SA1787 Datasheet, PDF (8/19 Pages) Silan Microelectronics Joint-stock – SINGLE-CHIP TUNER IC FOR CAR RADIOS

SA1787
Pin No.
24
25
Pin Name
AM/FM SM
GND
26
Stereo IND
27
MRC
28
SNC
29
HCC
30
Noise Cancel
31
AM/FM Det
IF S-meter and
32
MRC
33
Mute Driver
34
AGC
35
QD OUT
36
QD IN
I/O
Descriptions
O
AM/FM S-meter voltage output
I/O Ground for FMIF and AM
In FM mode:
Pin23 = 5V: pin26 operates linked to the IF counter buffer.
Pin23 = 2.5V: pin26 operates as the SD pin.
O
Pin23 = 0 V: pin26 operates as stereo indicator.
In AM mode:
Pin23 = 5 V: pin 26 operates as the seek SD pin.
Pin23 = 0 V: pin26 is not used.
The MRC detector time constant for Multipath-Noise Detector.
O
The time is determined by a 100Ω resistors and capacitor.
With the pin28 input voltage, the attenuation of (L-R) decode is
I
controlled, such as decrease sepatation and reduce the noise felt in
the stereo mode.
The pin29 can be controlled by the MRC output.
The pin29 can also be controlled with the pin 32 , using an external
I
resistors at least 100 kΩ.
At weak input, high pass is cut to reduce the noise feeling.
Noise canceller input.
I
The input impedance is 50 kΩ.
AM and FM detector output.
O
Output impedance
Low impedance in the FM mode and 10 kΩ in the AM mode
Pin32 is for NC noise extraction and for multipath noise extraction.
Attenuate the MRC AC input by adjust the resistor outside.
O
In AM mode, pin 32 outputs a 1-mA current. Thus the HCC circuit is
turned off.
The muting time constant is determined as follows by CR:
Attack time:
TA = 10 kΩ * C1
Release time:
O
TR = 50 kΩ* C1
Noise convergence adjustment
Muting off function
MUTE is turned OFF when pin 33 is shorted circuited through a 4-kΩ
resistor with GND.
A resistor R should be connected between pin34 and pin37;
R determines the bandwidth of the muting function.
I/O
Narrows the band by increasing the value of R.
Widens the band by reducing the value of R.
O
Detector output
I
Detector input
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.0
2008.08.29
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