Texas Instruments ADS868 Series, Manual

Page: 12 / 67

0
4000
8000
12000
16000
20000
32765 32766 32767 32768 32769 32770 32771
Num
b
e
r
o
f
Hi
ts
Output Codes
C007
0
4000
8000
12000
16000
20000
32765 32766 32767 32768 32769 32770 32771
Num
b
e
r
o
f
Hi
ts
Output Codes
C008
0
160
320
480
640
800
0.85 0.88 0.91 0.94 0.97 1 1.03 1.06 1.09 1.12 1.15
Num
b
e
r
o
f
S
a
m
p
les
Input Impedance (Mohm)
C006
±
10
±
6
±
2
2
6
10
±
40
±
7
26 59 92 125
In
p
u
t
Im
p
e
d
a
n
ce
Dr
ift
(p
p
m
)
Free- Air Temperature (
o
C) C005
-----
± 2.5*V
REF
-----
± 1.25*V
REF
----- ± 0.625*V
REF
------ +2.5*V
REF
------+1.25*V
REF
±
15
±
9
±
3
3
9
15
±
10
±
6
±
2 2 6 10
A
n
a
log
I
n
p
u
t
Cur
re
n
t
(u
A
)
Input Voltage (V)
C002
----- 25 C
----- -40 C
------ 125 C
±
15
±
9
±
3
3
9
15
±
10
±
6
±
2 2 6 10
A
n
a
log
I
n
p
u
t
Cur
re
n
t
(u
A
)
Input Voltage (V)
C001
-----
± 2.5*V
REF
-----
± 1.25*V
REF
----- ± 0.625*V
REF
------ +2.5*V
REF
------+1.25*V
REF
ADS8684, ADS8688
SBAS582C – JULY 2014 – REVISED APRIL 2015 www.ti.com
7.7 Typical Characteristics
At T
A
= 25°C, AVDD = 5 V, DVDD = 3 V, internal reference V
REF
= 4.096 V, and f
SAMPLE
= 500 kSPS, unless otherwise noted.
Input range = ±2.5 × V
REF
Figure 2. Input I-V Characteristic
Figure 3. Input Current vs Temperature
Number of samples = 1160
Figure 4. Input Impedance Variation vs Temperature
Figure 5. Typical Distribution of Input Impedance
Mean = 32767.8, sigma = 0.58, input = 0 V, Mean = 32768.1, sigma = 0.63, input = 0 V,
range = ±2.5 × V
REF
range = ±1.25 × V
REF
Figure 6. DC Histogram for Mid-Scale Inputs (±2.5 × V
REF
) Figure 7. DC Histogram for Mid-Scale Inputs (±1.25 × V
REF
)
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