Data sheet
AS1907, AS1908 , AS1909
L o w - Vo l ta g e M i c r o p r o c e s s o r R e s e t C i r c u i ts
1 General Description
The AS1907/AS1908/AS1909 microprocessor supervi-
sory circuits are ideal for monitoring the supply voltage
of digital systems and microprocessors.
The devices are designed to initiate a reset if the supply
voltage goes below a predefined threshold. The duration
of the reset is either 1.5, 30, or 150ms (typ.) after the
supply voltage has risen above the pre-set threshold
(see Ordering Information on page 9).
The devices are available as the standard products
listed in
Table 1.
Table 1. Standard Products
Model
AS1907
AS1908
AS1909
Output Type
Push/Pull
Push/Pull
Open-Drain
Reset Type
Active-Low
Active-High
Active-Low
2 Key Features
!
3 Output Types: Push/Pull RESET, Push Pull
RESETN, and Open Drain RESETN
Reset Threshold Range: 1.6 to 2.5V (~100mV incre-
ments)
RESET/RESETN:
- Valid to V
CC
= 0.7V (AS1907 and AS1908)
- Valid to V
CC
= 1.0V (AS1909)
Reset Pulse Widths: 1, 20, and 100ms
Supply Voltage Range: +0.7 to +3.6V
Supply Current Range: 2.6 to 7.0µA
Power Supply Transient Immunity
Requires No External Components
Operating Temperature Range: -40 to +125ºC
3-pin SOT23 Package
!
!
!
!
!
!
!
!
The reset thresholds are factory-set between 1.6 and
2.5V in steps of approximately 100mV
(see Table 5 on
page 7).
The devices exhibit excellent reliability, and can reduce
system costs by eliminating the need for external com-
ponents. The extremely low current consumption makes
the devices ideal for use in portable applications.
The integrated reset comparator was specifically
designed to ignore fast transients on V
CC
.
The devices are available in a 3-pin SOT23 package.
!
3 Applications
The devices are ideal for use in cordless and mobile
phones, MP3 players, CD and DVD players, PDAs,
handheld computers, digital cameras, hard drives, and
any other application where power supply supervisory
control is required.
Figure 1. Application Diagrams
V
CC
V
CC
3
V
CC
3
V
CC
V
CC
3
V
CC
3
V
CC
V
CC
3
V
CC
3
Micro-
processor
Micro-
processor
Micro-
processor
AS1907
RESETN
2
RESET I/O
AS1908
2
RESET
RESET I/O
AS1909
2
RESETN
RESET I/O
GND
1
GND
1
GND
1
GND
1
GND
1
GND
1
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AS1907/AS1908/AS1909
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
GND
1
AS1908/
AS1907/
AS1909
RESET,
RESETN
2
3
V
CC
Pin Descriptions
Table 2. Pin Descriptions
Pin Number
1
Pin Name
GND
RESET
2
RESETN
Ground
Active-High Reset Output
(AS1908). This pin stays high whenever V
CC
is
below the RESET threshold V
TH
(see page 7),
and for t
TP
(see page 4)
after V
CC
rises above V
TH
.
Active-Low Reset Output
(AS1907, AS1909). This pin remains low while V
CC
is below the RESET threshold V
TH
(see page 7),
and for t
TP
(see page 4)
after
V
CC
rises above V
TH
.
Note:
This pin is open-drain on the AS1909.
Positive Supply Voltage.
Connect to +0.7 to +3.6V supply.
Description
3
V
CC
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AS1907/AS1908/AS1909
Datasheet - 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 3
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 on page 4
is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
Table 3. Absolute Maximum Ratings
Parameter
V
CC
RESET, RESETN Push/Pull
RESETN Open Drain
Input Current (V
CC
)
Output Current (RESET, RESETN)
Continuous Power Dissipation
(T
AMB
= +70ºC)
Operating Temperature Range
Storage Temperature Range
-40
-65
Min
-0.3
-0.3
-0.3
Max
+5
V
CC
+ 0.3
+6
20
20
320
+125
+160
Units
V
V
V
mA
mA
mW
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020D “Moisture/Reflow
Sensitivity Classification for Non-Hermetic
Solid State Surface Mount Devices”
3-pin SOT23 derate 4mW/ºC above +70ºC
Comments
Package Body Temperature
+260
ºC
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AS1907/AS1908/AS1909
Datasheet - 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
CC
= Full Range, T
AMB
= -40 to +125ºC (unless otherwise specified). Typ values are at V
CC
= +3.0V, T
AMB
= +25ºC.
