Micrel MIC811 U Microprocessor reset circuit Datasheet

MIC811/MIC812 Microprocessor Reset Circuits
MIC811/MIC812
Microprocessor Reset Circuits
Description
Pin Configuration
The MIC811/MIC812 are inexpensive microprocessor
supervisory circuits that monitor power supplies in
microprocessor based systems.
The function of these devices 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 accomodate 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 designated
reset threshold level. The MIC811/MIC812 come in a 4pin SOT-143 package.
Typical Applications
· Portable Equipment
· Intelligent Instruments
· Critical Microprocessor Power Monitoring
· Printers/Computers
· Controllers
Reset Threshold
Voltage (V)
4.63
4.38
4.00
3.08
2.93
2.63
Device
Suffix
L
M
J
T
S
R
Top View
GND 1
4 VCC
MIC811
RESET 2
3 MR
GND 1
4 VCC
MIC812
RESET 2
Features
RESET Remains Valid with VCC as Low
· as
1.4V
Voltage Monitor for 3V, 3.3V
· Precision
or 5V Power Supplies
· Available in 4-Pin SOT-143 Package
· <15µA Supply Current
· 140ms Minimum Reset Pulse Width
· Manual Reset Input
Typical Operating Circuit
Ordering Information
Part
MIC811_U
MIC812_U
Package
4-Lead SOT-143
4-Lead SOT-143
Temp. Range
-40°C to +85°C
-40°C to +85°C
Place the device suffix of desired reset threshold voltage from table above in
blank to complete the part number.
3 MR
VCC
VCC
VCC
MIC811
µP
MR
RESET
RESET
1
MIC811/MIC812 Microprocessor Reset Circuits
Absolute Maximum Ratings
Terminal Voltage
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
MR . . . . . . . . . . . . . . . . . . . . . -0.3V to (VCC + 0.3V)
Input Current, VCC, MR . . . . . . . . . . . . . . . . . . . . 20mA
Output Current, RESET, RESET . . . . . . . . . . . . . .20mA
Rate of Rise, VCC . . . . . . . . . . . . . . . . . . . . . . 100V/µs
Operating Temperature Range
MIC81--U . . . . . . . . . . . . . . . . . . . . . . . . -40°C to 85°C
Storage Temperature Range . . . . . . . . . . . . .-65°C to 150°C
Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300°C
Power Dissipation (TA = +70°C) . . . . . . . . . . . . . . . . 320mW
Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute
maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed.
Electrical Characteristics
VCC = 5V for MIC81-L/M/J, VCC = 3.3V for MIC81-S/T, VCC = 3V for MIC81-R, TA = Operating Temperature Range, unless
otherwise noted.
Parameter
Conditions
Operating Voltage Range, VCC
TA = 0°C to 70°C
TA = -40°C to 85°C
Supply Current, ICC
MIC811L/M/J, MIC812L/M/J
VCC < 3.6V, MIC811R/S/T, MIC812R/S/T
Reset Voltage Threshold, VTH
MIC811L, MIC812L
MIC811M, MIC812M
MIC811J, MIC812J
MIC811T, MIC812T
MIC811S, MIC812S
MIC811R, MIC812R
Reset Timeout Period
RESET Output Voltage, VOH
ISource = 800µA, MIC811L/M/J
ISource = 500µA, MIC811R/S/T
RESET Output Voltage, VOL
VCC=VTH Min., ISink=3.2mA, MIC811L/M/J
VCC=VTH Min., ISink =1.2mA, MIC811R/S/T
VCC>1.4V, ISink =50µA, TA = 0°C to 70°C
VCC>1.6V, ISink =50µA, TA = -40°C to 85°C
RESET Output Voltage, VOH
1.8V < VCC < VTH Min.,
ISource = 150µA
RESET Output Voltage, VOL
ISink=3.2mA, MIC812L/M/J
ISink=1.2mA, MIC812R/S/T
MR Minimum Pulse Width
Min
Max
Units
5.5
5.5
V
9
6
15
10
µA
4.50
4.25
3.89
3.00
2.85
2.55
4.63
4.38
4.00
3.08
2.93
2.63
4.75
4.50
4.10
3.15
3.00
2.70
V
140
240
560
ms
1.4
1.6
VCC - 1.5V
0.8 X VCC
0.8 X VCC
0.4
0.3
MR Input Threshold, VIL
VCC > VTH Max., MIC81_L/M_
MIC81_R/S/T
2
µs
2.3
0.7 X VCC
10
V
µs
0.5
VCC > VTH Max., MIC81_L/M/J
MIC81_R/S/T
V
V
10
MR Input Threshold, VIH
MR Glitch Immunity
V
0.4
0.3
0.3
0.3
MR to Reset Delay
MR Pull-Up Resistance
Typ
V
20
100
0.8
0.25 X VCC
V
30
kΩ
ns
MIC811/MIC812 Microprocessor Reset Circuits
Pin Functions
Pin No.
