ADS5296 Datasheet, PDF (95/104 Pages) Texas Instruments – 10-Bit, 200-MSPS, 4-Channel and 12-Bit, 80-MSPS, 8-Channel Analog-to-Digital Converter

ADS5296
www.ti.com
SBAS606A – MAY 2013 – REVISED MAY 2013
LVDS OUTPUT DATA AND CLOCK BUFFERS
The equivalent circuit of each LVDS output buffer is shown in Figure 107. After reset, the buffer presents an
output impedance of 100 Ω to match with the external 100-Ω termination.
The V_DIFF voltage is nominally 400 mV, resulting in an output swing of ±400 mV with a 100-Ω external
termination. The buffer output impedance behaves in the same way as a source-side series termination. By
absorbing reflections from the receiver end, this impedance helps improve signal integrity.
V_DIFF
High
V_OCM
V_DIFF
Low
Low
High
OUTP
OUTM
External
100-W Load
(1)
R_OUT
(1) R_OUT = 100 Ω.
Figure 107. LVDS Buffer Equivalent Circuit
OUTPUT DATA FORMAT
Two output data formats are supported: twos complement and offset binary. These formats can be selected by
the BTC_MODE serial interface register bit. In the event of an input voltage overdrive, the digital outputs go to
the appropriate full-scale level. For a positive overload, the 12-bit output data (D[11:0]) is FFFh in offset binary
output format and 7FFh in twos complement output format. For a negative input overload, the output data is 000h
in offset binary output format and 800h in twos complement output format.
BOARD DESIGN CONSIDERATIONS
Grounding
A single ground plane is sufficient to give good performance, provided the analog, digital, and clock sections of
the board are cleanly partitioned. Refer to the EVM User Guide, ADS5295, 8-Channel ADC Evaluation Module,
(SLAU442) for details on layout and grounding.
Supply Decoupling
Minimal external decoupling can be used without loss in performance because the device already includes
internal decoupling. Note that decoupling capacitors can help filter external power-supply noise; thus, the
optimum number of capacitors depends on the actual application. The decoupling capacitors should be placed as
close as possible to the converter supply pins.
Exposed Pad
In addition to providing a path for heat dissipation, the pad is also electrically connected to the digital ground
internally. Therefore, the exposed pad must be soldered to the ground plane for best thermal and electrical
performance.
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: ADS5296
Submit Documentation Feedback
95