austria
m i c r o
s y s t e m s
AS1904, AS1905, AS1906
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 AS1904/5/6 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 device exhibits excellent reliability and can reduce
application costs by eliminating all external components.
The device is available with different output drivers:
2 Key Features
Low 150nA (typical) Supply Current
Precision Monitoring of 2.5-, 3-, and 3.3V-Power
Supplies
Supply Voltage Range 1.0 to 3.6V
Reset Threshold Available from 2.2 to 3.1V
Available in three Versions
- AS1904 Push-Pull RESETN
- AS1905 Push-Pull RESET
- AS1906 Open Drain RESETN
The AS1904 has a push-pull driver with an active low
reset.
The AS1905 uses the same output stage as the
AS1904, but has an active high reset.
The AS1906 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
SOT23-3 Package
Pin Compatible to MAX6326/6327/6328
Superior Upgrade to austriamicrosystems
AS1901/2/3 Device Family
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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 AS1904/5/6 family is offered with four
time-out periods of 5/20/100/500ms.
The extremely low current consumption of only 150nA
(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
AS1904
AS1905
RESET,
RESETN
GND
1
2
Microprocessor
AS1906
RESETN
2
Microprocessor
RESET
RESET I/O
GND
GND
1
GND
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Revision 1.4
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AS1904, AS1905, AS1906
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 the operational sec-
tions of the specifications 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
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
Limits
-0.3 to +5
-0.3 to V
DD
+ 0.3
20
20
100
-40 to +85
-65 to +150
Units
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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AS1904, AS1905, AS1906
Data Sheet
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5 Electrical Characteristics
V
DD
= Full Range; T
A
= -40º to +85°C; Unless Otherwise Specified
Table 2. Electrical Characteristics
Parameter
V
DD
Range
Supply Current
RESET Threshold
Voltage
1
Symbol
V
DD
I
DD
V
TH
T
A
= -40 to +85°C
V
DD
to Reset Delay
2
RESET Active Time-Out Period
3
RESETN Output Voltage
(AS1904/AS1906)
RESETN Output Voltage (AS1904)
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
150
V
TH
V
TH
20
t
TP
Typ
Max
3.6
3.6
290
V
TH
+
1.5%
V
TH
+
2.5%
50
t
TP
+
60%
0.4
0.4
Unit
V
V
nA
V
V
µs
ms
V
V
V
V
V
V
mV
µA
V
OL
V
OH
V
OH
RESET Output Voltage (AS1905)
V
OL
RESET Threshold Hysteresis
Open-Drain RESETN Output
Leakage Current (AS1906)
Notes:
1
2
3
V
HYST
I
LEAK
See Table 5, “Coding of Factory-Trimmed Reset Threshold Voltages,” on page 5.
Guaranteed by design.
See Table 3, “Coding of Factory-trimmed Reset Active Time-Out Period,” on page 5.
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AS1904, AS1905, AS1906
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. Temperature VCC = 3.3V
0.5
200
P o w er-D o w n R es et D elay
vs . T e m p era tu re V O D = 10m V
0.4
150
Supply Current (µA)
0.3
Reset Delay (µs)
100
0.2
50
0.1
0
-40
0
-20
0
20
40
60
80
-4 0
-2 0
0
20
40
60
80
Temperature (°C)
T e mpe rature (°C )
Power-Up Reset Timeout
vs. Temperature
200
Maximum Transient Duration
vs. Reset Threshold Overdrive
400
POWER-UP RESET TIMEOUT (ms)
160
Maximum Transient Duration (µs)
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 VDD 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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AS1904, AS1905, AS1906
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
Device
AS1904xxx
AS1905xxx
AS1906xxx
Output Functionality
Active Low (RESETN)
Active High (RESET)
Open Drain (RESETN)
Suffix
A
B
C
D
t
TP
in Milliseconds
Min
3
12
60
300
Typ
5
20
100
500
Max
8
32
160
800
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
Max
2.233
2.355
2.436
2.538
2.669
2.741
2.842
2.974
3.045
3.126
T
A
= -40 to +85°C
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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