SA9504 Datasheet, PDF (4/22 Pages) NXP Semiconductors – Dual-band, PCSCDMA/AMPS LNA and downconverter mixers

Philips Semiconductors
Dual-band, PCS(CDMA)/AMPS
LNA and downconverter mixers
Preliminary specification
SA9504
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 50Ω 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.
1999 Oct 28
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