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PDF AS1923 Data sheet ( Hoja de datos )
| Número de pieza | AS1923 | |
| Descripción | Quad-Voltage Microprocessor Supervisory Circuit | |
| Fabricantes | austriamicrosystems AG | |
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Datasheet
AS1923
Quad-Voltage Microprocessor Supervisory Circuit
1 General Description
The AS1923 microprocessor supervisory circuit was designed to
monitor up to four system supply voltages without the need for exter-
nal components, and asserts a single reset if any of the monitored
supply voltages drops below its reset threshold.
The AS1923 features an active-low reset output that is asserted
when any of the 4 monitored voltages are below their respective
reset threshold. The reset output is open-drain with a weak internal
pullup (10µA) to IN2. Reset remains low for a specified reset timeout
period (120ms min) after all voltages have stabilized. The output is
valid as long as the IN1 or IN2 input voltage remains >1V.
Minimal external component requirements, small size, and wide tem-
perature range (-40 to +85°C) greatly improves reliability compared
to individual supervisory circuits or discrete components.
A wide range of factory-trimmed threshold voltages are available to
accommodate many different supply voltages/tolerances with mini-
mal external component requirements.
Factory-trimmed options are available for monitoring +5.0, +3.3,
+3.0, +2.5, +1.8, and -5.0V supplies with -5% and/or -10% toler-
ances. The device is also available with one or two user-adjustable
threshold options (via external resistor-divider network) if non-stan-
dard voltage thresholds are required.
The AS1923 is available in an 6-pin SOT23 package.
Figure 1. AS1923 - Typical Application
2 Key Features
Simultaneous Quad-Voltage Monitoring
Precision Factory-Trimmed Reset Threshold Options: +5.0,
+3.3, +3.0, +2.5, +1.8, and -5.0V
User-Adjustable Voltage Monitoring Threshold Options
Low Supply Current: 55µA
Open-Drain – AS1923A
10µA Current Source Pullup – AS1923B
Reset Timeout Period: 120ms
RESET Valid to IN1 = 1V or IN2 = 1V
Immune to Fast INx Transients
External Components not Required
Guaranteed Performance: Operating Temperature Range = -40
to +85ºC
6-pin SOT23 Package
3 Applications
The device is ideal for portable and battery-powered systems,
embedded controllers, intelligent instruments, automotive systems,
critical CPU monitoring, and any multi-supply application.
Monitoring
Voltage 1
4
IN1
Monitoring
5
Voltage 2
IN2
3
AS1923
RESETN RESETN
Monitoring
6
Voltage 3 IN3
Monitoring
Voltage 4
1
IN4
GND 2
CPU
www.austriamicrosystems.com/Supervisors/AS1923
Revision 1.01
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1 page  
AS1923
Datasheet - Electrical Characteristics
Table 3. Electrical Characteristics (Continued)
Symbol
Parameter 1
VOL Output Low Voltage
VOH 6
IOH 5
Output High Voltage,
Output High Source Current
Output High Source Current
Conditions
VIN2 = 5V, ISINK = 2mA
VIN2 = 2.5V, ISINK = 1.2mA
VIN1 = VIN2 = 1V, ISINK = 50µA
VIN2 > 2.55V, ISOURCE = 6µA
(Reset Not Asserted)
VIN2 ≥ 2.55V (Reset Not Asserted),
VOUT ≥ 0.8 x VIN2
Min Typ Max Units
0.4
0.4 V
0.4
0.8 x
VIN2
V
6 10
µA
1. 100% production tested at TAMB = +25ºC. Limits over temperature guaranteed by design.
2. The device is powered from input IN2.
3. The RESETN output is guaranteed to be in the correct state for IN1 or IN2 down to 1V.
4. Monitored voltage at IN2 (+3.3V, +3.0V) is also the device power supply. Supply current split is 25µA for the resistor-divider network (for
the monitored voltage) and 30µA for other circuits.
5. Adjustable pin only.
6. AS1923B only.
Note: All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality
Control) methods.
www.austriamicrosystems.com/Supervisors/AS1923
Revision 1.01
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5 Page 
AS1923
Datasheet - Application Information
Negative Voltage Monitoring Beyond -5V
The AS1923 is available with options to monitor -5V supplies using internally trimmed thresholds. In cases where monitored supplies are more
negative than -5V, an external low-impedance resistor-divider network can be used as shown in Figure 14.
The current through the external resistor-divider should be greater than the input current for the -5V monitor options. For an input monitor current
error of <1%, the resistor-divider current should be ≥ 2mA (for IIN4 = 20µA max).
Figure 14. Negative Voltage Monitoring Beyond -5V
R2
-5V
R1
VINTH
VREF =
1.23V
+
–
–
+
For the circuit shown in Figure 14, calculate R1 based on the desired VINx reset threshold voltage:
R1
=
R2
×
⎛
⎝
V-----I--N---T---H--
1,23V
–
1⎠⎞
(EQ 3)
Where:
R2 ≤ 2.49kΩ
VINTH is the desired threshold voltage.
VTH is the internal threshold voltage.
For -VIN = -12V nominal:
VINTH = -11.1V,
VTH = -4.63V,
R2 = 2.49kΩ.
Using the equation given in (EQ 3), R1 can be calculated as:
R1
=
2,49k
Ω
×
⎛
⎝
–----1---1---,--1----V--
–4,63V
–
1⎠⎞
Therefore, R1 = 3.48kΩ
Power-Supply Bypassing and Grounding
The AS1923 is powered from the IN2 supply input. All monitor inputs are immune to fast supply transients.
If higher immunity is required in noisy systems, connect 0.1µF bypass capacitors from the IN2 input to ground (see Figure 15). Additional capac-
itance can be added to IN1, IN3, and IN4 to improve noise immunity at these inputs.
Figure 15. IN2 Additional Noise Immunity
3.0 to
3.3V
5
IN2
0.1µF
2
GND
AS1923
www.austriamicrosystems.com/Supervisors/AS1923
Revision 1.01
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AS1923.PDF ] | |
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