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MAX803SEXR+T

P1-P3P4-P6P7-P8
MAX803/MAX809/MAX810
3-Pin Microprocessor Reset Circuits
4
Maxim Integrated
225
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
245
250
MAX803-TOC5
TEMPERATURE (°C)
POWER-UP RESET TIMEOUT (ms)
235
230
240
-40
85
20
-20
0
60
40
MAX8_ _R/S/T/Z
MAX8_ _J/L/M
0.997
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
1.001
1.002
1.003
MAX803-TOC6
TEMPERATURE (°C)
NORMALIZED THRESHOLD
0.999
0.998
1.000
-40
85
20
-20
0
60
40
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _J/L/M)
80
100
120
140
MAX803-TOC4
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
40
20
60
-40
85
20
-20
0
60
40
V
OD
= V
TH
- V
CC
V
OD
= 10mV
V
OD
= 100mV
V
OD
= 200mV
V
OD
= 20mV
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _R/S/T/Z)
80
100
MAX803-TOC3
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
40
20
60
-40
85
20
-20
0
60
40
V
OD
= V
TH
- V
CC
V
OD
= 20mV
V
OD
= 10mV
V
OD
= 200mV
V
OD
= 100mV
Typical Operating Characteristics
(V
CC
= full range, T
A
= -40°C to +105°C, unless otherwise noted. Typical values are at T
A
= +25°C, V
CC
= +5V for L/M/J versions,
V
CC
= +3.3V for T/S versions, V
CC
= +3V for R version, and V
CC
= +2.5V for Z version.)
-40 20 40-20 0 60 85
SUPPLY CURRENT vs. TEMPERATURE
(SC70 PACKAGE, NO LOAD)
MAX803 toc01
TEMPERATURE (
°
C)
SUPPLY CURRENT (µA)
0
5
10
15
MAX8_ _R/S/T, V
CC
= 3.3V
MAX8_ _L/M/R/S/T/Z, V
CC
= 1V
MAX8_ _Z, V
CC
= 2.5V
MAX8_ _L/M, V
CC
= 5V
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= full range, T
A
= -40°C to +105°C (SOT23) or T
A
= -40°C to +125°C (SC70), unless otherwise noted. Typical values are at T
A
=
+25°C, V
CC
= 5V for L/M/J versions, V
CC
= 3.3V for T/S versions, V
CC
= 3V for R version, and V
CC
= 2.5V for Z version.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RESET Output Voltage High
(push-pull active high, MAX810)
V
OH
1.8V < V
CC
< V
TH
min, I
SOURCE
= 150µA 0.8V
CC
V
RESET Open-Drain Output
Leakage Current (MAX803)
(Note 3)
V
CC
> V
TH
, RESET deasserted 1 µA
Note 1: Production testing done at T
A
= +25°C; limits over temperature guaranteed by design only.
Note 2: RESET output for MAX803/MAX809; RESET output for MAX810.
Note 3: Guaranteed by design, not production tested.
MAX803/MAX809/MAX810
3-Pin Microprocessor Reset Circuits
5
Maxim Integrated
Detailed Description
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
reset signal whenever the V
CC
supply voltage declines
below a preset threshold, keeping it asserted for at
least 140ms after V
CC
has risen above the reset thresh-
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.
Applications Information
Negative-Going V
CC
Transients
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
negative-going V
CC
transients (glitches).
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
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
width a negative-going V
CC
transient can have without
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
the MAX8__L and MAX8__M, a V
CC
transient that goes
100mV below the reset threshold and lasts 20µs or less
will not cause a reset pulse. A 0.1µF bypass capacitor
mounted as close as possible to the V
CC
pin provides
additional transient immunity.
Ensuring a Valid Reset Output
Down to V
CC
= 0V
When V
CC
falls below 1V, the MAX809 RESET output
