DC1398A-GA Linear Technology, DC1398A-GA Datasheet - Page 19

• Manufacturer Part Number: DC1398A-GA
• Description: BOARD EVAL LTM9001-GA
• Manufacturer: Linear Technology
• Type: Baseband Receiverr

Specifications of DC1398A-GA

• Design Resources: Demo Circuit 1398A Schematic
• Frequency: 0Hz ~ 300MHz
• Kit Contents: Board, Manual
• Features: LTM9001 16bit Receiver Subsystem, DC-10MHz LPF
• Tool / Board Applications: Wireless Connectivity-ZigBee, RF, Infrared, USB
• Development Tool Type: Hardware - Eval/Demo Board
• Mcu Supported Families: LTM9001
• For Use With/related Products: LTM9001
• Lead Free Status / RoHS Status: Not applicable / Not applicable

APPLICATIONS INFORMATION
Output Clock
The ADC has a delayed version of the encode input available
as a digital output. Both a non-inverted version, CLKOUT
and an inverted version, CLKOUT
CLKOUT pins can be used to synchronize the converter
data to the digital system. This is necessary when using a
sinusoidal encode. Data will be updated as CLKOUT
and CLKOUT
of CLKOUT
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 (see fi gure 10). To decode, the reverse
operation is applied; that is, an exclusive-OR operation
+
–
or the falling edge of CLKOUT
rises. Data may be latched on the rising edge
–
, are provided. The
–
.
+
falls
+
,
is applied between the LSB and all other bits (see fi gure
11). 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
example, if the converter is driving a DSP powered by a
1.8V supply, then OV
supply. OV
to the 3.6V. OGND can be powered with any voltage from
ground up to 1V and must be less than OV
outputs will swing between OGND and OV
Internal Dither
The LTM9001 is a 16-bit receiver subsystem with a very
linear transfer function; however, at low input levels even
slight imperfections in the transfer function will result in
unwanted tones. Small errors in the transfer function are
usually a result of ADC element mismatches. An optional
internal dither mode can be enabled to randomize the input
location on the ADC transfer curve, resulting in improved
SFDR for low signal levels.
DD
can be powered with any logic voltage up
DD
should be tied to that same 1.8V
LTM9001-GA
DD
, should be tied
DD
DD
.
. The logic
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9001gaf