SDA 4331X

Semiconductor Group

5

04.96

2

Functional Description

and FM range.

3

Circuit Description

The reference frequency for the PLL is derived from the quartz oscillator OSC

R-prescaler can be adapted to quartz frequencies of 4, 8 or 10.25 MHz, respectively,

yielding an internal 50 kHz reference. Programming the R-counter sets the phase

detector reference frequency to 1, 5 or 10 kHz in the AM mode or to 12.5, 25 or 50 kHz

in the FM mode. The VCO frequency is set by programming the A/N-counter which

operates as dual-modulus counter for FM and AM using a divide by 4/5 swallow counter.

The phase detector drives two different charge pumps for AM and FM mode. Additional

source followers are connected to the charge pump. There are four programmable

current levels for each charge pump. The supply voltage for the charge pump and the

source followers is supplied via the

V

open drain output as well as the additional outputs SA1 … SA4 which are controlled by

programming all counters and functions. The transfer may be stopped optionally after

each word if the remaining functions are not to be altered. After power ON all control

signals are undefined, so that the complete write sequence must be executed.

… Series resistance of the quartz

… Quartz frequency

… Parallel capacitance of the quartz

… Load capacitance, including input capacitance of the IC