DC1241B-AA Linear Technology, DC1241B-AA Datasheet - Page 24

• Manufacturer Part Number: DC1241B-AA
• Description: BOARD EVAL LTM9001-AA
• Manufacturer: Linear Technology
• Type: Baseband Receiverr

Specifications of DC1241B-AA

• Design Resources: DC1241B Schematic
• Frequency: 0Hz ~ 300MHz
• Features: LTM9001 16bit Receiver Subsystem, 162MHz BPF
• Tool / Board Applications: Wireless Connectivity-ZigBee, RF, Infrared, USB
• Mcu Supported Families: LTM9001
• Development Tool Type: Hardware - Eval/Demo Board
• For Use With/related Products: LTM9001
• Lead Free Status / RoHS Status: Not applicable / Not applicable

LTM9001-Ax/LTM9001-Bx
APPLICATIONS INFORMATION
Output Clock
The ADC has a delayed version of the encode input available
as a digital output, CLKOUT. The CLKOUT pin can be used
to synchronize the converter data to the digital system.
This is necessary when using a sinusoidal encode.
In both CMOS modes, A bus data will be updated as CLK-
OUTA falls and CLKOUTB rises. In demultiplexed CMOS
mode the B bus data will be updated as CLKOUTA falls
and CLKOUTB rises.
In full rate CMOS mode, only the A data bus is active;
data may be latched on the rising edge of CLKOUTA or
the falling edge of CLKOUTB.
In demultiplexed CMOS mode CLKOUTA and CLKOUTB
will toggle at 1/2 the frequency of the encode signal. Both
the A bus and the B bus may be latched on the rising edge
of CLKOUTA or the falling edge of CLKOUTB.
Digital Output Randomizer
Interference from the ADC digital outputs is sometimes
unavoidable. Interference from the digital outputs may
be from capacitive or inductive coupling or coupling
through the ground plane. Even a tiny coupling factor can
result in discernible unwanted tones in the ADC output
spectrum.
By randomizing the digital output before it is transmitted
off chip, these unwanted tones can be randomized, trading
a slight increase in the noise fl oor for a large reduction in
unwanted tone amplitude.
The digital output is “randomized” by applying an exclusive-
OR logic operation between the LSB and all other data
output bits. To decode, the reverse operation is applied;
that is, an exclusive-OR operation is applied between the
LSB and all other bits. The LSB, OF and CLKOUT output
are not affected. The output randomizer function is active
when the RAND pin is high.
Output Driver Power
Separate output power and ground pins allow the output
drivers to be isolated from the analog circuitry. The power
supply for the digital output buffers, OV
to the same power supply as for the logic being driven. For
24
DD
, should be tied
Figure 12. Functional Equivalent of Digital Output Randomizer
RAND = HIGH,
RANDOMIZER
Figure 13. Derandomizing a Randomized Digital Output
PC BOARD
ENABLED
LTM9001
D0
RAND
LTM9001
D15 ⊕ D0
D14 ⊕ D0
D2 ⊕ D0
D1 ⊕ D0
CLKOUT
CLKOUT
D0
OF
D15
D14
D2
D1
OF
FPGA
•
•
•
9001 F12
•
•
•
D15
D14
D2
D1
D0
CLKOUT
OF
D15/D0
D14/D0
D2/D0
D1/D0
D0
9001 F13
9001fc