LSI L64777, Technical Manual

Page: 21 / 124

I/O 2-7
Figure 2.4 Analog I/Q Output Interface Diagram
The differential outputs terminate externally (the external components
must provide termination to both differential lines, and the DAC achieves
maximum linearity in differential mode).
The L64777 I and Q component outputs are available in 10-bit digital
format. The related clock depends on the PLL mode: OCLK is used in
Mode 1; PCLK is used in Mode 2. The output format can be programmed
either as a two’s complement, or as a sign magnitude representation.
The analog I- and Q-modulated output signals are at a sampling rate of
OCLK, which is four times the QAM symbol rate. The input to the
digital-to-analog conversion is available also in a digital format at the
DIG_I and DIG_Q bus pins.
AVDD1/COMP1
VREF1
10-Bit DAC
10
AVSS2
AVDD2/COMP2
Differential Q Output
Differential I Output
VSS
AVSS1
R
VDDX1
3
On-Chip Off-Chip
QAM_I, QAM_In
QAM_Q, QAM_Qn
Q Filter Output
I Filter Output
Functional
(Test mode is
selected using
VREF2
VDDX2
10
10-Bit DAC
R
3
2
10
Test Bus
FT mode pins)