3-4
The sample clock and digital output data signals are made
available through two connectors contained on the
evaluation board. The line buffering provided by the data
output latches allows for driving long leads or analyzer
inputs. These data latches are not necessary for the digital
output data if the load presented to the converter does not
exceed the data sheet load limits of 100
µ
A and 15pF. The P2
I/O connector allows the evaluation board to be interfaced to
the DSP evaluation boards available from Intersil.
Alternatively, the digital output data and sample clock can
also be accessed by clipping the test leads of a logic
analyzer or data acquisition system onto the I/O pins of
connector header P1.
HI5905 Performance Characterization
Dynamic testing is used to evaluate the performance of the
HI5905 A/D converter. Among the tests performed are
Signal-to-Noise and Distortion Ratio (SINAD), Signal-to-
Noise Ratio (SNR), Total Harmonic Distortion (THD),
Spurious Free Dynamic Range (SFDR) and InterModulation
Distortion (IMD).
Figure 4 shows the test system used to perform dynamic
testing on high-speed ADCs at Intersil. The clock (CLK) and
analog input (V
IN
) signals are sourced from low phase noise
HP8662A synthesized signal generators that are phase locked
to each other to ensure coherence. The output of the signal
generator driving the ADC analog input is bandpass filtered to
improve the harmonic distortion of the analog input signal. The
comparator on the evaluation board will convert the sine wave
CLK input signal to a square wave at TTL logic levels to drive
the sample clock input of the HI5905. The ADC data is
captured by a logic analyzer and then transferred over the GPIB
bus to the PC. The PC has the required software to perform the
Fast Fourier Transform (FFT) and do the data analysis.
Coherent testing is recommended in order to avoid the
inaccuracies of windowing. The sampling frequency and
analog input frequency have the following relationship: F
I
/F
S
= M/N, where F
I
is the frequency of the input analog
sinusoid, F
S
is the sampling frequency, N is the number of
samples, and M is the number of cycles over which the
samples are taken. By making M an integer and odd number
(1, 3, 5, ...) the samples are assured of being nonrepetitive.
Refer to the HI5905 data sheet for a complete list of test
definitions and the results that can be expected using the
evaluation board with the test setup shown. Evaluating the
part with a reconstruction DAC is only suggested when
doing bandwidth or video testing.
TABLE 2. TIMING SPECIFICATIONS
PARAMETER
DESCRIPTION
TYP
t
OD
HI5905 Digital Output Data Delay
50ns
t
PD1
U4 Prop Delay
4.5ns
t
PD2
U2/3 Prop Delay
9ns
HP8662A
HP8662A
FILTER
BANDPASS
HI5905EVAL2
PC
HI5905
COMPARATOR
REF
V
IN
CLK
DIGITAL DATA OUTPUT
14
GPIB
DAS9200
EVALUATION BOARD
V
IN
CLK
FIGURE 4. HIGH-SPEED A/D PERFORMANCE TEST SYSTEM
Application Note 9785
