MIC2774
Micrel
MIC2774
Dual Micro-Power Low Voltage Supervisor
Advance Information
General Description
The MIC2774 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 a choice of reset outputs. One under-voltage
detector compares V
DD
against a fixed threshold. Ten fac-
tory-programmed thresholds are available. The second, user-
adjustable input is compared against a 300mV reference.
This low reference voltage allows monitoring voltages lower
than those supported by previous supervisor ICs.
The reset outputs are asserted at power-on and any time
either voltage drops below the programmed threshold volt-
ages and remains asserted for 140ms (min.) after they
subsequently rise back above the threshold boundaries.
Manual reset functionality can be provided by a switch
connected between ground and the /MR input. A wide choice
of voltage thresholds provides for a variety of supply voltages
and tolerances. 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
• Choice of factory-programmed thresholds
• Adjustable input can monitor supplies as low as 0.3V
• Generates 140ms (minimum) power-on reset pulse
• Manual reset input
• Choice of active-high, active-low, or open-drain active-
low reset outputs
• Inputs may be pulled above V
DD
(7V abs. max.)
• Open-drain output can be pulled above V
DD
(7V 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
• Pin compatible upgrade for MAX6306/09/12
Applications
• Monitoring processor ASIC, or FAGA core and I/O
voltages
• PDAs, hand-held PCs
• Embedded controllers
• Telecommunications systems
• Power supplies
• Wireless / Cellular systems
• Networking hardware
Ordering Information
Part Number
MIC2774N-XXBM5
MIC2774H-XXBM5
MIC2774L-XXBM5
Marking
UGXX
UHXX
UIXX
Reset Output
Open-Drain, Active-Low (/RST)
Active-High, Complementary (RST)
Active-Low, Complementary (/RST)
Temperature Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
SOT-23-5
SOT-23-5
SOT-23-5
Typical Application
V
CORE
1.0V
V
I/O
2.5V
R1
R2
Power_Good
/MR
Manual
Reset
GND
MICROPROCESSOR
VCORE
VI/O
MIC2774L-23
VDD /RST
IN
/RESET GND
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 29, 2000
1
MIC2774
MIC2774
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
/MR GND RST
3
2
1
/MR GND /RST
3
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
MIC2774H
1
Pin Number
MIC2774L
MIC2774N
Pin Name
Pin Function
RST
Digital (Output): Asserted high whenever V
IN
or V
DD
falls below the thresh-
old voltage. It will remain asserted for no less than 140ms after V
IN
and V
DD
return above the threshold limits.
Digital (Output): Asserted low whenever V
IN
or V
DD
falls below the threshold
voltage. It will remain asserted for no less than 140ms after V
IN
and V
DD
return above the threshold limits. (open-drain for “N” version)
Ground
Digital (Input): Driving this pin low initiates immediate and unconditional
reset. Assuming V
IN
and V
DD
are above the thresholds 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): Power supply input for internal circuitry and input to the fixed
voltage monitor. The voltage on this pin is compared against the internal
reference. An undervoltage condition will trigger a reset sequence.
1
/RST
2
3
2
3
GND
/MR
4
5
4
5
IN
VDD
MIC2774
2
September 29, 2000
MIC2774
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
) ..................................... –0.3V to +7V
Input Voltages (V
IN
, V
/MR
) .............................. –0.3V to +7V
Output Voltages (V
/RST
, V
RST
) ....................... –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
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
= V
TH
+1.6%,
Note 5;
/MR, RST, /RST open
Min
Typ
3.5
Max
Units
µA
VDD VOLTAGE THRESHOLD
Under-Voltage Threshold On V
DD
(See Standard Voltage Options Table)
V
HYST
V
REF
V
HYST
I
IN
Hysteresis Voltage
V
TH
–1.5%
V
TH
1
V
TH
+1.5%
V
%
IN, UNDER-VOLTAGE DETECTOR INPUT
Under-Voltage Threshold
Hysteresis Voltage
Input Current
T
MIN
≤
T
A
≤
T
MAX
Propagation Delay
V
IN
= (V
REF(MAX)
+ 100mV) to
V
IN
= (V
REF(MIN)
– 100mV), /MR = open;
T
MIN
≤
T
A
≤
T
MAX
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
(H and L Version Only)
/MR INPUTS
V
IH
V
IL
t
PROP
t
MIN
I
PU
I
IN
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Note 5
295
300
3
5
305
mV
mV
10
pA
nA
µs
RST, /RST OUTPUTS
t
PROP
20
t
RST
V
OL
Reset Pulse Width
RST or /RST Output Voltage Low
140
280
0.3
0.3
ms
V
V
V
V
I
SOURCE
= 500µA;
V
DD
≥
1.5V
I
SOURCE
= 10µA;
V
DD
≥
1.2V;
Note 4
Note 5
Note 5
V
/MR
< (V
IL
–100mV);
Note 5
Reset Occurs, V
/MR
< V
IL
V
/MR
< V
IL
0.8V
DD
0.8V
DD
Input High Voltage
Input Low Voltage
Propagation Delay
Minimum Input Pulse Width
Internal Pull-up Current
Input Current, /MR
0.7V
DD
0.3V
DD
5
33
100
100
V
V
µs
ns
nA
nA
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 nominal “Typical Application (V
DD
)” as shown in “Standard Voltage Options Table.”
September 29, 2000
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MIC2774
MIC2774
Micrel
Timing Diagram
V
DD
0V
V
IN
0V
V
/MR
V
IH
V
IL
V
OH
V
OL
V
OH
V
OL
t
RST
> t
MIN
A
A
A
V
HYST
V
TH
V
HYST
V
REF
t
RST
t
RST
V
/RST
(ACTIVE LOW)
V
RST
(ACTIVE HIGH)
Propagation delays not shown for clarity.
Note A.
The MIC2774 ignores very brief transients.
See “Applications Information” for details.
MIC2774
4
September 29, 2000
MIC2774
Micrel
Functional Diagram
V
DD
R
V
REF
IN
Delay
Line
Q
/RST*
One Shot
S /Q
RST*
V
DD
I
PU
V
REF
/MR
GND
* Pinout and polarity vary by device type.
See ordering information table.
MIC2774
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 pin 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 MIC2774 is used to monitor the power supplies
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the appropriate reset output of a
MIC2774 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 output is asserted any time /MR is asserted or if V
IN
or V
DD
drops below the corresponding threshold voltage. The
reset output remains asserted for t
RST
(min) after V
IN
and/or
V
DD
subsequently return above the threshold boundaries
and/or /MR is released. A reset pulse is also generated at
power-on. Hysteresis is included in the comparators to pre-
vent chattering of the output 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 MIC2774’s automatic
supervisory functions. Driving the /MR input to a logic low
causes an immediate and unconditional reset to occur.
Assuming V
IN
and V
DD
are 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 connected such that /MR is shorted to ground when
the switch contacts close. Switch de-bouncing is performed
internally; the switch may be connected directly between /MR
and GND. /MR is internally pulled-up to V
DD
and may be left
open if unused.
September 29, 2000
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MIC2774
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