1999 Oct 05

15

Philips Semiconductors

Preliminary specification

noise frequency synthesizer

TSA5059

APPLICATION INFORMATION

An example of a typical application is given in Fig.4. In this application the VCO centre frequency is 1.5 GHz, with a slope

of 100 MHz/V; the expected loop bandwidth is 10 kHz with a charge pump current of 555

components need to be adapted to each application depending on the VCO characteristics and the required performance

of the loop.

Fig.4 Typical application.

handbook, full pagewidth

TSA5059

FCE123

1

VT

GND

RFB

RFA

VCC

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

AS

XT/COMP

XTAL

CP

SDA

SCL

P3

P2

P1 P0 ADC

2.2 nF

10 nF

1 nF

1 nF

3.9 k

Ω

2.7 k

Ω

5 V

33 V

27 k

Ω

18 pF

1 nF

tuning

voltage

VCO

output

VCO

MICRO-

CONTROLLER

47 nF

4 MHz

Loop bandwidth

Most of the applications the TSA5059 are dedicated for

require a large loop bandwidth, in the order of a few kHz to

a few tens of kHz. The calculation of the loop filter

elements has to be done for each application, while it

depends on the VCO slope and phase noise, as well as the

reference frequency and charge pump current.

A simulation of the loop can easily be done by using the

SIMPATA software from Philips.

Reference source

The TSA5059 is well suited to be used with a 4 MHz

crystal connected to pin XTAL. Philips crystal ordering

code 4322 143 04093 is recommended in this case.

It is however possible to use a crystal with an higher

frequency (up to 16 MHz) to improve the noise

performance. When choosing a crystal, one should take

notice to select a crystal able to withstand the drive level of

the TSA5059 without suffering from accelerated ageing.

It is also possible to feed pin XTAL with an external signal

between 2 and 20 MHz, coming from an external oscillator

or from the pin XT/COMP of another TSA5059, when more

than one synthesizer is present in the same application.

Then the application given in Fig.5 should be used.

If the signal at pin XT/COMP is not used in an application,

the output should be switched off (XCE = 0, XCS = 0).

This pin should then be open.