LTC2442IG Linear Technology, LTC2442IG Datasheet - Page 22

• Manufacturer Part Number: LTC2442IG
• Description: IC,A/D CONVERTER,SINGLE,24-BIT,CMOS,SSOP,36PIN
• Manufacturer: Linear Technology

LTC2442
Normal Mode Rejection and Antialiasing
One of the advantages delta-sigma ADCs offer over
conventional ADCs is on-chip digital fi ltering. Combined
with a large oversampling ratio, the LTC2442 signifi cantly
simplifi es antialiasing fi lter requirements.
The LTC2442’s speed/resolution is determined by the
oversample ratio (OSR) of the on-chip digital fi lter. The
OSR ranges from 64 for 3.5kHz output rate to 32,768 for
6.9Hz (in No Latency mode) output rate. The value of OSR
and the sample rate f
of the device. The fi rst NULL of the digital fi lter is at f
and multiples of f
Table 6. The rejection at the frequency f
than 80dB, see Figure 11.
APPLICATIO S I FOR ATIO
22
Figure 10. Normal Mode Rejection (Internal Oscillator)
–120
–140
–100
–20
–40
–60
–80
0
0
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
N
where f
U
SINC
S
60
determine the fi lter characteristics
4
ENVELOPE
U
N
= f
120
S
/OSR, see Figure 10 and
W
180
N
±14% is better
2442 F10
240
U
N
Table 6. OSR vs Notch Frequency (f
Running at 9MHz)
* Simultaneous 50/60Hz rejection
Figure 11. Normal Mode Rejection (Internal Oscillator)
32768*
16384
–100
–110
–130
–140
–120
1024
2048
4096
8192
OSR
–80
128
256
512
–90
64
47
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
49
51
53
55
N
) (with Internal Oscillator
57
59
NOTCH (f
28.13kHz
14.06kHz
7.03kHz
3.52kHz
1.76kHz
879Hz
439Hz
220Hz
110Hz
55Hz
61
2442 F11
63
N
)
2442f