Datasheet
LTC2364-16
12
236416fa
Table 1. SNR, THD vs R
IN
for ±10V Input Signal
R
IN
(Ω)
R1
(Ω)
R2
(Ω)
R3
(Ω)
R4
(Ω)
SNR
(dB)
THD
(dB)
2k 499 499 2k 402 94.6 –99.2
10k 2.49k 2.49k 10k 2k 94.4 –93.8
100k 24.9k 24.9k 100k 20k 92.4 –93.7
APPLICATIONS INFORMATION
ADC REFERENCE
The LTC2364-16 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 LTC2364-16. 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
LTC2364-16 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 LTC2364-16 draws charge (Q
CONV
) from
the 47µF bypass capacitor during each conversion cycle.
The reference replenishes this charge with a DC current,
I
REF
= Q
CONV
/t
CYC
. The DC current draw of the REF pin,
I
REF
, depends on the sampling rate and output code. If
the LTC2364-16 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 LTC2364-16 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
REF
quickly goes from approximately
0µA to a maximum of 0.2mA at 250ksps. 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
Figure 6. CNV Waveform Showing Burst Sampling
Figure 5a. LT6202 Converting a ±10V Bipolar Signal
to a 0V to 5V Input Signal
Figure 5b. 32k Point FFT Plot with f
IN
= 2kHz
for Circuit Shown in Figure 5a
–
+
1
3
4
LT6202
R4
402Ω
R1
499Ω
R
IN
2k
R3
2k
R2
499Ω
10µF
10V
–10V
0V
200pF
200pF
V
CM
= V
REF
/2
5V
0V
236416 F05a
CNV
IDLE
PERIOD
IDLE
PERIOD
236416 F06
FREQUENCY (kHz)
0
AMPLITUDE (dBFS)
–80
–60
–40
125
236416 F05b
–100
–120
–160
50
100
25
75
–140
0
–20
SNR = 94.6dB
THD = –99.2dB
SINAD = 92.2dB
SFDR = 99.9dB