MIC2777
Micrel
MIC2777
Dual Micro-Power Low Voltage Supervisor
General Description
The MIC2777 is a dual 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 two under-voltage detectors, one fixed and one
adjustable, and both active-high and active-low reset out-
puts. One under-voltage detector compares V
DD
against a
fixed threshold. Ten factory-programmed thresholds are avail-
able. The other under-voltage detector is user-adjustable.
The reset outputs are asserted for no less than 140ms at
power-on and any time V
DD
or the input voltage drops below
the corresponding reference voltage. They remain asserted
for the timeout period after the input voltage and V
DD
subse-
quently rise back above the threshold boundaries. A reset
can be generated at any time by pulling down on the adjust-
able input. Hysteresis is included to prevent chattering due to
noise. Typical supply current is a low 3.5µA.
Features
• Monitors two independent power supplies for under-
voltage conditions
• One fixed and one user adjustable input
• 1.5% theshold accuracy
• Choice of factory-programmed thresholds
• User-adjustable input can monitor supplies as low as
0.3V
• Generates 140ms (minimum) power-on RESET pulse
• Manual reset capability
• Both active-high and active-low RESET outputs
• Input may be pulled above V
DD
(abs. max.)
• /RST output valid down to 1.2V
• Ultra-low supply current, 3.5µA typical
• Rejects brief input transients
• IttyBitty™ 5-lead SOT-23 package
Applications
• Monitoring processor, ASIC, or FPGA core and I/O
voltages
• Computer systems
• PDAs, hand-held PCs
• Embedded controllers
• Telecommunications systems
• Power supplies
• Wireless / Cellular systems
• Networking hardware
Ordering Information
Part Number
MIC2777-XXBM5
Marking
UNXX
Junction Temp. Range
–40°C to +85°C
Package
SOT-23-5
Typical Application
V
CORE
1.0V
MICROPROCESSOR
V
CORE
V
I/O
MIC2777
VDD /RST
IN
R2
RST
/RESET
GND
V
I/O
1.8V
R1
GND
Manual
Reset
OTHER
LOGIC
Typical Application
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
September 2000
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MIC2777
MIC2777
Micrel
Standard Voltage Options*
Voltage
Code
46
44
31
29
28
26
25
23
22
17
Typical
Application (V
DD
)
5.0V
±5%
5.0V
±10%
3.3V
±5%
3.3V
±10%
3.0V
±5%
2.85V
±5%
2.70V
±5%
2.5V
±5%
2.4V
±5%
1.8V
±5%
Nominal Threshold
Voltage (V
TH
)
4.68
4.43
3.09
2.93
2.81
2.67
2.53
2.34
2.25
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 Configuration
RST GND /RST
3
2
1
4
5
IN
VDD
SOT-23-5 (M5)
Pin Description
Pin Number
1
Pin Name
/RST
Pin Function
Digital (Output): Asserted low whenever V
IN
or V
DD
falls below the reference
voltage. It will remain asserted for no less than 140ms after V
IN
and V
DD
return above the threshold limits.
Ground
Digital (Output): Asserted high whenever V
IN
or V
DD
falls below the refer-
ence voltage. It will remain asserted for no less than 140ms after V
IN
and
V
DD
return within above the threshold limit.
Analog (Input): The voltage on this pin is compared to the internal 300mV
reference. An undervoltage condition will trigger a reset sequence. Manual
reset capability can be achieved by adding a switch between this pin and
ground.
Analog (Input): Power supply input for internal circuitry and input to the fixed
voltage monitor: The votage on this pin is compared against the internal
voltage reference. An undervoltage condition will trigger a reset sequence.
2
3
GND
RST
4
IN
5
VDD
MIC2777
2
September 2000
MIC2777
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
) ..................................... –0.3V to +7V
Input Voltage (V
IN
) ......................................... –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
IN
) ........................................................... –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
Note 5;
T
A
= +25°C,
bold
values indicate –40°C
≤
T
A
≤
+85°C; unless noted
Symbol
I
DD
Parameter
Supply Current
Condition
V
DD
= V
IN
Note 5;
/MR, RST, /RST open
Min
Typ
3.5
Max
Units
µA
VDD VOLTAGE THRESHOLD
Under-Voltage Threshold On V
DD
V
HYST
V
REF
V
HYST
I
IN
Hysteresis Voltage
IN, UNDER-VOLTAGE DECTECTOR INPUT
Under-Voltage Threshold
Hysteresis Voltage
Input Current
T
MIN
≤
T
A
≤
T
MAX
RST, /RST OUTPUTS
t
PROP
Propagation Delay
V
IN
= (V
REF(MAX)
+ 100mV) to
V
IN
= (V
REF(MIN)
– 100mV) or
V
DD
= (V
TH
+ 2.5%) to (V
TH
– 2.5%), V
IN
=V
DD
140
I
SINK
= 1.6mA;
V
DD
≥
1.6V
I
SINK
= 100µA;
V
DD
≥
1.2V,
Note 4
V
OH
RST or /RST Output Voltage High
I
SOURCE
= 500µA;
V
DD
≥
1.5V
RST asserted, I
SOURCE
= 10µA;
V
DD
≥
1.2V,
Note 4
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
operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to V
DD
= 1.2V.
V
DD
equals the nominal “Typical Application (V
DD
)” as shown in “Standard Voltage Options Table.”
V
TH
-1.5%
V
TH
1
V
TH
+1.5%
V
%
295
300
3
5
305
mV
mV
pA
10
nA
µs
20
t
RST
V
OL
Reset Pulse Width
RST or /RST Output Voltage Low
280
0.3
0.3
ms
V
V
V
V
0.8V
DD
0.8V
DD
September 2000
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MIC2777
MIC2777
Micrel
Timing Diagram
V
DD
0V
V
IN
0V
V
/RST
(ACTIVE LOW)
A
A
V
HYST
V
TH
A
V
HYST
V
REF
V
OH
V
OL
V
OH
V
OL
t
RST
t
RST
V
RST
(ACTIVE HIGH)
Propagation delays not shown for clarity.
Note A.
The MIC2777 ignores very brief transients.
See “Applications Information” for details.
MIC2777
4
September 2000
MIC2777
Micrel
Functional Diagram
V
DD
R
V
REF
IN
Delay
Line
Q
/RST
One Shot
S /Q
RST
V
REF
MIC2777
GND
Functional Description
IN, Under-Voltage Detector Input
The voltage present at the IN pin is compared to the internal
300mV reference voltage. A reset is triggered if and when V
IN
falls below V
REF
. Typically, a resistor divider is used to scale
the input voltage to be monitored such that V
IN
will fall below
V
REF
as the voltage being monitored falls below the desired
trip-point. Hysteresis is employed to prevent chattering due to
noise. The comparator on the IN input is relatively immune to
very brief negative-going transients.
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 Output
Typically, the MIC2777 is used to monitor the power supplies
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the appropriate reset output of a
MIC2777 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.
The reset outputs are asserted any time V
DD
or V
IN
drops
below the corresponding threshold voltage. The reset out-
puts remain asserted for t
RST
(min) after V
IN
and/or V
DD
subsequent return above the threshold boundaries and/or
/MR is released. A reset pulse is also generated at power-on.
Manual Reset
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2777’s automatic
supervisory functions. Typically, a momentary push-button
switch is connected such that IN is shorted to ground when
the switch contacts close. Assuming V
DD
and V
IN
are within
tolerance when the switch is released, the reset outputs will
be de-asserted no less than 140ms later. IN can also be
driven by an open-drain or open-collector logic signal.
September 2000
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MIC2777
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