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SA614AN

更新时间: 2024-01-03 14:32:06
品牌 Logo 应用领域
恩智浦 - NXP 消费电路商用集成电路接收器集成电路光电二极管
页数 文件大小 规格书
14页 220K
描述
Low power FM IF system

SA614AN 技术参数

生命周期:Obsolete包装说明:,
Reach Compliance Code:unknown风险等级:5.64
Is Samacsys:N商用集成电路类型:AUDIO DEMODULATOR
解调类型:FMJESD-30 代码:R-PDIP-T16
功能数量:1端子数量:16
最高工作温度:85 °C最低工作温度:-40 °C
标称输出电压(调频):530 mV封装主体材料:PLASTIC/EPOXY
封装形状:RECTANGULAR封装形式:IN-LINE
认证状态:Not Qualified信噪比Nom(FM):68 dB
最大压摆率:4 mA最大供电电压 (Vsup):8 V
最小供电电压 (Vsup):4.5 V表面贴装:NO
温度等级:INDUSTRIAL端子形式:THROUGH-HOLE
端子位置:DUALBase Number Matches:1

SA614AN 数据手册

 浏览型号SA614AN的Datasheet PDF文件第6页浏览型号SA614AN的Datasheet PDF文件第7页浏览型号SA614AN的Datasheet PDF文件第8页浏览型号SA614AN的Datasheet PDF文件第10页浏览型号SA614AN的Datasheet PDF文件第11页浏览型号SA614AN的Datasheet PDF文件第12页 
Philips Semiconductors  
Product specification  
Low power FM IF system  
SA614A  
input level, the limited signal will begin to dominate the regeneration,  
and the demodulator will begin to operate in a “normal” manner.  
quadrature tank and the filters. Most filters demonstrate a large  
phase shift across their passband (especially at the edges). If the  
quadrature detector is tuned to the edge of the filter passband, the  
combined filter and quadrature phase shift can aggravate stability.  
This is not usually a problem, but should be kept in mind.  
There are three primary ways to deal with regeneration: (1)  
Minimize the feedback by gain stage isolation, (2) lower the stage  
input impedances, thus increasing the feedback attenuation factor,  
and (3) reduce the gain. Gain reduction can effectively be  
accomplished by adding attenuation between stages. This can also  
lower the input impedance if well planned. Examples of  
impedance/gain adjustment are shown in Figure 9. Reduced gain  
will result in reduced limiting sensitivity.  
Quadrature Detector  
Figure 7 shows an equivalent circuit of the SA614A quadrature  
detector. It is a multiplier cell similar to a mixer stage. Instead of  
mixing two different frequencies, it mixes two signals of common  
frequency but different phase. Internal to the device, a constant  
amplitude (limited) signal is differentially applied to the lower port of  
the multiplier. The same signal is applied single-ended to an  
A feature of the SA614A IF amplifiers, which is not specified, is low  
phase shift. The SA614A is fabricated with a 10GHz process with  
very small collector capacitance. It is advantageous in some  
applications that the phase shift changes only a few degrees over a  
wide range of signal input amplitudes.  
external capacitor at Pin 9. There is a 90° phase shift across the  
plates of this capacitor, with the phase shifted signal applied to the  
upper port of the multiplier at Pin 8. A quadrature tank (parallel L/C  
network) permits frequency selective phase shifting at the IF  
frequency. This quadrature tank must be returned to ground through  
a DC blocking capacitor.  
Stability Considerations  
The high gain and bandwidth of the SA614A in combination with its  
very low currents permit circuit implementation with superior  
performance. However, stability must be maintained and, to do that,  
every possible feedback mechanism must be addressed. These  
mechanisms are: 1) Supply lines and ground, 2) stray layout  
inductances and capacitances, 3) radiated fields, and 4) phase shift.  
As the system IF increases, so must the attention to fields and  
strays. However, ground and supply loops cannot be overlooked,  
especially at lower frequencies. Even at 455kHz, using the test  
layout in Figure 3, instability will occur if the supply line is not  
decoupled with two high quality RF capacitors, a 0.1µF monolithic  
The loaded Q of the quadrature tank impacts three fundamental  
aspects of the detector: Distortion, maximum modulated peak  
deviation, and audio output amplitude. Typical quadrature curves  
are illustrated in Figure 12. The phase angle translates to a shift in  
the multiplier output voltage.  
Thus a small deviation gives a large output with a high Q tank.  
However, as the deviation from resonance increases, the  
non-linearity of the curve increases (distortion), and, with too much  
deviation, the signal will be outside the quadrature region (limiting  
the peak deviation which can be demodulated). If the same peak  
deviation is applied to a lower Q tank, the deviation will remain in a  
region of the curve which is more linear (less distortion), but creates  
a smaller phase angle (smaller output amplitude). Thus the Q of the  
quadrature tank must be tailored to the design. Basic equations and  
an example for determining Q are shown below. This explanation  
includes first-order effects only.  
right at the V pin, and a 6.8µF tantalum on the supply line. An  
CC  
electrolytic is not an adequate substitute. At 10.7MHz, a 1µF  
tantalum has proven acceptable with this layout. Every layout must  
be evaluated on its own merit, but don’t underestimate the  
importance of good supply bypass.  
At 455kHz, if the layout of Figure 3 or one substantially similar is  
used, it is possible to directly connect ceramic filters to the input and  
between limiter stages with no special consideration. At frequencies  
above 2MHz, some input impedance reduction is usually necessary.  
Figure 9 demonstrates a practical means.  
Frequency Discriminator Design Equations for  
SA614A  
V
OUT  
As illustrated in Figure 10, 430external resistors are applied in  
parallel to the internal 1.6kload resistors, thus presenting  
approximately 330to the filters. The input filter is a crystal type for  
narrowband selectivity. The filter is terminated with a tank which  
transforms to 330. The interstage filter is a ceramic type which  
doesn’t contribute to system selectivity, but does suppress wideband  
noise and stray signal pickup. In wideband 10.7MHz IFs the input  
filter can also be ceramic, directly connected to Pin 16.  
SR00333  
Figure 11.  
In some products it may be impractical to utilize shielding, but this  
mechanism may be appropriate to 10.7MHz and 21.4MHz IF. One  
of the benefits of low current is lower radiated field strength, but  
lower does not mean non-existent. A spectrum analyzer with an  
active probe will clearly show IF energy with the probe held in the  
proximity of the second limiter output or quadrature coil. No specific  
recommendations are provided, but mechanical shielding should be  
considered if layout, bypass, and input impedance reduction do not  
solve a stubborn instability.  
(1a)  
C
S
1
+
V
IN  
V
O
=
C
+ C  
S
ω
ω
1
2
P
1
1 +  
1
( )  
Q S  
S
1
(1b)  
(1c)  
where ω =  
1
L(C + C )  
P
S
Q = R (C + C ) ω  
1
1
P
S
The final stability consideration is phase shift. The phase shift of the  
limiters is very low, but there is phase shift contribution from the  
9
1997 Nov 07  

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