MAX803/MAX809/
MAX810
Benefits of Highly Accurate Reset Threshold
3-Pin Microprocessor Reset Circuits
Most μP supervisor ICs have reset-threshold voltages
between 5% and 10% below the value of nominal supply
voltages. This ensures a reset will
not
occur within 5% of
the nominal supply, but
will
occur when the supply is 10%
below nominal.
When using ICs rated at only the nominal supply ±5%,
this leaves a zone of uncertainty where the supply is
between 5% and 10% low, and where the reset may or
may not be asserted.
The MAX8_ _L/T/Z use highly accurate circuitry to ensure
that reset is asserted close to the 5% limit, and long
before the supply has declined to 10% below nominal.
400
MAXIMUM TRANSIENT DURATION (µs)
320
240
T
A
= +25°C
V
CC
V
CC
V
CC
MAX803
160
MAX8_ _J/L/M
80
0
MAX8_ _R/S/T/Z
1
10
100
1000
GND
RESET
MOTOROLA
68HCXX
RESET
INPUT
µP
GND
RESET COMPARATOR OVERDRIVE, V
TH
- V
CC
(mV)
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset Comparator Overdrive
Figure 3. Interfacing to μPs with Bidirectional Reset I/O
+3.3V
V
CC
+5.0V
MAX809
RESET
R1
100kΩ
V
CC
R
PULLUP
V
CC
MAX803
RESET
5V SYSTEM
RESET
INPUT
GND
Figure 2.
RESET
Valid to V
CC
= Ground Circuit
GND
GND
Figure 4. MAX803 Open-Drain
RESET
Output Allows Use with
Multiple Supplies
www.maximintegrated.com
Maxim Integrated │ 6
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
