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SA9502

Dual-band, CDMA/AMPS downconverter IC

Philips Electronics 

Philips Semiconductors

Dual-band, CDMA/AMPS downconverter IC

Product specification

SA9502

PIN CONFIGURATION

FM IF 1

FM IFB 2

GND 3

PCS RF 4

PCS RFB 5

PCS/CEL SEL 6

PWR ON/OFF 7

CEL RF 8

GND 9

VCC 10

20 CDMA IF

19 CDMA IFB

18 GND

17 CDMA/FM SEL

16 CEL LO IN

15 GND

14 PCS LO

13 LO BUFFER ENABLE

12 GND

11 LO OUT

SR01760

Figure 2. Pin Configuration

PIN DESCRIPTION

PIN SYMBOL

1 FM IF

2 FM IFB

3 GND

4 PCS RF

5 PCS RFB

6 PCS/CEL SEL

7 PWR ON/OFF

8 CEL RF

9 GND

10 VCC

11 LO OUT

12 GND

13 LO BUFFER

ENABLE

14 PCS LO

15 GND

16 CEL LO

17 CDMA/FM SEL

18 GND

19 CDMA IFB

20 CDMA IF

DESCRIPTION

Non-inverting FM IF output

Inverting FM IF output

Analog ground

non-inverting PCS RF input

Inverting PCS RF input

PCS and cellular band select

Power enable

Cellular RF input

Ground

Power supply

LO output to synthesizer

Ground

Logic signal which switches the LO

buffer output ON or OFF

PCS mixer direct LO input

Ground

Cellular LO input

CDMA and FM mode select in cellular

band; LO direct or via frequency

doubler in PCS mode

Ground

Inverting CDMA IF output

Non-inverting CDMA IF output

FUNCTIONAL DESCRIPTION

Mode Selection Logic

The SA9502 downconverter IC has several modes of operation for

which the selection logic is summarized in Table 1 and defined in

detail in Table 2. Different mode selections require different portions

of the circuit to be active. It should be noted that only the states

specified in Table 2 are valid selections for operation.

Local Oscillator Section

Local oscillator drive for the mixers is provided through single ended

inputs on either pin 16 (CEL LO) or pin 14 (PCS LO). The LO signal

has to be AC-coupled into the circuit and needs to be externally

matched. Inside the circuit, the cellular band LO signal is amplified

and buffered to drive: Either the cellular CDMA mixer or FM mixer

or the frequency doubler for the PCS mixer LO and additionally the

LO output buffer. The mode selection summary in Table 1 shows the

logic to apply to pins 6 and 17 to choose one of four possible

modes. The LO output buffer can be programmed on or off via LO

Buffer Enable (Pin 13). The LO output buffer’s frequency is the

same as that used by the mixers.

Cellular and PCS Mixers

The SA9502 has one single ended cellular band RF input which

feeds either the cellular CDMA mixer or the cellular FM mixer

circuits. Each mixer is optimized to meet cellular band CDMA or

analog FM requirements. The cellular FM mixer has its own

dedicated differential output on pins 1 and 2 which should to be

externally matched to the FM IF SAW filter. The cellular CDMA

mixer shares the same output pins with the CDMA PCS mixer.

Selection between these two mixers is via pin 6 (PCS/CEL) and as

the two mixers are never on at the same time, it allows a common

CDMA SAW filter to be used for both bands. The CDMA PCS mixer

has a differential RF input which should be used with an external

balun matching circuit. To avoid upsetting the internal biasing, the

RF inputs at both cellular and PCS band mixers should be

AC-coupled in. The CDMA and FM IF mixer outputs are of the open

collector type. So, they should be biased to the supply voltage VCC

with external tuning inductors which can also serve in the matching

of the IF SAW filter.

1999 Mar 19

4

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