HI5805EVAL1 Intersil, HI5805EVAL1 Datasheet - Page 9

• Manufacturer Part Number: HI5805EVAL1
• Description: EVALUATION PLATFORM HI5805
• Manufacturer: Intersil

Specifications of HI5805EVAL1

• Number Of Adc's: 1
• Number Of Bits: 12
• Sampling Rate (per Second): 5M
• Data Interface: Parallel
• Inputs Per Adc: 1 Differential
• Input Range: 4 Vpp
• Power (typ) @ Conditions: 300mW @ 5MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: HI5805
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

†
Analog Input, Differential Connection
The analog input to the HI5805 can be configured in various
ways depending on the signal source and the required level
of performance. A fully differential connection (Figure 15) will
give the best performance for the converter.
Since the HI5805 is powered off a single +5V supply, the
analog input must be biased so it lies within the analog input
common mode voltage range of 1.0V to 4.0V. The
performance of the ADC does not change significantly with
the value of the analog input common mode voltage.
A 2.3V DC bias voltage source, V
top and bottom internal reference voltages, is made
available to the user to help simplify circuit design when
using a differential input. This low output impedance voltage
source is not designed to be a reference but makes an
excellent bias source and stays within the analog input
common mode voltage range over temperature.
The difference between the converter’s two internal voltage
references is 2V. For the AC coupled differential input,
degrees out of phase with V
sinewave riding on a DC bias voltage equal to V
V
to V
(Figure 15), if V
+Full Scale (+FS) -
+FS
-FS + 1
-Full Scale (-FS) +
+
-
IN
The voltages listed above represent the ideal center of each offset binary output code shown.
1
3
/
- is a 2V
/
4
DC
4
-
LSB
LSB
1
CODE CENTER
FIGURE 15. AC COUPLED DIFFERENTIAL INPUT
DESCRIPTION
. Consequently, the converter will be at positive full
3
1
/
/
4
4
-
V
V
LSB
LSB
IN
IN
P-P
IN
sinewave riding on a DC bias voltage equal
3
1
is a 2V
/
/
4
4
LSB
LSB
P-P
+1.99976V
1.99878V
732.4µV
-244.1µV
-1.99829V
-1.99927V
(USING INTERNAL
IN
INPUT VOLTAGE
sinewave with -V
9
DIFFERENTIAL
REFERENCE)
, then V
DC
, half way between the
IN
+ is a 2V
V
V
V
IN
DC
IN
†
+
-
HI5805
IN
MSB
D11
DC
being 180
P-P
1
1
1
0
0
0
and
D10
1
1
0
1
0
0
HI5805
TABLE 1.
D9
1
1
0
1
0
0
scale, all 1s digital data output code, when the V
at V
2V). Conversely, the ADC will be at negative full scale, all
0s digital data output code, when the V
V
this, the converter is seen to have a peak-to-peak
differential analog input voltage range of ±2V.
The analog input can be DC coupled (Figure 16) as long as
the inputs are within the analog input common mode voltage
range (1.0V ≤ VDC ≤ 4.0V).
The resistors, R, in Figure 16 are not absolutely necessary
but may be used as load setting resistors. A capacitor, C,
connected from V
frequency noise on the inputs, also improving performance.
Values around 20pF are sufficient and can be used on AC
coupled inputs as well. Note, however, that the value of
capacitor C chosen must take into account the highest
frequency component of the analog input signal.
Analog Input, Single-Ended Connection
The configuration shown in Figure 17 may be used with a
single ended AC coupled input. Sufficient headroom must be
provided such that the input voltage never goes above +5V
or below A
DC
D8
1
1
0
1
0
0
OFFSET BINARY OUTPUT CODE
DC
- 1V and V
VDC
VDC
FIGURE 16. DC COUPLED DIFFERENTIAL INPUT
+1V and the V
D7
1
1
0
1
0
0
GND .
V
IN
-
V
IN
IN
D6
1
1
0
1
0
0
IN
- is at V
+ to V
IN
D5
1
1
0
1
0
0
- input is at V
DC
IN
- will help filter any high
+ 1V (V
D4
1
1
0
1
0
0
R
R
D3
1
1
0
1
0
0
IN
C
DC
+ - V
IN
-1V (V
D2
+ input is equal to
1
1
0
1
0
0
IN
V
V
V
DC
IN
IN
- = -2V). From
-
+
HI5805
D1
IN
IN
1
1
0
1
0
0
+ - V
+ input is
IN
LSB
D0
1
0
0
1
1
0
- =