austria
m i c r o
s y s t e m s
AS1901, AS1902, AS1903
U l t r a L o w - P o w e r µP S u p e r v i s o r y C i r c u i t
D a ta S he e t
1 General Description
The AS1901/2/3 family is an ultra low-power supervisory
circuit device.
The device can be used to monitor the supply voltage of
digital systems and microprocessors and initiate a reset
when the voltage goes below a predefined threshold.
The duration of the reset is 5/20/100/500ms (typ.) after
the supply voltage has risen above the threshold.
The AS1901/2/3 exhibit excellent reliability and can
reduce application costs by eliminating all external com-
ponents.
The device is available with different output drivers:
2 Key Features
Low 230nA (typ) Supply Current
Precision Monitoring of 2.5-, 3-, and 3.3V-Power
Supplies
Supply Voltage Range: 1.0 to 3.6V
Reset Threshold Range: 2.2 to 3.1V
Available in 3 Versions:
- AS1901 Push Pull RESETN
- AS1902 Push Pull RESET
- AS1903 Open Drain RESETN
The AS1901 has a push-pull driver with an active low
reset.
The AS1902 uses the same output stage as the
AS1901, but has an active high reset.
The AS1903 has an open drain output with active low
reset.
4 Time-Out Periods Ranging from 5 to 500ms
Detection Voltage Accuracy: ±1.5%
Temperature Range: -40 to +85°C
Package: SOT23-3
Pin Compatible to MAX6326/6327/6328
All devices operate down to a voltage of 1V.
The reset thresholds are factory-trimmable between
2.2V and 3.08V in steps of approximately 100mV.
Each device of the AS1901/2/3 family is offered with four
time-out periods of 5/20/100/500ms.
The extremely low current consumption of only 230nA
(typ) at 3.3V makes the device ideal for use in portable
applications.
All devices are available in a 3-pin SOT23 package.
3 Applications
Computers
Intelligent Instruments
Controllers
Critical Microprocessor and Microcontroller
Power Monitoring
Portable/Battery-Powered Equipment
Automotive
Figure 1. Functional Block Diagrams
V
CC
3
V
DD
V
CC
V
CC
3
V
DD
V
CC
AS1901
AS1902
RESETN,
RESET
GND
1
2
Microprocessor
AS1903
2
Microprocessor
RESET
RESETN
RESET I/O
GND
GND
1
GND
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AS1901, AS1902, AS1903
Data Sheet
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4 Absolute Maximum Ratings
Stresses beyond those listed in Table 1 may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in Section 5 Electrical
Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Table 1. Absolute Maximum Ratings
(
T
A
= 25°C Unless Otherwise Noted)
Parameter
Limits
Unit
V
DD
to GND
RESET/RESETN to GND
Input Current (V
DD
)
Output Current (RESET, RESETN)
Rate of Rise (V
DD
)
Operating Temperature Range (T
A
)
Storage Temperature Range
-0.3 to +5
-0.3 to V
DD
+ 0.3
20
20
100
-40 to +85
-65 to +150
V
V
mA
mA
V/µs
°C
°C
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020C “Moisture/Reflow
Sensitivity Classification for non-hermetic
Solid State Surface Mount Devices”
Notes
Package-Body Peak Temperature
+260
°C
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AS1901, AS1902, AS1903
Data Sheet
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5 Electrical Characteristics
V
DD
= Full Range; T
A
= -40 to +85ºC; Unless Otherwise Specified
Table 2. Electrical Characteristics
Parameter
V
DD
Range
Supply Current (AS1901/2/3)
Reset Threshold Voltage
1
V
DD
to Reset Delay
2
Reset Active Time-Out Period
3
Symbol
V
DD
I
DD
V
TH
T
A
= -40 to +85°C
t
RD
t
TP
I
SINK
= 1.2mA, V
DD
= 2.1V, Reset
Asserted
I
SINK
= 400µA, V
DD
= 1.2V, Reset
Asserted
I
SOURCE
= 1.2mA, V
DD
= 3.2V
I
SOURCE
= 500µA, V
DD
= 2.1V,
Reset Asserted
I
SOURCE
= 100µA, V
DD
= 1.2V,
Reset Asserted
I
SINK
= 1.2mA, V
DD
= 3.2V,
Reset Not Asserted
10
0.1
0.8 x
V
DD
0.8 x
V
DD
0.8 x
V
DD
0.4
V
DD
= V
TH
to (V
TH
- 100mV)
t
TP
-
40%
Conditions
T
A
= 0 to +70°C
T
A
= -40 to +85°C
V
DD
= 3.3V, No Load
T
A
= +25°C
V
TH
-
1.5%
V
TH
-
2.5%
Min
1.0
1.2
230
V
TH
V
TH
20
t
TP
Typ
Max
3.6
3.6
430
V
TH
+
1.5%
V
TH
+
2.5%
50
t
TP
+
60%
0.4
0.4
Unit
V
nA
V
µs
ms
V
V
V
V
V
V
mV
µA
RESETN Output Voltage (AS1901/3)
V
OL
RESETN Output Voltage (AS1901)
V
OH
V
OH
RESET Output Voltage (AS1902)
V
OL
RESET Threshold Hysteresis
Open-Drain RESETN Output
Leakage Current (AS1903)
Notes:
1
2
V
HYST
I
LEAK
See Table 5, “Coding of Factory-Trimmed Reset Threshold Voltages,” on page 5.
