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AS111RCP10/SPACE 参数 Datasheet PDF下载

AS111RCP10/SPACE图片预览
型号: AS111RCP10/SPACE
PDF下载: 下载PDF文件 查看货源
内容描述: 电压比较器 [Voltage Comparator]
分类和应用: 比较器放大器
文件页数/大小: 22 页 / 1614 K
品牌: AUSTIN [ AUSTIN SEMICONDUCTOR ]
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Voltage  
Comparator  
AS111 RAD-TOL  
PRELIMINARY SPECIFICATION  
Austin Semiconductor, Inc.  
APPLICATION HINTS (CONTINUED)  
4. When comparator circuits use input resistors (eg.  
summing resistors), their value and placement are  
particularly important. In all cases the body of the resistor  
should be close to the device or socket. In other words  
there should be very little lead length or printed-circuit foil  
run between comparator and resistor to radiate or pick up  
signals. The same applies to capacitors, pots, etc. For  
power-supply bypass to be located immediately adjacent  
to the comparator.)  
6. It is a standard procedure to use hysteresis (positive  
feedback) around a comparator, to prevent oscillation, and  
to avoid excessive noise on the output because the  
comparator is a good amplifier for its own noise. In the  
circuit of Figure 2, the feedback from the output to the  
positive input will cause about 3 mV of hysteresis.  
example, if RS=10 kW, as little as 5 inches of lead between  
the resistors and the input pins can result in oscillations  
that are very hard to damp. Twisting these input leads  
tightly is the only(second best) alternative to placing re-  
sistors close to the comparator.  
However, if RS is larger than 100, such as 50 k, it would  
not be reasonable to simply increase the value of the  
positive feedback resistor above 510 k. The circuit of  
Figure 3 could be used, but it is rather awkward. See the  
notes in paragraph 7 below.  
5. Since feedback to almost any pin of a comparator can  
result in oscillation, the printed-circuit layout should be  
engineered thoughtfully. Preferably there should be a  
groundplane under the AS111 circuitry, for example, one  
side of a double-layer circuit card. Ground foil (or, positive  
supply or negative supply foil) should extend between the  
output and the inputs, to act as a guard. The foil  
connections for the inputs should be as small and compact  
as possible, and should be essentially surrounded by  
ground foil on all sides, to guard against capacitive  
coupling from any high-level signals (such as the output).  
If pins 5 and 6 are not used, they should be shorted  
together. If they are connected to a trim-pot, the trim-pot  
should be located, at most, a few inches away from the  
AS111, and the 0.01 µF capacitor should be installed. If  
this capacitor cannot be used, a shielding printed-circuit  
foil may be advisable between pins 6 and 7. The power  
supply bypass capacitors should be located within a couple  
inches of the AS111. (Some other comparators require the  
7. When both inputs of the AS111 are connected to active  
signals, or if a high-impedance signal is driving the  
positive input of the AS111 so that positive feedback would  
be disruptive, the circuit of Figure 1 is ideal. The positive  
feedback is to pin 5 (one of the offset adjustment pins). It is  
sufficient to cause 1 to 2 mV hysteresis and sharp  
transitions with input triangle waves from a few Hz to  
hundreds of kHz. The positive-feedback signal across the  
82resistor swings 240 mV below the positive supply.  
This signal is centered around the nominal voltage at pin 5,  
so this feedback does not add to the VOS of the  
comparator. As much as 8 mV of VOS can be trimmed out,  
using the 5 kpot and 3 kresistor as shown.  
8. These application notes apply specifically to the AS111  
family of comparators, and are applicable to all high-speed  
comparators in general, (with the exception that not all  
comparators have trim pins).  
NOTE: Pin connections shown are for the TO08 can package.  
AS111 RAD-TOL  
Rev. 1.1 06/05  
AustinSemiconductor,Inc.reservestherighttochangeproductsorspecificationswithoutnotice.  
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