AD9856/PCB Analog Devices Inc, AD9856/PCB Datasheet - Page 32

• Manufacturer Part Number: AD9856/PCB
• Description: BOARD EVAL FOR AD9856
• Manufacturer: Analog Devices Inc
• Type: DDS Modulatorsr

Specifications of AD9856/PCB

• Rohs Status: RoHS non-compliant
• For Use With/related Products: AD9856
• Lead Free Status / RoHS Status: Not Compliant

AD9856
The second method requires an f
externally 2× upsampled input data. The AD9856 is configured
for a CIC interpolation rate of 3 while bypassing the 3rd half-
band filter. The input I/Q sample rate is 12 MHz, which is
further upsampled by a factor of 12 MHz to 144 MHz.
For burst applications with relatively long nonbursting periods,
the sleep bit is useful for saving power. When in sleep mode,
power is reduced to below 6 mW. Consideration must be given
to wake-up time, which generally is in the 400 µs to 750 µs
range. For applications that cannot use the sleep bit due to this
wake-up time, there is an alternate method of reducing power
dissipation when not transmitting. By writing the bypass
REFCLK multiplier bit active, the power is reduced by nearly
the REFCLK multiplier factor. For example, if the external
reference clock is 16 MHz and REFCLK multiplier is set to 10×,
all clocks divide down by a factor of 10 when the REFCLK
multiplier is bypassed. This effectively scales down the power
dissipation by nearly a factor of 10. In this case, both the
REFCLK multiplier function and the DAC, which use relatively
little power, remain fully powered. The REFCLK multiplier
circuit is locked to the 16 MHz external reference clock, but its
output is driving a very small load—thus, there is little power
dissipation. When the REFCLK multiplier is reactivated, the
acquisition time is small. In this power reduction technique,
the larger the REFCLK multiplier factor, the larger the power
savings.
The AD9856 is specified for operation at +3.0 V ±5%. The
thermal impedance of the device in the 48-LQFP plastic
package is 38°C/W. At 200 MHz operation, power dissipation
MAX
of 144 MHz with
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is 1.5 W. This permits operation over the industrial temperature
range without exceeding the maximum junction temperature of
150°C. To realize this quoted thermal impedance, all power and
ground pins must be soldered down to a multilayer PCB with
power and ground copper planes directly available at the
package pins.
Under worst-case conditions, that is, with power supplies at
2.85 V and ambient temperatures of 85°C, device operation
at 200 MHz is guaranteed for single-tone mode only. For
modulation mode at 200 MHz, 85°C operation, the minimum
power supply voltage is 3.0 V.
AD9856 EVALUATION BOARD
An evaluation board is available to facilitate bench and system
analysis of AD9856 quadrature digital upconverter. The
AD9856 printed circuit board (PCB) contains the AD9856
device and Windows® software that the device to be controlled
via the printer port of a PC. The DAC output is provided on a
jack for spectral analysis. The AD9856/PCB provides a single-
ended 65 MHz, 5 Ω, elliptical low-pass filter on the output of
the DAC.
The user can also implement the AD8320/AD8321 program-
mable cable driver amplifier on the AD9856/PCB evaluation
board. The AD8320/AD8321 gain is programmed through the
AD9856 via the menu driven control software.
SUPPORT
Applications assistance is available for the AD9856 and the
AD9856/PCB evaluation board. Please call 1-800-ANALOGD
or visit
www.analog.com.