LT6203 LINER [Linear Technology], LT6203 Datasheet - Page 13

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

APPLICATIONS INFORMATION
code. In applications where the transient response of the
reference is important, the fast settling LTC6655-5 refer-
ence is also recommended.
In applications where power management is critical and
the external reference may be powered down, it is rec-
ommended that REF is kept greater than 2V in order to
guarantee a maximum shutdown current of 140µA. In such
applications, a Schottky diode can be placed between REF
and V
DYNAMIC PERFORMANCE
Fast Fourier Transform (FFT) techniques are used to test
the ADC’s frequency response, distortion and noise at the
rated throughput. By applying a low distortion sine wave
and analyzing the digital output using an FFT algorithm,
the ADC’s spectral content can be examined for frequen-
cies outside the fundamental. The LTC2370-16 provides
guaranteed tested limits for both AC distortion and noise
measurements.
Signal-to-Noise and Distortion Ratio (SINAD)
The signal-to-noise and distortion ratio (SINAD) is the
ratio between the RMS amplitude of the fundamental input
frequency and the RMS amplitude of all other frequency
components at the A/D output. The output is band-limited
to frequencies from above DC and below half the sampling
frequency. Figure 8 shows that the LTC2370-16 achieves
a typical SINAD of 93.9dB at a 2MHz sampling rate with
a 2kHz input.
Signal-to-Noise Ratio (SNR)
The signal-to-noise ratio (SNR) is the ratio between the
RMS amplitude of the fundamental input frequency and
Figure 7. A Schottky Diode Between REF and V
REF > 2V for Applications Where the Reference May Be
Powered Down
DD
, as shown in Figure 7.
REF
LTC2370-16
V
237016 F07
DD
DD
Maintains
the RMS amplitude of all other frequency components
except the first five harmonics and DC. Figure 8 shows
that the LTC2370-16 achieves a typical SNR of 94dB at a
2MHz sampling rate with a 2kHz input.
Total Harmonic Distortion (THD)
Total Harmonic Distortion (THD) is the ratio of the RMS sum
of all harmonics of the input signal to the fundamental itself.
The out-of-band harmonics alias into the frequency band
between DC and half the sampling frequency (f
THD is expressed as:
where V1 is the RMS amplitude of the fundamental fre-
quency and V2 through V
through Nth harmonics.
POWER CONSIDERATIONS
The LTC2370-16 provides two power supply pins: the
2.5V power supply (V
interface power supply (OV
allows the LTC2370-16 to communicate with any digital
logic operating between 1.8V and 5V, including 2.5V and
3.3V systems.
THD= 20log
Figure 8. 32k Point FFT with f
–100
–120
–140
–160
–180
–20
–40
–60
–80
0
0 100 200 300 400
V2
2
FREQUENCY (kHz)
DD
+ V3
N
are the amplitudes of the second
), and the digital input/output
500
DD
2
IN
). The flexible OV
600
+ V4
V1
= 2kHz of the LTC2370-16
SNR = 94dB
THD = –112dB
SINAD = 93.9dB
SFDR = 117dB
700
LTC2370-16
2
800 900 1000
+…+ V
237016 F08
N
2
DD
SMPL
13
supply
237016fa
/2).