User Guide

PAMS Technical Documentation 3. System Module
NSD-5
Issue 1 05/02 Nokia Corporation Page 21
nent, RXI, is RXD[11..8]. For load impedance and input/output rise/fall time and other
electric characteristics, refer to Reference 3 [CAFE application].
The transmitted signal is fed to the CAFE ASIC through data bus TXD[7:0] from MAD4
ASIC. The digital signal is registered inside CAFE ASIC. In-phase and quadrature compo-
nents are separated from each other by using IQSEL from MAD4, and are D/A converted
to analog signals. The transmitted signals (I and Q components) are then converted to
differential signals and sent to TIF of RF section. The output signal levels are described in
the section “CDMA I and Q transmit channel D/A converters and post filters” of the CAFE
design specification (Reference 3). Signal CAFE_TX_GATE is used to control the power for
transmits DAC and filters inside the CAFE ASIC. When it is high, the power to those two
blocks is turned on; otherwise, the power is turned off.
Clock
A 19.2 MHz sine wave clock is sent from RF to CAFE ASIC. It is squared inside the CAFE to
provide 19.2 MHz square wave clock to MAD4. There is about 1.4V DC offset to the
19.2 MHz sine wave clock. It has to be DC-coupled to the CAFE ASIC. A phase-locked
loop is used to generate a 9.83 MHz signal. This clock also is sent to MAD4 and used as
CDMA system clock, which is eight times the chip clock (1.2288 MHz). The electric char-
acteristics of the clock recovery circuit are described in the CAFE specification.
Audio
There are two kinds of audio inputs to the CAFE ASIC. The first is from the built-in micro-
phone. The second is from an external accessory. The signal from the built-in micro-
phone, MICP and MICN, is sent to CAFE differently, using pin F10 and pin E10. The
differential input signal range is from 200mVpp to 2.0Vpp, and depends on the gain set-
ting inside the CAFE. (CAFE provides up to 20 dB gain.) The internal microphone is biased
by a DC signal from pin D11. It also could be biased by VR1_SW.
The audio signal from an external accessory part (XMICP/XMICN) is differentially sent to
CAFE through pin F11 and pin E11. The external microphone bias is provided by AUXOUT
at pin B11 when CODEC_XMIC_BIAS = 1 in control register 2.
The audio receive path consists of D/A converter, lowpass filter and output attenuator
with three selectable outputs. Only one output can be activated at a time. The bias at the
outputs can be independently controlled to be ON at all outputs to avoid switching tran-
sients. EAR output from pin A9 and pin B10 of CAFE ASIC is intended to drive the phone
earpiece having typical 32-ohm resistance in the audio band. Output is differential, with
positive (EARP) and negative (EARN) output terminals.
HF output is intended to drive the phone external audio circuitry (XEAR). Output is sig-
nal-ended, but it also has another pin (HFCM), which drives the signal ground for it.
External microphone input and external speaker output can be detected by signal HOOK-
INT, EAD, and EAD_HEADINT. For detailed information, consult the audio accessory spec-
ification (Reference 7).