MAX809, MAX810
3-Pin Microprocessor
Reset Monitors
The MAX809 and MAX810 are cost–effective system supervisor
circuits designed to monitor V
CC
in digital systems and provide a reset
signal to the host processor when necessary. No external components
are required.
The reset output is driven active within 20
µsec
of V
CC
falling
through the reset voltage threshold. Reset is maintained active for a
minimum of 140msec after V
CC
rises above the reset threshold. The
MAX810 has an active–high RESET output while the MAX809 has
an active–low RESET output. The output of the MAX809 is
guaranteed valid down to V
CC
= 1V. Both devices are available in a
SOT–23 package.
The MAX809/810 are optimized to reject fast transient glitches on
the V
CC
line. Low supply current of 17µA (V
CC
= 3.3V) makes these
devices suitable for battery powered applications.
Features
•
Precision V
CC
Monitor for 3.0V, 3.3V, and 5.0V Supplies
•
140msec Guaranteed Minimum RESET, RESET
Output Duration
•
RESET Output Guaranteed to V
CC
= 1.0V (MAX809)
•
Low 17µA Supply Current
•
V
CC
Transient Immunity
•
Small SOT–23 Package
•
No External Components
•
Wide Operating Temperature: –40°C to 85°C
Typical Applications
•
Computers
•
Embedded Systems
•
Battery Powered Equipment
•
Critical
µP
Power Supply Monitoring
TYPICAL APPLICATION DIAGRAM
VCC
VCC
MAX809
RESET
VCC
PROCESSOR
RESET
INPUT
GND
SOT–23
(TO–236)
CASE 318
PIN CONFIGURATION
(Top View)
GND
1
3
RESET
(RESET)**
VCC
2
SOT–23*
NOTE: *SOT–23 is equivalent to JEDEC (TO–236)
** RESET is for MAX809
** RESET is for MAX810
ORDERING INFORMATION
Device
MAX809xTR
MAX810xTR
Package
SOT–23
SOT–23
Shipping
3000 Tape/Reel
3000 Tape/Reel
NOTE: The ”x” denotes a suffix for VCC threshold –
see table below
Suffix
L
M
J*
T
S
R
Reset VCC Threshold (V)
4.63
4.38
4.00
3.08
2.93
2.63
GND
NOTE: *J version is available for MAX809 only
1
MAX809, MAX810
MAX809, MAX810
ABSOLUTE MAXIMUM RATINGS*
Symbol
Parameter
Supply Voltage (VCC to GND)
RESET, RESET
Input Current, VCC
Output Current, RESET, RESET
dV/dt (VCC)
PD
TA
Tstg
Tsol
Power Dissipation (TA
≤
70°C)
SOT–23 (derate 4mW/°C above +70°C)
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10 Seconds)
Value
6.0
–0.3 to (VCC + 0.3)
20
20
100
230
–40 to +85
–65 to +150
+260
°C
°C
°C
Unit
V
V
mA
mA
V/µsec
mW
* Maximum Ratings are those values beyond which damage to the device may occur.
2
MAX809, MAX810
MAX809, MAX810
ELECTRICAL CHARACTERISTICS
(VCC = Full Range, TA =
–40°C to +85°C unless otherwise noted
. typical values are at TA
= +25C, VCC = 5V for L/M/J, 3.3V for T/S, 3.0V for R)
(Note NO TAG)
Symbol
VCC Range
TA = 0°C to +70°C
TA = –40°C to +85°C
ICC
Supply Current
MAX8xxL/M/J: VCC < 5.5V
MAX8xxR/S/T: VCC < 3.6V
Reset Threshold (Note NO TAG)
MAX8xxL: TA = 25°C
TA = –40°C to +85°C
MAX8xxM: TA = 25°C
TA = –40°C to +85°C
MAX809J: TA = 25°C
TA = –40°C to +85°C
MAX8xxT: TA = 25°C
TA = –40°C to +85°C
MAX8xxS: TA = 25°C
TA = –40°C to +85°C
MAX8xxR: TA = 25°C
TA = –40°C to +85°C
Reset Threshold Temperature Coefficient
VCC to Reset Delay VCC = VTH to (VTH – 100mV)
Reset Active Timeout Period
VOL
RESET Output Voltage Low (MAX809)
MAX809R/S/T: VCC = VTH min, ISINK = 1.2mA
MAX809L/M/J: VCC = VTH min, ISINK = 3.2mA
VCC > 1.0V, ISINK = 50µA
RESET Output Voltage High (MAX809)
MAX809R/S/T: VCC > VTH max, ISOURCE = 500µA
MAX809L/M/J: VCC > VTH max, ISOURCE = 800µA
RESET Output Voltage Low (MAX810)
MAX810R/S/T: VCC = VTH max, ISINK = 1.2mA
MAX810L/M/J: VCC = VTH max, ISINK = 3.2mA
RESET Output Voltage High (MAX810)
1.8 < VCC < VTH min, ISOURCE = 150µA
Characteristic
Min
1.0
1.2
—
—
4.56
4.50
4.31
4.25
3.93
3.89
3.04
3.00
2.89
2.85
2.59
2.55
—
—
140
—
—
—
0.8 VCC
VCC – 1.5
—
—
0.8 VCC
Typ
—
—
24
17
4.63
—
4.38
—
4.00
—
3.08
—
2.93
—
2.63
—
30
20
240
—
—
—
—
—
—
—
—
Max
5.5
5.5
µA
60
50
V
4.70
4.75
4.45
4.50
4.06
4.10
3.11
3.15
2.96
3.00
2.66
2.70
—
—
560
0.3
0.4
0.3
V
—
—
V
0.3
0.4
V
—
ppm/°C
µsec
msec
V
Unit
V
VTH
VOH
VOL
VOH
1. Production testing done at TA = 25°C, over temperature limits guaranteed by design.
PIN DESCRIPTION
Á
Á
Á
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Á
Á
Á
Á
Á
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ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
Á
Á
Á Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁ
Á
1
2
2
3
GND
Ground
RESET (MAX809)
RESET output remains low while VCC is below the reset voltage threshold, and for 240msec (typ.)
after VCC rises above reset threshold
RESET (MAX810)
VCC
RESET output remains high while VCC is below the reset voltage threshold, and for 240msec (typ.)
after VCC rises above reset threshold
Supply Voltage (typ.)
