MIC811/812
Micrel
MIC811/812
Microprocessor Reset Circuits
General Description
The MIC811 and MIC812 are inexpensive microprocessor
supervisory circuits that monitor 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 or /MR is forced low. Several different reset threshold
levels are available to accommodate 3V, 3.3V or 5V powered
systems.
The MIC811 has an active low /RESET output, while the
MIC812 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 designed reset threshold level.
Having a push-pull output stage, the MIC811/812 does not
require a pull-up resistor at the output. The MIC811/812
comes in a 4-pin SOT-143 package.
If a microprocessor voltage supervisor with an open-drain
output stage is needed, see MIC6315.
Features
• Precision voltage monitor for 3V, 3.3V or 5V power sup-
plies
• /RESET remains valid with V
CC
as low as 1V
• 5µA typical supply current
• 140ms minimum reset pulse width available
• Manual reset input
• Available in 4-pin SOT-143 package
Applications
•
•
•
•
•
Portable equipment
Intelligent instruments
Critical microprocessor power monitoring
Printers/computers
Embedded controllers
Typical Application
VCC
VCC
VCC
MIC81 1
MR
µP
RESET
RESET
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 2005
1
MIC811/812
MIC811/812
Micrel
Ordering Information
Part Number
Standard
MIC811LU
MIC811MU
MIC811JU
MIC811TU
MIC811SU
MIC811RU
MIC812LU
MIC812MU
MIC812JU
MIC812TU
MIC812SU
MIC812RU
Pb-Free
MIC811LUY
MIC811MUY
MIC811JUY
MIC811TUY
MIC811SUY
MIC811RUY
MIC812LUY
MIC812MUY
MIC812JUY
MIC812TUY
MIC812SUY
MIC812RUY
Marking
Standard
KL
KM
KJ
KT
KS
KR
LL
LM
LJ
LT
LS
LR
Pb-Free
KL
KM
KJ
KT
KS
KR
LL
LM
LJ
LT
LS
LR
Threshold
Voltage
4.63
4.38
4.00
3.08
2.93
2.63
4.63
4.38
4.00
3.08
2.93
2.63
Operating Temp.
Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
4-lead SOT-143
MIC811/812
2
September 2005
MIC811/812
Micrel
Pin Configuration
GND
1
4
V
CC
MIC811
RESET
2
3
MR
GND
1
4
V
CC
MIC812
RESET
2
3
MR
MIC811 4-Lead SOT-143
MIC812 4-Lead SOT-143
Pin Description
Pin Number
MIC811
1
2
Pin Number
MIC812
1
N/A
Pin Name
GND
/RESET
Pin Function
IC Ground Pin
/RESET goes low if V
CC
falls below the reset threshold and remains as-
serted for one reset timeout period (140ms min.) after V
CC
exceeds the reset
threshold
RESET goes high if V
CC
falls below the reset threshold and remains as-
serted for one reset timeout period (140ms min.) after V
CC
exceeds the reset
threshold
Manual Reset Input. A logic low on /MR forces a reset. The reset will remain
asserted as long as /MR is held low and for one reset timeout period (140ms
min.) after /MR goes high. This input can be shorted to ground via a switch
or driven from CMOS or TTL logic. Float if unused.
Power Supply Input.
N/A
2
RESET
3
3
/MR
4
4
VCC
September 2005
3
MIC811/812
MIC811/812
Micrel
Absolute Maximum Ratings
(Note 1)
Terminal Voltage (V
CC
) .................................–0.3V to +6.0V
Input Current (V
CC
, /MR) ............................................ 20mA
Output Current (/RESET, RESET) .............................. 20mA
Lead Temperature (soldering, 10 sec.) ...................... 300°C
Storage Temperature (T
S
) .......................... –65°C to 150°C
Rate of Rise (V
CC
) .................................................. 100V/µs
ESD Rating,
Note 3
....................................................... 3kV
Operating Ratings
(Note 2)
Operating Temperature Range
MIC811 ..................................................... –40°C to 85°C
MIC812 ..................................................... –40°C to 85°C
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 –40°C
≤ T
A
≤ +85°C; unless noted
Symbol
V
CC
I
CC
Parameter
Condition
Min
1
5
5
5
4.50
4.25
3.89
3.00
2.85
2.55
140
I
SOURCE
= 500µA, MIC811R/S/T
I
SOURCE
= 800µA, MIC811L/M/J
V
CC
–1.5V
0.8×V
CC
0.4
0.3
0.3
0.8×V
CC
0.4
0.3
10
0.5
MIC81_R/S/T
/MR Input Threshold
/MR Pull-Up Resistance
/MR Glitch Immunity
Note 1.
Note 2.
Note 3.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Typ
Max
5.5
15
10
10
Units
V
µA
µA
µA
V
V
V
V
V
V
ms
V
V
V
V
V
V
V
V
µs
µs
V
V
Operating Voltage Range
Supply Current
T
A
= –40°C to 85°C
MIC811L/M/J, MIC812L/M/J:
V
CC
= 5.0V, no load
MIC811S/T, MIC812S/T
V
CC
= 3.3V, no load
MIC811L, MIC812L
V
TH
Reset Voltage Threshold
MIC811R, MIC812R: V
CC
= 3.0V, no load
MIC811M, MIC812M
MIC811J, MIC812J
MIC811T, MIC812T
MIC811S, MIC812S
MIC811R, MIC812R
4.63
4.38
4.00
3.08
2.93
2.63
240
4.75
4.50
4.10
3.15
3.00
2.70
560
t
RST
V
OH
V
OL
Reset Timeout Period
/RESET Output Voltage
/RESET Output Voltage
V
CC
= V
TH
min., I
SINK
= 1.2mA, MIC811R/S/T
RESET Output Voltage
RESET Output Voltage
/MR Minimum Pulse Width
/MR to Reset Delay
V
CC
> 1V, I
SINK
= 50µA, T
A
= –40° to +85°C
I
SINK
= 3.2mA, MIC812L/M/J
1.8V < V
CC
< V
TH
min., I
SOURCE
= 150µA
V
CC
= V
TH
min., I
SINK
= 3.2mA, MIC811L/M/J
V
OH
V
OL
I
SINK
= 1.2mA, MIC812R/S/T
V
IH
V
IL
/MR Input Threshold
V
CC
> V
TH
max., MIC81_L/M/J
2.3
0.7×V
CC
0.8
20
100
0.25×V
CC
30
V
CC
. V
TH
max., MIC81-L/M/J
MIC81-R/S/T
V
kΩ
ns
10
MIC811/812
4
September 2005
MIC811/812
Micrel
Timing Diagram
V
CC
V
TH
/MR
t
RST
/RESET
t
RST
Reset Timing Diagram
Functional Diagram
VCC (4)
+
Reset
Threshold (V)
-
RESET
GENERATOR
RESET (2)
RESET (MIC812)
MR (3)
GND (1)
September 2005
5
MIC811/812
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