Micrel MIC8114TU Microprocessor reset circuit Datasheet

MIC8114 Microprocessor Reset Circuit
MIC8114
Microprocessor Reset Circuit
Description
Pin Configuration
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.
Top View
GND 1
4 VCC
MIC81 14
RESET 2
3 MR
Features
Typical Applications
· Portable Equipment
· Intelligent Instruments
· Critical Microprocessor Power Monitoring
· Printers/Computers
· Controllers
· RESET Remains Valid with VCC as Low
as 1.4V
Voltage Monitor for 3.3V
· Precision
Power Supplies
· Available in 4-Pin SOT-143 Package
· <15µA Supply Current
· 790ms Minimum Reset Pulse Width
· Manual Reset Input
· Specifically tailored to the reset
requirements of the
AMD Elan SC400/410
Typical Operating Circuit
VCC
Ordering Information
Part
MIC8114TU
Package
4-Lead SOT-143
Temp. Range
-40°C to +85°C
Place the device suffix of desired reset threshold voltage from table above in
blank to complete the part number.
VCC
VCC
MIC81 14
µP
MR
RESET
RESET
1
MIC8114 Microprocessor Reset Circuit
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/µs
Operating Temperature Range
MIC8114TU . . . . . . . . . . . . . . . . . . . . . . . . -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 = 3.3V for MIC8114T, TA = Operating Temperature Range, unless otherwise noted.
Parameter
Operating Voltage Range, VCC
Conditions
TA = 0°C to 70°C
TA = -40°C to 85°C
Min
Typ
Max
Units
5.5
5.5
V
9
15
µA
1.4
1.6
Supply Current, ICC
Reset Voltage Threshold, VTH
3.00
3.08
3.15
V
Reset Timeout Period
790
1200
1800
ms
RESET Output Voltage, VOH
ISource = 500µA
RESET Output Voltage, VOL
VCC=VTH Min., ISink =1.2mA
VCC>1.4V, ISink =50µA, TA = 0°C to 70°C
VCC>1.6V, ISink =50µA, TA = -40°C to 85°C
MR Minimum Pulse Width
0.8 X VCC
0.3
0.3
0.3
MR Glitch Immunity
2
µs
0.5
0.7 X VCC
V
MR Input Threshold, VIL
MR Pull-Up Resistance
10
V
V
V
µs
10
MR to Reset Delay
MR Input Threshold, VIH
V
20
100
0.25 X VCC
V
30
kΩ
ns
MIC8114 Microprocessor Reset Circuit
Pin Functions
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 20kΩ resistor. Float if unused.
VCC
4
Power supply input.
3
MIC8114 Microprocessor Reset Circuit
Block Diagram
VCC
MR (3)
RESET
GENERATOR
+
VCC (4)
Reset
-
Threshold (V)
GND (1)
Figure 1. MIC8114 Block Diagram
4
RESET (2)
MIC8114 Microprocessor Reset Circuit
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 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 failure. 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 25µs or less will not cause
an unwanted reset.
VCC
VCC
VCC
MIC81 14
µP
RESET
RESET
100K
VCC
Vthr
MR
t1
t1
RESET
Figure 2. Reset Timing Diagram
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
MIC8114 Microprocessor Reset Circuit
6
MIC8114 Microprocessor Reset Circuit
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
NVXX = MIC8114
7
MIC8114 Microprocessor Reset Circuit
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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