3
Pin No.
Symbol
Description
MAX809, MAX810
MAX809, MAX810
APPLICATIONS INFORMATION
VCC Transient Rejection
The MAX809/810 provides accurate V
CC
monitoring and
reset timing during power–up, power–down, and
brownout/sag conditions, and rejects negative–going
transients (glitches) on the power supply line. Figure 1
shows the maximum transient duration vs. maximum
negative excursion (overdrive) for glitch rejection. Any
combination of duration and overdrive which lies
under
the
curve will
not
generate a reset signal. Combinations above
the curve are detected as a brownout or power–down.
Transient immunity can be improved by adding a capacitor
in close proximity to the V
CC
pin of the MAX809/810.
VCC
VTH
Overdrive
hold the output low (Figure 2). This resistor value, though
not critical, should be chosen such that it does not
appreciably load RESET under normal operation (100k
W
will be suitable for most applications). Similarly, a pull–up
resistor to V
CC
is required for the MAX810 to ensure a valid
high RESET for V
CC
below 1.0V.
VCC
VCC
MAX809
RESET
R1
100 k
GND
Duration
MAXIMUM TRANSIENT DURATION (
m
sec)
400
TA = +25° C
Figure 2. Ensuring RESET Valid to VCC = 0 V
Processors With Bidirectional I/O Pins
320
240
160
MAX8xxL/M/J
90
0
1
MAX8xxR/S/T
10
100
1000
RESET COMPARATOR OVERDRIVE,
(VTH – VCC (mV)
Some
µP’s
(such as Motorola 68HC11) have
bi–directional reset pins. Depending on the current drive
capability of the processor pin, an indeterminate logic level
may result if there is a logic conflict. This can be avoided
by adding a 4.7k
W
resistor in series with the output of the
MAX809/810 (Figure 3). If there are other components in
the system which require a reset signal, they should be
buffered so as not to load the reset line. If the other
components are required to follow the reset I/O of the
µP,
the
buffer should be connected as shown with the solid line.
BUFFER
VCC
Figure 1. Maximum Transient Duration vs. Overdrive
for Glitch Rejection at 25° C
RESET Signal Integrity During Power–Down
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
VCC
m
P
RESET
GND
VCC
MAX809
47 k
RESET
GND
The MAX809 RESET output is valid to V
CC
= 1.0V.
Below this voltage the output becomes an ”open circuit” and
does not sink current. This means CMOS logic inputs to the
µP
will be floating at an undetermined voltage. Most digital
systems are completely shutdown well above this voltage.
However, in situations where RESET must be maintained
valid to V
CC
= 0V, a pull–down resistor must be connected
from RESET to ground to discharge stray capacitances and
Figure 3. Interfacing to Bidirectional Reset I/O
4
MAX809, MAX810
MAX809, MAX810
TYPICAL CHARACTERISTICS
35
30
SUPPLY CURRENT (
m
A)
25
20
15
10
5
0
–40
VCC = 1 V
VCC = 3 V
VCC = 5 V
SUPPLY CURRENT (
m
A)
30
VCC = 5 V
25
20
15
10
5
0
–40
VCC = 1 V
VCC = 3 V
–20
0
20
40
TEMPERATURE (C°)
60
85
–20
0
20
40
TEMPERATURE (C°)
60
85
Figure 4. Supply Current vs Temperature
(No Load, MAX8xxR/S/T)
Figure 5. Supply Current vs Temperature
(No Load, MAX8xxL/M/J/)
100
POWER–DOWN RESET DELAY (
m
sec)
80
60
40
20
0
–40
POWER–DOWN RESET DELAY (
m
sec)
VOD = VTH – VCC
VOD = 10 mV
140
VOD = VTH – VCC
120
VOD = 10 mV
100
80
60
40
20
0
–40
VOD = 200 mV
–20
0
20
40
TEMPERATURE (C°)
60
85
VOD = 100 mV
VOD = 20 mV
VOD = 10 mV
VOD = 100 mV
VOD = 200 mV
–20
0
20
40
TEMPERATURE (C°)
60
85
Figure 6. Power–Down Reset Delay vs
Temperature and Overdrive (MAX8xxR/S/T)
Figure 7. Power–Down Reset Delay vs
Temperature and Overdrive (MAX8xxL/M/J)
POWER–UP RESET TIMEOUT (msec)
250
NORMALIZED THRESHOLD
245
MAX8xxL/M/J
240
235
230
225
–40
MAX8xxR/S/T
1.003
1.002
1.001
1.000
0.999
0.998
0.997
–20
0
20
40
TEMPERATURE (C°)
60
85
–40
–20
0
20
40
TEMPERATURE (C°)
60
85
Figure 8. Power–Up Reset Timeout vs
Temperature
Figure 9. Normalized Reset Threshold vs
Temperature
5
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