UM823/824/825
Voltage Supervisory Circuits with Watchdog Timer and Manual
Reset Input
UM823/824/825 SOT23-5/SOT353
General Description
The UM823/824/825 series are cost effective system power supply supervisory circuits designed to
monitor the power supplies in digital systems. This family provides circuit initialization and timing
supervision. Independent watchdog monitoring circuitry and manual reset input are included. They
significantly improve system reliability and accuracy compared to separate ICs or discrete
components.
The UM823/824/825 are specifically designed to ignore fast transients on VCC. Seven
preprogrammed reset threshold voltages are available. All three devices have an active-low reset
output, which is guaranteed to be in the correct state for VCC down to 1V. The UM823 also offers a
watchdog input and manual reset input. The UM824 offers a watchdog input and a complementary
active-high reset. The UM825 offers a manual reset input and a complementary active-high reset.
Applications
Features
z
z
z
z
z
z
z
z
z
z
Applications Using DSPs, Microcontrollers
or Microprocessors
Programmable Controls
Computers
Embedded Systems
Industrial Equipments
Intelligent Instruments
Wireless Communications Systems
z
z
z
z
z
z
Wide Operation Voltage Range of 1V to 7V
Correct Logic Output Guaranteed to VCC=1.0V
Precision Supply-Voltage Monitor:
2.19V, 2.63V, 2.93V, 3.08V, 4.38V, 4.63V
200ms Reset Pulse Width
Independent Watchdog Timer-1.6s Timeout
Operating Current:
4µA for L/M
3µA for T/S/R/Z/Y
Temperature Range: -40°C to +85°C
Power-Supply Transient Immunity
SOT23-5 and SOT353 packages
Selection Guide
Function
Active-Low Reset
Active-High Reset
Watchdog Input
Manual Reset Input
UM823
√
√
√
UM824
√
√
√
-
UM825
√
√
√
Pin Configurations
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UM823/824/825
Ordering Information
UM8 XX Z P
Z: Reset Threshold (V)
=L
4.63
=M 4.38
=T 3.08
=S
2.93
=R 2.63
=Z 2.32
=Y
2.19
P: Package Type
=S SOT23-5
=P
SOT353
Typical Operating Circuit
Functional Diagram
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UM823/824/825
Pin Description
Pin Name
GND
Function
Ground Reference for all signals.
______________
RESET
Active-Low Reset Output. Pulses low for 200ms when
triggered, and remains low
_______
whenever VCC is below the reset threshold or when MR is a logic low. It remains
low for 200ms after one of the following
occurs: VCC rises above the reset
________
threshold, the watchdog triggers a reset, or M R goes low to high.
_____________
RESET
Active-High Reset Output. Inverse of RESET.
Manual-Reset Input triggers a reset pulse when pulled below 0.3VCC. The
active-low input has an internal 52kΩ pull-up resistor. It can be driven from a
TTL or CMOS logic line as well as shorted to ground with a switch. Leave open or
connect to VCC if unused.
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.
_______
MR
WDI
VCC
Supply Voltage
Absolute Maximum Ratings (Note 1)
Symbol
VCC
Parameter
Value
Supply Voltage
_____________
-0.3 to +8.0
_______
RESET, RESET, MR, WDI
ICC
-0.3 to (VCC+0.3)
_______
Input Current, VCC, MR , WDI
_____________
Unit
V
20
mA
mA
mW
IO
Output Current, RESET, RESET
PD
Continuous Power Dissipation
TA
Operating Temperature Range
20
300
247
-40 to +85
Storage Temperature Range
-65 to +150
°C
+300
°C
TSTG
SOT23-5
SOT353
Lead Temperature (Soldering, 10s)
°C
Note 1: Stresses beyond those listed under “Absolute maximum Ratings” may cause permanent
damage to the device. These are stress ratings only and functional operation of the device at these or
