Datasheet

LTC2389-16
23
238916f
applications inFormation
Figure 7a. LT6201 Converting a 0V to 4.096V Single-Ended Signal to a ±4.096V Fully-Differential Signal
Figure 7b. 32k Point FFT f
SMPL
= 2.5Msps, f
IN
= 2kHz,
for Circuit Shown in Figure 7a
238916 F07a
IN
–
IN
+
1nF
10Ω
10Ω
LOWPASS FILTERS
LTC2389-16
330pF
1nF
4.096V
0V
4.096V
0V
4.096V
0V
+
–
+
–
402Ω402Ω
1/2 LT6201
V
CM
= 2.048V
1/2 LT6201
+
–
330pF
49.9Ω
49.9Ω
FREQUENCY (kHz)
0
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
500250 750 1000 1250
–160
–180
–120
0
–140
238916 F07b
SNR = 95.6dB
THD = –112dB
SINAD = 95.6dB
SFDR = 114dB
Single-Ended to Differential Conversion
In some applications it may be desirable to convert a
single-ended unipolar or bipolar signal to a fully-differential
signal prior to driving the LTC2389-16 to take advantage
of the higher SNR of the LTC2389-16 in fully differential
input mode. The LT6201 ADC driver configured in the
topology shown in Figure 7a can be used to convert a 0V
to 4.096V single-ended input signal to a fully-differential
±4.096V output signal. The RC time constant of the
output lowpass filters is chosen to allow for sufficient
transient settling of the LTC2389-16 analog inputs dur-
ing acquisition. This wide filter bandwidth, coupled with
the relatively high wideband noise of the single-ended
to differential conversion circuit, limits the achievable
SNR of this topology to 95.6dB, as shown in the FFT
plot in Figure 7b.