LC72148V Datasheet, PDF(19/21 Page) Sanyo Semicon Device – Electronic Tuning PLL Frequency Synthesizer for Car Stereo Systems

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LC72148V Datasheet, PDF (19/21 Pages) Sanyo Semicon Device – Electronic Tuning PLL Frequency Synthesizer for Car Stereo Systems

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LC72148V

3. Notes on using IF counting with the HCTR/I-6 and LCTR/I-7 pins

If IF counting is used, the microcontroller must test the state of the IF IC SD (station detect) signal, and only if the SD

signal is present, turn on the IF counter buffer output and perform an IF count operation. Methods in which auto-

search operations are implemented only using the IF count may incorrectly stop at frequencies where no station is

present due to leakage from the IF counter buffer.

4. Using the DO pin

At times other than data output mode, the DO pin can also be used to check for general-purpose counter count

operation completion, to output the unlock state detection signal, and to check for changes in the input pins.

Note that the states of the input pins (I/O-1 and I/O-2) can be input to the system microcontroller through the DO pin.

5. Power supply pins

Capacitors must be inserted between the VDD and VSSd power supply pins to reduce noise. These capacitors must be

located as close to the VDD and VSSd pins as possible.

6. Notes on VCO design

The VCO (local oscillator) must be designed so that the VCO oscillation does not stop if the control voltage (Vtune)

becomes 0 V. If it is possible for this oscillator to stop, use the charge pump control data (DLC) to forcible set Vtune

to VCC temporarily to prevent the PLL circuit from deadlocking. (This function is called a deadlock clear circuit.)

7. Notes on the PD pin

When switching from the LC72146 (5 V system) to this IC (3 V system), the charge pump output voltage will be

reduced, thus reducing the loop gain. Thus various aspects of the circuit, such as the loop filter coefficients, and the

locking time (the SD wait time) must be reviewed.

8. Microcontroller interface

Although this IC is a 3 V system IC, it can accept 5 V system inputs over the microcontroller interface (the CE, DI,

and CL pins).

Pin states after a power-on reset

State Power-on reset

O-7

O-6

I-5

I-4

I-3

I-2

I-1

O: Open, L: Low, F: Floating

XOUT

O-7

O-6

I/O-5

I/O-4

I/O-3

I/O-2

I/O-1

LC72148V

XIN

VSSa

AOUT

AIN

PD0

PD1

VSSd

FMIN

AMIN

VDD

HCTR/I-6

LCTR/I-7

Power-on reset State

I-6

I-7

No. 6974-19/21

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