Pin Name
Description
MIC811
MIC812
GND
1
1
RESET
2
N/A
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
N/A
2
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.
MR
3
3
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.
VCC
4
4
Power supply input, 3V, 3.3V or 5V.
IC Ground Pin.
3
MIC811/MIC812 Microprocessor Reset Circuits
Block Diagram
+
VCC (4)
Reset
-
RESET
Threshold (V)
GENERATOR
MR (3)
GND (1)
Figure 1. MIC811/812 Block Diagram
4
RESET (2)
RESET (MIC812)
MIC811/MIC812 Microprocessor Reset Circuits
Circuit Description
Microprocessor Reset
The RESET pin is asserted whenever VCC falls below
the reset threshold voltage or if MR (manual reset) is
forced low. The reset pin remains asserted for a period
of 240ms after VCC has risen above the reset threshold
voltage or MR has returned high. The reset function
ensures the microprocessor is properly reset and powers
up into a known condition after a power failure. RESET
will remain valid with VCC as low as 1.4V.
VCC Transients
The MIC811/MIC812 are relatively immune to negativegoing VCC glitches below the reset threshold. Typically,
a negative-going transient 125mV below the reset
threshold with a duration of 50µs (25µs for
MIC81_R/S/T) or less will not cause an unwanted reset.
VCC
Vthr
MR
t1
t1
RESET
Figure 2. Reset Timing Diagram
Interfacing to Bidirectional Reset Pins
The MIC811/MIC812 can interface with µPs with
bidirectional reset pins by connecting a 4.7KΩ resistor in
series with the MIC811/MIC812 output and the µP reset
pin.
VCC
VCC
VCC
MIC811
µP
RESET
RESET
100K
RESET Valid to 0V
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 RESET
to ground is recommended. The size of the resistor
should be large enough to not load the RESET output
and small enough to pull-down any stray leakage
currents.
Figure 3. RESET Valid to VCC = 0V.
5
MIC811/MIC812 Microprocessor Reset Circuits
Alternate Source Cross Reference Guide
Industry P/N
6
MIC Direct
Replacement
MAX811JEUS-T
MIC811JU
MAX811LEUS-T
MAX811MEUS-T
MAX811REUS-T
MAX811SEUS-T
MAX811TEUS-T
MAX812JEUS-T
MIC811LU
MIC811MU
MIC811RU
MIC811SU
MIC811TU
MIC812JU
MAX812LEUS-T
MAX812MEUS-T
MIC812LU
MIC812MU
MAX812REUS-T
MAX812SEUS-T
MIC812RU
MIC812SU
MAX812TEUS-T
MIC812TU
MIC811/MIC812 Microprocessor Reset Circuits
Packaging Information
U Package, 4-Pin SOT-143 Small-Outline Transistor Package
0.079
0.071
0.055
0.047
0.098
0.083
0.021
0.037
0.030
0.015
0.120
0.105
0.040
0.031
0.080
0.070
0.0059
0.0035
0.004
0.001
0-8¼
0.010
0.005
Dimensions are in inches.
Device Marking Information
Lot Code
KJXX
KLXX
KMXX
KRXX
KSXX
KTXX
LJXX
LLXX
LMXX
LRXX
LSXX
LTXX
=
=
=
=
=
=
=
=
=
=
=
=
MIC811J
MIC811L
MIC811M
MIC811R
MIC811S
MIC811T
MIC812J
MIC812L
MIC812M
MIC812R
MIC812S
MIC812T
7
MIC811/MIC812 Microprocessor Reset Circuits
Packaging Information
Tape and Reel Information
4.0–0.1
fl1.5–0.1
1.75–0.1
2.0–0.05
3.5–0.05
8.0–0.3
4.0–0.1
2.7–0.1
1.2–0.1
3.1–0.1
Dimensions are in millimeters.
8
fl1.1–0.1
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