Micrel MIC8115TU Microprocessor reset circuit Datasheet

MIC8115
Micrel
MIC8115
Microprocessor Reset Circuit
General Description
Features
The MIC8115 is an inexpensive microprocessor supervisory
circuit that monitors power supplies 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 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.
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Precision voltage monitor for 3.3V power supplies
Specifically tailored to the AMD Elan SC500 Series
/RESET remains valid with VCC as low as 1V
5µA typical supply current
1100ms minimum reset pulse width
Manual reset input
Available in 4-Pin SOT-143 Package
Applications
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•
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Portable equipment
Intelligent instruments
Critical microprocessor power monitoring
Printers/computers
Embedded controllers
Ordering Information
Part Number
Marking
Operating Temp. Range
Package
Pb-Free
MIC8115TU
NT
–40°C to +85°C
4-lead SOT-143
No
MIC8115TUY
NT
–40°C to +85°C
4-lead SOT-143
Yes
Typical Application
VCC
VCC
VCC
MIC8115
µP
MR
RESET
RESET
MIC8115 Typical Application
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2005
1
MIC8115
MIC8115
Micrel
Pin Configuration
GND 1
4 VCC
MIC8115
3 MR
RESET 2
4-Lead SOT-143
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
1100ms min. After both VCC exceeds the supply reset threshold voltage and
/MR is deasserted.
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
(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
20kΩ resistor. Float if unused.
4
VCC
Power supply Input.
MIC8115
2
July 2005
MIC8115
Micrel
Absolute Maximum Ratings(Note 1)
Operating Ratings(Note 2)
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 Temperature Range
MIC8115TU ............................................ –40°C to +85°C
Power Dissipation (TA = +70°C) .............................. 320mW
Electrical Characteristics
For typical values, VCC = 3.3V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol
Parameter
Condition
VCC
Operating Voltage Range
TA = –40°C to 85°C
VTH
Reset Voltage Threshold
ICC
Supply Current
tRST
/RESET Output Voltage
VOL
/RESET Output Voltage
/MR Minimum Pulse Width
Typ
1
Reset Timeout Period
VOH
Min
VCC = VTH min, ISINK = 1.2mA
VCC = 1V, ISINK = 50µA, TA = –40°C to +85°C
Units
5.5
V
5
15
µA
3.00
3.08
3.15
V
1100
1700
2500
ms
0.8×VCC
ISOURCE = 500µA
Max
V
0.3
V
0.3
V
10
/MR to Reset Delay
µs
0.5
/MR Input Threshold, VIH
0.7×VCC
/MR Pull-Up Resistance
10
/MR Input Threshold, VIL
/MR Glitch Immunity
V
20
100
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.
µs
0.25×VCC
30
kΩ
ns
Timing Diagram
VCC
VTH
/MR
/RESET
July 2005
tRST
tRST
3
MIC8115
MIC8115
Micrel
Functional Diagram
VCC
MR (3)
RESET
GENERATOR
RESET (2)
+
VCC (4)
Reset
Threshold (V)
-
GND (1)
MIC8115
4
July 2005
MIC8115
Micrel
Applications Information
/RESET Valid at Low Voltage
A resistor can be added from the /RESET pin-to-the 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.
Microprocessor Reset
The /RESET pin is asserted whenever VCC falls below the
reset threshold voltage. The reset pin remains asserted for a
period of 1100ms after VCC has risen above the reset threshold 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 MIC8115 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.
VCC
VCC
VCC
MIC81 15
µP
RESET
RESET
100K
/RESET Valid to VCC = 0V
July 2005
5
MIC8115
MIC8115
Micrel
Package Information
0.950 (0.0374) TYP
1.40 (0.055) 2.50 (0.098)
1.20 (0.047) 2.10 (0.083)
CL
CL
DIMENSIONS:
MM (INCH)
1.12 (0.044)
0.81 (0.032)
3.05 (0.120)
2.67 (0.105)
0.800 (0.031) TYP
0.400 (0.016) TYP 3 PLACES
8
0
0.10 (0.004)
0.013 (0.0005)
0.150 (0.0059)
0.089 (0.0035)
0.41 (0.016)
0.13 (0.005)
4-Lead SOT-143 (UT)
MICREL, INC.
1849 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 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.
© 2003 Micrel, Incorporated.
MIC8115
6
July 2005
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