ADC14DS105KARB/NOPB National Semiconductor, ADC14DS105KARB/NOPB Datasheet - Page 9

• Manufacturer Part Number: ADC14DS105KARB/NOPB
• Description: BOARD EVAL FOR ADC14DS105KARB
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of ADC14DS105KARB/NOPB

• Design Resources: ADC14DS105KARB Ref Design
• Number Of Adc's: 2
• Number Of Bits: 14
• Sampling Rate (per Second): 105M
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Power (typ) @ Conditions: 1W @ 105MSPS
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: ADC14DS105
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADC14DS105KARB

5.0 Functional Description
5.1 Dual Analog Inputs with LMH6552 High Speed
Differential Amplifier
This evaluation board is configured to accept dual
analog inputs via SMA(f) connectors. Figure 8
illustrates the input configuration for the amplifiers. The
inputs are 50 ohms, DC-coupled. Each input drives an
LMH6552 differential amplifier that is configured for the
single-ended-to-differential
VCOM output of the ADC (ADC14DS105) is used as
the common mode input to the amplifier. Each amplifier
is configured for 6 dB of gain, so the maximum input
signal level is 1 Vp-p, producing 2Vp-p at the output of
the amplifier. It is recommended that the amplifiers be
powered by dual supply rails (+/- 5VDC), but the board
can also be configured to operate in single supply
mode by installing jumpers at VCCAA- and VCCAB-.
Please refer to the LMH6552 datasheet for a
description of operating the LMH6552 with a single
supply.
N
To obtain the best distortion results (best
-10
-12
-14
-16
-18
-2
-4
-6
-8
0
Figure 9. 2
0
mode
Figure 8. Analog Input Circuit for ADC14DS105KARB
10
nd
conversion.
ADC14DS105KARB Reference Design Board User’s Guide
Order Lowpass Filter Profile for ADC14DS105KARB
20
The
Input Frequency (MHz)
30
- 9 -
SFDR), a low noise signal generator such as the
HP8644B
Schwarz) is recommended to drive the signal inputs of
the evaluation board.
generator should be bandpass filtered to suppress any
harmonic distortion produced by the signal generator
and to allow accurate measurement of the noise and
distortion performance. See Figure 4. The low pass
filter (F
improve the noise performance of the ADC by filtering
the broadband noise of the signal generator.
5.2 Bandpass Anti-Aliasing Filter
The output of the LMH6552 amplifier drives a passive
2
Figure 8. The filter output is sampled by the analog to
digital converter. The combined channel response of
the differential amplifier, bandpass filter and ADC is
shown in the Figure 9.
nd
order lowpass filter with F
40
c
≈ 35 MHz) following the LMH6552 will further
(HP/Agilent)
50
ChanA
ChanB
60
or
The output of the signal
c
SMA100A
≈ 35 MHz as shown in
www.national.com
(Rohde
Rev 0.2
&