SP5070

3

FUNCTIONAL DESCRIPTION

The SP5070, when used with a voltage controlled

oscillator, forms a complete phase locked loop frequency

synthesiser.

The

phase

comparator

comparison

frequency

is

obtained by dividing the reference frequency. This may be

generated on-chip by means of an external crystal, or from

an external reference oscillator.

The output of the prescaler is divided by the fixed

modulus divider, producing an output frequency which is

phased locked to the comparison frequency.

The divider stages are arranged to give a fixed ratio

between the synthesised frequency and the reference of

256:1. Any frequency within the range of 300MHz to 2.4GHz

may be achieved by using the appropriate reference or

crystal frequency.

A single external transistor, driven from the charge

pump output, provides the output drive necessary for the

oscillator varicap line.

A test facility which disables the charge pump is also

provided. This is activated when a negative voltage is

applied to pin 11, see electrical characteristics above. When

at outputs TEST1 and TEST2 respectively. These are open

collector outputs and are each capable of sinking a minimum

of 1mA. In normal mode of operation these outputs are high

impedance.

For compatibility with SP5060/SP5062, pin 11 may be

Fig.3 Typical application and test circuit (1024MHz with 4MHz reference crystal)

Fig.4 Application using external reference oscillator

1

2

3

4

5

6

7

14

13

12

11

DP14

10

9

8

S

P

5

0

7

0

+5V

1n

1n

FROM

VCO

2N3904

10K

47K

10n

22K

22K

47n

180n

+30V

100p

FROM

REFERENCE

OSCILLATOR

VARICAP

INPUT

VCO

1

2

3

4

5

6

7

14

13

12

11

10

9

8

S

P

5

0

7

0

+5V

1n

1n

FROM

VCO

2N3904

10K

47K

10n

22K

22K

47n

180n

+30V

68p

4MHz

REFERENCE

CRYSTAL

VARICAP

INPUT

VCO

47P