any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
ESD Ratings
Symbol
ESD Mode
Value
HBM
Human Body Mode
±2000
CDM
Charged Device Mode
±500
Unit
V
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UM823/824/825
Electrical Characteristics
(VCC=4.75V to 5.5V for L version, VCC=4.5V to 5.5V for M version, VCC=3.15V to 3.6V for T
version, VCC=3.0V to 3.6V for S version, VCC=2.7V to 3.6V for R version, VCC=2.38V to 2.75V for
Z version, VCC=2.25V to 2.75V for Y version, TA=-40°C to +85°C (SOT353), TA=-40°C to
+125°C(SOT23-5),unless otherwise noted. Typical values are at TA=+25°C.) (Note 2)
Symbol
Parameter
Conditions
VCC
Supply Voltage
Range
TA=0°C to +70°C
TA=TMIN to TMAX
WDI and MR
unconnected
ICC
Supply Current
MR
unconnected
L Version
M Version
T Version
VTH+
Reset Threshold
S Version
R Version
Z Version
Y Version
tRP
Reset Threshold
Hysteresis
Reset Threshold
Tempco
Reset Timeout
Period
_____________
VCC to RESET
Delay
Min
Max
Unit
1.0
7
V
1.2
7
V
UM823L/M
UM824L/M
UM823T/S/R/Z/Y
UM824T/S/R/Z/Y
Typ
4
6
3
6
UM825L/M
4
6
UM825T/S/R/Z/Y
3
6
4.63
4.70
TA=+25°C
4.56
TA=TMIN to TMAX
4.50
TA=+25°C
4.31
TA=TMIN to TMAX
4.25
TA=+25°C
3.04
TA=TMIN to TMAX
3.00
TA=+25°C
2.89
TA=TMIN to TMAX
2.85
TA=+25°C
2.59
TA=TMIN to TMAX
2.55
TA=+25°C
2.28
TA=TMIN to TMAX
2.25
TA=+25°C
2.16
TA=TMIN to TMAX
2.13
L/M
T/S/R/Z/Y
140
VRST-VCC=100mV
μA
4.75
4.38
4.45
4.50
3.08
3.11
3.15
2.93
2.96
3.00
2.63
V
2.66
2.70
2.32
2.35
2.38
2.19
2.22
2.25
20
10
mV
100
ppm/°C
200
20
280
ms
μs
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UM823/824/825
Electrical Characteristics (Continued)
(VCC=4.75V to 5.5V for L version, VCC=4.5V to 5.5V for M version, VCC=3.15V to 3.6V for T
version, VCC=3.0V to 3.6V for S version, VCC=2.7V to 3.6V for R version, VCC=2.38V to 2.75V for
Z version, VCC=2.25V to 2.75V for Y version, TA=-40°C to +85°C (SOT353), TA=-40°C to
+125°C(SOT23-5),unless otherwise noted. Typical values are at TA=+25°C.) (Note 2)
Symbol
Parameter
VOH
Conditions
Min
VCC=VRST max
ISOURCE=1mA
0.8VCC
Typ
Max
Unit
_____________
RESET RESET
Output Voltage
V
VCC=VRST min
ISINK=4mA
VOL
0.3
WATCHDOG INPUT(UM823/824)
tWD
Watchdog Timeout
Period
tWDI
WDI Pulse Width
VIL
VIH
1.12
VIL0.85VCC
2.40
s
ns
50
0.15VCC
WDI Input Voltage
(Note 4)
WDI Input Current
1.60
0.85VCC
WDI=VCC
1
20
WDI=GND
-20
-1
V
μA
MANUAL RESET INPUT(UM823/825)
VIL
VIH
0.15VCC
_______
MR Input Voltage
_______
MR Pulse Width
0.85VCC
1.0
V
μs
_______
MR Noise
Immunity(Pulse
width with no reset)
_______
MR to Reset Delay
100
ns
500
ns
_______
MR Pullup
Resistamce(internal)
35
52
75
kΩ
Note 2: Over temperature limits are guaranteed by design and not production tested.
_____________
______________
Note 3: The RESET short-circuit current is the maximum pullup current when RESET is driven
low by a μP bidirectional reset pin.
Note 4: WDI is internally serviced within the watchdog period if WDI is left unconnected.
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UM823/824/825
Detailed Description
______________
RESET Output
A Microprocessor’s reset input starts the µP in a known state. The UM823/824/825 µP supervisory
circuits assert
a reset to prevent code-execution errors during power-up, power-down, and brownout
_____________
a logic low for VCC down to 1V. Once VCC exceeds the
conditions. RESET is guaranteed to be_____________
reset threshold,
an internal timer keeps RESET low for the specified reset timeout period, after this
_____________
interval, RESET returns high.
