PCF50732 Datasheet, PDF (11/64 Pages) NXP Semiconductors – Baseband and audio interface for GSM

Philips Semiconductors
Baseband and audio interface for GSM
Objective specification
PCF50732
20
handbook, full pagewidth
gain
(dB)
0
MBL025
−20
ZIF
−40
NZIF
−60
−80
−100
0
100
200
300
400
500
600
f (kHz)
3
Fig.3 Transfer functions for the baseband receive filter.
9.3 Baseband Serial Interface (BSI)
9.3.1 OVERVIEW
The digital part of the baseband consists of a receive
section and a transmit section. The receive section is a
FIR filter that reduces the 6.5 MHz (13 MHz for
NZIF mode) bitstream from the sigma-delta converters
into 2 × 12-bit values at 270.833 kHz (541.667 kHz for
NZIF mode).
The transmit section converts the 270.833 kHz data
stream from the DSP into a GMSK signal sampled at
4.333 MHz. The 10-bit I and Q signals are then fed into
two 10-bit DACs. The power ramping signal is also
generated by the transmit section with the 10-bit
AUXDAC3 block.
9.3.2 TRANSMIT PATH BLOCK DESCRIPTION
9.3.2.1 Transmit serial interface
The power-up of the BSI transmit path is controlled via the
TXON pin. When TXON is pulled HIGH, the transmit path
recovers from power-down. The MCLK/48 = 270.833 kHz
output signal BIOCLK is activated. When the BIEN0 period
has elapsed the output signal BIEN goes LOW and the bits
to be transmitted are clocked out of the DSP.
BIEN0 must be at least 10 quarterbits long to allow settling
of the analog filters. Bits are clocked out of the DSP by the
falling edge and clocked into the PCF50732 by the rising
edge of BIOCLK. After the BIEN1 period has elapsed,
BIEN is set HIGH again and transmission from the DSP
ends. Logic 1s are modulated whenever BIEN is HIGH
and the baseband transmit (BBTX) block is active. Values
for BIEN0 and BIEN1 can be set in the Burst control
register.
Figure 5 shows the timing for the BSI data transmission.
In power-down the de-asserted value of BIOCLK is high-Z
and BIEN is HIGH. Typical connection to the system DSP
is defined in Table 1.
Table 1 Connection of BSI transmit signals to
PCF5087X
PCF50732
PCF5087X
PIN
TXON
BDIO
BIEN
BIOCLK
I/O
PIN
I/O
I
RFSIG[y]
O
I/O
SIOXD
I/O
O
SOXEN_N
I
O
SIOXCLK
I
1999 May 03
11