1
The MIC809/MIC810 are inexpensive microprocessor
supervisory circuits that monitor power supplies in
microprocessor based systems.
The function of these devices is to assert a reset if the
power supply drops below a designated reset threshold
level. Several different reset threshold levels are
available to accomodate 3V, 3.3V or 5V powered
systems.
The MIC809 has an active low RESET output, while the
MIC810 offers an active high RESET output. The reset
output is guaranteed to remain asserted for a minimum
of 140ms after VCC has risen above the designated
reset threshold level. The MIC809/MIC810 come in a 3-
pin SOT-23 package.
1
2
3 V
CC
GND
MIC809
RESET
1
2
3 V
CC
GND
MIC810
RESET
Top View
Part
Package
Temp. Range
MIC809_U
3-Lead SOT23
-40C to +85C
MIC810_U
3-Lead SOT23
-40C to +85C
Place the device suffix of desired reset threshold voltage from table above in
blank to complete the part number.
Portable Equipment
Intelligent Instruments
Critical Microprocessor Power Monitoring
Printers/Computers
Controllers
RESET Remains Valid with VCC as Low
as 1.4V
Precision Voltage Monitor for 3V, 3.3V
or 5V Power Supplies
Available in 3-Pin SOT23 Package
<15
A Supply Current
140ms Minimum Reset Pulse Width
No External Components Required
8++
4-5-6
P
4-5-6
8++
MIC809
8++
Typical Operating Circuit
Features
Description
Pin Configuration
Ordering Information
Typical Applications
Reset Threshold
Device
Voltage (V)
Suffix
4.63
L
4.38
M
4.00
J
3.08
T
2.93
S
2.63
R
MIC809/MIC810 Microprocessor Reset Circuits
MIC809/MIC810
Microprocessor Reset Circuits
MIC809/MIC810 Microprocessor Reset Circuits
2
Electrical Characteristics
VCC = 5V for MIC8--L/M/J, VCC = 3.3V for MIC8--S/T, VCC = 3V for MIC8--R, T
A
= Operating Temperature Range, unless
otherwise noted.
Parameter
Conditions
Min
Typ
Max
Units
Operating Voltage Range, VCC TA = 0C to 70C
1.4
5.5
V
TA = -40C to 85C
1.6
5.5
Supply Current, ICC
MIC809L/M/J, MIC810L/M/J
9
15
A
VCC < 3.6V, MIC809R/S/T, MIC810R/S/T
6
10
Reset Voltage Threshold, VTH
MIC809L, MIC810L
4.50
4.63
4.75
V
MIC809M, MIC810M
4.25
4.38
4.50
MIC809J, MIC810J
3.89
4.00
4.10
MIC809T, MIC810T
3.00
3.08
3.15
MIC809S, MIC810S
2.85
2.93
3.00
MIC809R, MIC810R
2.55
2.63
2.70
Reset Timeout Period
140
240
560
ms
RESET Output Voltage, VOH
ISource = 800
A, MIC809L/M/J
VCC - 1.5V
V
ISource = 500
A, MIC809R/S/T
0.8 X VCC
RESET Output Voltage, VOL
VCC=VTH Min., ISink=3.2mA, MIC809L/M/J
0.4
V
VCC=VTH Min., ISink =1.2mA, MIC809R/S/T
0.3
VCC>1.4V, ISink =50
A, TA = 0C to 70C
0.3
VCC>1.6V, ISink =50
A, TA = -40C to 85C
0.3
RESET Output Voltage, VOH
1.8V < VCC < VTH Min., 0.8
X
VCC
V
ISource = 150
A
RESET Output Voltage, VOL
ISink=3.2mA, MIC810L/M/J
0.4
V
ISink=1.2mA, MIC810R/S/T
0.3
Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute
maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed.
Absolute Maximum Ratings
Terminal Voltage
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
Input Current, VCC, . . . . . . . . . . . . . . . . . . . . . . . 20mA
Output Current, RESET, RESET . . . . . . . . . . . . . .20mA
Rate of Rise, VCC . . . . . . . . . . . . . . . . . . . . . . 100V/
s
Operating Temperature Range
MIC809-U, MIC810-U . . . . . . . . . . . . . . . -40C to 85C
Storage Temperature Range . . . . . . . . . . . . .-65C to 150C
Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300C
Power Dissipation (TA = +70C) . . . . . . . . . . . . . . . . 320mW
MIC809/MIC810 Microprocessor Reset Circuits
Pin Functions
3
IC Ground Pin.
RESET goes low if VCC falls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after VCC exceeds
the reset threshold.
RESET goes high if VCC falls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after VCC exceeds
the reset threshold.
Power supply input, 3V, 3.3V or 5V.
Pin No.
Pin Name
MIC809
MIC810
GND
1
1
RESET
2
N/A
RESET
N/A
2
VCC
3
3
4
+
-
Reset
Threshold (V)
VCC (3)
RESET (2)
RESET (MIC810)
GND (1)
RESET
GENERATOR
Figure 1. MIC809/810 Block Diagram
Block Diagram
MIC809/MIC810 Microprocessor Reset Circuits
5
Microprocessor Reset
The RESET pin is asserted whenever VCC falls below
the reset threshold voltage. The reset pin remains
asserted for a period of 240ms after VCC has risen
above the reset threshold voltage. The reset function
ensures the microprocessor is properly reset and powers
up into a known condition after a power failure. RESET
will remain valid with VCC as low as 1.4V.
VCC Transients
The MIC809/MIC810 are relatively immune to negative-
going VCC glitches below the reset threshold. Typically,
a negative-going transient 125mV below the reset
threshold with a duration of 50
s (25
s for
MIC8__R/S/T) or less will not cause an unwanted reset.
Interfacing to Bidirectional Reset Pins
The MIC809/MIC810 can interface with
Ps with
bidirectional reset pins by connecting a 4.7K
resistor in
series with the MIC809/MIC810 output and the
P reset
pin.
RESET Valid to 0V
A resistor can be added from the RESET pin to ground
to ensure the RESET output remains low with VCC
down to 0V. A 100K
resistor connected from RESET
to ground is recommended. The size of the resistor
should be large enough to not load the RESET output
and small enough to pull-down any stray leakage
currents.
Circuit Description
Figure 2. Reset Timing Diagram
Figure 3. RESET Valid to VCC = OV
8++
8JDH
4-5-6
J
J
8JDH
VCC
RESET
P
RESET
VCC
MIC809
VCC
100K
MIC809/MIC810 Microprocessor Reset Circuits
PDF 
ZIP