ISL267450_14 Datasheet, PDF (13/19 Pages) Intersil Corporation – 12-Bit, 1MSPS SAR ADCs

ISL267450
VCM
5.0
4.0
3.0
2.0
1.0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
VREF
FIGURE 23. RELATIONSHIP BETWEEN V_REF AND VCM FOR V_DD = 5V
VCM
3.0
2.5
2.0
1.5
1.0
0.5
0.5 1.0 1.5 2.0 2.5
VREF
FIGURE 24. RELATIONSHIP BETWEEN VREF AND VCM FOR V_DD = 3V
Voltage Reference Input
The voltage magnitude applied to the V_REF pin defines the full
scale span of the ADC as 2* V_REF. The device is specified with a
voltage reference of 2.5V for 5V operation and with a voltage
reference of 2.0V for 3V operation. But, V_REF input accepts
voltages ranging from 0.1V to 3.5V for operation from 5 V V_DD
and voltages ranging from 0.1V to 2.2V for operation from a 3V
V_DD.
Figures 25 and 26 illustrate possible voltage reference options
for the ISL267450. Figure 25 uses the ISL21090 precision
voltage reference, which exhibits exceptionally low drift and low
noise. The ISL21090 must use a power supply greater than 4.7V.
The V_REF input pin on the ISL267450 uses very low current, so
the decoupling capacitor can be small (0.1µF).
Figure 26 illustrates the ISL21010 voltage reference. The
ISL21010 is available in various output voltages. It has higher
noise and drift than the ISL26090, but consumes very low
operating current, which makes it an excellent choice for
battery-powered applications.
5V
0.1µF
+ ^BULK
1 DNC DNC 8
2 VIN
DNC 7
2.5V
3 COMP VOUT 6
4 GND TRIM 5
ISL267450 ^VDD
V_REF
0.1µF
ISL21090
FIGURE 25. PRECISION VOLTAGE REFERENCE FOR +5V SUPPLY
0.1µF
+3.0V TO +3.3V
OR +5V
VIN 1
VOUT 2
GND
3
ISL21010
+
BULK
0.1µF
ISL267450 ^VDD
VREF
1.25, 2.048 OR 2.5V
0.1µF
0.1µF
FIGURE 26. VOLTAGE REFERENCE FOR +3.0V TO +3.3V, OR FOR +5V SUPPLY
13
FN8341.0
August 10, 2012