Guaranteed by design.
Table 3, “Coding of Factory-trimmed Reset Active Time-Out Period,” on page 5.
3
See
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Data Sheet
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Interfacing to Microprocessors with Bi-Directional Reset Pins
6 Operation
6.1 Interfacing to Microprocessors with Bi-Directional Reset Pins
The device has an open drain RESETN output, which enables easy interfacing to microprocessors (µP) with bi-direc-
tional reset pins, such as the Motorola 68HC11. The RESETN pin of the microcontroller (µC) can be connected directly
to the µP supervisor's RESETN output with a single pull-up resistor (see Figure 1 on page 1).
6.2 Operating Characteristics
Supply Current vs. Tem perature,
VCC=3.3V
0.5
200
Pow er-Dow n Reset Delay
vs. Tem perature, VOD = 10m V
0.4
Supply Current (µA)
RESET DELAY (µs)
- 20
0
20
40
60
80
150
0.3
0.2
100
0.1
50
0
-40
0
-40
-20
0
20
40
60
80
Temperature (°C)
Temperature (°C)
Power-Up Reset Timeout
vs. Temperature
200
Maximum Transient Duration
vs. Reset Threshold Overdrive
400
Power Up Reset Timeout
(ms)
Maximum Transient Duration (µs)
160
300
120
200
80
100
40
0
-40
-20
0
20
40
60
80
0
1
10
100
1000
Temperature (°C)
Reset Threshold Overdrive
Vth-Vcc (mV)
6.3 Negative-Going V
DD
Transients
The device is optimized to ignore short-duration, negative-going V
DD
transients (glitches) in order to avoid incorrect
resets.
In the graph Maximum Transient Duration vs. Reset Threshold Overdrive (page 4), the conditions are shown, for which
the reset pulses are not generated. In the graph the maximum pulse width that a negative V
DD
transient may have
when a reset signal is generated. As the amplitude of the transient increases, the maximum allowable pulse width
decreases.
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AS1901, AS1902, AS1903
Data Sheet
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7 Options
Table 3. Coding of Factory-trimmed Reset Active Time-Out Period
Device
AS190x_xx
AS190x_xx
AS190x_xx
AS190x_xx
Table 4. Output Variants
Suffix
A
B
C
D
t
TP
in Milliseconds
Min
3
12
60
300
Typ
5
20
100
500
Max
8
32
160
800
Device
AS1901xxx
AS1902xxx
AS1903xxx
Output Functionality
Active Low (RESETN)
Active High (RESET)
Open Drain (RESETN)
Table 5. Coding of Factory-Trimmed Reset Threshold Voltages
Reset Threshold Voltage, V
TH
in V
Device
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
AS190xx__
Suffix
Min
22
23
24
25
26
27
28
29
30
31
2.167
2.285
2.364
2.463
2.591
2.660
2.758
2.886
2.955
3.034
T
A
= +25°C
Typ
2.2
2.32
2.4
2.5
2.63
2.7
2.8
2.93
3.0
3.08
T
A
= -40 to +85°C
Max
2.233
2.355
2.436
2.538
2.669
2.741
2.842
2.974
3.045
3.126
Min
2.145
2.262
2.340
2.438
2.564
2.633
2.730
2.857
2.925
3.003
Max
2.255
2.378
2.460
2.563
2.696
2.768
2.870
3.003
3.075
3.157
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