MIC2775
Micrel, Inc.
MIC2775
Micro-Power Voltage Supervisor
General Description
The MIC2775 is a power supply supervisor that provides
under-voltage monitoring, manual reset capability, and
power-on reset generation in a compact 5-pin SOT package.
Features include an under-voltage detector, a delay genera-
tor, a manual reset input, and both active-high and active-low
reset outputs. The under-voltage detector compares V
DD
against a fixed threshold. Ten factory-programmed thresholds
are available.
The reset outputs are asserted for no less than 140ms at
power-on and any time the input voltage drops below the
reference voltage. It remains asserted for the timeout period
after the input voltage subsequently rises back above the
threshold boundary. A reset can be generated at any time
by asserting the manual reset input, /MR. This reset output
will remain active at least 140ms after the release of /MR.
The /MR input can also be used to daisy-chain the MIC2775
onto existing power monitoring circuitry or other supervisors.
Hysteresis is included to prevent chattering due to noise.
Typical supply current is a low 3.5µA.
Features
•
•
•
•
•
•
•
•
•
•
•
Monitors power supply for under-voltage conditions
Choice of factory-programmed thresholds
Generates 140ms (minimum) power-on RESET pulse
Manual reset capability
Both active-high and active-low RESET outputs
/RST output valid down to 1.2V
Ultra-low supply current, 3.5µA typical
Rejects brief input transients
No external components
Pin compatible upgrade for MAX825
IttyBitty™ 5-pin SOT-23 package
Applications
•
•
•
•
•
•
Monitoring processor core and input/output voltages
Computer systems
PDAs, hand-held PCs
Embedded controllers
Telecommunications systems
Power supplies
Ordering Information
Part Number
Standard
MIC2775-XXBM5
Marking
Pb-Free
UJXX
MIC2775-XXYM5
Marking
UJXX
Junction Temp. Range
–40ºC to +85ºC
Package
SOT-23-5
Typical Application
1.8V
MIC2775-17
VDD RST
/MR
/RST
MICROPROCESSOR
VDD
/RESET
GND
OTHER
LOGIC
GND
Manual
Reset
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 2180Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2009
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MIC2775
MIC2775
Micrel, Inc.
Standard Voltage Options*
Voltage
Code
46
44
31
29
28
26
25
23
22
17
Typical
Application (V
DD
)
5.0V ±5%
3.3V ±5%
3.3V ±10%
3.0V ±5%
2.85V ±5%
2.70V ±5%
2.5V ±5%
2.4V ±5%
1.8V ±5%
5.0V ±10%
Nominal Threshold
Voltage (V
TH
)
4.68
3.09
2.93
2.81
2.67
2.53
2.34
2.25
1.69
4.43
*There are ten standard versions available with an order increment of 3000 pieces. Samples of standard versions are
normally available from stock. Contact factory for information on non-standard versions. Available in tape-and-reel only.
Pin Configuration
RST GND /RST
3
2
1
4
5
/MR
VDD
SOT-23-5 (M5)
Pin Description
Pin Number
1
Pin Name
/RST
Pin Function
Digital (Output): Asserted low whenever V
DD
falls below the reference volt-
age. It will remain asserted for no less than 140ms after V
DD
returns above
the threshold limit.
Ground
Digital (Output): Asserted high whenever V
DD
falls below the reference volt-
age. It will remain asserted for no less than 140ms after V
DD
returns above
the threshold limit.
Digital (Input): Driving this pin low initiates an immediate and unconditional
reset. Assuming V
DD
is above the threshold when /MR is released (returns
high), the reset output will be de-asserted no less than 140ms later. /MR
may be driven by a logic signal or a mechanical switch. /MR has an internal
pull-up to V
DD
and may be left open if unused.
Analog (Input): Power supply input and the voltage being monitored.
2
3
GND
RST
4
/MR
5
VDD
MIC2775
2
June 2009
MIC2775
Micrel, Inc.
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
)
.......................................–0.3V
to +7V
Input Voltage (V
/MR
)
........................................–0.3V
to +7V
RST, (/RST) Current
................................................... 20mA
Storage Temperature (T
S
)
........................
–65°C to +150°C
ESD Rating,
Note 3
.................................................... 1.5kV
Operating Ratings
(Note 2)
Supply Voltage (V
DD
)
..................................
+1.5V to +5.5V
Input Voltage (V
/MR
)
.....................................–0.3V
to +6.0V
Ambient Temperature Range (T
A
)
..............
