hi5766 Intersil Corporation, hi5766 Datasheet - Page 12

• Manufacturer Part Number: hi5766
• Description: 10-bit, 60msps A/d Converter
• Manufacturer: Intersil Corporation

two-bit multiplying digital-to-analog converter, follow the S/H
circuit with the ninth stage being a two bit flash converter.
Each converter stage in the pipeline will be sampling in one
phase and amplifying in the other clock phase. Each
individual subconverter clock signal is offset by 180 degrees
from the previous stage clock signal resulting in alternate
stages in the pipeline performing the same operation.
The output of each of the eight identical two-bit subconverter
stages is a two-bit digital word containing a supplementary bit
to be used by the digital error correction logic. The output of
each subconverter stage is input to a digital delay line which is
controlled by the internal sampling clock. The function of the
digital delay line is to time align the digital outputs of the eight
identical two-bit subconverter stages with the corresponding
output of the ninth stage flash converter before applying the
eighteen bit result to the digital error correction logic. The
digital error correction logic uses the supplementary bits to
correct any error that may exist before generating the final
10-bit digital data output of the converter.
Because of the pipeline nature of this converter, the digital
data representing an analog input sample is output to the
digital data bus on the 7th cycle of the clock after the analog
sample is taken. This time delay is specified as the data
latency. After the data latency time, the digital data
representing each succeeding analog sample is output during
the following clock cycle. The digital output data is
synchronized to the external sampling clock by a double
buffered latching technique. The output of the digital error
correction circuit is available in two’s complement or offset
binary format depending on the state of the Data Format
Select (DFS) control input (see Table 1, A/D Code Table).
Reference Voltage Inputs, V
The HI5766 is designed to accept two external reference
voltage sources at the V
the converter requires V
be set at 2.0V. However, it should be noted that the input
structure of the V
resistive voltage divider with one resistor of the divider
(nominally 500Ω) connected between V
the other resistor of the divider (nominally 2000Ω) connected
between V
option of supplying only the +2.5V V
with the +2.0V V
voltage division action of the input structure.
The HI5766 is tested with V
equal to +2.5V yielding a fully differential analog input voltage
range of ±0.5V. V
voltages.
In order to minimize overall converter noise it is
recommended that adequate high frequency decoupling be
provided at both of the reference voltage input pins, V
and V
REF
-.
REF
- and analog ground. This allows the user the
REF
REF
REF
- being generated internally by the
+ and V
+ and V
REF
REF
REF
+ to be set at +2.5V and V
input pins. Typical operation of
REF
12
REF
- equal to +2.0V and V
- input pins consists of a
- can differ from the above
REF
REF
- and V
REF
+ voltage reference
+ and V
REF
REF
+
REF
REF
REF
- and
- to
+
+
HI5766
Analog Input, Differential Connection
The analog input to the HI5766 is a differential input that can
be configured in various ways depending on the signal
source and the required level of performance. A fully
differential connection (Figure 25 and Figure 26) will give the
best performance for the converter.
Since the HI5766 is powered by a single +5V analog supply,
the analog input is limited to be between ground and +5V.
For the differential input connection this implies the analog
input common mode voltage can range from 0.25V to 4.75V.
The performance of the ADC does not change significantly
with the value of the analog input common mode voltage.
A DC voltage source, V
available to the user to help simplify circuit design when using
an AC coupled differential input. This low output impedance
voltage source is not designed to be a reference but makes
an excellent DC bias source and stays well within the analog
input common mode voltage range over temperature.
For the AC coupled differential input (Figure 25) assume
the difference between V
typically 2V, is 0.5V. Full scale is achieved when the V
and -V
180 degrees out of phase with V
at positive full scale when the V
V
negative full scale when the V
The analog input can be DC coupled (Figure 26) as long as
the inputs are within the analog input common mode voltage
range (0.25V ≤ VDC ≤ 4.75V).
V
0.25V and V
DC
IN
VDC
VDC
- = +0.5V). Conversely, the converter will be at
+ 0.25V and the V
FIGURE 25. AC COUPLED DIFFERENTIAL INPUT
FIGURE 26. DC COUPLED DIFFERENTIAL INPUT
IN
V
-V
input signals are 0.5V
IN
V
IN
IN
-
V
IN
IN
- is at V
DC
DC
IN
REF
, equal to 3.2V (Typ), is made
- input is at V
+ 0.25V (V
R
R
R
R
+, typically 2.5V, and V
IN
P- P
IN
+ input is equal to V
IN
C
+ input is at
. The converter will be
, with -V
IN
DC
+ - V
V
V
V
DC
IN
IN
V
V
V
-
DC
IN
- 0.25V (V
+
IN
HI5766
IN
-
+
HI5766
IN
being
- = -0.5V).
REF
IN
DC
+ -
IN
-
-,