MAX792 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – Microprocessor and Non-Volatile Memory Supervisory Circuits

19-0147; Rev. 2; 6/98
Microprocessor and Non-Volatile
Memory Supervisory Circuits
General Description
The MAX792/MAX820 microprocessor (µP) supervisory
circuits provide the most functions for power-supply
and watchdog monitoring in systems without battery
backup. Built-in features include the following:
1) µP reset: Assertion of RESET and RESET outputs dur-
ing power-up, power-down, and brownout condi-
tions. RESET is guaranteed valid for V_CC down to 1V.
2) Manual-reset input.
3) Two-stage power-fail warning: A separate low-line
comparator compares V_CC to a preset threshold
120mV above the reset threshold; the low-line and
reset thresholds can be programmed externally.
4) Watchdog fault output: Assertion of WDO if the watch-
dog input is not toggled within a preset timeout
period.
5) Pulsed watchdog output: Advance warning of
impending WDO assertion from watchdog timeout
that causes hardware shutdown.
6) Write protection of CMOS RAM, EEPROM, or other
memory devices.
The MAX792 and MAX820 are identical, except the
MAX820 guarantees higher low-line and reset threshold
accuracy (±2%).
Applications
Computers
Controllers
Intelligent Instruments
Critical µP Power Monitoring
Features
o Manual-Reset Input
o 200ms Power-OK / Reset Time Delay
o Independent Watchdog Timer—Preset or Adjustable
o On-Board Gating of Chip-Enable Signals
o Memory Write-Cycle Completion
o 10ns (max) Chip-Enable Gate Propagation Delay
o Voltage Monitor for Overvoltage Warning
o ±2% Reset and Low-Line Threshold Accuracy
(MAX820, external programming mode)
Ordering Information
PART**
TEMP. RANGE
PIN-PACKAGE
MAX792_CPE
0°C to +70°C
16 Plastic DIP
MAX792_CSE
0°C to +70°C
16 Narrow SO
MAX792_C/D
0°C to +70°C
Dice*
Ordering Information continued at end of data sheet.
* Dice are tested at T_A = +25°C, DC parameters only.
**These parts offer a choice of five different reset threshold volt-
ages. Select the letter corresponding to the desired nominal
reset threshold voltage and insert it into the blank to complete the
part number.
SUFFIX
RESET THRESHOLD (V)
L
4.62
M
4.37
T
3.06
S
2.91
R
2.61
Typical Operating Circuit
V_CC
3
0.1µF
V_CC
V_CC
4
CE OUT
RESET IN/INT
13
MAX792
5 _LLIN/
14
CE IN
REFOUT
OVO ⁶
ADDRESS
DECODER
µP
RAM
A0-A15
7 _OVI
LOW LINE ¹⁰
RESET ¹
NMI
RESET
8 _SWT
MR ⁹
GND
GND
12
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