Datasheet

Benets of Highly Accurate Reset Threshold
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.
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset Comparator Overdrive
Figure 3. Interfacing to μPs with Bidirectional Reset I/O
Figure 2. RESET Valid to V
CC
= Ground Circuit
Figure 4. MAX803 Open-Drain RESET Output Allows Use with
Multiple Supplies
400
320
0
1 100 1000
160
80
240
RESET COMPARATOR OVERDRIVE, V
TH
- V
CC
(mV)
MAXIMUM TRANSIENT DURATION (µs)
10
T
A
= +25°C
MAX8_ _J/L/M
MAX8_ _R/S/T/Z
RESET
GND
RESET
INPUT
MAX803
MOTOROLA
68HCXX
µP
GND
V
CC
V
CC
V
CC
R1
100kΩ
V
CC
GND
MAX809
RESET
RESET
GND
RESET
INPUT
R
PULLUP
MAX803
5V SYSTEM
GND
V
CC
+3.3V
+5.0V
V
CC
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
www.maximintegrated.com
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