LTC2440 Linear Technology, LTC2440 Datasheet - Page 24

• Manufacturer Part Number: LTC2440
• Description: 24-Bit High Speed Differential delta-sigma ADC
• Manufacturer: Linear Technology

LTC2440
APPLICATIO S I FOR ATIO
fastest expected input signal. Figure 20 shows the large
signal response of the circuit in Figure 19.
3. Measure noise performance of the complete circuit. A
good technique is to build one amplifier for each input,
even if only one will be used in the end application. Bias
both amplifier outputs to midscale, with the inputs tied
together. Verify that the noise is as expected, taking into
account the bandwidth of the LTC2440 inputs for the OSR
being used, the amplifier’s broadband voltage noise and
1/f corner (if any) and any additional noise due to the
amplifier’s current noise and source resistance.
24
Figure 20. Large Signal Input Settling Time Indicates Completed
Settling with Selected Load Capacitance.
IN+
IN–
Figure 19. Buffering the LTC2440 from High Impedance Sources Using A Chopper Amplifier
U
100µs/DIV
–
+
–
+
U
1
1
/
/
2
2
LTC2051HV
LTC2051HV
C1
C4
W
0.01µF
0.01µF
2440 F20
10Ω
10Ω
R1
R2
R4
R5
5k
5k
8-12V
U
C2
C5
LT1236-5
1µF
1µF
For more information on testing high linearity ADCs, refer
to Linear Technology Design Solutions 11.
Input Bandwidth and Frequency Rejection
The combined effect of the internal SINC
the digital and analog autocalibration circuits determines
the LTC2440 input bandwidth and rejection characteris-
tics. The digital filter’s response can be adjusted by setting
the oversample ratio (OSR) through the SPI interface or by
supplying an external conversion clock to the F
Table 6 lists the properties of the LTC2440 with various
Capacitance and Completly Settled Before the Next Conversion
Figure 21. Dynamic Input Current is Attenuated by Load
Sample Resulting in No Reduction in Performance.
4.7µF
C2, C5 TAIYO YUDEN JMK107BJ105MA
0.1µF
1, 8, 9, 16
4
5
6
V
REF
REF
IN
IN
CC
+
–
LTC2440
+
–
5ns/DIV
BUSY
0.01µF
SDO
SCK
EXT
SDI
CS
F
O
15
14
13
12
11
7
10
2440 F19
10µF
5V
4
2440 F21
digital filter and
sn2440, 2440fas
O
pin.