L64777 LSI Logic Corporation, L64777 Datasheet - Page 21

• Manufacturer Part Number: L64777
• Description: DVB Qam Modulator
• Manufacturer: LSI Logic Corporation

Figure 2.4
FT mode pins)
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.
I/O
selected using
(Test mode is
Functional
Test Bus
I Filter Output
Q Filter Output
10
10
10
Analog I/Q Output Interface Diagram
10-Bit DAC
10-Bit DAC
On-Chip
3
2
3
Off-Chip
AVSS1
VSS
R
R
AVSS2
VDDX1
AVDD1/COMP1
Differential I Output
QAM_I, QAM_In
VREF1
VREF2
VDDX2
AVDD2/COMP2
Differential Q Output
QAM_Q, QAM_Qn
2-7