signal) to reset the processor.
When connected to a push-button switch, the TC70/71
provides contact debounce.
The integrated battery backup circuit on-board the TC70/
71 converts CMOS RAM into nonvolatile memory by first
write-protecting, then switching the V
CC
line of the RAM over
to an external battery.
The TC71 incorporates an additional 1.3V threshold
detector for power fail warning, low battery detection or to
monitor power supply voltages other than +5V.
TC70/71-1 11/18/96