AS1907, AS1908 , AS1909
Low-Voltage Microprocessor Reset Circuits
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 preset 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
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.
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
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
Microprocessor
AS1907
RESETN
2 RESET I/O
V
CC
V
CC
3 V
CC
3
Microprocessor
AS1908
2
RESET RESET I/O
V
CC
V
CC
3
AS1909
2
RESETN
V
CC
3
Microprocessor
RESET I/O
GND 1 GND 1 GND 1 GND 1 GND 1 GND 1 www.ams.com/Supervisors/AS1907-09 Revision 1.8
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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
RESET,
RESETN
2
AS1908/
AS1907/
AS1909
3 VCC
4.1 Pin Descriptions
Table 2. Pin Descriptions
Pin Number
1
Pin Name
GND
RESET
2
RESETN
3
VCC
Description
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.
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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
Min
-0.3
-0.3
-0.3
Max
+5.0
+6.0
V
CC
+
0.3
20
20
Units
V
V
V mA mA
Comments
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
±1
320
+150
+150 kV mW
ºC
ºC
Norm: MIL 883 E Method 3015
3-pin SOT23 derate 4mW/ºC above +70ºC
Package Body Temperature +260 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).
Humidity non-condensing
Moisture Sensitive Level
8
1
85 %
Represents a maximum floor life time of unlimited www.ams.com/Supervisors/AS1907-09 Revision 1.8
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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 Typ Unit
V
I
V
CC
CC
TH
Supply Voltage Range
Supply Current
1
RESET Threshold Voltage
T
Conditions
AS1907, AS1908
T
AMB
= 0 to +85ºC
AS1909
AMB
= -40 to +85ºC
AS1907, AS1908
AS1909
T
AMB
= -40 to +125ºC
V
CC
= 1.8V, no load
V
CC
= 2.5V, no load
T
AS1909C17, AS1909C168, AS1909C188 only
T
T
AMB
AMB
AMB
= +25ºC
= 0ºC to +50°C;
= -40 to +125ºC
V
V
V
Min
0.7
1.0
0.78
1.2
1.2
TH
0.9%
TH
1.2%
TH
3%
-
-
-
V
V
V
2.4
2.6
TH
TH
TH
3.6
3.6
6.0
7.0
Max
3.6
3.6
3.6
V
TH
+
0.9%
V
TH
+
1.2%
V
TH
+
3%
V
µA
V
V
V t
RD
V
CC
Falling Reset Delay µs t
V
TP
OL
RESET Active
Time-Out Period
RESETN Output Low Voltage; RESET asserted
(AS1907/AS1909)
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
1
20
100
33
1.5
30
150
2
40
200
0.4
0.3
ms
V
V
V
OH
OH
RESETN Output High Voltage; RESET
Not Asserted (AS1907)
RESET Output Voltage; RESET
Asserted (AS1908)
I
I
I
SOURCE
SOURCE
I
SOURCE
SOURCE
= 200µA, V
= 500µA, V
= 1µA, V
CC
= 200µA, V
CC
CC
CC
≥ 1.0V
≥ 1.8V
≥ 2.7V
≥ 1.8V
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
V
V
V
OL
RESET Output Voltage; RESET Not
Asserted (AS1908)
I
SINK
= 500µA, V
CC
≥ 1.8V
I
SINK
= 1.2mA, V
CC
≥ 2.7V
0.3
0.3
V
I
LEAK
RESETN Output Leakage Current;
RESETN
Deasserted (AS1909)
V
CC
> V
TH
0.5
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
Figure 4. Supply Current vs. Supply Voltage
6
3
2.8
V
CC
= 2.5V
5
4
2.6
2.4
2.2
V
CC
= 1.8V
2
-50 -25 0 25 50 75 100 125
Temperature (°C)
3
2
1
0
1.4
1.8
2.2
2.6
3
Supply Voltage (V)
3.4
3.8
Figure 5. Normalized Reset Timeout Period vs.
