HI5746 Datasheet, PDF (14/17 Pages) Intersil Corporation – 10-Bit, 40 MSPS A/D Converter

HI5746
TABLE 1. A/D CODE TABLE
OFFSET BINARY OUTPUT CODE
(DFS LOW)
TWO’S COMPLEMENT OUTPUT CODE
(DFS HIGH)
CODE CENTER
DESCRIPTION
M
LM
L
S
SS
S
DIFFERENTIAL _B
BB
B
INPUT VOLTAGE
(V_IN+ - V_IN-) D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
+Full Scale (+FS) -
1_{/4 LSB}
+FS - 1¹/₄ LSB
+³/₄ LSB
-¹/₄ LSB
-FS + 1³/₄ LSB
0.499756V
0.498779V
732.422µV
-244.141µV
-0.498291V
11111111110111111111
11111111100111111110
10000000000000000000
01111111111111111111
00000000011000000001
-Full Scale (-FS) +
3_{/4 LSB}
-0.499268V
00000000001000000000
NOTES:
8. The voltages listed above represent the ideal center of each output code shown as a function of the reference differential voltage,
(V_REF + - V_REF-) = 0.5V.
9. V_REF+ = 2.5V and V_REF- = 2V.
The output enable pin, OE, when pulled high will three-state
the digital outputs to a high impedance state. Set the OE
input to logic low for normal operation.
OE INPUT
0
1
DIGITAL DATA OUTPUTS
Active
High Impedance
Supply and Ground Considerations
The HI5746 has separate analog and digital supply and
ground pins to keep digital noise out of the analog signal
path. The digital data outputs also have a separate supply
pin, DV_CC2 , which can be powered from a 3V or 5V supply.
This allows the outputs to interface with 3V logic if so
desired.
The part should be mounted on a board that provides
separate low impedance connections for the analog and
digital supplies and grounds. For best performance, the
supplies to the HI5746 should be driven by clean, linear
regulated supplies. The board should also have good high
frequency decoupling capacitors mounted as close as
possible to the converter. If the part is powered off a
single supply then the analog supply should be isolated
with a ferrite bead from the digital supply.
Refer to the application note “Using Intersil High Speed A/D
Converters” (AN9214) for additional considerations when
using high speed converters.
Static Performance Definitions
Offset Error (V_OS)
The midscale code transition should occur at a level ¹/₄ LSB
above half-scale. Offset is defined as the deviation of the
actual code transition from this point.
Full-Scale Error (FSE)
The last code transition should occur for an analog input that
is ³/₄ LSB below positive Full scale (+FS) with the offset
error removed. Fullscale error is defined as the deviation of
the actual code transition from this point.
Differential Linearity Error (DNL)
DNL is the worst case deviation of a code width from the
ideal value of 1 LSB.
Integral Linearity Error (INL)
INL is the worst case deviation of a code center from a best
fit straight line calculated from the measured data.
Power Supply Sensitivity
Each of the power supplies are moved plus and minus 5% and
the shift in the offset and full scale error (in LSBs) is noted.
Dynamic Performance Definitions
Fast Fourier Transform (FFT) techniques are used to evaluate
the dynamic performance of the HI5746. A low distortion sine
wave is applied to the input, it is coherently sampled, and the
output is stored in RAM. The data is then transformed into the
frequency domain with an FFT and analyzed to evaluate the
dynamic performance of the A/D. The sine wave input to the
part is -0.5dB down from Fullscale for all these tests.
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