_____________
If
a brownout condition occurs(VCC dips below reset threshold), RESET goes low. Each time
_____________
reset timeout period. Any time VCC goes below the reset
RESET is asserted it stays low for the_____________
threshold the internal timer _____________
restarts. RESET both sources and sinks current, RESET on the
UM824/825 is the inverse of RESET .
Manual Reset Input (UM823/825)
Many µP-based products require manual reset capability allowing the operator, a________
test technician, or
external logic circuitry to initiate
a
reset.
On
the
UM823/825,
a
logic
low
on
M
R asserts reset.
________
________
Reset remains asserted while M R is low, and for tRP (200ms nominal) after it returns high. M R
has an internal 52kΩ pull up resistor, so it can be left open if not used. This input can be driven
with CMOS logic
________ levels or with open-drain/collector outputs. Connect a normally open momentary
switch from________
M R to GND to create a manual-reset function; external debounce circuitry is not
required. If M R is driven
________ from long cables or the device is used in a noisy environment, connect a
0.1µF capacitor from M R to GND to provide additional noise immunity.
Watchdog Input (UM823/824)
In the UM823/824, the watchdog circuit monitors the µP’s activity. If the µP does not toggle the
watchdog input (WDI) within tWD(1.6s), reset asserts. The internal 1.6s timer is cleared by either a
reset pulse or by toggling WDI, which detects pulses as short as 50ns. While reset is asserted, the
timer remains cleared and does not count. As soon as reset is released, the timer starts counting.
Disable the watchdog function by leaving WDI unconnected or by three-stating the driver connected
to WDI.
Microprocessor with Bidirectional Reset
To prevent contention for microprocessor
with a bidirectional reset line, a current limiting resistor is
_____________
to be inserted between the RESET output pin and the microprocessor reset pin. This limits the
current to a safe level if there are conflicting output reset levels. A suitable resistor value is 4.7kΩ.
If the reset output is required for other uses, it should be buffered as shown in the figure below.
BUFFERED RESET TO OTHER SYSTEM COMPONENTS
VCC
VCC
µP
RESET
GND
4.7kΩ
RESET
GND
Bidirectional Reset I/O
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UM823/824/825
Typical Operating Characteristics
VCC=+5V, TA=25℃,unless otherwise noted.
Quiescent Current vs. Input Voltage@Ta=20°C
Quiescent Current vs. Temperature @VCC=5V
6
5
Quiescent Current (μA)
Quiescent Current (μA)
6
4
3
2
1
0
5
4
3
2
1
1
2
3
4
5
6
-40
7
-20
0
20
Input Voltage (V)
RESET Timeout Period vs.
Temperature@VCC=5V
60
80
100
240
225
210
195
180
165
150
1.75
1.7
1.65
1.6
1.55
1.5
1.45
1.4
-40
-20
0
20
40
60
80
100
120
-40
-20
0
20
40
60
80
100
Temperature(°C)
Temperature(°C)
Normalized Input Threshold Voltage vs.
Temperature
1.04
Normalized Input Threshold
Voltage(V)
120
Watchdog Timeout Period vs.
Temperature @VCC=5V
1.8
Watchdog Timeout Period(S)
RESET Timeout Period(mS)
255
40
Temperature(°C)
1.03
1.02
1.01
1
0.99
0.98
0.97
0.96
-40
-20
0
20
40
60
80
100
120
Temperature(°C)
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120
UM823/824/825
Package Information
UM823S/824S/825S SOT23-5
Outline Drawing
Symbol
A
A1
A2
b
c
D
E
E1
e
e1
L
θ
DIMENSIONS
MILLIMETERS
INCHES
Min Typ Max Min
Typ
Max
1.013 1.15 1.40 0.040 0.045 0.055
0.00 0.05 0.10 0.000 0.002 0.004
1.00 1.10 1.30 0.039 0.043 0.051
0.30
0.50 0.012
0.020
0.10 0.15 0.20 0.004 0.006 0.008
2.82
3.10 0.111
0.122
1.50 1.60 1.70 0.059 0.063 0.067
2.60 2.80 3.00 0.102 0.110 0.118
0.95REF
0.037REF
1.90REF
0.075REF
0.30
0.60 0.012
0.024
0°
8°
0°
8°
Land Pattern
NOTES:
1. Compound dimension: 2.92×1.60;
2. Unit: mm;
3. General tolerance ±0.05mm unless otherwise
specified;
