LTAEY LINEAR [Linear Integrated Systems], LTAEY Datasheet - Page 24

• Manufacturer Part Number: LTAEY
• Description: Differential Input 16-Bit No Latency DS ADC
• Manufacturer: LINEAR [Linear Integrated Systems]

LTC2433-1
APPLICATIO S I FOR ATIO
translates into about 7.15 • 10
error. Figure 23 shows the typical INL error due to the
source resistance driving the REF
large C
resistance on the two reference pins is additive with
respect to this INL error. In general, matching of source
impedance for the REF
gain or the INL error. The user is thus advised to minimize
the combined source impedance driving the REF
REF
The magnitude of the dynamic reference current depends
upon the size of the very stable internal sampling capaci-
tors and upon the accuracy of the converter sampling
clock. The accuracy of the internal clock over the entire
temperature and power supply range is typical better than
0.5%. Such a specification can also be easily achieved by
an external clock. When relatively stable resistors
(50ppm/ C) are used for the external source impedance
seen by REF
current gain error will be insignificant (about 1% of its
value over the entire temperature and voltage range). Even
for the most stringent applications a one-time calibration
operation may be sufficient.
24
Figure 23. INL vs Differential Input Voltage (V
and Reference Source Resistance (R
for Large C
–
pins rather than to try to match it.
REF
REF
values are used. The effect of the source
+
–1
1
0
and REF
–0.5 –0.4–0.3–0.2–0.1 0 0.1 0.2 0.3 0.4 0.5
Values (C
V
REF+ = 5V
REF– = GND
V
CC
INCM
= 5V
U
= 0.5 • (IN
–
+
, the expected drift of the dynamic
REF
and REF
V
U
+
INDIF
+ IN
1 F)
–6
/V
–
REFDIF
) = 2.5V
• f
R
–
SOURCE
EOSC
SOURCE
pins does not help the
W
+
or REF
F
C
T
O
A
REF
LSB additional INL
= 1000
= GND
= 25 C
at REF
= 10 F
24331 F23
IN
= IN
–
+
pins when
U
+
and REF
– IN
+
–
and
)
–
In addition to the reference sampling charge, the reference
pins ESD protection diodes have a temperature dependent
leakage current. This leakage current, nominally 1nA
( 10nA max), results in a small gain error. A 100 source
resistance will create a 0.05 V typical and 0.5 V maxi-
mum full-scale error.
Output Data Rate
When using its internal oscillator, the LTC2433-1 can
produce up to 6.8 readings per second. The actual output
data rate will depend upon the length of the sleep and data
output phases which are controlled by the user and which
can be made insignificantly short. When operated with an
external conversion clock (F
oscillator), the LTC2433-1 output data rate can be in-
creased as desired. The duration of the conversion phase
is 20510/f
haves as if the internal oscillator is used with simultaneous
50Hz/60Hz. There is no significant difference in the
LTC2433-1 performance between these two operation
modes.
An increase in f
translate into a proportional increase in the maximum
output data rate. This substantial advantage is neverthe-
less accompanied by three potential effects, which must
be carefully considered.
First, a change in f
in the internal notch position and in a reduction of the
converter differential mode rejection at the power line
frequency. In many applications, the subsequent perfor-
mance degradation can be substantially reduced by rely-
ing upon the LTC2433-1’s exceptional common mode
rejection and by carefully eliminating common mode to
differential mode conversion sources in the input circuit.
The user should avoid single-ended input filters and
should maintain a very high degree of matching and
symmetry in the circuits driving the IN
Second, the increase in clock frequency will increase
proportionally the amount of sampling charge transferred
through the input and the reference pins. If large external
EOSC
. If f
EOSC
EOSC
EOSC
over the nominal 139,800Hz will
will result in a proportional change
= 139,800Hz, the converter be-
O
connected to an external
+
and IN
–
pins.
24331fa