L64777 A LSI Logic Corporation, L64777 A Datasheet - Page 8

• Manufacturer Part Number: L64777 A
• Description: Communications, DVB QAM Modulator
• Manufacturer: LSI Logic Corporation

8
Figure 6
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.
L64777 DVB QAM Modulator
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