LTC2498IUHF#PBF Linear Technology, LTC2498IUHF#PBF Datasheet - Page 30

• Manufacturer Part Number: LTC2498IUHF#PBF
• Description: IC ADC 24BIT 16CH 38-QFN
• Manufacturer: Linear Technology

Specifications of LTC2498IUHF#PBF

• Number Of Bits: 24
• Sampling Rate (per Second): 7.5
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 480µW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 38-WFQFN, Exposed Pad
• Number Of Elements: 1
• Resolution: 24Bit
• Architecture: Delta-Sigma
• Sample Rate: 0.008KSPS
• Input Polarity: Bipolar
• Input Type: Voltage
• Rated Input Volt: ±2.75V
• Differential Input: Yes
• 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: 10ppm of Vref
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 38
• Package Type: QFN EP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

applications inForMation
LTC2498
The LTC6078 is an excellent amplifier for this function.
It operates with supply voltages as low as 2.7V and its
noise level is 18nV/√Hz. The Easy Drive input technology
of the LTC2498 enables an RC network to be added directly
to the output of the LTC6078. The capacitor reduces the
magnitude of the current spikes seen at the input to the
ADC and the resistor isolates the capacitor load from the
op-amp output enabling stable operation.
Reference Current
Similar to the analog inputs, the LTC2498 samples the
differential reference pins (REF
small amounts of charge to and from these pins, thus
producing a dynamic reference current. If incomplete set-
tling occurs (as a function the reference source resistance
and reference bypass capacitance) linearity and gain errors
are introduced.
For relatively small values of external reference capaci-
tance (C
settles for reference impedances of many kΩ (if C
100pF up to 10k will not degrade the performance), see
Figures 14, 15.
In cases where large bypass capacitors are required on
the reference inputs (C
ity errors are proportional to the value of the reference
0
Figure 14. +FS Error vs R
REF
–10
90
80
70
60
50
40
30
20
10
0
< 1nF), the voltage on the sampling capacitor
0
V
V
V
V
f
T
O
A
CC
REF
IN
IN
= GND
= 25°C
+
–
= 5V
= 3.75V
= 1.25V
= 5V
C
10
C
REF
C
REF
REF
C
= 0.001µF
REF
= 0.01µF
= 100pF
REF
= 0pF
100
R
SOURCE
> 0.01µF) full-scale and linear-
SOURCE
(Ω)
1k
+
and REF
at V
10k
REF
2498 F14
(Small C
100k
–
) transferring
REF
)
REF
=
resistance. Every ohm of reference resistance produces
a full-scale error of approximately 0.5ppm (while operat-
ing in simultaneous 50Hz/60Hz mode), see Figures 16
and 17. If the input common mode voltage is equal to
the reference common mode voltage, a linearity error of
approximately 0.67ppm per 100Ω of reference resistance
results, see Figure 18. In applications where the input and
reference common mode voltages are different, the errors
increase. A 1V difference in between common mode input
and common mode reference results in a 6.7ppm INL error
for every 100Ω of reference resistance.
In addition to the reference sampling charge, the reference
ESD projection diodes have a temperature dependent leak-
age current. This leakage current, nominally 1nA (±10nA
max) results in a small gain error. A 100Ω reference
resistance will create a 0.5µV full scale error.
Normal Mode Rejection and Anti-Aliasing
One of the advantages delta-sigma ADCs offer over
conventional ADCs is on-chip digital filtering. Combined
with a large oversample ratio, the LTC2498 significantly
simplifies anti-aliasing filter requirements. Additionally,
the input current cancellation feature allows external
lowpass filtering without degrading the DC performance
of the device.
Figure 15. –FS Error vs R
–10
–20
–30
–40
–50
–60
–70
–80
–90
10
0
0
V
V
V
V
f
T
O
A
CC
REF
IN
IN
= GND
= 25°C
+
–
C
= 5V
= 1.25V
= 3.75V
= 5V
C
REF
C
REF
10
REF
C
= 0.001µF
REF
= 0.01µF
= 100pF
= 0pF
100
R
SOURCE
SOURCE
( )
1k
at V
10k
REF
2498 F15
(Small C
100k
REF
)
2498fe