Temperature, V
TH
= 2.3VReset Asserted
1.3
1.2
1.1
1
0.9
-50 -25 0 25 50 75 100 125
Temperature (°C)
Figure 6. Output Voltage Low vs. Temperature
75
65
55
45
35
V
CC
I
SINK
= 1.8V
= 500µA
V
CC
= 2.2V
I
SINK
= 500µA
25 V
CC
I
SINK
= 0.7V
= 50µA
15
I
V
CC
= 1.0V
SINK
= 50µA
5
-50 -25 0 25 50 75 100 125
Temperature (°C) www.ams.com/Supervisors/AS1907-09 Revision 1.8
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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
Figure 7. Max. Transient Duration vs.
Reset Comparator OverdriveTemperature
700
600
500
400
300
200
Reset does not Occur
Reset Occurs
100
0
0.1
1 10 100 1000
Reset Comparator Overdrive (mV)
Figure 9. Output Voltage Low vs. V
CC
, I
SINK
= 50µA
60
50
Temp = -40°C
Temp = +25°C
Temp = +85°C
Temp = +125°C
40
30
20
10
0
0.7
1 1.3
1.6
V
CC
(V)
1.9
2.2
Figure 11. Output Voltage Low vs. V
CC
, I
SINK
= 500µA
250
200
Temp = -40°C
Temp = +25°C
Temp = +85°C
Temp = +125°C
150
100
50
0
0.7
1 1.3
1.6
V
CC
(V)
1.9
2.2
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Figure 8. V
CC
falling Propagation Delay vs.
140
120
100
V
CC
falling at 1V/ms
80
60
40
V
CC
falling at 10V/ms
20
0
-50 -25 0 25 50 75 100 125
Temperature (°C)
Figure 10. Output Voltage Low vs. V
CC
, I
SINK
= 100µA
80
70
60
Temp = -40°C
Temp = +25°C
Temp = +85°C
Temp = +125°C
50
40
30
20
10
0
0.7
1 1.3
1.6
V
CC
(V)
1.9
2.2
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AS1907/AS1908/AS1909
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
8 Application Information
8.1 Negative Going V
CC
Transients
All devices are effectively immune to short-duration, negative-going V
CC
transients (glitches). The Maximum Transient Duration vs. Reset
Comparator Overdrive graph
(see page 5)
shows the maximum pulse width that a negative-going V
CC
transient may typically have without issuing a reset signal. As the amplitude of the transient increases, the maximum allowable pulse width decreases.
22
21
20
19
Suffix
25
24
23
18
17
16
8.2 Valid Reset Output
If V
CC
falls below 1V and approaches the minimum operating voltage of 0.7V, push/pull-type reset sinking/sourcing capabilities greatly decrease.
High-impedance CMOS-logic inputs connected to RESET can drift to indeterminate voltages, although this is normally not a problem since most microprocessors do not operate at V
CC
< 1V.
For the AS1908, where RESET must be valid to V
CC
= 0, a 100k Ω pull-up resistor between RESET and V
CC
(see Figure 1 on page 1)
will hold
RESET high if V
CC
falls below 0.7V.
For the AS1907, where RESET must be valid down to 0V, add a pull-down resistor between RESET and GND
(see Figure 1 on page 1)
to eliminate stray leakage currents and hold RESET low. A pull-down resistor of 100k Ω is large enough not to load RESET yet small enough to pull it low.
Since the AS1909 has an open-drain, active-low output, it typically uses a pull-up resistor. With this device, RESET will most likely not maintain an active condition, but will drift to a non-active level due to the pull-up resistor and the reduced sinking capability of the open drain device.
Therefore, this device is not recommended for applications where the RESET pin is required to be valid down to V
CC
= 0.
