LA1143 데이터 시트보기 (PDF) - SANYO -> Panasonic

부품명

상세내역

일치하는 목록

LA1143

FM IF System for Car Radios

SANYO -> Panasonic 

LA1143

Continued from preceding page.

output will be omitted, since they are the same as those used in conventional quadrature detector ICs ( such as LA1230,

LA1231N).

The inverted output of the signal strength indication output is obtained as illustrated below.

By referring to the illustration, V14 is given by the formula : V14=Vr–(I0+I1–aI2)RL–VBE.

Conditions are : Vr≈4.9V, I0≈0.2mA, a≈2, RL=22kΩ, VBE≈0.6V, I1=V15/R15-G,

I2=V16/R16-G, where V16 is a constant equal to 4.1V (typ.) for medium or lower

signal input levels, where the muting drive output is required. Since the V15

increases proportionally to the increase of the input signal strength, I1 will also

increase. Therefore the V14 will decrease with increasing signal strength. Thus the

required muting drive output can be obtained by selecting proper values of R15-G

and R16-G.

For example, the muting drive output moves toward strong input signal level if th R16-G is decreased, or the muting

drive output becomes zero due to the offset current IO under a weak signal input condition, if the R16-G is increased to

infinity (namely pin 16 is opened). However the muting drive output caused by a hole detector still exists in this case. In

creasing R15-G decreases the slope of the curve for the muting drive output vs. antenna signal input level, or decreasing

the R15-G increases the slope of the curve. Furthermore, varying the value of a resistor connected between the muting

drive output (pin 14) and the muting control input (pin 6) changes the value of the muting control current required to

obtain the same muting drive output, accordingly a slope of curve for muting attenuation vs. antenna signal input level is

also changed.

These characteristics investigated by using an actual receiver are shown on the curves below. The general method to

adjust the muting circuit of the LA1143 is : to set the signal input level required to actuate the muting circuit with the

R16-G, to adjust the slope of the curve for the muting attenuation vs. antenna signal input with the R15-G, and to adjust

the maximum muting attenuation (determined by setting the noise level at no signal) with the R5-G. The slope of the

curve for the muting attenuation vs. antenna signal input level can also be adjusted by the resistor connected between

pins 14 and 6 in addition to R15-G, however, selecting a resistor too high does not allow the muting control current

flowing into pin 6 to reach 120µA even though the maximum muting drive output (V14) is applied, namely the muting

attenuation does not reach its maximum value. Accordingly a recommended value of the resistor between pins 14 and 6

is about 22kΩ.

No.1140-4/5

Share Link: