MAX1276EVKIT Maxim Integrated, MAX1276EVKIT Datasheet - Page 11

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MAX1276EVKIT

Manufacturer Part Number
MAX1276EVKIT
Description
Data Conversion IC Development Tools Evaluation Kit/Evaluation System for the MAX1070/71/72/75#79/MAX1224/25/MAX1274#79
Manufacturer
Maxim Integrated
Series
MAX1276, MAX1278r
Datasheet

Specifications of MAX1276EVKIT

Interface Type
QSPI, Serial (SPI, Microwire)
In this mode of operation, members of the device family
requiring an external reference can be evaluated by
direct connection of an external source through the
VREF pad. Sufficient decoupling is included on the
board so most external sources or references should be
able to adequately supply the requirements of the ADC.
Be sure to verify the level at the pins of the test device
using the VREF_SENSE and RGND_SENSE pads.
In this mode of operation, parts with an external refer-
ence input are evaluated by supplying the positive sup-
ply (VDD) directly to the part’s reference input. The
VREF pad is not connected, but the VREF_SENSE and
RGND_SENSE pads remain valid.
The MAX1276EVKIT was designed to demonstrate the
full capabilities of the MAX1276 family of devices. The
board comes supplied with components and options
selected for proven performance. Additionally, the EV
kit allows for extensive user customization. These cus-
tom options allow customers to configure the board in
several different ways to evaluate potential tradeoffs in
performance. The following sections describe several
such options and include application notes, which may
be of interest to those wishing to design the MAX1276
family into their applications.
To obtain peak performance from the MAX1276 at high
sample rates, the analog inputs should be actively
buffered. In selecting a buffer, it is the settling time of
the buffer amplifier that is critical to observed converter
performance at high speeds. This means that the input
buffers need to be designed to fully settle the analog
inputs during the conversion sampling interval. The
bandwidth required to do so may exceed the band-
width required to process the input-signal frequency
content, thus a designer must ensure both settling
bandwidth and input-signal bandwidth considerations
are addressed when placing a high-speed data con-
verter into a system context. Refer to the device data
sheet for details of the load presented by the MAX1276
family of devices and the duration of the sampling inter-
val. Note that the sampling interval is dependent on
sampling rate and clock speed.
On the MAX1276 EV kit board, U2 and U3 (MAX4430
op amps) are input amplifiers that can be configured to
drive a variety of input signal levels. The AIN+ channel
Detailed Description of Hardware
External Reference Operation (Default)
MAX1276 Evaluation Kit/Evaluation System
External Reference Operation
______________________________________________________________________________________
with VDD Reference
Input Buffer Stage
buffer (U2) is placed in a noninverting configuration
while the AIN- channel buffer (U3) is placed in an
inverting configuration. Each amplifier can be connect-
ed to the analog input (ACIN) and to DC voltages (CMP
and CMM) to set input common-mode levels.
See
different input configurations.
The amplifier outputs connect to the ADC input pins
(AIN+ and AIN-) through lowpass filters consisting of
R1, R2, and input capacitor C1 (see the Input
Filter section).
The MAX4430 buffers are capable of fully demonstrat-
ing the performance of the MAX1276 family well above
maximum Nyquist rates. These buffers should always
be used when evaluating the performance of the
MAX1276 family at high speeds (even with DC inputs).
While the EV kit does support passive input connec-
tions through JU1 and JU2 settings, these are intended
for applications where external sources/buffers are to
be evaluated. Otherwise, passive operation is only rec-
ommended for low sampling rates, which allow extend-
ed sampling intervals.
Analog input signals selected through JU1 and JU2
connect to the MAX1276 inputs through an input filter
consisting of R1, R2, and C1. The values supplied with
the EV kit were chosen for optimal performance, provid-
ing excellent stability and peak linearity. See the device
data sheet for notes on source-impedance effects on
ADC linearity.
The EV kit comes supplied with a single input capacitor
(C1) mounted across the analog inputs of the
MAX1276. This arrangement typically offers the best
dynamic performance in most applications. Some users
may prefer or require a dual capacitor arrangement on
the analog inputs instead of the single capacitor sup-
plied with the MAX1276 EV kit. The board layout makes
it possible to replace the single capacitor with dual
capacitors to ground.
alternate capacitor mounting.
Regardless of configuration, C0G-type capacitors are
highly recommended in this application. C0G capaci-
tors typically demonstrate better sample recovery char-
acteristics and are often used in critical analog signal
path applications. When designing the input stage, be
sure to consider the combination of buffer amplifiers
and input capacitors to achieve the desired stability,
source impedance, and filtering characteristics.
Table
5 for information on setting the jumpers for
Figure
7 shows the preferred and
Input Filter
11

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