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The MIC8115 is an inexpensive microprocessor reset
circuit 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.
The MIC8115 has an active low RESET output. The
reset output is guaranteed to remain asserted for a
minimum of 1100ms after VCC has risen above the
designated reset threshold level. The MIC8115 comes
in a 4-pin SOT-143 package.
Top View
Part Package Temp. Range
MIC8115TU 4-Lead SOT-143 -40°C to +85°C
Place the device suffix of desired reset threshold voltage from table above in
blank to complete the part number.
·
Portable Equipment
·
Intelligent Instruments
·
Critical Microprocessor Power Monitoring
·
Printers/Computers
·
Controllers
·
RESET Remains Valid with VCCas Low
as 1.4V
·
Precision Voltage Monitor for 3.3V
Power Supplies
·
Available in 4-Pin SOT-143 Package
·
<15µA Supply Current
·
1100ms Minimum Reset Pulse Width
·
Manual Reset Input
·
Specifically tailored to the reset
requirements of the
AMD Elan SC500 Series
Typical Operating Circuit
Features
Description Pin Configuration
Ordering Information
Typical Applications
MIC8115 Microprocessor Reset Circuit
MIC8115
Microprocessor Reset Circuit
1
GND
MIC8115
2
RESET 3
4 V
CC
MR
V
CC
V
CC
MIC8115
RESET
MR
V
RESET
CC
µP
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Electrical Characteristics
VCC= 3.3V for MIC8115T, TA= Operating Temperature Range, unless otherwise noted.
Parameter Conditions Min Typ Max Units
Operating Voltage Range, V
CC
TA= 0°C to 70°C 1.4 5.5 V
TA= -40°C to 85°C 1.6 5.5
Supply Current, I
CC
915µA
Reset Voltage Threshold, V
TH
3.00 3.08 3.15 V
Reset Timeout Period 1100 1700 2500 ms
RESET Output Voltage, V
OH
I
Source
= 500µA 0.8 X
V
CC
V
RESET Output Voltage, V
OL
VCC=VTHMin., I
Sink
=1.2mA
0.3 V
VCC>1.4V, I
Sink
=50µA,
TA= 0°C to 70°C 0.3 V
VCC>1.6V, I
Sink
=50µA,
TA= -40°C to 85°C 0.3 V
MR Minimum Pulse Width 10 µs
MR to Reset Delay 0.5 µs
MR Input Threshold, V
IH
0.7 X
V
CC
V
MR Input Threshold, V
IL
0.25 X
V
CC
V
MR Pull-Up Resistance
10 20 30 kΩ
MR Glitch Immunity
100 ns
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 . . . . . . . . . . . . . . 20mA
Rate of Rise, V
CC
. . . . . . . . . . . . . . . . . . . . . . 100V/µs
Operating Temperature Range
MIC8115TU . . . . . . . . . . . . . . . . . . . . . . . . -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.
MIC8115 Microprocessor Reset Circuit
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Pin Functions
3
Pin Name Pin No. Description
GND 1 IC Ground Pin.
RESET 2 RESET goes low if either VCCfalls below the supply reset threshold or if MR is
asserted. RESET remains asserted for one reset timeout period 1100ms min.) after
both VCCexceeds the supply reset threshold and MR is deasserted.
MR 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 (1100ms) min.) after MR
goes high. This input can be shorted to ground via a switch or driven from CMOS or
TTl logic. Pulled high internally through a 20k
Ω
resistor. Float if unused.
V
CC
4 Power supply input.
MIC8115 Microprocessor Reset Circuit
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Figure 1. MIC8115 Block Diagram
Block Diagram
MIC8115 Microprocessor Reset Circuit
V
CC
MR (3)
VCC(4)
RESET
GENERATOR
+
Reset
Threshold (V)
-
GND (1)
RESET (2)
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Microprocessor Reset
The RESET pin is asserted whenever V
CC
falls below
the reset threshold voltage or if MR (manual reset) is
forced low. The reset pin remains asserted for a period
of at least 1100ms after VCChas 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 VCCas low as 1.4V.
VCCTransients
The MIC8115 is relatively immune to negative-going
VCCglitches below the reset threshold. Typically, a
negative-going transient 125mV below the reset
threshold with a duration of 25µs or less will not cause
an unwanted reset.
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.
Circuit Description
Figure 2. Reset Timing Diagram
Figure 3. RESET Valid to VCC= 0V.
5
V
CC
RESET
µP
RESET
V
CC
MIC8115
V
CC
100K
MIC8115 Microprocessor Reset Circuit
V
CC
MR
RESET
V
thr
t1t1
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MIC8115 Microprocessor Reset Circuit
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Packaging Information
U Package, 4-Pin SOT-143 Small-Outline Transistor Package
Device Marking Information
Lot Code
NTXX = MIC8115TU
Dimensions are in inches.
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MIC8115 Microprocessor Reset Circuit
0.079
0.071
0.037
0.030
0.120
0.105
0.080
0.070
0.055
0.047
0.021
0.015
0.004
0.001
0.098
0.083
0.040
0.031
0.0059
0.0035
0.010
0.005
0-8¼
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Packaging Information
Tape and Reel Information
Dimensions are in millimeters.
MIC8115 Microprocessor Reset Circuit
2.7–0.1
3.1–0.1
4.0–0.1
2.0–0.05
4.0–0.1
1.2–0.1
fl1.5–0.1
fl1.1–0.1
1.75–0.1
3.5–0.05
8.0–0.3
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