Datasheet

LTC2381-16
12
238116f
APPLICATIONS INFORMATION
238116 F06
LT6350
R1 = 1k
R2 = 1k
R3 = 2k
R4 = 680
V
CM
= V
REF
/2
V
REF
75pF
150pF
0V to
2.5V
2.5V to
0V
0V to 5V
OUT1
R
INT
10µF
R
INT
R
IN
= 2k
OUT2
8
4
5
2
1
+
–
+
–
–
+
Figure 6. LT6350 Converting a 0V-5V Single-Ended Signal to
a ±2.5V Differential Input Signal
Figure 6a. 32k Point FFT Plot for Circuit Shown in Figure 6
238116 F07
LT6350
R1 = 1.24k
R2 = 1.24k
R3 = 10k
R4 = 1.1k
V
CM
= V
REF
/2
V
CM
0V to
2.5V
2.5V to
0V
±10V
OUT1
R
INT
R
INT
R
IN
= 10k
OUT2
8
4
5
2
1
+
–
+
–
–
+
220pF
10µF
200pF
Table 1. SNR, THD vs R
IN
for 0-5V Single-Ended Input Signal
R
IN
(Ω)
R1
(Ω)
R2
(Ω)
R3
(Ω)
R4
(Ω)
SNR
(dB)
THD
(dB)
2k 1k 1k 2k 680 92 –100
10k 5k 5k 10k 3.3k 91 –100
50k 25k 25k 50k 16k 91 –97
Figure 7. LT6350 Converting a ±10V Single-Ended Signal to
a ±2.5V Differential Input Signal
Figure 7a. 32k Point FFT Plot for Circuit Shown in Figure 7
FREQUENCY (kHz)
0 25 50 75 100 125
–180
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
–120
–140
–160
0
238116 F06a
SNR = 91.7dB
THD = –100dB
SINAD = 91.2dB
SFDR = 103.5dB
FREQUENCY (kHz)
0 25 50 75 100 125
–180
AMPLITUDE (dBFS)
–60
–40
–20
–80
–100
–120
–140
–160
0
238116 F07a
SNR = 91.8dB
THD = –95.5dB
SINAD = 91.4dB
SFDR = 96.9dB
Table 2. SNR, THD vs R
IN
for ±10V Single-Ended Input Signal
R
IN
(Ω)
R1
(Ω)
R2
(Ω)
R3
(Ω)
R4
(Ω)
SNR
(dB)
THD
(dB)
10k 1.24k 1.24k 10k 1.1k 92 –96
50k 6.19k 6.19k 50k 5.49k 91 –96
100k 12.4k 12.4k 100k 11k 91 –97
ADC REFERENCE
The LTC2381-16 requires an external reference to define its
input range. A low noise, low temperature drift reference
is critical to achieving the full datasheet performance
of the ADC. Linear Technology offers a portfolio of high
performance references designed to meet the needs of
many applications. With its small size, low power and high
accuracy, the LTC6652-2.5 is particularly well suited for
use with the LTC2381-16. The LTC6652-2.5 offers 0.05%
(max) initial accuracy and 5ppm/°C (max) temperature
coefficient for high precision applications. The LTC6652-2.5
is fully specified over the H-grade temperature range and
complements the extended temperature operation of the
LTC2381-16 up to 125°C. We recommend bypassing the
LTC6652-2.5 with a 47µF ceramic capacitor (X5R, 0805
size) close to the REF pin. All performance curves shown
in this datasheet were obtained using the LTC6652-2.5.