Document
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.
Ordering Information
Part Number Pb-Free
Marking(1)
MIC811LUY
KL
MIC811MUY
KM
MIC811JUY
KJ
MIC811TUY
KT
MIC811SUY
KS
MIC811RUY
KR
MIC812LUY
LL
MIC812MUY
LM
MIC812JUY
LJ
MIC812TUY
LT
MIC812SUY
LS
MIC812RUY
LR
Note: 1. “_” underbar symbol not to scale
Pin Configuration
MIC811/812
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
MIC811 4-Pin SOT-143 (U)
MIC812 4-Pin SOT-143 (U)
Pin Description
MIC811 1
MIC812 1
2 N/A
N/A 2
33 44
Pin Name GND
/RESET
RESET
/MR VCC
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.
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 (TA = +70°C) ...............................320mW Thermal Resistance
SOT-143 (θJA) ..................................................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; TA = 25°C, bold values indicate – 40°C to ≤ TA ≤ +85°C; unless noted.
Symbol Parameter
Condition
Min Typ Max Units
VCC
Operating Voltage Range
TA = –40°C to 85°C
MIC811L/M/J, MIC812L/M/J: VCC = 5.0V,
no load
1 5.5 V 5 15 µA
IVCC Supply Current
MIC811S/T, MIC812S/T: VCC = 3.3V, no
load
5 10 µA
MIC811R, MIC812R: VCC = 3.0V, no load
5 10 µA
MIC811L, MIC812L
4.50 4.63
4.75
V
MIC811M, MIC812M
4.25 4.38
4.50
V
MIC811J, MIC812J VTH Reset Voltage Threshold
MIC811T, MIC812T
3.89 4.00 3.00 3.08
4.10 3.15
V V
MIC811S, MIC812S
2.85 2.93
3.00
V
MIC811R, MIC812R
2.55 2.63
2.70
V
tRST Reset Timeout Period
140 240 560 ms
ISOURCE = 800µA, MIC811L/M/J VOH /RESET Output Voltage
ISOURCE = 500µA, MIC811R/S/T
VCC–1.5V 0.8xVCC
V V
VCC = VTH min.,.