Texas Instruments DAC5668, Manual

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User's Guide
SLAU241A – June 2008 – Revised March 2010
DAC5668/88/89EVM
1 Overview
1.1 Purpose
The DAC5668/88/89EVM provides a platform for evaluating the DAC5668, DAC5688, and DAC5689
digital-to-analog (DAC) converter under various signal, reference, and supply conditions. All three DACs
are dual channel, 800MSPS interpolating DACs with DAC5668 being a 12-bit DAC and
DAC5688/DAC5689 being 16-bit DACs. Also, both the DAC5668 and the DAC5688 have internal
PLL/VCO, which is useful when a high-rate clock is not available at the system level. The table below
summarizes the comparisons among the DAC family. The evaluation module also allows designers to
analyze either a transformer-coupled output from the DAC or an RF-modulated output using Texas
Instruments (TI) TRF3703 analog quadrature modulator. Use this document with the EVM schematic
diagram and the corresponding device datasheet.
Table 1. Device Comparisons
12-Bit 16-Bit PLL/VCO EVM Software
DAC5668 X X DAC5688
DAC5688 X X DAC5688
DAC5689 X DAC5689
1.2 EVM Basic Functions
Digital inputs to the DAC can be provided with CMOS-level signals up to 250 MSPS through two 34-pin
headers. The analog outputs from the DAC are available via SMA connectors. Because of its flexible
design, the analog outputs of the DAC device can be configured to drive a 50-
Ω terminated cable using a
4:1 or 1:1 impedance ratio transformer, or single-ended referred to AVDD. The EVM also allows for an
option to use TI’s TRF3703 analog quadrature modulator to mix the DAC outputs to RF.
The EVM also includes a TI CDCM7005 clock distribution device to clock the system. The CDCM7005 can
be used with an onboard VCXO for full PLL functionality or with an external signal source, in which case
the CDCM7005 functions as a buffer.
Power connections to the EVM are via banana jack sockets. In addition to the internal bandgap reference
provided by the DAC device, the EVM allows an external reference to be provided to the DAC.
The DAC5668/88/89EVM allows the user to program the DAC and CDCM7005 registers through a USB
port. The interface allows read and write access to all the DAC5668/88/89 registers and write-only access
to the CDCM7005 registers.
1.3 Power Requirements
The DAC5668/88/89EVM requires 1.8-Vdc and 3.3-Vdc supplies for normal operation. An additional 5-Vdc
supply is required to power up the TRF3703 for RF measurements.
1 SLAU241A – June 2008 – Revised March 2010 DAC5668/88/89EVM
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