LTC2428IG#PBF Linear Technology, LTC2428IG#PBF Datasheet - Page 28
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LTC2428IG#PBF
Manufacturer Part Number
LTC2428IG#PBF
Description
IC ADC 20BIT 8CH MICROPWR 28SSOP
Manufacturer
Linear Technology
Datasheet
1.LTC2424CGPBF.pdf
(36 pages)
Specifications of LTC2428IG#PBF
Number Of Bits
20
Sampling Rate (per Second)
7.5
Data Interface
MICROWIRE™, Serial, SPI™
Number Of Converters
1
Power Dissipation (max)
1mW
Voltage Supply Source
Single Supply
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-SSOP (0.200", 5.30mm Width)
Number Of Elements
1
Resolution
20Bit
Architecture
Delta-Sigma
Sample Rate
0.008KSPS
Input Polarity
Unipolar
Input Type
Voltage
Rated Input Volt
6.188V
Differential Input
No
Power Supply Requirement
Single
Single Supply Voltage (typ)
3.3/5V
Single Supply Voltage (min)
2.7V
Single Supply Voltage (max)
5.5V
Dual Supply Voltage (typ)
Not RequiredV
Dual Supply Voltage (min)
Not RequiredV
Dual Supply Voltage (max)
Not RequiredV
Integral Nonlinearity Error
20ppm of Vref
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Mounting
Surface Mount
Pin Count
28
Package Type
SSOP
Input Signal Type
Single-Ended
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
APPLICATIONS
LTC2424/LTC2428
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 LTC2424/LTC2428 signifi-
cantly simplify antialiasing filter requirements.
The digital filter provides very high rejection except at
integer multiples of the modulator sampling frequency
(f
28
S
), see Figure 29. The modulator sampling frequency is
–10
–20
–10
10
–2
–4
–6
–8
50
40
30
20
10
Figure 27. INL Error vs R
Figure 28. INL Error vs R
8
6
4
2
0
0
1
0
V
V
T
A
CC
REF
= 25 C
= 5V
= 5V
200
10
C
C
C
C
C
C
VREF
VREF
VREF
VREF
VREF
VREF
U
C
RESISTANCE AT V
RESISTANCE AT V
VREF
C
C
VREF
VREF
= 22 F
= 10 F
= 1 F
= 0.1 F
= 0.01 F
= 0.001 F
400
100
= 0.01 F
INFORMATION
= 1000pF
= 100pF
U
600
1k
REF
REF
VREF
VREF
( )
( )
C
W
VREF
V
V
T
800
10k
A
CC
REF
(Small C)
(Large C)
= 25 C
= 0pF
24248 F28
24248 F27
= 5V
= 5V
1000
100k
U
REF
ESD
256 • F
or 60Hz). The bandwidth of signals not rejected by the
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 LTC2424/LTC2428. If passive RC components are
placed in front of the LTC2424/LTC2428, the input dy-
namic current should be considered. 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 LTC2424/LTC2428
can handle large-signal level perturbations without satu-
rating. Signal levels up to 40% of V
analog modulator. These signals are limited by the input
ESD protection to 300mV below ground and 300mV above
V
Using a Low Power Precision Reference
The circuit in Figure 30 shows the connections and by-
passing for an LT1461-2.5 as a 2.5V reference. The
LT1461 is a bandgap reference capable of 3ppm/ C tem-
perature stability yet consumes only 45 A of current. The
1k resistor between the reference and the ADC reduces the
transient load changes associated with sampling and
produces optimal results. This reference will not impact
the noise level of the LTC2424/LTC2428 if signals are less
CC
.
O
, where F
–100
–140
–120
–20
–60
–40
–80
0
0
Figure 29. Sync
f
S
= 15,360Hz
O
is the notch frequency (typically 50Hz
INPUT FREQUENCY
f
S
4
/2
Filter Rejection
REF
do not saturate the
24248 F29
f
S