MIC811/812
Microprocessor Reset Circuits
General Description
The MIC811 and MIC812 are inexpensive microprocessor
supervisory circuits that monitor power supplies in
microprocessor 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 VCC 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.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Features
•
Precision voltage monitor for 3V, 3.3V or 5V power
supplies
•
/RESET remains valid with VCC 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
Controllers
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
September 9, 2014
Revision 2.0
Micrel, Inc.
MIC811/812
Ordering Information
Part Number
Pb-Free
MIC811LUY
MIC811MUY
MIC811JUY
MIC811TUY
MIC811SUY
MIC811RUY
MIC812LUY
MIC812MUY
MIC812JUY
MIC812TUY
MIC812SUY
MIC812RUY
Note:
1. “_” underbar symbol not to scale
Marking
(1)
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-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
4-pin SOT-143
Pin Configuration
MIC811 4-Pin SOT-143 (U)
MIC812 4-Pin SOT-143 (U)
Pin Description
MIC811
1
2
MIC812
1
N/A
Pin Name
GND
/RESET
Pin Name
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.
Manual Reset Input. A logic low on /MR will force 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 9, 2014
2
Revision 2.0
Micrel, Inc.
MIC811/812
Absolute Maximum Ratings
(2)
Terminal Voltage (VCC) ................................ -0.3V to +6.0V
Input Current (VCC, /MR)............................................ 20mA
Output Current (/RESET, RESET) .............................. 20mA
Lead Temperature (soldering, 10s) ............................ 300°C
Storage Temperature (Ts)............................... 5°C to 150°C
Rate of Rise (VCC) ................................................. 100V/µs
ESD Rating
(4)
.................................................................. 3kV
Operating Ratings
(3)
Operating Temperature Range
MIC811 ................................................. –40°C to +85°C
MIC812 ................................................. –40°C to +85°C
Power Dissipation (T
A
= +70°C) ............................... 320mW
Thermal Resistance
SOT-143 (θ
JA
) .................................................. 265°C/W
Electrical Characteristics
(5)
For typical values, VCC = 5V for MIC8_L/M/J, VCC = 3.3V for MIC8_S/T, VCC = 3V for MIC8_R; T
A
= 25°C,
bold
values indicate –
40°C to ≤ T
A
≤ +85°C; unless noted.
Symbol
VCC
Parameter
Operating Voltage Range
Condition
T
A
= –40°C to 85°C
MIC811L/M/J, MIC812L/M/J: V
CC
= 5.0V,
no load
I
VCC
Supply Current
MIC811S/T, MIC812S/T: V
CC
= 3.3V, no
load
MIC811R, MIC812R: V
CC
= 3.0V, no load
MIC811L, MIC812L
MIC811M, MIC812M
V
TH
Reset Voltage Threshold
MIC811J, MIC812J
MIC811T, MIC812T
MIC811S, MIC812S
MIC811R, MIC812R
t
RST
V
OH
Reset Timeout Period
/RESET Output Voltage
I
SOURCE
= 800µA, MIC811L/M/J
I
SOURCE
= 500µA, MIC811R/S/T
V
CC
= V
TH
min., I
SINK
= 3.2mA, MIC811L/M/J
V
OL
/RESET Output Voltage
V
CC
= V
TH
min., I
SINK
= 1.2mA,
MIC811R/S/T
V
CC
>1V, I
SINK
= 50µA, T
A
= –40°C to +85°C
V
OH
V
OL
Notes:
2. Exceeding the absolute maximum ratings may damage the device.
3. The device is not guaranteed to function outside its operating ratings.
4. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.
5. Specification for packaged product only
Min
1
Typ
Max
5.5
Units
V
µA
µA
µA
V
V
V
V
V
V
ms
V
V
5
5
5
4.50
4.25
3.89
3.00
2.85
2.55
140
VCC–1.5V
0.8xVCC
4.63
4.38
4.00
3.08
2.93
2.63
240
15
10
10
4.75
4.50
4.10
3.15
3.00
2.70
560
0.4
0.3
0.3
0.8xVCC
0.4
0.3
V
V
V
V
V
V
RESET Output Voltage
RESET Output Voltage
1.8V <V
CC
<V
TH
min., I
SOURCE
= 150µA
I
SINK
= 3.2mA, MIC812L/M/J
I
SINK
= 1.2mA, MIC812R/S/T
September 9, 2014
3
Revision 2.0
Micrel, Inc.
MIC811/812
Electrical Characteristics (Continued)
(5)
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 to
≤ T
A
≤ +85°C; unless noted.
Symbol
Parameter
/MR Minimum Pulse Width
/MR to Reset Delay
V
IH
/MR Input Threshold
VCC > V
TH
max., MIC81_L/M/J
MIC81_R/S/T
V
IL
/MR Input Threshold
VCC > V
TH
max., MIC81-L/M/J
MIC81_R/S/T
/MR Pull-Up Resistance
/MR Glitch Immunity
10
20
100
2.3
0.7xVCC
0.8
0.25xVCC
30
Condition
Min
10
0.5
Typ
Max
Units
µs
µs
V
V
V
V
kΩ
ns
Timing Diagram
Reset Timing Diagram
Functional Diagram
September 9, 2014
4
Revision 2.0
Micrel, Inc.
MIC811/812
/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 100kΩ resistor connected from the /RESET to
ground is recommended. The size of the resistor should
be large enough not to load the output excessively and
small enough to pull-down any stray leakage currents.
Application Information
Microprocessor Reset
The /RESET (or RESET) pin is asserted whenever VCC
falls below the reset threshold voltage. The /RESET pin
remains asserted for a period of 140ms after VCC has
risen above the reset threshold voltage. The reset
function ensures that the microprocessor is properly reset
and powers up in a known condition after a power failure.
/RESET will remain valid with VCC as low as 1V.
VCC Transients
The MIC811/812 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 20μs or less will not cause a
reset.
Interfacing to Bidirectional Reset Pins
The MIC811/812 can interface with µPs with bidirectional
reset pins by connecting a 4.7kΩ resistor in series with
the MIC811/812 output and the µP reset pin.
Reset Valid to VCC = 0V
September 9, 2014
5
Revision 2.0
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