Philips Semiconductors

Product specification

SA630

Single pole double throw (SPDT) switch

1997 Nov 07

6

The isolation and matching of the two channels over frequency is

shown in Figures 15 and 17, respectively.

The SA630 is a very versatile part and can be used in many

applications. Figure 5 shows a block diagram of a typical Digital RF

transceiver front-end. In this application the SA630 replaces the

duplexer which is typically very bulky and lossy. Due to the low

power consumption of the device, it is ideally suited for handheld

applications such as in CT2 cordless telephones. The SA630 can

also be used to generate Amplitude Shift Keying (ASK) or On-Off

Keying (OOK) and Frequency Shift Keying (FSK) signals for digital

RF communications systems. Block diagrams for these applications

are shown in Figures 6 and 7, respectively.

For applications that require a higher isolation at 1GHz than

obtained from a single SA630, several SA630s can be cascaded as

shown in Figure 8. The cascaded configuration will have a higher

loss but greater than 35dB of isolation at 1GHz and greater than

65dB @ 500MHz can be obtained from this configuration. By

modifying the enable control, an RF multiplexer/ de-multiplexer or

antenna selector can be constructed. The simplicity of SA630

coupled with its ease of use and high performance lends itself to

many innovative applications.

The SA630 switch terminates the OFF channel in 50

Ω. The 50Ω

resistor is internal and is in series with the external AC bypass

capacitor. Matching to impedances other than 50

Ω can be achieved

by adding a resistor in series with the AC bypass capacitor (e.g.,

25

Ω additional to match to a 75Ω environment).

5200

630

MODULATION

602A

IF OUT

5200

VCO

MICRO

Tx/Rx

KEYPAD

&

DISPLAY

CONTROLLER

SR00582

Figure 5. A Typical TDMA/Digital RF Transceiver System Front-End

630

ASK OUTPUT

ENABLE

CH1

OSCILLATOR

TTL DATA

50

Ω

SR00583

Figure 6. Amplitude Shift Keying (ASK) Generator

630

FSK OUTPUT

ENABLE

CH1

TTL DATA

f1

f2

SR00584

Figure 7. Frequency Shift Keying (FSK) Gnerator

630

IN/OUT

630

630

OUT1/IN1

OUT2/IN2

ENABLE

SR00585

Figure 8.