MIC2776
Micrel, Inc.
MIC2776
Micro-Power Low Voltage Supervisor
General Description
The MIC2776 is a power supply supervisor which provides
under-voltage monitoring and power-on reset generation in a
compact 5-pin SOT package. Features include an adjustable
under-voltage detector, a delay-generator, a manual reset
input, and a choice of active-high, active-low, or open-drain
active-low reset output. The user-adjustable monitoring input
is compared against a 300mV reference. This low reference
voltage allows monitoring voltages lower than those supported
by previous supervisor ICs.
The reset output is 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. The reset output will remain ac-
tive at least 140ms after the release of /MR. The /MR input
can also be used to daisy-chain the MIC2776 onto existing
power monitoring circuitry or other supervisors. Hysteresis
is included to prevent chattering due to noise. Typical supply
current is a low 3.0µA.
Features
• User-adjustable input can monitor supplies as low as
0.3V
• ±1.5% threshold accuracy
• Separate V
DD
input
• Generates power-on reset pulse (140ms min.)
• Manual reset input
• Choice of active-high, active-low or open-drain active-
low reset output
• Inputs can be pulled above V
DD
(7V abs. max.)
• Open-drain output can be pulled above V
DD
(7V abs.
max.)
• Ultra-low supply current, 3.0µA typical
• Rejects brief input transients
• IttyBitty™ SOT-23-5 package
Applications
•
•
•
•
•
•
•
•
Monitoring processor, ASIC, or FPGA core voltage
Computer systems
PDAs/Hand-held PCs
Embedded controllers
Telecommunications systems
Power supplies
Wireless / cellular systems
Networking hardware
Typical Application
V
CORE
1.0V
V
I/O
2.5V
R1
R2
MIC2776L
VDD /RST
IN
/MR
GND
MICROPROCESSOR
VCORE
VI/O
/RESET GND
Power_Good
Manual
Reset
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
November 2005
1
MIC2776
MIC2776
Micrel, Inc
Ordering Information
Part Number
Standard
MIC2776N-BM5
MIC2776H-BM5
MIC2776L-BM5
Marking
UKAA
ULAA
UMAA
Pb-Free
MIC2776N-YM5
MIC2776H-YM5
MIC2776L-YM5
Marking
UKAA
ULAA
UMAA
Reset Output
Open-Drain, Active-Low / RST
Active-High, Complementary RST
Active-Low, Complementary /RST
Temperature Range
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
Package
SOT-23-5
SOT-23-5
SOT-23-5
Pin Configuration
/MR
GND
RST
3
/MR
GND
/RST
3
2
1
2
1
4
5
4
5
IN
VDD
IN
VDD
SOT-23-5 (M5)
“H” Version
SOT-23-5 (M5)
“L” and “N” Version
Pin Description
Pin Number
MIC2776H
1
Pin Number
MIC2776L
MIC2776N
Pin Name
Pin Function
RST
Digital (Output): Asserted high whenever V
IN
falls below the reference volt-
age. It will remain asserted for no less than 140ms after V
IN
returns above
the threshold limit.
Digital (Output): Asserted low whenever V
IN
falls below the reference volt-
age. It will remain asserted for no less than 140ms after V
IN
returns above
the threshold limit. (open-drain for “N” version)
Ground
Digital (Input): Driving this pin low initiates an immediate and unconditional
reset. Assuming IN 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): The voltage on this pin is compared to the internal 300mV
reference. An under-voltage condition will trigger a reset sequence.
Analog (Input): Independent supply input for internal circuitry.
1
/RST
2
3
2
3
GND
/MR
4
5
4
5
IN
VDD
MIC2776
2
November 2005
MIC2776
Micrel, Inc.
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
).......................................–0.3V to +7V
Input Voltages (V
IN
, 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 Voltages (V
IN
, V
/MR
) ............................–0.3V to +6.0V
Output Voltages
V
/RST
(N version) ......................................–0.3V to +6.0V
V
/RST
, V
RST
(H and L versions)........ –0.3V to V
DD
+ 0.3V
Ambient Temperature Range (T
A
) .............. –40°C to +85°C
Package Thermal Resistance (θ
JA
) ....................... 256°C/W
Min
Typ
3.0
295
300
3
5
T
MIN
≤ T
A
≤ T
MAX
V
IN
= (V
REF(MAX)
+ 100mV) to
V
IN
= (V
REF(MIN)
– 100mV)
I
SINK
= 1.6mA;
V
DD
≥ 1.6V
20
140
280
0.3
0.3
0.8V
DD
0.8V
DD
10
305
Max
Units
µA
mV
mv
pA
nA
µs
ms
V
V
V
V
Electrical Characteristics
Symbol
Parameter
Condition
I
DD
Supply Current
Under-Voltage Threshold
Hysteresis Voltage
Input Current
V
DD
= 3.3V; T
A
= +25°C,
bold
values indicate –40°C ≤ T
A
≤ +85°C; unless noted
V
DD
= V
IN
= 3.3V; /MR, RST, /RST open
T
A
= 25°C
IN, UNDER-VOLTAGE DETECTOR INPUT
V
REF
I
IN
V
HYST
RESET OUTPUTS (/RST, RST)
t
PROP
t
RST
V
OL
Propagation Delay
Reset Pulse Width
RST or /RST Output Voltage Low
V
OH
RST or /RST Output Voltage High
(H and L Version Only)
MANUAL RESET INPUTS (/MR)
V
IH
V
IL
t
PROP
t
MIN
I
PU
I
IN
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
1.5V ≤ V
DD
≤ 5.5V
1.5V ≤ V
DD
≤ 5.5V
V
/MR
< V
IL
Reset Occurs, V
/MR
< V
IL
I
SOURCE
= 500µA;
V
DD
≥ 1.5V
I
SINK
= 100µA;
V
DD
≥ 1.2V,
Note 4
0.7V
DD
5
33
100
100
V
0.3V
DD
V
µs
ns
nA
nA
V
/MR
< V
IL
Note 1.
Note 2.
Note 3.
Note 4.
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.
November 2005
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MIC2776
MIC2776
Micrel, Inc
Timing Diagram
V
DD
0V
A
A
V
HYST
V
REF
V
IN
0V
V
/MR
V
OH
V
OL
V
RST
V
OH
V
OL
>t
min
t
RST
t
RST
t
RST
t
RST
V
/RST
V
OH
V
OL
Propagation delays not shown for clarity.
Note A.
The MIC2776 ignores very brief transients.
See “Applications Information” for details.
MIC2776
4
November 2005
MIC2776
Micrel, Inc.
V
DD
I
PU
Functional Diagram
/MR
IN
Delay
One Shot
R
Q
/RST*
S
/Q
RST*
V
REF
GND
MIC2776
* Pinout and polarity vary by device type.
See ordering information table.
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 chat-
tering due to noise.
RST, /RST Reset Output
Typically, the MIC2776 is used to monitor the power supply
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the reset output of a MIC2776 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 condi-
tions. 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
IN
drops below the threshold voltage. The reset outputs
remain asserted for t
RST
(min) after V
IN
subsequently returns
above the threshold boundary and /MR is released. A reset
pulse is also generated at power-on.
/MR, Manual Reset Input
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2776’s automatic
supervisory functions. Driving the /MR input to a logic low
causes an immediate and unconditional reset to occur. As-
suming V
IN
is within tolerance when /MR is released (returns
high), the reset output 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 con-
nected 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.
November 2005
5
MIC2776
PCB设计
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