May 2003
1
MIC809/810
MIC809/810
Micrel
MIC809/810
Microprocessor Reset Circuits
Final Information
General Description
The MIC809 and MIC810 are inexpensive microprocessor
supervisory circuit that monitors power supplies in micropro-
cessor based systems.
The function of this device is to assert a reset if either the
power supply drops below a designated reset threshold level.
Several different reset threshold levels are available to ac-
commodate 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 V
CC
has risen above the designated reset threshold
level. The MIC809/810 comes in a 3-pin SOT-23 package.
The MIC809 is also available with a shorter reset timeout
(30ms min.). See the MIC809-5.
Typical Application
8++
4-5-6
P
4-5-6
8++
MIC809
8++
Features
Precision voltage monitor for 3V, 3.3V or 5V power
supplies
/RESET remains valid with V
CC
as low as 1.4V
<15
A supply current
20ms, 40ms, or 1100ms minimum reset pulse widths
available
Manual reset input
Available in 3-pin SOT-23 package
Applications
Portable equipment
Intelligent instruments
Critical microprocessor power monitoring
Printers/computers
Controllers
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
Ordering Information
Threshold
Operating
Part Number
Marking
Voltage
Temp. Range
Package
MIC809LU
IL
4.63
40
C to +85C
3-lead SOT-23
MIC809MU
IM
4.38
40
C to +85C
3-lead SOT-23
MIC809JU
IJ
4.00
40
C to +85C
3-lead SOT-23
MIC809TU
IT
3.08
40
C to +85C
3-lead SOT-23
MIC809SU
IS
2.93
40
C to +85C
3-lead SOT-23
MIC809RU
IR
2.63
40
C to +85C
3-lead SOT-23
MIC810LU
JL
4.63
40
C to +85C
3-lead SOT-23
MIC810MU
JM
4.38
40
C to +85C
3-lead SOT-23
MIC810JU
JJ
4.00
40
C to +85C
3-lead SOT-23
MIC810TU
JT
3.08
40
C to +85C
3-lead SOT-23
MIC810SU
JS
2.93
40
C to +85C
3-lead SOT-23
MIC810RU
JR
2.63
40
C to +85C
3-lead SOT-23
MIC809/810
Micrel
MIC809/810
2
May 2003
Pin Description
Pin Number
Pin Number
Pin Name
Pin Function
MIC809
MIC810
1
1
GND
IC Ground Pin
2
N/A
/RESET
/RESET goes low if V
CC
falls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after V
CC
exceeds the
reset threshold
N/A
2
RESET
RESET goes high if V
CC
falls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after V
CC
exceeds the
reset threshold
3
3
VCC
Power Supply Input.
Pin Configuration
1
2
3 V
CC
GND
MIC809
RESET
1
2
3 V
CC
GND
MIC810
RESET
MIC809 3-Lead SOT23
MIC810 3-Lead SOT23
May 2003
3
MIC809/810
MIC809/810
Micrel
Absolute Maximum Ratings
(Note 1)
Terminal Voltage (V
CC
) ................................. 0.3V to 6.0V
Input Current (V
CC
) .................................................... 20mA
Output Current (RESET, /RESET) ............................. 20mA
Lead Temperature (soldering, 10 sec.) ..................... 300
C
Storage Temperature (T
S
) ......................... 65
C to 150C
Rate of Rise (V
CC
) ................................................. 100V/
s
ESD Rating, Note 3
Operating Ratings
(Note 2)
Operating Temperature Range
MIC809 ..................................................... 40
C to 85C
MIC810 ..................................................... 40
C to 85C
Power Dissipation (T
A
= +70
C) .............................. 320mW
Electrical Characteristics
For typical values, V
CC
= 5V for MIC8_L/M/J, V
CC
= 3.3V for MIC8_S/T, V
CC
= 3V for MIC8_R; T
A
= 25
C, bold values indicate 40C
T
A
+85C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
V
CC
Operating Voltage Range
T
A
= 0
C to 70C
1.4
5.5
V
T
A
= 40
C to 85C
1.6
5.5
V
I
CC
Supply Current
MIC809L/M/J, MIC810L/M/J
9
15
A
V
CC
< 3.6V, MIC809R/S/T, MIC810R/S/T
6
10
A
V
TH
Reset Voltage Threshold
MIC809L, MIC810L
4.50
4.63
4.75
V
MIC809M, MIC810M
4.25
4.38
4.50
V
MIC809J, MIC810J
3.89
4.00
4.10
V
MIC809T, MIC810T
3.00
3.08
3.15
V
MIC809S, MIC810S
2.85
2.93
3.00
V
MIC809R, MIC810R
2.55
2.63
2.70
V
t
RST
Reset Timeout Period
140
240
560
ms
V
OH
/RESET Output Voltage
I
SOURCE
= 800
A, MIC809L/M/J
V
CC
1.5V
V
I
SOURCE
= 500
A, MIC809R/S/T
0.8
V
CC
V
V
OL
/RESET Output Voltage
V
CC
= V
TH
min., I
SINK
= 3.2mA, MIC809L/M/J
0.4
V
V
CC
= V
TH
min., I
SINK
= 1.2mA, MIC809R/S/T
0.3
V
V
CC
> 1.4V, I
SINK
= 50
A, T
A
= 0
C to +70C
0.3
V
V
CC
> 1.6V, I
SINK
= 50
A, T
A
= 40
to +85C
0.3
V
V
OH
RESET Output Voltage
1.8V < V
CC
< V
TH
min., I
SOURCE
= 150
A
0.8
V
CC
V
V
OL
RESET Output Voltage
I
SINK
= 3.2mA, MIC810L/M/J
0.4
V
I
SINK
= 1.2mA, MIC810R/S/T
0.3
V
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Timing Diagram
V
CC
V
TH
V
TH
/RESET
t
RST
t
RST
Reset Timing Diagram
MIC809/810
Micrel
MIC809/810
4
May 2003
Functional Diagram
+
-
Reset
Threshold (V)
VCC (3)
RESET (2)
RESET (MIC810)
GND (1)
RESET
GENERATOR
May 2003
5
MIC809/810
MIC809/810
Micrel
Applications Information
Microprocessor Reset
The /RESET (or RESET) pin is asserted whenever V
CC
falls
below the reset threshold voltage. The /RESET pin remains
asserted for a period of 140ms after V
CC
has risen above the
reset threshold voltage. The reset function ensures the
microprocessor is properly reset and powers up in a known
condition after a power failure. /RESET will remain valid with
V
CC
as low as 1.4V.
V
CC
Transients
The MIC809/810 are relatively immune to negative-going
V
CC
glitches below the reset threshold. Typically, a negative-
going transient 125mV below the reset threshold with a
duration of 50
s (25s for MIC8_R/S/T) or less will not cause
a reset.
Interfacing to Bidirectional Reset Pins
The MIC809/810 can interface with
Ps with bidirectional
reset pins by connecting a 4.7k
resistor in series with the
MIC809/810 output and the
P reset pin.
/RESET Valid at Low Voltage
A resistor can be added from the /RESET pin to ground to
ensure the /RESET output remains low with V
CC
down to 0V.
A 100k
resistor connected from the /RESET to ground is
recommended. The resistor should be small enough to pull-
down any stray leakage currents and large enough not to load
the reset output . See Figure below.
VCC
RESET
P
RESET
VCC
MIC809
VCC
100K
Reset Valid to V
CC
= 0V
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