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0
100
200
300
400
500
600
-1
-0.6
-0.2
0.2
0.6
1
Num
b
e
r
o
f
Device
s
Error in REFIO Voltage (mV)
C064
ADC
4.096 V
REF
REFCAP
REFIO
AGND
22
P
F
REFGND
10
P
F
REFSEL
AVDD
1
P
F
SBAS686 – JULY 2015
8.3.8.1 Internal Reference
The devices have an internal 4.096-V (nominal value) reference. In order to select the internal reference, the
REFSEL pin must be tied low or connected to AGND. When the internal reference is used, REFIO (pin 5)
becomes an output pin with the internal reference value. Placing a 10-µF (minimum) decoupling capacitor
between the REFIO pin and REFGND (pin 6) is recommended, as shown in
. The capacitor must be
placed as close to the REFIO pin as possible. The output impedance of the internal band-gap circuit creates a
low-pass filter with this capacitor to band-limit the noise of the reference. The use of a smaller capacitor value
allows higher reference noise in the system, thus degrading SNR and SINAD performance. Do not use the
REFIO pin to drive external ac or dc loads because REFIO has limited current output capability. The REFIO pin
can be used as a source if followed by a suitable op amp buffer (such as the
Figure 57. Device Connections for Using an Internal 4.096-V Reference
The device internal reference is factory trimmed to a maximum initial accuracy of ±1 mV. The histogram in
shows the distribution of the internal voltage reference output taken from more than 3300 production
devices.
Figure 58. Internal Reference Accuracy at Room Temperature Histogram
26
Copyright © 2015, Texas Instruments Incorporated
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