LT6203 LINER [Linear Technology], LT6203 Datasheet - Page 12

• Manufacturer Part Number: LT6203
• Description: 16-Bit, 2Msps, Pseudo-Differential Unipolar SAR
• Manufacturer: LINER [Linear Technology]

LTC2370-16
APPLICATIONS INFORMATION
Table 1. SNR, THD vs R
12
100k
10k
R
(Ω)
2k
IN
Figure 5a. LT6202 Converting a ±10V Bipolar Signal
to a 0V to 5V Input Signal
CNV
10µF
V
CM
Figure 5b. 32k Point FFT Plot with f
for Circuit Shown in Figure 5a
–100
–120
–140
–160
–180
–60
–20
–40
–80
2.49k
24.9k
–10V
= V
499
(Ω)
R1
10V
0
0V
REF
R2
499
R3
2k
0
/2
100
PERIOD
IDLE
200pF
402
200
2.49k
24.9k
R4
(Ω)
499
R2
IN
300
R
2k
FREQUENCY (kHz)
IN
for ±10V Input Signal
400
3
4
100k
500
(Ω)
10k
R3
2k
+
–
600
LT6202
SNR = 93.9dB
THD = –97.8dB
SINAD = 91.4dB
SFDR = 99.6dB
700
499
200pF
R1
402
(Ω)
20k
R4
2k
800 900
Figure 6. CNV Waveform Showing Burst Sampling
237016 F05b
IN
1
= 2kHz
1000
SNR
(dB)
93.9
92.2
94
237016 F05a
–97.8
–92.9
–93.2
THD
(dB)
5V
0V
ADC REFERENCE
The LTC2370-16 requires an external reference to define
its input range. A low noise, low temperature drift refer-
ence is critical to achieving the full data sheet 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 LTC6655-5 is particularly well suited for
use with the LTC2370-16. The LTC6655-5 offers 0.025%
(max) initial accuracy and 2ppm/°C (max) temperature
coefficient for high precision applications. The LTC6655-5
is fully specified over the H-grade temperature range and
complements the extended temperature operation of the
LTC2370-16 up to 125°C. We recommend bypassing the
LTC6655-5 with a 47µF ceramic capacitor (X5R, 0805 size)
close to the REF pin.
The REF pin of the LTC2370-16 draws charge (Q
the 47µF bypass capacitor during each conversion cycle.
The reference replenishes this charge with a DC current,
I
I
the LTC2370-16 is used to continuously sample a signal
at a constant rate, the LTC6655-5 will keep the deviation
of the reference voltage over the entire code span to less
than 0.5LSBs.
When idling, the REF pin on the LTC2370-16 draws only
a small leakage current (< 1µA). In applications where a
burst of samples is taken after idling for long periods as
shown in Figure 6, I
0µA to a maximum of 1.3mA at 2Msps. This step in DC
current draw triggers a transient response in the reference
that must be considered since any deviation in the refer-
ence output voltage will affect the accuracy of the output
REF
REF
, depends on the sampling rate and output code. If
= Q
CONV
PERIOD
IDLE
/t
CYC
. The DC current draw of the REF pin,
REF
quickly goes from approximately
237016 F06
CONV
) from
237016fa