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DAC5688
CLK2 CLK1
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DAC5668/88/89 Hardware Description
Figure 5. EVM Block Diagram
3.1.1 DAC5668/88/89
The DAC5668/88/89 are dual-channel, 800-MSPS interpolating DACs with dual CMOS digital data bus,
integrated 2x-8x interpolation filters, a fine frequency mixer with 32-bit complex numerically controlled
oscillator (NCO), IQ compensation, and internal voltage reference. Different modes of operation enable or
bypass various signal processing blocks. The DAC5668 and the DAC5688 also include an internal 2x-32x
clock multiplying PLL/VCO. This feature is useful when a high-rate clock is not available at the system
level.
The DAC5668/88/89 dual-CMOS data bus provides 250-MSPS input data transfer per DAC channel.
Several input data options are available: dual-bus data, single-bus interleaved data, even and odd
multiplexing at half-rate, and an input FIFO with either external or internal clock to ease interface timing.
Input data can be interpolated 2x, 4x, or 8x by onboard digital interpolating FIR filters with over 80 dB of
stop-band attenuation.
The DAC5668/88/89 allows both complex and real output. An optional 32-bit NCO/mixer in complex mode
provides frequency upconversion and the dual DAC output produces a complex Hilbert Transform pair. A
digital inverse sinc filter compensates for natural DAC Sin(X)/X frequency rolloff. The digital Quadrature
Modulator Correction (QMC) feature allows IQ compensation of phase, gain, and offset to maximize
sideband rejection and minimize LO feedthrough of an external quadrature modulator performing the final
single-sideband RF upconversion.
3.1.2 CDCM7005
The CDCM7005 is a high-performance, low-phase noise and low-skew clock synchronizer that
synchronizes a VCXO (voltage-controlled crystal oscillator) or VCO (voltage-controlled oscillator)
frequency to a reference clock. The CDCM7005 is used to generate and synchronize the clock outputs to
the system. The device has five outputs which can be configured to LVPECL or LVCMOS levels and can
be divided down by 1, 2, 3, 4, 6, 8, and 16. The divide by 16 can be replaced with a divide by 4 or 8 with a
90 degree phase shift.
3.1.3 TRF3703
The TRF3703 is a very-low-noise direct quadrature modulator, capable of converting complex modulated
signals from baseband or IF directly up to RF based on the LO frequency.
4 DAC5668/88/89 Hardware Description
The DAC5668/88/89EVM can be set up in a variety of configurations to accommodate a specific mode of
operation. Before starting evaluation, the user should decide on the configuration and make the
appropriate connections or changes. The demonstration board comes with the following factory-set
configuration:
5 SLAU241A – June 2008 – Revised March 2010 DAC5668/88/89EVM
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