September 29, 2000
1
MIC2775
MIC2775
Micrel
MIC2775
Micro-Power Voltage Supervisor
Advance Information
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. Fea-
tures include an under-voltage detector, a delay generator, 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 3.5
A.
Typical Application
RST
/RST
VDD
/MR
GND
MIC2775-17
VDD
OTHER
LOGIC
/RESET
GND
MICROPROCESSOR
Manual
Reset
1.8V
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, 3.5
A typical
Rejects brief input transients
No external components
Pin compatible upgrade for MAX825
IttyBittyTM 5-lead SOT-23 package
Applications
Monitoring processor core and input/output voltages
Computer systems
PDAs, hand-held PCs
Embedded controllers
Telecommunications systems
Power supplies
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
IttyBittyTM is a trademark of Micrel, Inc.
Ordering Information
Part Number
Marking
Junction Temp. Range
Package
MIC2775-XXBM5
UJXX
40
C to +85C
SOT-23-5
MIC2775
Micrel
MIC2775
2
September 29, 2000
Pin Configuration
/RST
VDD
/MR
RST
1
3
4
5
2
GND
SOT-23-5 (M5)
Standard Voltage Options*
Voltage
Typical
Nominal Threshold
Code
Application (V
DD
)
Voltage (V
TH
)
46
5.0V
5%
4.68
44
5.0V
10%
4.43
31
3.3V
5%
3.09
29
3.3V
10%
2.93
28
3.0V
5%
2.81
26
2.85V
5%
2.67
25
2.70V
5%
2.53
23
2.5V
5%
2.34
22
2.4V
5%
2.25
17
1.8V
5%
1.69
*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 Description
Pin Number
Pin Name
Pin Function
1
RST
Digital (Output): Asserted high whenever V
DD
falls below the reference
voltage. It will remain asserted for no less than 140ms after V
DD
returns
above the threshold limit.
2
GND
Ground
3
/RST
Digital (Output): Asserted low whenever V
DD
falls below the reference
voltage. It will remain asserted for no less than 140ms after V
DD
returns
above the threshold limit.
4
/MR
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.
5
VDD
Analog (Input): Power supply input and the voltage being monitored.
September 29, 2000
3
MIC2775
MIC2775
Micrel
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 +150C
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 +85C
Package Thermal Resistance (
JA
) ...................... 256
C/W
Electrical Characteristics
Note 5; T
A
= +25
C, bold values indicate 40C T
A
+85C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
I
DD
Supply Current
V
DD
= V
TH
+1.6%, /MR, RST, /RST
3.5
A
open, Note 5
VDD VOLTAGE THRESHOLD
Under-Voltage Threshold On V
DD
V
TH
1.5%
V
TH
V
TH
+1.5%
V
V
V
HYST
Hysteresis Voltage
1
%
RST, /RST OUTPUTS
t
PROP
Propagation Delay
V
DD
= V
TH
+ 1.5% + 100mV to
20
s
V
DD
= V
TH
1.5% - 100 mV
t
RST
Reset Pulse Width
140
280
ms
V
OL
RST or /RST Output Voltage Low
I
SINK
= 1.6mA;
0.3
V
V
DD
1.6V
I
SINK
= 100
A;
0.3
V
V
DD
1.2V; Note 4
V
OH
RST or /RST Output Voltage High
I
SOURCE
= 500
A;
0.8V
DD
V
V
DD
1.5V
I
SOURCE
= 10
A;
0.8V
DD
V
V
DD
1.2V; Note 4
/MR INPUT
V
IH
Input High Voltage
0.7V
DD
V
V
IL
Input Low Voltage
0.3V
DD
V
t
PROP
Propagation Delay
From V
/MR
< (V
IL
100mV)
5
s
t
MIN
Minimum Input Pulse Width
Reset Occurs, V
/MR
< V
IL
33
ns
I
PU
Internal Pull-up Current
100
nA
I
IN
Input Current, /MR
V
/MR
< V
IL
100
nA
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.
