Datasheet

LTC2389-16
22
238916f
applications inFormation
Figure 6a. LT6231 Buffering a Fully-Differential or Single-Ended Signal Source
Figure 6b. 32k Point FFT f
SMPL
= 2.5Msps,
f
IN
= 2kHz, for Circuit Shown in Figure 6a;
Driven with Fully Differential Inputs
Figure 6c. 32k Point FFT f
SMPL
= 2.5Msps,
f
IN
= 2kHz, for Circuit Shown in Figure 6a;
Driven with Unipolar Inputs
Figure 6d. 32k Point FFT f
SMPL
= 2.5Msps,
f
IN
= 2kHz, for Circuit Shown in Figure 6a;
Driven with Bipolar Inputs
238916 F06a
IN
–
IN
+
1nF
15Ω
15Ω
1/2 LT6231
LOWPASS FILTERS
1/2 LT6231
LTC2389-16
1nF
+
–
+
–
49.9Ω
49.9Ω
4.096V
0V
0V
4.096V
0V
4.096V
0V
4.096V
0V
2.048V
FREQUENCY (kHz)
0
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
500250 750 1000 1250
–160
–180
–120
0
–140
238916 F06b
SNR = 95.7dB
THD = –115dB
SINAD = 95.6dB
SFDR = 116dB
FREQUENCY (kHz)
0
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
500250 750 1000 1250
–160
–180
–120
0
–140
238916 F06c
SNR = 92.4dB
THD = –112dB
SINAD = 92.3dB
SFDR = 113dB
FREQUENCY (kHz)
0
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
500250 750 1000 1250
–160
–180
–120
0
–140
238916 F06d
SNR = 92.7dB
THD = –110dB
SINAD = 92.6dB
SFDR = 111dB
In applications where slightly degraded SNR and
THD performance is acceptable, it is possible to drive
the LTC2389-16 using the lower power LT6231 ADC
driver configured as two unity-gain buffers, as shown in
Figure6a. The RC time constant of the output lowpass
filter is larger in this topology to limit the high frequency
noise contribution of the LT6231. As shown in the FFT
plots in Figures 6b-6d, this circuit achieves 95.7dB SNR
and –115dB THD in fully differential input mode, 92.4dB
SNR and –112dB THD in unipolar input mode, and 92.7dB
SNR and –110dB THD in bipolar input mode.