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LM231A

更新时间： 2024-01-30 19:17:46
品牌 Logo 应用领域
美国国家半导体 - NSC 转换器
页数 文件大小 规格书
15页 371K
描述
Precision Voltage-to-Frequency Converters

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LM231A 技术参数

是否Rohs认证： 不符合生命周期：Obsolete
包装说明：SOP, SOP14,.4Reach Compliance Code：unknown
ECCN代码：EAR99HTS代码：8542.39.00.01
风险等级：5.82转换器类型：VOLTAGE TO FREQUENCY CONVERTER
JESD-30 代码：R-PDSO-G14JESD-609代码：e0
最大线性误差 (EL)：0.02%功能数量：1
端子数量：14最大工作频率：0.1 MHz
最高工作温度：85 °C最低工作温度：-25 °C
封装主体材料：PLASTIC/EPOXY封装代码：SOP
封装等效代码：SOP14,.4封装形状：RECTANGULAR
封装形式：SMALL OUTLINE峰值回流温度（摄氏度）：NOT SPECIFIED
电源：5 V认证状态：Not Qualified
子类别：Analog Special Function Converters最大压摆率：6 mA
最大供电电压：40 V最小供电电压：4 V
标称供电电压：5 V表面贴装：YES
技术：BIPOLAR温度等级：OTHER
端子面层：Tin/Lead (Sn/Pb)端子形式：GULL WING
端子节距：1.27 mm端子位置：DUAL
处于峰值回流温度下的最长时间：NOT SPECIFIEDBase Number Matches：1

LM231A 数据手册

 浏览型号LM231A的Datasheet PDF文件第3页浏览型号LM231A的Datasheet PDF文件第4页浏览型号LM231A的Datasheet PDF文件第5页浏览型号LM231A的Datasheet PDF文件第7页浏览型号LM231A的Datasheet PDF文件第8页浏览型号LM231A的Datasheet PDF文件第9页 
Typical Performance Characteristics (Continued)  
Power Drain vs VSUPPLY  
Output Saturation Voltage vs  
IOUT (Pin 3)  
Nonlinearity Error, Precision  
F-to-V Converter (Figure 7)  
DS005680-34  
DS005680-36  
DS005680-35  
Typical Applications  
PRINCIPLES OF OPERATION OF A SIMPLIFIED  
VOLTAGE-TO-FREQUENCY CONVERTER  
The LM231/331 are monolithic circuits designed for accu-  
racy and versatile operation when applied as  
voltage-to-frequency  
(V-to-F)  
converters  
or  
as  
frequency-to-voltage (F-to-V) converters. A simplified block  
diagram of the LM231/331 is shown in Figure 3 and consists  
of a switched current source, input comparator, and 1-shot  
timer.  
The operation of these blocks is best understood by going  
through the operating cycle of the basic V-to-F converter,  
Figure 3, which consists of the simplified block diagram of  
the LM231/331 and the various resistors and capacitors con-  
nected to it.  
DS005680-4  
The voltage comparator compares a positive input voltage,  
V1, at pin 7 to the voltage, Vx, at pin 6. If V1 is greater, the  
comparator will trigger the 1-shot timer. The output of the  
timer will turn ON both the frequency output transistor and  
FIGURE 3. Simplified Block Diagram of Stand-Alone  
Voltage-to-Frequency Converter and  
External Components  
=
the switched current source for a period t 1.1 RtCt. During  
this period, the current i will flow out of the switched current  
DETAIL OF OPERATION, FUNCTIONAL BLOCK  
DIAGRAM (Figure 2)  
=
source and provide a fixed amount of charge, Q i x t, into  
the capacitor, CL. This will normally charge Vx up to a higher  
level than V1. At the end of the timing period, the current i will  
turn OFF, and the timer will reset itself.  
The block diagram shows a band gap reference which pro-  
vides a stable 1.9 VDC output. This 1.9 VDC is well regulated  
over a VS range of 3.9V to 40V. It also has a flat, low tem-  
perature coefficient, and typically changes less than  
over a 100˚C temperature change.  
Now there is no current flowing from pin 1, and the capacitor  
1
⁄2  
%
C
L will be gradually discharged by RL until Vx falls to the level  
of V1. Then the comparator will trigger the timer and start an-  
other cycle.  
The current pump circuit forces the voltage at pin 2 to be at  
=
=
1.9V, and causes a current i 1.90V/RS to flow. For Rs 14k,  
=
The current flowing into CL is exactly IAVE i x (1.1xRtCt) x  
=
i
135 µA. The precision current reflector provides a current  
f, and the current flowing out of CL is exactly Vx/RL VIN/RL.  
If VIN is doubled, the frequency will double to maintain this  
balance. Even a simple V-to-F converter can provide a fre-  
quency precisely proportional to its input voltage over a wide  
range of frequencies.  
equal to i to the current switch. The current switch switches  
the current to pin 1 or to ground depending on the state of  
the RS flip-flop.  
The timing function consists of an RS flip-flop, and a timer  
comparator connected to the external RtCt network. When  
the input comparator detects a voltage at pin 7 higher than  
pin 6, it sets the RS flip-flop which turns ON the current  
switch and the output driver transistor. When the voltage at  
2
pin 5 rises to  
⁄3 VCC, the timer comparator causes the RS  
flip-flop to reset. The reset transistor is then turned ON and  
the current switch is turned OFF.  
However, if the input comparator still detects pin 7 higher  
than pin 6 when pin 5 crosses 2  
⁄ VCC, the flip-flop will not be  
3
reset, and the current at pin 1 will continue to flow, in its at-  
tempt to make the voltage at pin 6 higher than pin 7. This  
www.national.com  
6
1...3456789...15

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