Micrel MIC812TU Microprocessor reset circuit Datasheet

MIC811/812
Micrel
MIC811/812
Microprocessor Reset Circuits
General Description
Features
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.
• 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
•
•
•
•
•
Typical Application
Portable equipment
Intelligent instruments
Critical microprocessor power monitoring
Printers/computers
Embedded controllers
VCC
VCC
VCC
MIC81 1
µP
MR
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
Marking
Pb-Free
Standard
Pb-Free
Threshold
Voltage
Operating Temp.
Range
Package
MIC811LU
MIC811LUY
KL
KL
4.63
–40°C to +85°C
4-lead SOT-143
MIC811MU
MIC811MUY
KM
KM
4.38
–40°C to +85°C
4-lead SOT-143
MIC811JU
MIC811JUY
KJ
KJ
4.00
–40°C to +85°C
4-lead SOT-143
MIC811TU
MIC811TUY
KT
KT
3.08
–40°C to +85°C
4-lead SOT-143
MIC811SU
MIC811SUY
KS
KS
2.93
–40°C to +85°C
4-lead SOT-143
MIC811RU
MIC811RUY
KR
KR
2.63
–40°C to +85°C
4-lead SOT-143
MIC812LU
MIC812LUY
LL
LL
4.63
–40°C to +85°C
4-lead SOT-143
MIC812MU
MIC812MUY
LM
LM
4.38
–40°C to +85°C
4-lead SOT-143
MIC812JU
MIC812JUY
LJ
LJ
4.00
–40°C to +85°C
4-lead SOT-143
MIC812TU
MIC812TUY
LT
LT
3.08
–40°C to +85°C
4-lead SOT-143
MIC812SU
MIC812SUY
LS
LS
2.93
–40°C to +85°C
4-lead SOT-143
MIC812RU
MIC812RUY
LR
LR
2.63
–40°C to +85°C
4-lead SOT-143
MIC811/812
2
September 2005
MIC811/812
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
Pin Number
MIC812
Pin Name
Pin Function
IC Ground Pin
1
1
GND
2
N/A
/RESET
/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
N/A
2
RESET
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
3
3
/MR
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.
4
4
VCC
Power Supply Input.
September 2005
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MIC811/812
MIC811/812
Micrel
Absolute Maximum Ratings(Note 1)
Operating Ratings(Note 2)
Terminal Voltage (VCC) .................................–0.3V to +6.0V
Input Current (VCC, /MR) ............................................ 20mA
Output Current (/RESET, RESET) .............................. 20mA
Lead Temperature (soldering, 10 sec.) ...................... 300°C
Storage Temperature (TS) .......................... –65°C to 150°C
Rate of Rise (VCC) .................................................. 100V/µs
ESD Rating, Note 3 ....................................................... 3kV
Operating Temperature Range
MIC811 ..................................................... –40°C to 85°C
MIC812 ..................................................... –40°C to 85°C
Power Dissipation (TA = +70°C) .............................. 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 = 25°C, bold values indicate –40°C
≤ TA ≤ +85°C; unless noted
Symbol
Parameter
Condition
VCC
Operating Voltage Range
TA = –40°C to 85°C
ICC
Supply Current
Min
Reset Voltage Threshold
tRST
/RESET Output Voltage
VOL
/RESET Output Voltage
RESET Output Voltage
VOL
RESET Output Voltage
/MR Minimum Pulse Width
µA
5
10
µA
MIC811R, MIC812R: VCC = 3.0V, no load
MIC811L, MIC812L
5
10
µA
4.50
4.63
4.75
V
MIC811M, MIC812M
4.25
4.38
4.50
V
MIC811J, MIC812J
3.89
4.00
4.10
V
MIC811T, MIC812T
3.00
3.08
3.15
V
MIC811S, MIC812S
2.85
2.93
3.00
V
MIC811R, MIC812R
2.55
2.63
2.70
V
140
240
560
ms
ISOURCE = 800µA, MIC811L/M/J
ISOURCE = 500µA, MIC811R/S/T
VCC = VTH min., ISINK = 3.2mA, MIC811L/M/J
VCC > 1V, ISINK = 50µA, TA = –40° to +85°C
1.8V < VCC < VTH min., ISOURCE = 150µA
ISINK = 3.2mA, MIC812L/M/J
ISINK = 1.2mA, MIC812R/S/T
VCC–1.5V
V
0.8×VCC
V
0.8×VCC
0.4
V
0.3
V
0.3
V
V
0.4
0.3
10
/MR to Reset Delay
/MR Input Threshold
VCC > VTH max., MIC81_L/M/J
VIL
/MR Input Threshold
VCC . VTH max., MIC81-L/M/J
MIC81_R/S/T
V
0.7×VCC
10
/MR Glitch Immunity
V
0.8
20
100
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.
4
V
µs
2.3
MIC81-R/S/T
/MR Pull-Up Resistance
V
µs
0.5
VIH
MIC811/812
V
15
VCC = VTH min., ISINK = 1.2mA, MIC811R/S/T
VOH
Units
5.5
5
Reset Timeout Period
VOH
Max
MIC811L/M/J, MIC812L/M/J:
VCC = 5.0V, no load
MIC811S/T, MIC812S/T
VCC = 3.3V, no load
VTH
Typ
1
0.25×VCC
30
V
kΩ
ns
September 2005
MIC811/812
Micrel
Timing Diagram
VCC
VTH
/MR
tRST
tRST
/RESET
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
Applications Information
/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 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.
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.
MIC811/812
VCC
VCC
VCC
MIC81 1
µP
RESET
RESET
100K
Reset Valid to VCC = 0V
6
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)
CL
CL
DIMENSIONS:
MM (INCH)
1.12 (0.044)
0.81 (0.032)
3.05 (0.120)
2.67 (0.105)
0.800 (0.031) TYP
0.400 (0.016) TYP 3 PLACES
8
0
0.10 (0.004)
0.013 (0.0005)
0.150 (0.0059)
0.089 (0.0035)
0.41 (0.016)
0.13 (0.005)
4-lead SOT-143 (M3)
MICREL, INC.
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
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
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© 2005 Micrel, Incorporated.
September 2005
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MIC811/812
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