AS1907, AS1908 , AS1909
L o w - Vo l t a 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 t s
1 General Description
The AS1907/AS1908/AS1909 microprocessor supervisory 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 increments)
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 components. 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
Micro-
processor
V
CC
V
CC
3
V
CC
3
Micro-
processor
V
CC
V
CC
3
V
CC
3
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 A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
GND
1
AS1908/
AS1907/
AS1909
RESET,
RESETN
2
3
VCC
4.1 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
VCC
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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
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
Electrical Parameters
V
CC
to GND
Open-Drain RESETN
Push/Pull RESET, RESETN
Input Current (V
CC
)
Output Current (RESET, RESETN)
Electrostatic Discharge
Electrostatic Discharge HBM
Continuous Power Dissipation
Continuous Power Dissipation
(T
AMB
= +70ºC)
Temperature Ranges and Storage Conditions
Junction Temperature
Storage Temperature Range
-55
+150
+150
ºC
ºC
The reflow peak soldering temperature (body temperature)
specified is in accordance with
IPC/JEDEC J-STD-020
“Moisture/Reflow Sensitivity Classification for Non-
Hermetic Solid State Surface Mount Devices”.
The lead finish for Pb-free leaded packages is matte tin
(100% Sn).
Represents a maximum floor life time of unlimited
320
mW
3-pin SOT23 derate 4mW/ºC above +70ºC
±1
kV
Norm: MIL 883 E Method 3015
-0.3
-0.3
-0.3
+5.0
+6.0
V
CC
+
0.3
20
20
V
V
V
mA
mA
Min
Max
Units
Comments
Package Body Temperature
+260
ºC
Humidity non-condensing
Moisture Sensitive Level
8
1
85
%
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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.
All limits are guaranteed.
The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods.
Table 4. Electrical Characteristics
Symbol
Parameter
Conditions
T
AMB
= 0 to +85ºC
V
CC
Supply Voltage Range
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
I
CC
Supply Current
1
V
CC
= 1.8V, no load
V
CC
= 2.5V, no load
T
AMB
= +25ºC
V
TH
RESET Threshold Voltage
T
AMB
= 0ºC to +50°C;
AS1909C17, AS1909C168, AS1909C188 only
T
AMB
= -40 to +125ºC
t
RD
t
TP
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)
V
CC
falling at 10V/ms
AS190x-Azz-T
AS190x-Bzz-T
AS190x-Czz-T
I
SINK
= 50µA, V
CC
≥
1.0V
I
SINK
= 500µA, V
CC
≥
1.8V
I
SOURCE
= 200µA, V
CC
≥
1.8V
I
SOURCE
= 500µA, V
CC
≥
2.7V
I
SOURCE
= 1µA, V
CC
≥
1.0V
I
SOURCE
= 200µA, V
CC
≥
1.8V
I
SINK
= 500µA, V
CC
≥
1.8V
I
SINK
= 1.2mA, V
CC
≥
2.7V
V
CC
> V
TH
V
OL
V
OH
V
V
OH
RESET Output Voltage; RESET
Asserted (AS1908)
RESET Output Voltage; RESET Not
Asserted (AS1908)
RESETN Output Leakage Current;
RESETN
Deasserted (AS1909)
V
V
OL
I
LEAK
V
µA
1. Not valid if V
CC
= V
TH
.
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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
2.4
2.2
2
-50
V
CC
= 2.5V
Figure 4. Supply Current vs. Supply Voltage
6
5
4
3
2
1
0
Supply Current (µA)
.
V
CC
= 1.8V
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
= 2.3VReset Asserted
1.3
Figure 6. Output Voltage Low vs. Temperature
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)
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