MAX823/4/5
Voltage Supervisor with Watchdog Timer
and Manual Reset
Revision 1.0
General Description
The MAX823/4/5 voltage supervisory circuits combine
low-current, manual reset input, watchdog timer, active-
high and active-low push-pull outputs. The reset outputs
are asserted and held when the supply voltage falls below
the factory-programmed threshold voltage, when the /MR
pin is pulled low, or if the watchdog times out. Reset is
asserted for the reset timeout delay after the supply
voltage increases above the rising threshold voltage or
when manual reset input is asserted high.
The MAX823/4/5 features an integrated pull-up resistor on
the /MR pin. An active-low push-pull reset output (/RESET)
and an active-high reset output (RESET) provide flexibility
when interfacing with various microcontrollers, PMICs, or
load switches. The watchdog input can be left
unconnected for applications that do not require watchdog
monitoring.
The MAX823/4/5 consumes a quiescent current of only
3.8µA and is offered in standard SOT23-5 and SC70-5
packages. It is rated for the –40°C to +125°C temperature
range.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Features
Precision 1.665V to 4.625V power supply monitor
±0.5% threshold accuracy at TA = +25°C
±1.5% threshold accuracy from TA = –40°C to +125°C
3.8µA supply current (S,R,T,W,Y,Z options)
4.8µA supply current (L,M options)
Manual reset input (MAX823/5)
140ms (min.) reset timeout period
1.6s (typ.) watchdog timeout period
Active-high and active-low push-pull outputs
Guaranteed reset output valid to VCC = 1V
40°C
to +125°C junction temperature range
5-pin SOT23 & SC70 packages
8x lower watchdog input current than competition
Applications
Computers and Controllers
Embedded Controllers
Intelligent Instruments
Automotive Systems
Critical µP Monitoring
Portable/ Battery-Powered Equipment
Typical Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
January 14, 2014
Revision 1.0
Micrel, Inc.
FUNCTION
Active-Low Reset
Active-High Reset
Watchdog Input
Manual Reset Input
MAX823
−
MAX824
−
MAX825
−
MAX823/4/5
Ordering Information
(1)
Part Number
MAX823LEUK
MAX823MEUK
MAX823REUK
MAX823SEUK
MAX823TEUK
MAX823WEUK
MAX823YEUK
MAX823ZEUK
MAX823LEXK
MAX823MEXK
MAX823REXK
MAX823SEXK
MAX823TEXK
MAX823WEXK
MAX823YEXK
MAX823ZEXK
Top Marking
X3L
X3M
X3R
X3S
X3T
X3W
X3Y
X3Z
XA
XB
XF
XE
XC
XL
XK
XJ
V
RST
: Nominal Threshold
Voltage (V)
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
Package
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
January 14, 2014
2
Revision 1.0
Micrel, Inc.
MAX823/4/5
Ordering Information (Continued)
(1)
Part Number
MAX824LEUK
MAX824MEUK
MAX824REUK
MAX824SEUK
MAX824TEUK
MAX824WEUK
MAX824YEUK
MAX824ZEUK
MAX824LEXK
MAX824MEXK
MAX824REXK
MAX824SEXK
MAX824TEXK
MAX824WEXK
MAX824YEXK
MAX824ZEXK
Top Marking
X4L
X4M
X4R
X4S
X4T
X4W
X4Y
X4Z
4Y
YA
YD
YC
YB
YG
YF
YE
V
RST
: Nominal Threshold
Voltage (V)
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
Package
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
Part Number
MAX825LEUK
MAX825MEUK
MAX825REUK
MAX825SEUK
MAX825TEUK
MAX825WEUK
MAX825YEUK
MAX825ZEUK
MAX825LEXK
MAX825MEXK
MAX825REXK
MAX825SEXK
MAX825TEXK
MAX825WEXK
MAX825YEXK
MAX825ZEXK
Note:
Top Marking
X5L
X5M
X5R
X5S
X5T
X5W
X5Y
X5Z
YE
YI
YO
YK
YJ
YT
YS
YR
V
RST
: Nominal Threshold
Voltage (V)
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
4.625
4.375
2.625
2.925
3.075
1.665
2.188
2.315
Package
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SOT23-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
1. All devices are available in tape-and-reel only. Contact Micrel for tape-and-reel options.
January 14, 2014
3
Revision 1.0
Micrel, Inc.
MAX823/4/5
Pin Configuration
MAX823
SOT23(EUK) &SC70(EXK)
Top View
MAX824
SOT23(EUK) &SC70(EXK)
Top View
MAX825
SOT23(EUK) &SC70(EXK)
Top View
Pin Description
Pin Number
MAX823
Pin Number
MAX824
Pin Number
MAX825
Pin Name
Pin Function
Active-Low Reset Output. Pulses low for 200ms when triggered, and
remains low whenever V
CC
is below the reset threshold or when /MR is
a logic low. It remains low for 200ms after one of the following occurs:
V
CC
rises above the reset threshold, the watchdog triggers a reset, or
/MR goes low to high.