–40°C to +85°C
Package Thermal Resistance (θ
JA
)
.......................
256°C/W
Electrical Characteristics
Symbol
I
DD
Note 5;
T
A
= +25°C,
bold
values indicate –40°C ≤ T
A
≤ +85°C; unless noted
Parameter
Condition
Supply Current
V
DD
= V
TH
+1.6%, /MR, RST, /RST
open, Note 5
V
TH
–1.5%
Min
Typ
3.5
Max
Units
µA
VDD VOLTAGE THRESHOLD
Under-Voltage Threshold On V
DD
V
HYST
t
PROP
t
RST
V
OL
Hysteresis Voltage
Propagation Delay
Reset Pulse Width
RST or /RST Output Voltage Low
V
DD
= V
TH
+ 1.5% + 100mV to
V
DD
= V
TH
– 1.5% - 100 mV
I
SINK
= 1.6mA;
V
DD
≥ 1.6V
V
TH
1
20
140
280
0.3
0.3
0.8V
DD
0.8V
DD
V
TH
+1.5%
V
V
%
µs
ms
V
V
V
V
RST, /RST OUTPUTS
V
OH
RST or /RST Output Voltage High
I
SINK
= 100µA;
V
DD
≥ 1.2V;
Note 4
I
SOURCE
= 500µA;
V
DD
≥ 1.5V
/MR INPUT
V
IL
V
IH
Input High Voltage
Input Low Voltage
Propagation Delay
Minimum Input Pulse Width
Internal Pull-up Current
Input Current, /MR
I
SOURCE
= 10µA;
V
DD
≥ 1.2V;
Note 4
0.7V
DD
From V
/MR
< (V
IL
–100mV)
Reset Occurs, V
/MR
< V
IL
5
33
100
100
V
0.3V
DD
V
µs
ns
nA
nA
t
PROP
t
MIN
I
IN
I
PU
V
/MR
< V
IL
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
V
DD
equals nominal “ Typical Application (V
DD
)” as shown in “Standard Voltage Options Table.”
V
DD
operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to V
DD
= 1.2V.
June 2009
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MIC2775
MIC2775
Micrel, Inc.
V
DD
0V
V
/MR
V
IH
V
IL
V
OH
V
OL
V
OH
V
OL
Propagation delays not shown for clarity.
Note A.
The MIC2775 ignores very brief transients.
See “Applications Information” for details.
Timing Diagram
A
A
> t
MIN
V
HYST
V
TH
t
RST
t
RST
t
RST
(ACTIVE LOW)
V
/RST
(ACTIVE HIGH)
V
RST
MIC2775
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June 2009
MIC2775
Micrel, Inc.
Functional Diagram
V
DD
R
V
REF
V
DD
I
PU
/MR
GND
Delay
Line
One Shot
Q
/RST
S /Q
MIC2775
RST
Functional Description
V
DD
Input
The V
DD
pin is both the power supply terminal and a monitored
input voltage. The voltage at this pin is continually compared
against the internal reference. The trip-point at which a reset
occurs is factory programmed. A reset is triggered if and
when V
DD
falls below the trip-point. Hysteresis is employed
to prevent chattering due to noise. The comparator on the
V
DD
input is relatively immune to very brief negative-going
transients.
RST, /RST Reset Outputs
Typically, the MIC2775 is used to monitor the power supply
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the appropriate reset output of a
MIC2775 to the reset input of a µC or µP, the processor will
be properly reset at power-on and during power-down and
brown-out conditions. In addition, asserting /MR, the manual
reset input, will activate the reset function.
The reset outputs are asserted any time /MR is asserted or
if V
DD
drops below the threshold voltage. The reset outputs
remain asserted for t
RST
(min) after V
DD
subsequently returns
above the threshold boundary and/or /MR is released. A reset
pulse is also generated at power-on. Hysteresis is included
in the comparator to prevent chattering of the outputs due
to noise.
/MR, Manual Reset Input
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2775’s automatic su-
pervisory functions. Driving the /MR input to a logic low causes
an immediate and unconditional reset to occur. Assuming
V
DD
is within tolerance when /MR is released (returns high),
the reset outputs will be de-asserted no less than t
RST
later.
/MR may be driven by a logic signal or mechanical switch.
Typically, a momentary push-button switch is connected
such that /MR is shorted to ground when the switch contacts
close. The switch may be connected directly between /MR
and GND. /MR has an internal 100nA pull-up current to V
DD
and may be left open if unused.
June 2009
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MIC2775
嵌入式系统
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