July 2005 1 MIC8114
MIC8114 Micrel
Ordering Information
Part Number Marking Operating Temp. Range Package Pb-Free
MIC8114TU NV –40°C to +85°C 4-lead SOT-143 No
MIC8114TUY NV –40°C to +85°C 4-lead SOT-143 Yes
MIC8114
Microprocessor Reset Circuit
General Description
The MIC8114 is an inexpensive microprocessor supervisory
circuit that monitors the power supply in microprocessor
based systems.
The function of this device is to assert a reset if 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 MIC1814 comes in a 4-pin SOT-143
package.
Typical Application
VCC
RESET
µP
RESET
VCC
MIC81 14
VCC
MR
Features
• Precision voltage monitor for 3.3V power supplies
• Specifically tailored to the AMD Elan SC400/410
• /RESET remains valid with VCC as low as 1V
• 5µA typical supply current
• 790ms minimum reset pulse width
• Manual reset input
• Available in 4-Pin SOT-143 Package
Applications
• Portable equipment
• Intelligent instruments
• Critical microprocessor power monitoring
• Printers/computers
• Embedded controllers
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC8114 Micrel
MIC8114 2 July 2005
Pin Description
Pin Number Pin Name Pin Function
1 GND IC Ground Pin
2 /RESET /RESET goes low if either VCC falls below the supply reset threshold voltage
or if /MR is asserted. /RESET remains asserted for one reset timeout period
after both VCC exceeds the supply reset threshold voltage and /MR is deas-
serted.
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 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.
4 VCC Power supply Input.
Pin Configuration
MR
1
2
4V
CC
GND
MIC8114
RESET
3
4-Lead SOT-143
July 2005 3 MIC8114
MIC8114 Micrel
Electrical Characteristics
For typical values, VCC = 3.3V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol Parameter Condition Min Typ Max Units
VCC Operating Voltage Range TA = –40°C to 85°C 1 5.5 V
ICC Supply Current 5 15 µA
VTH Reset Voltage Threshold 3.00 3.08 3.15 V
tRST Reset Timeout Period 790 1200 1800 ms
VOH /RESET Output Voltage ISOURCE = 500µA 0.8×VCC V
VOL /RESET Output Voltage, VOL VCC = VTH min, ISINK = 1.2mA 0.3 V
VCC = 1V, ISINK = 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, VIH 0.7×VCC V
/MR Input Threshold, VIL 0.25×VCC
/MR Pull-Up Resistance 10 20 30 kΩ
/MR Glitch Immunity 100 ns
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.
Absolute Maximum Ratings(Note 1)
Terminal Voltage
(VCC) .........................................................–0.3V to +6.0V
(/MR) ..................................................–0.3V (VCC + 0.3V)
Input Current (VCC, /MR) ............................................ 20mA
Output Current (/RESET) ........................................... 20mA
Rate of Rise (VCC) ..................................................100V/µS
Lead Temperature (soldering, 10 sec.) ...................... 300°C
Storage Temperature (TS) ........................ –65°C to +150°C
ESD Rating .................................................................... 3kV
Operating Ratings(Note 2)
Operating Temperature Range
MIC8114TU ............................................ –40°C to +85°C
Power Dissipation (TA = +70°C) .............................. 320mW
Timing Diagram
VCC
/MR
/RESET
tRST tRST
VTH
Reset Timing Diagram
MIC8114 Micrel
MIC8114 4 July 2005
Functional Diagram
+
-
Reset
Threshold (V)
VCC (4)
RESET (2)
GND (1)
RESET
GENERATOR
MR (3)
VCC
July 2005 5 MIC8114
MIC8114 Micrel
Applications Information
Microprocessor Reset
The /RESET pin is asserted whenever VCC falls below the
reset threshold voltage. The reset pin remains asserted for a
period of 790ms after VCC has risen above the reset thresh-
old voltage. 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 1V.
VCC Transients
The MIC8114 is relatively immune to the 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.
/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 /RESET-to-ground is
recommended. The resistor should be large enough not to
load the /RESET output and small enough to pull-down any
stray leakage currents
VCC
RESET
µP
RESET
VCC
MIC81 14
VCC
100K
/RESET Valid to VCC = 0V
MIC8114 Micrel
MIC8114 6 July 2005
Package Information
0.150 (0.0059)
0.089 (0.0035)
8
0
0.400 (0.016) TYP 3 PLACES
2.50 (0.098)
2.10 (0.083)
1.40 (0.055)
1.20 (0.047)
0.950 (0.0374) TYP
3.05 (0.120)
2.67 (0.105)
0.800 (0.031) TYP
1.12 (0.044)
0.81 (0.032)
0.10 (0.004)
0.013 (0.0005)
DIMENSIONS:
MM (INCH)
0.41 (0.016)
0.13 (0.005)
C
L
C
L
4-Lead SOT-143 (UT)
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
Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Incorporated.
