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MIC811/812
Micrel
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.
Features
* Precision voltage monitor for 3V, 3.3V or 5V power supplies * /RESET remains valid with VCC as low as 1V * 5A 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
P
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
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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 -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C 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
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Micrel
Pin Configuration
GND 1
4 VCC
MIC811
RESET 2
3 MR
GND 1
4 VCC
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 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 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
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MIC811/812
Micrel
Absolute Maximum Ratings(Note 1)
Terminal Voltage (VCC) .................................-0.3V to +6.0V Input Current (VCC, /MR) ............................................ 20mA Output Current (/RESET, RESET) .............................. 20mA Lead Temperature (soldering, 10 sec.) ...................... 300C Storage Temperature (TS) .......................... -65C to 150C Rate of Rise (VCC) .................................................. 100V/s ESD Rating, Note 3 ....................................................... 3kV
Operating Ratings(Note 2)
Operating Temperature Range MIC811 ..................................................... -40C to 85C MIC812 ..................................................... -40C to 85C Power Dissipation (TA = +70C) .............................. 320mW
Electrical Characteristics
For typical values, VCC = 5V for MIC8_L/M/J, VCC = 3.3V for MIC8_S/T, VCC = 3V for MIC8_R; TA = 25C, bold values indicate -40C TA +85C; unless noted Symbol VCC ICC Parameter Condition Min 1 5 5 5 4.50 4.25 3.89 3.00 2.85 2.55 140 ISOURCE = 500A, MIC811R/S/T ISOURCE = 800A, MIC811L/M/J VCC-1.5V 0.8xVCC 0.4 0.3 0.3 0.8xVCC 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 A A A V V V V V V ms V V V V V V V V s s V V
Operating Voltage Range Supply Current
TA = -40C to 85C
MIC811L/M/J, MIC812L/M/J: VCC = 5.0V, no load MIC811S/T, MIC812S/T VCC = 3.3V, no load
VTH
Reset Voltage Threshold
MIC811R, MIC812R: VCC = 3.0V, no load MIC811L, MIC812L 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
tRST VOH VOL
Reset Timeout Period /RESET Output Voltage /RESET Output Voltage
VCC = VTH min., ISINK = 1.2mA, MIC811R/S/T RESET Output Voltage RESET Output Voltage /MR Minimum Pulse Width /MR to Reset Delay VCC > 1V, ISINK = 50A, TA = -40 to +85C ISINK = 3.2mA, MIC812L/M/J 1.8V < VCC < VTH min., ISOURCE = 150A
VCC = VTH min., ISINK = 3.2mA, MIC811L/M/J
VOH VOL
ISINK = 1.2mA, MIC812R/S/T
VIH VIL
/MR Input Threshold
VCC > VTH max., MIC81_L/M/J
2.3 0.7xVCC 0.8 20 100 0.25xVCC 30
VCC . VTH max., MIC81-L/M/J MIC81-R/S/T
V k ns
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Micrel
Timing Diagram
VCC VTH
/MR tRST
/RESET
tRST
Reset Timing Diagram
Functional Diagram
VCC (4)
+
Reset Threshold (V)
-
RESET GENERATOR
RESET (2) RESET (MIC812)
MR (3)
GND (1)
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MIC811/812
MIC811/812
Micrel /RESET Valid at Low Voltage 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 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.
VCC
Applications 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 20s or less will not cause a reset. Interfacing to Bidirectional Reset Pins The MIC811/812 can interface with Ps with bidirectional reset pins by connecting a 4.7k resistor in series with the MIC811/812 output and the P reset pin.
VCC
VCC
MIC81 1
RESET
100K
P
RESET
Reset Valid to VCC = 0V
MIC811/812
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September 2005
MIC811/812
Micrel
Package Information
0.950 (0.0374) TYP
1.40 (0.055) 2.50 (0.098) 1.20 (0.047) 2.10 (0.083)
C L C L
DIMENSIONS: MM (INCH)
1.12 (0.044) 0.81 (0.032)
8 0 0.150 (0.0059) 0.089 (0.0035)
3.05 (0.120) 2.67 (0.105)
0.800 (0.031) TYP
0.400 (0.016) TYP 3 PLACES
0.10 (0.004) 0.013 (0.0005)
0.41 (0.016) 0.13 (0.005)
4-lead SOT-143 (M3)
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this datasheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2005 Micrel, Incorporated.
MICREL, INC.
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
September 2005
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MIC811/812

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