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TC70/71
MICROMASTER™ – SYSTEM SUPERVISOR WITH POWER SUPPLY
MONITOR, WATCHDOG AND BATTERY BACKUP
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
2
3
4
5
6
7
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.
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TYPICAL APPLICATIONS
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All Microprocessor-based Systems
Test Equipment
Instrumentation
Set-Top Boxes
FUNCTIONAL BLOCK DIAGRAM
ORDERING INFORMATION
VCC
CEI
(TC70)
VBATT
BATTERY
BACK-UP
CONTROL
VCCO
CEO
(TC70)
PF
(TC71)
Part No.
TC70COA
TC70CPA
TC70EOA
TC70EPA
TC71COA
TC71CPA
TC71EOA
TC71EPA
Package
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
Temp. Range
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
VREF1
WDD
(TC70)
WATCHDOG
TIMER
∆V
DETECTOR
RS
VREF2
DELAY
TIMER
GND
VREF3
TDI
(TC71)
TDO
(TC71)
TC70/71
PIN CONFIGURATIONS
(DIP and SOIC)
VCCO
VCC
GND
CEI
1
2
3
4
8
7
VBATT
RS
WDD
CEO
VCCO
VCC
GND
TDI
1
2
3
4
8
7
VBATT
RS
PF
TDO
TC70
TC71
6
5
6
5
8
TC70/71-1 11/18/96
TELCOM SEMICONDUCTOR, INC.
5-7
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
