LC72121M View Datasheet(PDF) - ON Semiconductor

Part Name

Description

Manufacturer

LC72121M

PLL Frequency Synthesizers for Electronic Tuning

ON Semiconductor 

LC72121, 72121M, 72121V

• DO pin usage

The DO pin can be used for IF counter count completion checking and as an unlock detection output in addition to its

use in data output mode. It is also possible to have the DO pin reflect the state of an input pin to input that state to the

microcontroller.

• Power supply pins

Capacitors must be inserted between the power supply VDD and VSS pins for noise exclusion. These capacitors must be

placed as close as possible to the VDD and VSS pins.

• VCO setup

Applications must be designed so that the VCO (local oscillator) does not stop, even if the control voltage (Vtune) goes

to 0 V. If it is possible for the oscillator to stop, the application must use the control data (DLC) to temporarily force

Vtune to VCC to prevent deadlock from occurring. (Deadlock clear circuit)

• Front end connection example

Since this product (and the LC72131 as well) is designed with the relatively high resistance of 200 kΩ for the pull-

down (on) resistors built in to the FMIN and AMIN pins, a common AM/FM local oscillator buffer can be used as

shown in the following circuit.

• PD pin

Note that the charge pump output voltage is reduced when this IC, which is a 3-V system, is used to replace the

LC72131, which is a 5-V system. This means that since the loop gain is reduced, the loop filter constants, the lock time

(SD wait time), and other related parameters must be reevaluated in the end product design.

No. 5815-22/23

Share Link: