LTC2351HUH-12#TRPBF Linear Technology, LTC2351HUH-12#TRPBF Datasheet - Page 14

• Manufacturer Part Number: LTC2351HUH-12#TRPBF
• Description: IC ADC 12BIT 1.5MSPS 32-QFN
• Manufacturer: Linear Technology

Specifications of LTC2351HUH-12#TRPBF

• Number Of Bits: 12
• Sampling Rate (per Second): 1.5M
• Data Interface: Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 16.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC2351-12
current. If the source impedance of the driving circuit is
low, then the LTC2351-12 inputs can be driven directly. As
source impedance increases, so will acquisition time. For
minimum acquisition time with high source impedance,
a buffer amplifi er must be used. The main requirement is
that the amplifi er driving the analog input(s) must settle
after the small current spike before the next conversion
starts (the time allowed for settling must be at least 39ns
for full throughput rate). Also keep in mind while choos-
ing an input amplifi er the amount of noise and harmonic
distortion added by the amplifi er.
CHOOSING AN INPUT AMPLIFIER
Choosing an input amplifi er is easy if a few requirements
are taken into consideration. First, to limit the magnitude
of the voltage spike seen by the amplifi er from charging
the sampling capacitor, choose an amplifi er that has a low
output impedance (< 100Ω) at the closed-loop bandwidth
frequency. For example, if an amplifi er is used in a gain
of 1 and has a unity-gain bandwidth of 50MHz, then the
output impedance at 50MHz must be less than 100Ω.
The second requirement is that the closed-loop band-
width must be greater than 40MHz to ensure adequate
small-signal settling for full throughput rate. If slower op
amps are used, more time for settling can be provided by
increasing the time between conversions. The best choice
for an op amp to drive the LTC2351-12 depends on the
application. Generally, applications fall into two categories:
AC applications where dynamic specifi cations are most
critical and time domain applications where DC accuracy
and settling time are most critical. The following list is a
summary of the op amps that are suitable for driving the
LTC2351-12. (More detailed information is available in
the Linear Technology Databooks and on the website at
www.linear.com.)
LTC1566-1: Low Noise 2.3MHz Continuous Time
Lowpass Filter.
LT
2.7V to ±15V supplies. Very high A
520ns settling to 0.5LSB for a 4V swing. THD and noise
are –93dB to 40kHz and below 1LSB to 320kHz (A
2V
14
®
P-P
1630: Dual 30MHz Rail-to-Rail Voltage FB Amplifi er.
into 1kΩ, V
S
= 5V), making the part excellent for AC
VOL
, 500μV offset and
V
= 1,
applications (to 1/3 Nyquist) where rail-to-rail performance
is desired. Quad version is available as LT1631.
LT1632: Dual 45MHz Rail-to-Rail Voltage FB Amplifi er.
2.7V to ±15V supplies. Very high A
400ns settling to 0.5LSB for a 4V swing. It is suitable for
applications with a single 5V supply. THD and noise are
–93dB to 40kHz and below 1LSB to 800kHz (A
2V
AC applications where rail-to-rail performance is desired.
Quad version is available as LT1633.
LT1801: 80MHz GBWP , –75dBc at 500kHz, 2mA/amplifi er,
8.5nV/√Hz.
LT1806/LT1807: 325MHz GBWP , –80dBc distortion at
5MHz, unity gain stable, rail-to-rail in and out, 10mA/am-
plifi er, 3.5nV/√Hz.
LT1810: 180MHz GBWP , –90dBc distortion at 5MHz,
unity gain stable, rail-to-rail in and out, 15mA/amplifi er,
16nV/√Hz.
LT1818/LT1819: 400MHz, 2500V/μs, 9mA, Single/Dual
Voltage Mode Operational Amplifi er.
LT6200: 165MHz GBWP , –85dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 15mA/amplifi er,
0.95nV/√Hz.
LT6203: 100MHz GBWP , –80dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 3mA/amplifi er,
1.9nV/√Hz.
LT6600: Amplifi er/Filter Differential In/Out with 10MHz
Cutoff Frequency.
INPUT FILTERING AND SOURCE IMPEDANCE
The noise and the distortion of the input amplifi er and
other circuitry must be considered since they will add to
the LTC2351-12 noise and distortion. The small-signal
bandwidth of the sample-and-hold circuit is 50MHz. Any
noise or distortion products that are present at the analog
inputs will be summed over this entire bandwidth. Noisy
input circuitry should be fi ltered prior to the analog inputs.
A simple 1-pole RC fi lter is suffi cient for many applica-
tions. For example, Figure 1 shows a 47pF capacitor from
CHO
P-P
+
into 1kΩ, V
to ground and a 51Ω source resistor to limit the
S
= 5V), making the part excellent for
VOL
, 1.5mV offset and
V
235112fa
= 1,