LTC1867AIGN#TRPBF Linear Technology, LTC1867AIGN#TRPBF Datasheet - Page 10

• Manufacturer Part Number: LTC1867AIGN#TRPBF
• Description: IC ADC 16BIT 8CH 200KSPS 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC1867AIGN#TRPBF

• Number Of Bits: 16
• Sampling Rate (per Second): 200k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 9mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC1863/LTC1867
APPLICATIONS INFORMATION
Driving the Analog Inputs
The analog inputs of the LTC1863/LTC1867 are easy to
drive. Each of the analog inputs can be used as a single-
ended input relative to the GND pin (CH0-GND, CH1-GND,
etc) or in pairs (CH0 and CH1, CH2 and CH3, CH4 and CH5,
CH6 and CH7) for differential inputs. In addition, CH7 can
act as a COM pin for both single-ended and differential
modes if the COM bit in the input word is high. Regard-
less of the MUX confi guration, the “+” and “–” inputs are
sampled at the same instant. Any unwanted signal that is
common mode to both inputs will be reduced by the com-
mon mode rejection of the sample-and-hold circuit. The
inputs draw only one small current spike while charging
the sample-and-hold capacitors during the acquire mode.
In conversion mode, the analog inputs draw only a small
leakage current. If the source impedance of the driving
circuit is low then the LTC1863/LTC1867 inputs can be
driven directly. More acquisition time should be allowed
for a higher impedance source.
The following list is a summary of the op amps that are
suitable for driving the LTC1863/LTC1867. More detailed
information is available in the Linear Technology data
books or Linear Technology website.
LT1007 - Low noise precision amplifi er. 2.7mA supply
current ± 5V to ±15V supplies. Gain bandwidth product
8MHz. DC applications.
LT1097 - Low cost, low power precision amplifi er. 300μA
supply current. ±5V to ± 15V supplies. Gain bandwidth
product 0.7MHz. DC applications.
LT1227 - 140MHz video current feedback amplifi er. 10mA
supply current. ±5V to ±15V supplies. Low noise and low
distortion.
10
LT1360 - 37MHz voltage feedback amplifi er. 3.8mA supply
current. ±5V to ±15V supplies. Good AC/DC specs.
LT1363 - 50MHz voltage feedback amplifi er. 6.3mA supply
current. Good AC/DC specs.
LT1364/LT1365 - Dual and quad 50MHz voltage feedback
amplifi ers. 6.3mA supply current per amplifi er. Good
AC/DC specs.
LT1468 - 90MHz, 22V/μs 16-bit accurate amplifi er
LT1469 - Dual LT1468
Input Filtering
The noise and the distortion of the input amplifi er and
other circuitry must be considered since they will add to
the LTC1863/LTC1867 noise and distortion. Noisy input
circuitry should be fi ltered prior to the analog inputs to
minimize noise. A simple 1-pole RC fi lter is suffi cient for
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.
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