CXA1991N Просмотр технического описания (PDF) - Sony Semiconductor

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CXA1991N

FM Pager/FM Multiplex Tuner

Sony Semiconductor 

CXA1991N

Notes on Operation

1.De-emphasis time constant

Time constants are determined by R4, R5 and C13. The calculation formula is as follows.

{R4 • R5/(R4 + R5)} • C13

2.FM discriminator

Quadrature detection is used for FM detection. A ceramic resonator is used in the phase shifter so that no

adjustment is required. In order to eliminate problems of distortion and offset with IF band center

frequency, the CF1 (FM • IF) and FM discrete pair combination should be of the same level.

A red

B blue

C orange

D black

E white

CF1 and Discrete fo

10.70 MHz

10.67 MHz

10.73 MHz

10.64 MHz

10.76 MHz

3.Battery save function

The battery save function operates when Pin 8 is grounded. Current consumption is 1 µA or less during

battery save. To switch from battery save mode to normal mode, Pin 8 is connected to VCC. At this time

the DET OUT (Pin 9) rise time is affected by the rise time of Pins 4, 10 and 14. For faster rise time, lower

the capacitance values of bias capacitors C5, C6 and C8, taking care that characteristics do not

deteriorate. Also, decrease or eliminate R3 and C11 time constants and control Pin 10 directly with DC

voltage of approximately 1.1 V to improve rise time.

4.Notes on pattern preparation

i) FM antenna, OSC coil configuration

Change the direction 90 degrees in order to avoid M coupling. Also, insert Pin 14 pattern between

Pins 13 and 16 and the pattern between the coils. (See "Standard Board Diagram".)

ii) Tuning circuit

The capacitance value of the tuning circuit varies according to the board; investigate the time

constants for new boards.

iii) GND pins

Pin 5 is the ground pin for IF and Pin 19 is the ground pin for FE. Use as thick a pattern as possible

for the antenna input, BPF and Pin 19 grounds, as they have a significant effect on stability and NF

characteristics.

iv) The ground point for by-pass capacitors C5 and C6 connected to Pin 14 should be as close to Pin 14

as possible.

v) When the tuning indicator is not used, connect Pin 11 to ground. This will put the tuning indicator drive

circuit into low power consumption mode and current ceases to flow to the indicator. Also, the current

consumption ICC is eliminated.

vi) Use the BPF for FM.

—10—

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