参数资料
| 型号： | AS1922-18-T |
| 厂商： | ams |
| 文件页数： | 9/15页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR OPEN-DRAIN SOT23-5 |
| 标准包装： | 1 |
| 类型： | 多压监控器 |
| 监视电压数目： | 3 |
| 输出： | 开路漏极或开路集电极 |
| 复位： | 低有效 |
| 复位超时： | 最小为 140 ms |
| 电压 - 阀值： | 1.683V，2.805V，可调 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SC-74A，SOT-753 |
| 供应商设备封装： | SOT-23-5 |
| 包装： | 标准包装 |
| 其它名称： | AS1922-18-TDKR |
AS1920/AS1922
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
Supply Monitoring
The AS1920/AS1922 are low-power, high-accuracy triple-supply monitoring circuits with a single 200ms microproces-
sor reset output.
All V CC inputs (V CC18 , V CC3 , and V CCA ) must be above their thresholds to prevent a reset from being asserted. The
AS1920/AS1922 will assert a reset during powerup, powerdown and brownout conditions on one or all of the V CC
inputs.
Power Detect
The AS1920/AS1922 is powered from the 3V input pin (V CC3 ). The power detect circuitry ensures that the device pulls
pin RESETN low as soon as the primary input pin is ≥ 1V or the secondary input pin is ≥ 1V.
Powerup
The power detect circuitry ensures that RESETN will be low when either V CC18 or V CC3 ≥ 1V. As long as any one of the
V CC inputs is below its reset threshold, RESETN will stay at a logic low. When all V CC inputs have stabilized, an inter-
nal timer will be started and RESETN will be driven high after 200ms.
Powerdown
On powerdown, if any of the V CC inputs drop below its threshold, RESETN is held at a logic low (0.3V) and is guaran-
teed until V CC3 and V CC18 < 1V.
Override Functions
As the trip points for V CC3 and V CC18 will always be greater than the trip point for V CCA , if pin V CCA is not used, it
should be tied to V CC3 or V CC18 . In a similar manner if pin V CC18 is not used it should be tied to V CC3 . Tying V CC3 to
V CC18 and operating from a 1.8V supply will assure the continuous assertion of RESETN.
Note: Pin V CC3 must be used in all configurations.
Ensuring RESETN Valid for Supply Voltages < 1V
When the supplies drops below 1V the RESETN output current sink capability is greatly reduced. Stray currents and
stray capacitance to signals other than GND can cause the RESETN output to float. This is not relevant for most appli-
cations since most microprocessors and other circuits do not operate with a supply voltage < 1V.
In applications where the RESETN output must be valid down to 0V, a pulldown resistor from pin RESETN to ground
will ensure RESETN is held low (see Figure 12) .
Figure 12. Typical Application w/Resistor on RESETN Output to GND
3V
5
V CC3
1.8V
4
V CC18
AS1920/
AS1922
1
RESETN
Adjustable
3
2
R 3
100k Ω
Supply
R 1
V CCA
GND
R 2
The value of the pulldown resistor (R 3 ) is a trade-off between pulldown strength and loading of the RESETN pin. If the
value of R 3 is too large RESETN may still float, and if the value of R 3 is too small it may load RESETN and also use
excess supply current, therefore a value of 100k Ω is recommended for the pulldown resistor.
www.austriamicrosystems.com
Revision 1.00
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