
M
Full-Featured μP S upervisory Circ uit with
±1.5% Reset Ac c urac y
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
1
19-0433; Rev 0; 9/95
_______________General Desc ription
The MAX807 microprocessor (μP) supervisory circuit
reduces the complexity and number of components
needed to monitor power-supply and battery-control func-
tions in μP systems. A 70μA supply current makes the
MAX807 ideal for use in portable equipment, while a 2ns
chip-enable propagation delay and 250mA output current
capability (20mA in battery-backup mode) make it suit-
able for larger, higher-performance equipment.
The MAX807 comes in 16-pin DIP and SO packages, and
provides the following functions:
1) μP reset. The active-low RESET output is asserted dur-
ing power-up, power-down, and brownout conditions,
and is guaranteed to be in the correct state for V
CC
down to 1V.
2) Active-high RESET output.
3) Manual-reset input.
4) Two-stage power-fail warning. A separate low-line
comparator compares V
to a threshold 52mV above
the reset threshold. This low-line comparator is more
accurate than those in previous μP supervisors.
5) Backup-battery switchover for CMOS RAM, real-time
clocks, μPs, or other low-power logic.
6) Write protection of CMOS RAM or EEPROM.
7) 2.275V threshold detector—provides for power-fail
warning and low-battery detection, or monitors a
power supply other than +5V.
8) BATT OK status flag indicates that the backup-battery
voltage is above 2.275V.
9) Watchdog-fault output—asserted if the watchdog input
has not been toggled within a preset timeout period.
________________________Applic ations
Computers
Controllers
Intelligent Instruments
Critical μP Power Monitoring
Portable/Battery-Powered Equipment
____________________________Features
o
Precision 4.675V (MAX807L) or 4.425V
(MAX807M), or 4.575V (MAX807N) Voltage
Monitoring
o
200ms Power OK / Reset Time Delay
o
RESET and RESET Outputs
o
Independent Watchdog Timer
o
1μA Standby Current
o
Power Switching:
250mA in V
CC
Mode
20mA in Battery-Backup Mode
o
On-Board Gating of Chip-Enable Signals:
2ns CE Gate Propagation Delay
o
MaxCap and SuperCap Compatible
o
Voltage Monitor for Power-Fail
o
Backup-Battery Monitor
o
Guaranteed RESET Valid to V
CC
= 1V
o
±1.5% Low-line Threshold Accuracy 52mV above
Reset Threshold
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
RESET
RESET
WDO
CE IN
GND
V
CC
OUT
BATT
TOP VIEW
MAX807
CE OUT
WDI
LOW LINE
MR
BATT OK
PFI
PFO
BATT ON
DIP/SO
__________________Pin Configuration
Ordering Information and Typical Operating Circuit appear at end of data sheet.
SuperCap is a trademark of Baknor Industries. MaxCap is a trademark of The Carborundum Corp.