LTC1867LIGN#PBF Linear Technology, LTC1867LIGN#PBF Datasheet - Page 11

• Manufacturer Part Number: LTC1867LIGN#PBF
• Description: IC ADC 16BIT 8CH 175KSPS 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC1867LIGN#PBF

• Number Of Bits: 16
• Sampling Rate (per Second): 175k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 2.7mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Number Of Elements: 1
• Resolution: 16Bit
• Architecture: SAR
• Sample Rate: 175KSPS
• Input Polarity: Unipolar/Bipolar
• Input Type: Voltage
• Rated Input Volt: 2.5/±1.25V
• Differential Input: Yes
• Power Supply Requirement: Analog and Digital
• Single Supply Voltage (typ): 3.3V
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 3.6V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Power Dissipation: 2.7mW
• Differential Linearity Error: -2LSB(Min)
• Integral Nonlinearity Error: ±4LSB
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Package Type: SSOP N
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
many applications. For instance, Figure 1 shows a 50Ω
source resistor and a 2000pF capacitor to ground on the
input will limit the input bandwidth to 1.6MHz. The source
impedance has to be kept low to avoid gain error and
degradation in the AC performance. The capacitor also
acts as a charge reservoir for the input sample-and-hold
and isolates the ADC input from sampling glitch sensitive
circuitry. High quality capacitors and resistors should be
used since these components can add distortion. NPO
and silver mica type dielectric capacitors have excellent
linearity. Carbon surface mount resistors can also generate
distortion from self heating and from damage that may
occur during soldering. Metal fi lm surface mount resistors
are much less susceptible to both problems.
DC Performance
One way of measuring the transition noise associated
with a high resolution ADC is to use a technique where
a DC signal is applied to the input of the ADC and the
resulting output codes are collected over a large number
of conversions. For example, in Figure 2 the distribution
of output codes is shown for a DC input that had been
digitized 4096 times. The distribution is Gaussian and the
RMS code transition noise is about 1.6LSB.
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
Figure 2. LTC1867L Histogram for 4096 Conversions
1200
1000
800
600
400
200
0
20
7
58
21
170
22
465
23
1044
24
895
25
CODE
830
26
333
27
V
INTERNAL REF
261
28
DD
= 2.7V
23 9
29
1863L7L G12
30
31
1
algorithm, the ADC’s spectral content can be examined
for frequencies outside the fundamental.
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 frequency
components at the A/D output. The output is band limited
to frequencies from above DC and below half the sampling
frequency. Figure 3a shows a typical SINAD of 81.4dB
with a 175kHz sampling rate and a 1kHz input. Higher
SINAD can be obtained with a 3V supply. For example,
when an external 3V is applied to REFCOMP (tie V
GND), a SINAD of 83.5dB can be achieved as shown in
Figure 3b.
Figure 3a. LTC1867L Nonaveraged 4096 Point
FFT Plot with 2.7V Supply
Figure 3b. LTC1867L Nonaveraged 4096 Point
FFT Plot with 3V Supply
–100
–120
–140
–100
–120
–140
–20
–60
–20
–60
–40
–80
–40
–80
0
0
0
0
LTC1863L/LTC1867L
21.875
21.875
FREQUENCY (kHz)
FREQUENCY (kHz)
43.75
43.75
f
f
SNR = 84.7dB
SINAD = 83.5dB
THD = 90dB
REFCOMP = EXT 3V
SAMPLE
IN
f
f
SNR = 82.9dB
SINAD = 81.4dB
THD = 86.8dB
SAMPLE
IN
= 1kHz
= 1kHz
65.625
65.625
= 175ksps
= 175ksps
1863L7L F03b
1863L7L G03
87.5
87.5
11
REF
1863l7lfc
to