LTC1605-1CG#TRPBF Linear Technology, LTC1605-1CG#TRPBF Datasheet - Page 12

• Manufacturer Part Number: LTC1605-1CG#TRPBF
• Description: IC A/D CONV 16BIT SAMPLNG 28SSOP
• Manufacturer: Linear Technology

Specifications of LTC1605-1CG#TRPBF

• Number Of Bits: 16
• Sampling Rate (per Second): 100k
• Data Interface: Parallel
• Number Of Converters: 1
• Power Dissipation (max): 80mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC1605-1/LTC1605-2
APPLICATIONS
Dynamic Performance
FFT (Fast Fourier Transform) test 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 frequencies outside the fundamental. Figure 11 shows
a typical LTC1605-2 FFT plot which yields a SINAD of
87dB and THD of –101.1dB.
Signal-to-Noise Ratio
The Signal-to-Noise and Distortion Ratio (SINAD) is the
ratio between the RMS amplitude of the fundamental
input frequency to the RMS amplitude of all other fre-
quency components at the A/D output. The output is band
limited to frequencies from above DC and below half the
sampling frequency. Figure 11 shows a typical SINAD of
87dB with a 100kHz sampling rate and a 1kHz input.
Total Harmonic Distortion
Total Harmonic Distortion (THD) is the ratio of the RMS
sum of all harmonics of the input signal to the fundamen-
tal itself. The out-of-band harmonics alias into the fre-
quency band between DC and half the sampling fre-
quency. THD is expressed as:
12
THD = 20log
Figure 11. LTC1605-2 Nonaveraged 4096-Point FFT Plot
–100
–110
–120
–130
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
0
V
5
2
U
2
10 15 20 25 30 35 40 45 50
+ V
INFORMATION
FREQUENCY (kHz)
3
U
2
+ V
V
1
4
f
f
SINAD = 87dB
THD = 101.1dB
SNR = 87.2dB
2
SAMPLE
IN
... + V
= 1kHz
W
= 100kHz
1605-1/2 G07/F11
N
2
U
where V
frequency and V
second through Nth harmonics.
Board Layout, Power Supplies and Decoupling
Wire wrap boards are not recommended for high resolu-
tion or high speed A/D converters. To obtain the best
performance from the LTC1605-1/LTC1605-2, a printed
circuit board is required. Layout for the printed circuit
board should ensure the digital and analog signal lines
are separated as much as possible. In particular, care
should be taken not to run any digital track alongside an
analog signal track or underneath the ADC. The analog
input should be screened by AGND.
Figures 12 through 15 show a layout for a suggested
evaluation circuit which will help obtain the best perfor-
mance from the 16-bit ADC. Additional information re-
garding the evaluation circuit and Gerber files for the PC
board layout are available from Linear Technology or
your local sales office. Pay particular attention to the
design of the analog and digital ground planes. The
DGND pin of the LTC1605-1/LTC1605-2 can be tied to the
analog ground plane. Placing the bypass capacitor as
close as possible to the power supply, the reference and
reference buffer output is very important. Low imped-
ance common returns for these bypass capacitors are
essential to low noise operation of the ADC, and the PC
track width for these lines should be as wide as possible.
Also, since any potential difference in grounds between
the signal source and ADC appears as an error voltage in
series with the input signal, attention should be paid to
reducing the ground circuit impedance as much as
possible. The digital output latches and the onboard
sampling clock have been placed on the digital ground
plane. The two ground planes are tied together at the
power supply ground connection.
1
is the RMS amplitude of the fundamental
2
through V
N
are the amplitudes of the