1
The MIC8114 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 MIC8114 has an active low RESET output. The
reset output is guaranteed to remain asserted for a
minimum of 790ms after VCC has risen above the
designated reset threshold level. The MIC8114 comes
in a 4-pin SOT-143 package.
MR
1
2
4 V
CC
GND
MIC8114
RESET
3
Top View
Part
Package
Temp. Range
MIC8114TU
4-Lead SOT-143
-40C to +85C
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 VCC as Low
as 1.4V
Precision Voltage Monitor for 3.3V
Power Supplies
Available in 4-Pin SOT-143 Package
<15
A Supply Current
790ms Minimum Reset Pulse Width
Manual Reset Input
Specifically tailored to the reset
requirements of the
AMD Elan SC400/410
VCC
RESET
P
RESET
VCC
MIC8114
VCC
MR
Typical Operating Circuit
Features
Description
Pin Configuration
Ordering Information
Typical Applications
MIC8114 Microprocessor Reset Circuit
MIC8114
Microprocessor Reset Circuit
MIC8114 Microprocessor Reset Circuit
2
Electrical Characteristics
VCC = 3.3V for MIC8114T, T
A
= Operating Temperature Range, unless otherwise noted.
Parameter
Conditions
Min
Typ
Max
Units
Operating Voltage Range, VCC TA = 0C to 70C
1.4
5.5
V
TA = -40C to 85C
1.6
5.5
Supply Current, ICC
9
15
A
Reset Voltage Threshold, VTH
3.00
3.08
3.15
V
Reset Timeout Period
790
1200
1800
ms
RESET Output Voltage, VOH
ISource = 500
A
0.8 X VCC
V
RESET Output Voltage, VOL
VCC=VTH Min., ISink =1.2mA
0.3
V
VCC>1.4V, ISink =50
A, TA = 0C to 70C
0.3
V
VCC>1.6V, ISink =50
A, TA = -40C to 85C
0.3
V
MR Minimum Pulse Width
10
s
MR to Reset Delay
0.5
s
MR Input Threshold, VIH
0.7 X VCC
V
MR Input Threshold, VIL
0.25 X VCC
V
MR Pull-Up Resistance
10
20
30
k
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, VCC . . . . . . . . . . . . . . . . . . . . . . 100V/
s
Operating Temperature Range
MIC8114TU . . . . . . . . . . . . . . . . . . . . . . . . -40C to 85C
Storage Temperature Range . . . . . . . . . . . . .-65C to 150C
Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300C
Power Dissipation (TA = +70C) . . . . . . . . . . . . . . . . 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.
MIC8114 Microprocessor Reset Circuit
Pin Functions
3
Pin Name
Pin No.
Description
GND
1
IC Ground Pin.
RESET
2
RESET goes low if either VCC falls below the supply reset threshold or if MR is
asserted. RESET remains asserted for one reset timeout period (790ms min.) after
both VCC exceeds 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 (790ms) 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
resistor. Float if unused.
VCC
4
Power supply input.
4
+
-
Reset
Threshold (V)
VCC (4)
RESET (2)
GND (1)
RESET
GENERATOR
MR (3)
VCC
Figure 1. MIC8114 Block Diagram
Block Diagram
MIC8114 Microprocessor Reset Circuit
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 at least 790ms 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 fail-
ure. RESET will remain valid with VCC as low as 1.4V.
VCC Transients
The MIC8114 is 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 25
s 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 VCC
down to 0V. A 100K
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.
VCC
MR
RESET
t1
t1
Vthr
5
VCC
RESET
P
RESET
VCC
MIC8114
VCC
100K
MIC8114 Microprocessor Reset Circuit
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