4. The layout is just for reference.
Tape and Reel Orientation
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UM823/824/825
UM823P/824P/825P SOT353
Outline Drawing
D
Symbol
5
1
4
3
2
b
e
Top View
Side View
c
End View
A
A1
A2
b
c
D
E
E1
e
L
θ
DIMENSIONS
MILLIMETERS
INCHES
Min Typ Max Min
Typ Max
0.85
1.10 0.033
0.043
0.00
0.10 0.000
0.004
0.80
1.00 0.031
0.039
0.10
0.35 0.004
0.014
0.08
0.22 0.003
0.009
1.80 2.15 2.20 0.071 0.085 0.087
1.15 1.30 1.35 0.045 0.051 0.053
2.00
2.45 0.079
0.096
0.65BSC
0.026REF
0.25
0.46 0.010
0.018
0°
8°
0°
8°
Land Pattern
NOTES:
1. Compound dimension: 2.15×1.30;
2. Unit: mm;
3. General tolerance ±0.05mm unless otherwise
specified;
4. The layout is just for reference.
Tape and Reel Orientation
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UM823/824/825
Selection Table
Part
Number
UM823LS
UM823MS
UM823TS
UM823SS
UM823RS
UM823ZS
UM823YS
UM823LP
UM823MP
UM823TP
UM823SP
UM823RP
UM823ZP
UM823YP
UM824LS
UM824MS
UM824TS
UM824SS
UM824RS
UM824ZS
UM824YS
UM824LP
UM824MP
UM824TP
UM824SP
UM824RP
UM824ZP
UM824YP
UM825LS
UM825MS
UM825TS
UM825SS
UM825RS
UM825ZS
UM825YS
UM825LP
UM825MP
UM825TP
UM825SP
UM825RP
UM825ZP
UM825YP
RESET Threshold (V)
Top Marking
4.63
4.38
3.08
2.93
2.63
2.32
2.19
4.63
4.38
3.08
2.93
2.63
2.32
2.19
4.63
4.38
3.08
2.93
2.63
2.32
2.19
4.63
4.38
3.08
2.93
2.63
2.32
2.19
4.63
4.38
3.08
2.93
2.63
2.32
2.19
4.63
4.38
3.08
2.93
2.63
2.32
2.19
23L
23M
23T
23S
23R
23Z
23Y
3LP
3MP
3TP
3SP
3RP
3ZP
3YP
24L
24M
24T
24S
24R
24Z
24Y
4LP
4MP
4TP
4SP
4RP
4ZP
4YP
25L
25M
25T
25S
25R
25Z
25Y
5LP
5MP
5TP
5SP
5RP
5ZP
5YP
Package Type
Shipping
Quantity
SOT23-5
3000pcs/7Inch
Tape Reel
SOT353
3000pcs/7Inch
Tape Reel
SOT23-5
3000pcs/7Inch
Tape Reel
SOT353
3000pcs/7Inch
Tape Reel
SOT23-5
3000pcs/7Inch
Tape Reel
SOT353
3000pcs/7Inch
Tape Reel
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GREEN COMPLIANCE
Union Semiconductor is committed to environmental excellence in all aspects of its
operations including meeting or exceeding regulatory requirements with respect to the use
of hazardous substances. Numerous successful programs have been implemented to reduce
the use of hazardous substances and/or emissions.
All Union components are compliant with the RoHS directive, which helps to support
customers in their compliance with environmental directives. For more green compliance
information, please visit:
http://www.union-ic.com/index.aspx?cat_code=RoHSDeclaration
IMPORTANT NOTICE
The information in this document has been carefully reviewed and is believed to be accurate.
Nonetheless, this document is subject to change without notice. Union assumes no
responsibility for any inaccuracies that may be contained in this document, and makes no
commitment to update or to keep current the contained information, or to notify a person or
organization of any update. Union reserves the right to make changes, at any time, in order
to improve reliability, function or design and to attempt to supply the best product possible.
Union Semiconductor, Inc
Add: Unit 606, No.570 Shengxia Road, Shanghai 201210
Tel: 021-51093966
Fax: 021-51026018
Website: www.union-ic.com
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