3-Pin Microprocessor Reset Circuits
39J,AX810LMRST/Z
Selector Guide
TOP MARK
PART/SUFFIX
RESET THRESHOLD (V)
OUTPUT TYPE
SOT
SC70
MAX803L
MAX803M
MAX803T
MAX803S
MAX803R
MAX803Z
MAX809L
MAX809M
MAX809J
MAX809T
MAX809S
MAX809R
MAX809Z
MAX810L
MAX810M
MAX810T
MAX810S
MAX810R
MAX810Z
4.63
4.38
3.08
2.93
2.63
2.32
4.63
4.38
4.00
3.08
2.93
2.63
2.32
4.63
4.38
3.08
2.93
2.63
2.32
OPEN-DRAIN RESET
OPEN-DRAIN RESET
OPEN-DRAIN RESET
OPEN-DRAIN RESET
OPEN-DRAIN RESET
OPEN-DRAIN RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
PUSH-PULL RESET
⎯
⎯
⎯
⎯
⎯
AAZ
ABA
ABB
ABC
ABD
ABE
AAN
AAO
⎯
AAP
AAQ
AAR
AAS
AAT
AAU
AAV
AAX
AAW
AAY
⎯
AAAA
ABAA
CWAA
ACAA
ADAA
AFAA
⎯
AGAA
AHAA
AJAA
AKAA
ALAA
⎯
Detailed Description
Applications Information
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX803/MAX809/MAX810 assert
reset to prevent code-execution errors during power-
up, power-down, or brownout conditions. They assert a
Negative-Going V
Transients
CC
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX803/
MAX809/MAX810 are relatively immune to short-duration
reset signal whenever the V
supply voltage declines
CC
negative-going V transients (glitches).
CC
below a preset threshold, keeping it asserted for at
least 140ms after V has risen above the reset thresh-
Figure 1 shows typical transient duration vs. reset com-
parator overdrive, for which the MAX803/MAX809/
MAX810 do not generate a reset pulse. The graph was
CC
old. The MAX803 uses an open-drain output, and the
MAX809/MAX810 have a push-pull output stage.
Connect a pullup resistor on the MAX803’s RESET out-
put to any supply between 0 and 6V.
generated using a negative-going pulse applied to V
,
CC
starting 0.5V above the actual reset threshold and end-
ing below it by the magnitude indicated (reset compara-
tor overdrive). The graph indicates the maximum pulse
Pin Description
width a negative-going V
transient can have without
CC
PIN
NAME
FUNCTION
causing a reset pulse. As the magnitude of the transient
increases (goes farther below the reset threshold), the
maximum allowable pulse width decreases. Typically, for
1
GND
Ground
RESET Output remains low while V
is below the reset threshold, and for at
CC
RESET
(MAX803/
MAX809)
the MAX8__L and MAX8__M, a V
transient that goes
CC
100mV below the reset threshold and lasts 20µs or less
will not cause a reset pulse. A 0.1µF bypass capacitor
least 140ms after V
reset threshold.
rises above the
CC
2
3
mounted as close as possible to the V
additional transient immunity.
pin provides
CC
RESET Output remains high while V
is below the reset threshold, and for at
CC
RESET
(MAX810)
least 140ms after V
rises above the
CC
Ensuring a Valid Reset Output
Down to V = 0V
falls below 1V, the MAX809 RESET output
reset threshold.
CC
Supply Voltage (+5V, +3.3V, +3.0V, or
+2.5V)
When V
CC
V
CC
no longer sinks current—it becomes an open circuit.
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