LTC2400 Linear Technology, LTC2400 Datasheet - Page 25

• Manufacturer Part Number: LTC2400
• Description: 24-Bit uPower No Latency ADC in SO-8
• Manufacturer: Linear Technology

APPLICATIONS
In addition to the dynamic reference current, the V
protection diodes have a temperature dependent leakage
current. This leakage current, nominally 1nA ( 10nA max),
results in a fixed full-scale shift of 10 V for a 10k source
resistance.
ANTIALIASING
One of the advantages delta-sigma ADCs offer over con-
ventional ADCs is on-chip digital filtering. Combined with
a large oversampling ratio, the LTC2400 significantly
simplifies antialiasing filter requirements.
The digital filter provides very high rejection except at
integer multiples of the modulator sampling frequency
(f
256 • F
or 60Hz). The bandwidth of signals not rejected by the
S
), see Figure 26. The modulator sampling frequency is
O
, where F
160
140
120
100
–20
80
60
20
40
0
Figure 25. INL Error vs R
0
V
V
T
A
CC
REF
= 25 C
= 5V
O
= 5V
200
is the notch frequency (typically 50Hz
U
RESISTANCE AT V
C
C
VREF
C
VREF
VREF
400
INFORMATION
= 0.1 F
= 10 F
U
= 1 F
600
REF
C
VREF
VREF
( )
W
= 0.01 F
800
(Large C)
2400 F25
1000
U
REF
ESD
digital filter is narrow ( 0.2%) compared to the bandwidth
of the frequencies rejected.
As a result of the oversampling ratio (256) and the digital
filter, minimal (if any) antialias filtering is required in front
of the LTC2400. If passive RC components are placed in
front of the LTC2400 the input dynamic current should be
considered (see Input Current section). In cases where
large effective RC time constants are used, an external
buffer amplifier may be required to minimize the effects of
input dynamic current.
The modulator contained within the LTC2400 can handle
large-signal level perturbations without saturating. Signal
levels up to 40% of V
lator. These signals are limited by the input ESD protection
to 300mV below ground and 300mV above V
–140
–100
–120
–20
–60
–40
–80
0
0
Figure 26. Sinc
REF
INPUT FREQUENCY
do not saturate the analog modu-
f
S
4
/2
Filter Rejection
2400 F26
LTC2400
f
S
CC
.
25