datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

ADC0804LCN View Datasheet(PDF) - Renesas Electronics

Part Name
Description
View to exact match
ADC0804LCN Datasheet PDF : 17 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
ADC0803, ADC0804
applied to the VlN(-) pin to absorb the offset, the reference
voltage can be made equal to 1/2 of the 3V span or 1.5V. The
A/D now will encode the VlN(+) signal from 0.5V to 3.5V with the
0.5V input corresponding to zero and the 3.5V input
corresponding to full scale. The full 8 bits of resolution are
therefore applied over this reduced analog input voltage range.
The requisite connections are shown in Figure 13. For
expanded scale inputs, the circuits of Figures 14 and 15 can be
used.
V+
(VREF) 20
R
VREF/2
9
DIGITAL
CIRCUITS
R
DECODE
ANALOG
CIRCUITS
VIN 10V
5V
(VREF)
R
2R
6 VIN(+) V+ 20
+
ADC0803-
10F
2R
ADC0804
7 VIN(-)
FIGURE 14. HANDLING 10V ANALOG INPUT RANGE
VIN 5V
5V
(VREF)
R
R
6 VIN(+)
20
V+
+
ADC0803-
10F
ADC0804
7 VIN(-)
AGND 8
DGND 10
FIGURE 12. THE VREFERENCE DESIGN ON THE IC
VREF
(5V)
ICL7611 5V
FS
“SPAN”/2
-
+
ADJ.
300
0.1F
ZERO SHIFT VOLTAGE
TO VREF/2
TO VIN(-)
FIGURE 13. OFFSETTING THE ZERO OF THE ADC080X AND
PERFORMING AN INPUT RANGE (SPAN)
ADJUSTMENT
FN3094 Rev 4.00
August 2002
FIGURE 15. HANDLING 5V ANALOG INPUT RANGE
Reference Accuracy Requirements
The converter can be operated in a pseudo-ratiometric mode
or an absolute mode. In ratiometric converter applications, the
magnitude of the reference voltage is a factor in both the
output of the source transducer and the output of the A/D
converter and therefore cancels out in the final digital output
code. In absolute conversion applicatIons, both the initial value
and the temperature stability of the reference voltage are
important accuracy factors in the operation of the A/D
converter. For VREF/2 voltages of 2.5V nominal value, initial
errors of 10mV will cause conversion errors of 1 LSB due to
the gain of 2 of the VREF/2 input. In reduced span applications,
the initial value and the stability of the VREF/2 input voltage
become even more important. For example, if the span is
reduced to 2.5V, the analog input LSB voltage value is
correspondingly reduced from 20mV (5V span) to 10mV and 1
LSB at the VREF/2 input becomes 5mV. As can be seen, this
reduces the allowed initial tolerance of the reference voltage
and requires correspondingly less absolute change with
temperature variations. Note that spans smaller than 2.5V
place even tighter requirements on the initial accuracy and
stability of the reference source.
In general, the reference voltage will require an initial
adjustment. Errors due to an improper value of reference
voltage appear as full scale errors in the A/D transfer function.
Page 10 of 17
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]