Note 4.
V
DD
operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to V
DD
= 1.2V.
Note 5.
V
DD
equals nominal " Typical Application (V
DD
)" as shown in "Standard Voltage Options Table."
MIC2775
Micrel
MIC2775
4
September 29, 2000
Timing Diagram
V
/MR
V
IH
V
IL
V
TH
V
DD
0V
V
/RST
(ACTIVE LOW)
V
OH
V
OL
V
RST
(ACTIVE HIGH)
V
OH
V
OL
t
RST
t
RST
> t
MIN
t
RST
V
HYST
A
A
Propagation delays not shown for clarity.
Note A.
The MIC2775 ignores very brief transients.
See "Applications Information" for details.
September 29, 2000
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MIC2775
MIC2775
Micrel
Functional Diagram
GND
V
DD
/MR
MIC2775
V
REF
RST
R
S
Q
/Q
/RST
Delay
Line
One Shot
V
DD
I
PU
Functional Description
V
DD
Input
The V
DD
pin is both the power supply terminal and a moni-
tored 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. Hyster-
esis 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
C or P, 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
supervisory 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.
MIC2775
Micrel
MIC2775
6
September 29, 2000
Application Information
Ensuring Proper Operation at Low Supply
At levels of V
DD
below 1.2V, the MIC2775's /RST output
cannot turn on sufficiently to produce a valid logic-low on
/RST. In this situation, circuits driven by /RST could be
allowed to float, causing undesired operation. (In most cases,
however, it is expected that the circuits driven by the MIC2775
will be similarly inoperative at V
DD
1.2V.)
If a given application requires that /RST be valid below V
DD
= 1.2V, this can be accomplished by adding a pull-down
resistor to the /RST output. A value of 100k
is recom-
mended as this is usually an acceptable compromise of
quiescent current and pull-down current. The resistor's value
is not critical, however. See Figure 1.
/RST
RST
VDD
/MR
Manual
Reset
GND
MIC2775-XX
/RESET
VCC
GND
V
CC
MICROPROCESSOR
100k
Figure 1. MIC2775 Valid /Reset Below 1.2V
The statements above also apply to the MIC2775's RST
output. That is, to ensure valid RST signal levels at V
DD
<
1.2V, a pull-up resistor (as opposed to a pull-down) should be
added to the RST output. A value of 100k
is typical for this
application as well. See Figure 2.
/RST
RST
VDD
/MR
GND
MIC2775-XX
/RESET
VCC
GND
V
CC
Manual
Reset
MICROPROCESSOR
100k
Rpull-down
Figure 2. MIC2775 Valid Reset Below 1.2V
Transient response
The MIC2775 is inherently immune to very short negative-
going "glitches." Very brief transients may exceed the voltage
threshold without tripping the output.
As shown in Figure 3, in general the narrower the transient,
the deeper the threshold overdrive that will be ignored by the
MIC2775. The graph represents the typical allowable tran-
sient duration for a given amount of threshold overdrive that
will not generate a reset.
0
20
40
60
80
100
0
500
1000
1500
2000
MAX. TRANSIENT DURATION (
s)
RESET COMP. OVERDRIVE, V
REF
V
DD
(mV)
Typical V
DD
Transient Response
Figure 3. Typical V
DD
Transient Response
September 29, 2000
7
MIC2775
MIC2775
Micrel
Package Information
0.20 (0.008)
0.09 (0.004)
0.60 (0.024)
0.10 (0.004)
3.02 (0.119)
2.80 (0.110)
10
0
3.00 (0.118)
2.60 (0.102)
1.75 (0.069)
1.50 (0.059)
0.95 (0.037) REF
1.30 (0.051)
0.90 (0.035)
0.15 (0.006)
0.00 (0.000)
DIMENSIONS:
MM (INCH)
0.50 (0.020)
0.35 (0.014)
1.90 (0.075) REF
SOT-23-5 (M5)
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
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
2000 Micrel Incorporated
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