Ground.
Active-High Reset Output. Pulses high for 200ms when triggered, and
remains high whenever V
CC
is below the reset threshold or when /MR
is a logic low. It remains high for 200ms after one of the following
occurs: V
CC
rises above the reset threshold, the watchdog triggers a
reset, or /MR goes low to high. RESET is the inverse of /RESET.
Watchdog Input. If WDI remains either high or low for longer than the
watchdog timeout period, the internal watchdog timer runs out and a
reset is triggered. The internal watchdog timer clears whenever reset
is asserted, or whenever WDI sees a rising or falling edge. If WDI is
left unconnected or is connected to a three-stated buffer output, the
watchdog feature is disabled.
Manual Reset Input. A logic low on /MR asserts reset. Reset remains
asserted as long as /MR is held low and for 200ms after /MR returns
high. The active-low input has an internal 52kΩ pull-up resistor. It can
be driven from a CMOS logic line or shorted to ground with a switch.
Leave open or connect to VCC if unused.
Supply Voltage Pin. VCC is the input to the supply voltage monitor.
When the supply voltage falls below the reset threshold voltage, reset
outputs (/RESET and RESET) are triggered immediately. When the
supply voltage rises above the reset threshold plus hysteresis voltage,
the reset outputs remain asserted for the duration of the reset timeout
period. An optional 0.1µF bypass capacitor mounted close to VCC
provides additional transient immunity.
1
1
1
/RESET
2
2
2
GND
-
3
3
RESET
4
4
-
WDI
3
-
4
/MR
5
5
5
VCC
January 14, 2014
4
Revision 1.0
Micrel, Inc.
MAX823/4/5
Absolute Maximum Ratings
(2)
Supply Voltage (V
CC
) ....................................
0.3V
to
6.0V
/MR, WDI, RESET, /RESET..................
0.3V
to V
CC
+0.3V
Input Current (All Pins except RESET, /RESET) ........ 20mA
Output Current (RESET, /RESET) .............................. 20mA
Junction Temperature (T
J
) ........................
40°C
to +150°C
Storage Temperature (Ts).........................
65°C
to +150°C
(4)
ESD Rating (Human Body Model)(MAX823/4/5) ........ 3kV
Operating Ratings
(3)
Supply Voltage (V
CC
) .................................... +1.0V to +5.5V
Watchdog Input (WDI)........................................... 0V to V
CC
Junction Temperature (T
J
) ........................ –40°C to +125°C
Junction Thermal Resistance
5-Pin SOT23 .................................................... 215°C/W
5-Pin SC70 ...................................................... 250°C/W
Electrical Characteristics
(5)
V
CC
= 4.7V to 5.5V for MAX823/4/5L, V
CC
= 4.5V to 5.5V for MAX823/4/5M, V
CC
= 3.15V to 3.6V for MAX823/4/5T, V
CC
= 3.0V to 3.6V
for MAX823/4/5S, V
CC
= 2.7V to 3.6V for MAX823/4/5R, V
CC
= 2.38V to 2.75V for MAX823/4/5Z, V
CC
= 2.25V to 2.75V for
(6)
MAX823/4/5Y, V
CC
= 1.75V to 2.0V for MAX823/4/5W; T
J
= +25˚C, bold values indicate –40˚C ≤ T
J
≤ +125˚C, unless otherwise noted.
Parameter
Power Suppy Input
Supply Voltage (V
CC
)
Supply Current (I
VCC
)
Reset Threshold Voltage
L (falling) T
A
= 25C
L (falling)
40C
T
A
+125C
M (falling) T
A
= 25C
M (falling) –40C
T
A
+125C
T (falling) T
A
= 25C
T (falling) –40C
T
A
+125C
S (falling) T
A
= 25C
Reset Threshold Voltage
(V
RST
)
S (falling) –40C
T
A
+125C
R (falling) T
A
= 25C
R (falling) –40C
T
A
+125C
Z (falling) T
A
= 25C
Z (falling) –40C
T
A
+125C
Y (falling) T
A
= 25C
Y (falling) –40C
T
A
+125C
W (falling) T
A
= 25C
W (falling) –40C
T
A
+125C
Reset Threshold
Hysteresis
Reset Threshold Tempco
L, M
T, S, R, Z, Y, W
4.602
4.556
4.353
4.309
3.060
3.029
2.910
2.881
2.612
2.586
2.303
2.280
2.177
2.155
1.657
1.640
10
5
40
1.665
2.188
2.315
2.625
2.925
3.075
4.375
4.625
4.648
4.694
4.397
4.441
3.090
3.121
2.940
2.969
2.638
2.664
2.327
2.350
2.199
2.221
1.673
1.690
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
mV
mV
ppm/˚C
L/M (WDI and /MR unconnected)
T/S/R/Z/Y/W (WDI and /MR unconnected)
1.0
4.8
3.8
5.5
14
8.4
V
µA
µA
Condition
Min.
Typ.
Max.
Units
January 14, 2014
5
Revision 1.0
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