LTC2373-16_15 Datasheet, PDF (23/50 Pages) Linear Technology – 16-Bit, 1Msps, 8-Channel SAR ADC with 96dB SNR

LTC2373-16
Applications Information
Maximizing SNR with a Single-Ended to Differential
Conversion
A single-ended input signal may be converted to a fully
differential signal prior to driving the MUX analog inputs
of the LTC2373-16 to take advantage of the higher SNR
of the LTC2373-16 in the fully differential input range.
The LT6350 ADC driver shown in Figure 9a can be used
to convert a 0V to 4.096V input signal to a fully differential
±4.096V output signal. The RC time constant is larger in
this case to limit the high frequency noise contribution
of the LT6350. This topology provides a 3dB increase in
SNR over single-ended operation and achieves the full
data sheet SNR performance of the fully differential input
range of 96dB as shown in the FFT plot in Figure 9b. The
maximum supply current of 10.4mA makes the LT6350 a
good companion to the low power LTC2373-16.
0
SNR = 96dB
–20
THD = –108.7dB
SINAD = 95.8dB
–40
SFDR = 111.3dB
–60
–80
–100
–120
–140
–160
–180
0
100 200 300 400 500
FREQUENCY (kHz)
237316 G09b
Figure 9b. 32k Point FFT f_SMPL = 1Msps,
f_IN = 1kHz for Circuit Shown in Figure 9a
Maximizing SNR for Eight Single-Ended Inputs Using
a Shared Amplifier Between MUXOUT^+/– and ADCIN^+/–
While converting a single-ended signal to a fully differ-
ential signal offers the benefit of higher SNR, two input
channels are required per single-ended input, leading to
a reduced number of single-ended input signals that can
be interfaced to the LTC2373-16. Performing the sin-
gle-ended to differential conversion using the LT6237
4.096V
0V
V⁺
3
LT6350
OUT1
8+
1–
R_INT
R_INT
–
2+
6
V^–
V_CM = 2.048V _–+
OUT2
4.096V
0V
10Ω
4
3300pF
10Ω
5
4.096V
0V
3300pF
3300pF
MUX CHANNELS
CH0 AND CH1
SELECTED
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
LTC2373-16
+
16-BIT ADC CORE
–
MUXOUT^+/–
SHORTED TO
ADCIN^+/–
Figure 9a. LT6350 Converting a 0V to 4.096V Single-Ended Signal to a ±4.096V Fully Differential Signal
237316 F09a
For more information www.linear.com/LTC2373-16
237316f
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