LTC2449CUHF Linear Technology, LTC2449CUHF Datasheet - Page 22

• Manufacturer Part Number: LTC2449CUHF
• Description: IC ADC 24BIT HI SPEED 38QFN
• Manufacturer: Linear Technology

Specifications of LTC2449CUHF

• Number Of Bits: 24
• Sampling Rate (per Second): 8k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 40mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 38-WFQFN, Exposed Pad
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
LTC2444/LTC2445/
LTC2448/LTC2449
Normal Mode Rejection and 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 LTC2444/LTC2445/
LTC2448/LTC2449 significantly simplify antialiasing filter
requirements.
The LTC2444/LTC2445/LTC2448/LTC2449’s speed/reso-
lution is determined by the over sample ratio (OSR) of the
on-chip digital filter. 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
determine the filter characteristics of the device. The first
NULL of the digital filter is at f
f
frequency f
22
N
= f
S
/OSR, see Figure 10 and Table 7. The rejection at the
Figure 10. LTC2444/LTC2445/LTC2448/LTC2449
Normal Mode Rejection (Internal Oscillator)
–100
–120
–140
–20
–60
–40
–80
N
0
±14% is better than 80dB, see Figure 11.
0
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
SINC
U
60
4
ENVELOPE
U
120
N
and multiples of f
180
W
2440 F11
240
U
N
where
S
Table 7. OSR vs Notch Frequency (f
Running at 9MHz)
*Simultaneous 50/60Hz rejection
Figure 11. LTC2444/LTC2445/LTC2448/LTC2449
Normal Mode Rejection (Internal Oscillator)
–100
–110
–130
–140
–120
32768*
–80
–90
16384
1024
2048
4096
8192
OSR
128
256
512
64
47
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
49
51
53
55
N
57
) (with Internal Oscillator
59
NOTCH (f
28.16kHz
14.08kHz
7.04kHz
3.52kHz
1.76kHz
880Hz
440Hz
220Hz
110Hz
61
55Hz
2440 F12
63
N
)
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