SA9504 datasheet(4/22 Pages) PHILIPS

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Philips Semiconductors

Preliminary specification

SA9504

Dual-band, PCS(CDMA)/AMPS

LNA and downconverter mixers

1999 Oct 28

FUNCTIONAL DESCRIPTION

Mode selection

The SA9504 has several modes of operation for which the selection

logic is defined in Table 1. Different mode selections require different

portions of the circuit to be active. Modes from unlisted combinations

of logic pins are not permitted. The LNA and downconverter together

can be programmed to operate in the PCS or cellular bands using

the PCS/CEL logic input pin.

In order for the SA9504 to function correctly, a reset must be applied

on first power-up. The whole circuit (LNAs and mixers) is powered

down when control lines S0 and S1 are simultaneously held HIGH.

An internal reset is applied upon releasing the circuit from

power-down (on taking S0 = S1 from HIGH to LOW).

LNA

The SA9504 has two LNAs, one for cellular FM, and one for PCS

(CDMA). The LNAs have been designed for high gain, low noise

figure and good linearity with low power consumption. External

components can be used to match the LNA inputs for the Cellular

and PCS bands. The LNAs employ a cascode output structure

allowing high gain and excellent reverse isolation. The LNA outputs

are internally matched to drive 50

Ω external loads. The input and

output return loss of better than 10 dB can be achieved in all modes.

Downconverter

The SA9504 has two mixers, one for Cellular FM, and one for PCS

(CDMA). Each mixer is individually optimized for its specific

requirements. The Cellular FM mixer has a common single-ended

RF input. The PCS mixer’s RF input port is differential, and requires

an external balun when used with a single-ended source. Both the

PCS and the Cellular mixer RF inputs should be AC coupled.

Local oscillator drive for the mixers is provided through pins

CEL LO_IN and/or PCS LO_IN. The local oscillator inputs are

single-ended, AC-coupled. The CEL LO_IN signal is internally

buffered to drive the following:

– (Tx) LO output buffer,

– cellular FM mixer,

– PCS LO frequency doubler.

In the PCS mode, mixer LO drive can be either direct (PCS LO_IN)

or through the frequency doubler after CEL LO_IN. The mixer local

oscillator signal is made available externally via the (Tx) LO output

buffer for potential use elsewhere in the radio. For example, this

signal typically can be used with the transmitter circuitry. The

(Tx) LO output buffer can be powered down independently, using

the (Tx) LO_ENABLE logic input. The (Tx) LO output buffer has

open collector differential outputs which should be externally biased

to power supply rail.

The PCS and Cellular FM mixers have open collector differential IF

outputs. The differential IF outputs must be biased at the supply

voltage through external inductors that may also be part of the

matching circuit to the SAW filter.

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