Table 4. Electrical Characteristics
Parameter
Symbol
Conditions
T
AMB
= 0 to +85ºC
Supply Voltage Range
V
CC
T
AMB
= -40 to +85ºC
AS1907, AS1908
AS1909
AS1907, AS1908
AS1909
Min
0.7
1.0
0.78
1.2
1.2
2.4
2.6
V
TH
-
0.9%
V
TH
-
1.2%
V
TH
-
3%
1
20
100
V
TH
V
TH
V
TH
33
1.5
30
150
2
40
200
0.4
0.3
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
0.3
0.3
0.5
V
ms
Typ
Max
3.6
3.6
3.6
3.6
3.6
6.0
7.0
V
TH
+
0.9%
V
TH
+
1.2%
V
TH
+
3%
µA
V
V
V
µs
V
Unit
T
AMB
= -40 to +125ºC
Supply Current
1
I
CC
V
CC
= 1.8V, no load
V
CC
= 2.5V, no load
T
AMB
= +25ºC
RESET Threshold Voltage
V
TH
T
AMB
= 0ºC to +50°C;
AS1909C17 and AS1909C168 only
T
AMB
= -40 to +125ºC
V
CC
Falling Reset Delay
RESET Active
Time-Out Period
RESETN Output Low Voltage;
RESET asserted
(AS1907/AS1909)
RESETN Output High Voltage;
RESET Not Asserted (AS1907)
t
RD
t
TP
V
CC
falling at 10V/ms
AS190x-Azz-T
AS190x-Bzz-T
AS190x-Czz-T
I
SINK
= 50µA, V
CC
≥
1.0V
V
OL
I
SINK
= 500µA, V
CC
≥
1.8V
I
SOURCE
= 200µA, V
CC
≥
1.8V
V
OH
I
SOURCE
= 500µA, V
CC
≥
2.7V
I
SOURCE
= 1µA, V
CC
≥
1.0V
V
OH
I
SOURCE
= 200µA, V
CC
≥
1.8V
V
OL
I
LEAK
I
SINK
= 500µA, V
CC
≥
1.8V
I
SINK
= 1.2mA, V
CC
≥
2.7V
V
CC
> V
TH
V
RESET Output Voltage; RESET
Asserted (AS1908)
RESET Output Voltage; RESET
Not Asserted (AS1908)
RESETN Output Leakage
Current; RESETN
Deasserted (AS1909)
1. Not valid if V
CC
= V
TH
.
V
V
µA
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or
SQC (Statistical Quality Control) methods.
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AS1907/AS1908/AS1909
Datasheet - 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
T
AMB
= +25ºC (unless otherwise specified).
Figure 3. Supply Current vs. Temperature
3.2
3
2.8
2.6
V
CC
= 1.8V
V
CC
= 2.5V
Figure 4. Supply Current vs. Supply Voltage
6
5
4
3
2
1
0
Supply Current (µA)
.
2.4
2.2
2
-50
Supply Current (µA)
.
-25
0
25
50
75
100
125
1.4
1.8
2.2
2.6
3
3.4
3.8
Temperature (°C)
Supply Voltage (V)
Figure 5. Normalized Reset Timeout Period vs.
Temperature, V
TH
= 2.3V
1.3
Figure 6. Output Voltage Low vs. Temperature
Reset Asserted
75
.
.
Norm. Reset Timeout Period
65
55
45
35
25
15
5
-50
V
CC
= 1.0V
I
SINK
= 50µA
1.2
Output Voltage Low (mV)
V
CC
= 1.8V
I
SINK
= 500µA
1.1
V
CC
= 2.2V
I
SINK
= 500µA
1
V
CC
= 0.7V
I
SINK
= 50µA
0.9
-50
-25
0
25
50
75
100
125
-25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
Figure 7. Max. Transient Duration vs.
Reset Comparator Overdrive
700
Figure 8. V
CC
falling Propagation Delay vs.
Temperature
140
120
100
80
60
40
20
0
-50
V
CC
falling at 10V/ms
V
CC
falling at 1V/ms
.
600
500
400
Reset Occurs
Max. Transient Duration (µs)
300
200
100
0
0.1
Reset does
not Occur
1
10
100
1000
Propagation Delay (µs)
.
-25
0
25
50
75
100 125
Reset Comparator Overdrive (mV)
Temperature (°C)
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