May 2003
1
MIC1810
Micrel
MIC1810
Microprocessor Reset Circuit
Final Information
General Description
The MIC1810 is an inexpensive microprocessor supervisory
circuit that monitors power supplies in microprocessor based
systems.
The function of these devices is to assert a reset if the power
supply drops below a designated reset threshold level. Sev-
eral different reset threshold levels are available to accom-
modate 5%, 10%, or 15% drop in 5V powered systems.
The MIC1810 has an active low /RESET output. The reset
output is guaranteed to remain asserted for a minimum of
100ms after V
CC
has risen above the designated reset thresh-
old level. The MIC1810 comes in a 3-pin SOT-23 package.
Typical Application
8++
4-5-6
P
4-5-6
8++
MIC1810
8++
Features
Precision voltage monitor for 5%, 10%, or 15% drop in
5V power supplies
/RESET remains valid with V
CC
as low as 1.4V
9
A supply current (typical)
100ms minimum reset pulse width
No external components required
Available in 3-pin SOT-23 package
Applications
Portable equipment
Intelligent instruments
Critical microprocessor power monitoring
Printers/computers
Embedded controllers
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
Ordering Information
Threshold
Part Number
Marking
Voltage
Operating Temp. Range
Package
MIC1810-5U
NA
4.62V
40
C to +85C
SOT-23
MIC1810-10U
NB
4.37V
40
C to +85C
SOT-23
MIC1810-15U
NC
4.12V
40
C to +85C
SOT-23
MIC1810
Micrel
MIC1810
2
May 2003
Pin Description
Pin Number
Pin Name
Pin Function
1
/RESET
/RESET goes low if V
CC
falls below the reset threshold and remains
asserted for one reset timeout period (100ms min) after V
CC
exceeds the
reset threshold.
2
VCC
Power supply input.
3
GND
IC ground pin
Pin Configuration
1
2
3
V
CC
GND
MIC1810
RESET
3-Lead SOT-23
May 2003
3
MIC1810
Micrel
Absolute Maximum Ratings
(Note 1)
Terminal Voltage (V
CC
) .................................. 0.3V to +6V
Input Current (V
CC
) .................................................... 20mA
Output Current, /RESET ............................................ 20mA
Rate of Rise (V
CC
) ................................................. 100V/
s
Lead Temperature (soldering, 10 sec.) ..................... 300
C
Storage Temperature (T
S
) ......................... 65
C to 150C
ESD Rating, Note 3
Operating Ratings
(Note 2)
Operating Temperature Range
MIC1810-5U ........................................... 40
C to +85C
MIC1810-10U ......................................... 40
C to +85C
MIC1810-15U ......................................... 40
C to +85C
Power Dissipation (T
A
= +70
C) .............................. 320mW
Electrical Characteristics
For typical values V
CC
= 5V, T
A
= 25
C; bold values indicate 40C T
A
+85C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
Operating Voltage Range
T
A
= 0
C to +70C
1.7
5.5
V
T
A
= 40
C to +85C
1.5
5.5
V
I
CC
Supply Current
9
20
A
V
TH
Reset Voltage Threshold
MIC1810-5
4.50
4.62
4.75
V
MIC1810-10
4.25
4.37
4.50
V
MIC1810-15
4.00
4.12
4.24
V
t
RST
Reset Timeout Period
100
150
250
ms
V
OH
/RESET Output Voltage, High
I
SOURCE
= 800
A
V
CC
1.5
V
V
OL
/RESET Output Voltage, Low
V
CC
= V
TH
min., I
SINK
= 3.2mA
0.4
V
V
CC
> 1.4V, I
SINK
= 50
A
0.3
V
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.
Timing Diagram
/RESET
V
CC
t
RST
t
RST
V
TH
V
TH
Reset Timing Diagram
MIC1810
Micrel
MIC1810
4
May 2003
Functional Diagram
+
-
Reset
Threshold (VTH)
VCC (2)
RESET (1)
GND (3)
RESET
GENERATOR
May 2003
5
MIC1810
Micrel
Applications Information
Microprocessor Reset
The /RESET pin is asserted whenever V
CC
falls below the
reset threshold voltage. The reset pin remains asserted for a
period of t
RST
after V
CC
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 V
CC
as low as
1.4V.
V
CC
Transients
The MIC1810 is relatively immune to negative-going V
CC
glitches below the reset threshold. Typically, a negative-
going transient 125mV below the reset threshold with a
duration of 50
s or less will not cause an unwanted 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 V
CC
down to 0V.
A 100k
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. See Figure below.
VCC
RESET
P
RESET
VCC
MIC1810
VCC
100K
/RESET Valid to V
CC
= 0V
MIC1810
Micrel
MIC1810
6
May 2003
Package Information
0.15 (0.006)
0.076 (0.0030)
0.41 (0.016)
0.13 (0.005)
3.05 (0.120)
2.67 (0.105)
8
0
0.445 (0.0175) TYP 3 PLACES
2.50 (0.098)
2.10 (0.083)
1.40 (0.055)
1.19 (0.047)
0.10 (0.004)
0.013 (0.0005)
1.15 (0.045)
0.76 (0.030)
DIMENSIONS:
MM (INCH)
2.36 (0.093)
2.28 (0.090)
C
L
C
L
3-Pin SOT-23 Small Outline Transistor
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 designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
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.
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