AS1901, AS1902, AS1903
Ultra Low-Power µP Supervisory Circuit
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
!
!
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
The devices are ideal for computers, intelligent instru-
ments, controllers, critical microprocessor and micro-
controller, power monitoring and portable/battery-
powered equipment.
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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Revision 1.51
1-9
AS1901, AS1902, AS1903
Data Sheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
Top View
GND
1
AS1901
AS1902
AS1903
3
V
DD
RESETN,
RESET
2
SOT23-3
Pin Descriptions
Table 1. Pin Descriptions
Pin Number
AS1901/AS1903
1
2
AS1902
1
-
Pin Name
GND
RESETN
Description
Ground
Active-low reset output. RESETN remains low while V
DD
is
below the reset threshold and for t
TP
after V
DD
rises above
the reset threshold. RESETN is open-drain on the AS1903
and push-pull on the AS1901.
Active-high reset output. RESET remains high while V
DD
is
below the reset threshold and for t
TP
after V
DD
rises above
the reset threshold.
Supply voltage.
-
3
2
3
RESET
V
DD
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Revision 1.51
2-9
AS1901, AS1902, AS1903
Data Sheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 2 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 6 Electrical
Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Table 2. 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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Revision 1.51
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AS1901, AS1902, AS1903
Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
DD
= Full Range; T
A
= -40 to +85ºC; Unless Otherwise Specified
Table 3. 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 6, “Coding of Factory-Trimmed Reset Threshold Voltages,” on page 6.
Guaranteed by design.
Table 4, “Coding of Factory-trimmed Reset Active Time-Out Period,” on page 6.
3
See
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Revision 1.51
4-9
AS1901, AS1902, AS1903
Data Sheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
Figure 3. Supply Current vs. Temperature
0.5
Figure 4. Power Down Reset Delay vs. Temp.
200
175
V
OD
= 10mV
.
.
Reset Delay (µs)
0.4
Supply Current (mA)
150
125
100
75
50
25
0.3
0.2
0.1
0
-40
-15
10
35
60
85
0
-40
-15
10
35
60
85
Temperature(°C)
Temperature(°C)
Figure 5. Power-Up Reset Timeout vs. Temperature
.
200
Figure 6. Max. Trans. Duration vs. Reset Th. Overdrive
200
.
Power-Up Reset Timeout (ms)
Max. Transient Duration (µs)
175
150
125
100
75
50
25
0
-40
175
150
125
100
75
50
25
0
-15
10
35
60
85
1
10
100
1000
Temperature(°C)
Reset Th. Overdrive V
TH
-V
CC
(mV)
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