no longer sinks current—it becomes an open circuit.
2
RESET
(MAX803/
MAX809)
RESET Output remains low while V
CC
is below the reset threshold, and for at
least 140ms after V
CC
rises above the
reset threshold.
1 GND Ground
PIN NAME FUNCTION
RESET
(MAX810)
RESET Output remains high while V
CC
is below the reset threshold, and for at
least 140ms after V
CC
rises above the
reset threshold.
3 V
CC
Supply Voltage (+5V, +3.3V, +3.0V, or
+2.5V)
Selector Guide
TOP MARK
PART/SUFFIX RESET THRESHOLD (V) OUTPUT TYPE
SOT SC70
MAX803L 4.63 OPEN-DRAIN RESET ⎯ AAZ
MAX803M 4.38 OPEN-DRAIN RESET ⎯ ABA
MAX803T 3.08 OPEN-DRAIN RESET ⎯ ABB
MAX803S 2.93 OPEN-DRAIN RESET ⎯ ABC
MAX803R 2.63 OPEN-DRAIN RESET ⎯ ABD
MAX803Z 2.32 OPEN-DRAIN RESET ⎯ ABE
MAX809L 4.63 PUSH-PULL RESET AAAA AAN
MAX809M 4.38 PUSH-PULL RESET ABAA AAO
MAX809J 4.00 PUSH-PULL RESET CWAA ⎯
MAX809T 3.08 PUSH-PULL RESET ACAA AAP
MAX809S 2.93 PUSH-PULL RESET ADAA AAQ
MAX809R 2.63 PUSH-PULL RESET AFAA AAR
MAX809Z 2.32 PUSH-PULL RESET ⎯ AAS
MAX810L 4.63 PUSH-PULL RESET AGAA AAT
MAX810M 4.38 PUSH-PULL RESET AHAA AAU
MAX810T 3.08 PUSH-PULL RESET AJAA AAV
MAX810S 2.93 PUSH-PULL RESET AKAA AAX
MAX810R 2.63 PUSH-PULL RESET ALAA AAW
MAX810Z 2.32 PUSH-PULL RESET ⎯ AAY
Pin Description
MAX803/MAX809/MAX810
3-Pin Microprocessor Reset Circuits
6
Maxim Integrated
Therefore, high-impedance CMOS logic inputs con-
nected to RESET can drift to undetermined voltages.
This presents no problem in most applications since
most µP and other circuitry is inoperative with V
CC
below 1V. However, in applications where RESET must
be valid down to 0V, adding a pull-down resistor to
RESET causes any stray leakage currents to flow to
ground, holding RESET low (Figure 2). R1’s value is not
critical; 100kΩ is large enough not to load RESET and
small enough to pull RESET to ground.
A 100kΩ pullup resistor to V
CC
is also recommended
for the MAX810 if RESET is required to remain valid for
V
CC
< 1V.
Interfacing to µPs with
Bidirectional Reset Pins
Since the RESET output on the MAX803 is open drain,
this device interfaces easily with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11.
Connecting the µP supervisor’s RESET output directly
to the microcontroller’s (µC’s) RESET pin with a single
pullup resistor allows either device to assert reset
(Figure 3).
MAX803 Open-Drain
RESET
Output
Allows Use with Multiple Supplies
Generally, the pullup connected to the MAX803 will
connect to the supply voltage that is being monitored at
the IC’s V
CC
pin. However, some systems may use the
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by some other supply
(Figure 4). Note that as the MAX803’s V
CC
decreases
RESET
GND
RESET
INPUT
R
PULLUP
MAX803
5V SYSTEM
GND
V
CC
+3.3V
+5.0V
V
CC
Figure 4. MAX803 Open-Drain RESET Output Allows Use with
Multiple Supplies
RESET
GND
RESET
INPUT
MAX803
MOTOROLA
68HCXX
µP
GND
V
CC
V
CC
V
CC
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
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
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset Comparator Overdrive
R1
100k
V
CC
GND
MAX809
RESET
Figure 2. RESET Valid to V
CC
= Ground Circuit
P1-P3P4-P6P7-P8

MAX803SEXR+T

Mfr. #:
Buy MAX803SEXR+T
Manufacturer:
Maxim Integrated
Description:
Supervisory Circuits 3-Pin MPU Supervisor
Lifecycle:
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