Table 5. Reset Thresholds
Reset Thresholds
Min
2.478
2.378
2.279
2.180
2.081
1.982
1.883
1.784
1.685
1.586
T
AMB
= +25ºC
2.20
2.10
2.00
1.90
Typ
2.50
2.40
2.30
1.80
1.70
1.60
Max
2.523
2.422
2.321
2.220
2.119
2.018
1.917
1.816
1.715
1.614
2.13
2.04
1.94
1.84
Min
2.43
2.33
2.23
1.75
1.65
1.55
T
AMB
= -40 to +125ºC
2.27
2.18
2.06
1.96
Max
2.58
2.47
2.37
1.85
1.75
1.65
8.3 Bi-Directional Microprocessor Interface
The RESET output on the AS1909 is open-drain, thus this device can interface easily with microprocessors that have bi-directional reset pins, such as the Motorola 68HC11.
Connect the RESET output of this device directly to the microprocessor’s RESET I/O pin with a single pull-up resistor to allow either device to
assert reset (see Figure 1 on page 1)
.
8.4 Layout Considerations
The devices require proper layout and design procedures for optimum performance.
Short, wide traces should be used to reduce stray inductance and capacitance.
Bypass capacitors should be as close to the device as possible.
Large ground planes should be used wherever possible.
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AS1907/AS1908/AS1909
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
9 Package Drawings and Markings
Figure 12. 3-pin SOT23 Package
Top Marking
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Bottom Marking
Revision 1.8
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AS1907/AS1908/AS1909
Datasheet - O r d e r i n g I n f o r m a t i o n
10 Ordering Information
The devices are available as the standard products shown in Table 6 .
Table 6. Ordering Information
Ordering Code
AS1908C18-T
AS1908C20-T
AS1907C16-T
AS1907C18-T
AS1907C20-T
AS1907C22-T
AS1907B23-T
Marking
ASHU
ASHV
ASHP
ASHQ
ASHR
ASNB
ASHX
Reset Type
Active High
Active High
Active Low
Active Low
Active Low
Active Low
Active Low
Reset Threshold
1.8V
2.0V
1.6V
1.8V
2.0V
2.2V
2.3V
Minimum Reset
Timeout
100ms
100ms
100ms
100ms
100ms
100ms
20ms
Delivery Form
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
AS1909C16-T
AS1909C168-T
AS1909C17-T
AS1909C18-T
AS1909C188-T
AS1909C20-T
AS1909C22-T
AS1909C23-T
ASHY
ASSB
ASHZ
ASND
ASTE
ASH1
ASNC
ASH2
Open Drain
Open Drain
Open Drain
Open Drain
Open Drain
Open Drain
Open Drain
Open Drain
1.6V
1.68V
1.7V
1.8V
1.88V
2.0V
2.2V
2.3V
100ms
100ms
100ms
100ms
100ms
100ms
100ms
100ms
Non-standard versions require a minimum order of 30,000 units. Contact ams AG for availability of non-standard versions.
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Table 7. Coding of Factory-Trimmed Reset Active Time-Out Period
Device
AS1907xyy-T*
AS1908xyy-T*
AS1909xyy-T*
Suffix
A
B
C
Min
1
20
100 t
TP
in Milliseconds
Typ
1.5
30
150
Max
2
40
200
* These devices are available in factory-set V
CC
reset thresholds from 1.6V to 2.5V, in approximately 100mV increments. Choose the desired reset threshold suffix from
(see Table 5 on page 7) and insert it instead of “yy” in the part number.
Factory-programmed reset timeout periods are also available. Insert the code corresponding to the desired nominal reset timeout period (see
Table 7)
instead of “x” in the part number. All devices available in tape-and-reel only.
Note:
All products are RoHS compliant and ams green.
Buy our products or get free samples online at www.ams.com/ICdirect
Technical Support is available at www.ams.com/Technical-Support
For further information and requests, email us at [email protected]
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AS1907/AS1908/AS1909
Datasheet
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Copyright © 1997-2013, ams AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location.
The information furnished here by ams AG is believed to be correct and accurate. However, ams AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or other services.
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A-8141 Unterpremstaetten, Austria
Tel : +43 (0) 3136 500 0
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