LTC2351-12 LINER [Linear Technology], LTC2351-12 Datasheet - Page 13

• Manufacturer Part Number: LTC2351-12
• Description: 6 Channel, 12-Bit, 1.5Msps Simultaneous Sampling ADC with Shutdown
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
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 mini-
mum acquisition time with high source impedance, a
buffer amplifier must be used. The main requirement is
that the amplifier 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 choosing
an input amplifier the amount of noise and harmonic
distortion added by the amplifier.
CHOOSING AN INPUT AMPLIFIER
Choosing an input amplifier is easy if a few requirements
are taken into consideration. First, to limit the magnitude
of the voltage spike seen by the amplifier from charging
the sampling capacitor, choose an amplifier that has a low
output impedance (< 100Ω) at the closed-loop bandwidth
frequency. For example, if an amplifier 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 bandwidth
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 catego-
ries: AC applications where dynamic specifications 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.)
LinearView is a trademark of Linear Technology Corporation.
U
U
W
U
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
applications (to 1/3 Nyquist) where rail-to-rail perfor-
mance is desired. Quad version is available as LT1631.
LT1632: Dual 45MHz Rail-to-Rail Voltage FB Amplifier.
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
applications where rail-to-rail performance is desired.
Quad version is available as LT1633.
LT1801: 80MHz GBWP, –75dBc at 500kHz, 2mA/ampli-
fier, 8.5nV/√Hz.
LT1806/LT1807: 325MHz GBWP, –80dBc distortion at
5MHz, unity gain stable, rail-to-rail in and out,
10mA/amplifier, 3.5nV/√Hz.
LT1810: 180MHz GBWP, –90dBc distortion at 5MHz,
unity gain stable, rail-to-rail in and out, 15mA/amplifier,
16nV/√Hz.
LT1818/LT1819: 400MHz, 2500V/µs, 9mA, Single/Dual
Voltage Mode Operational Amplifier.
LT6200: 165MHz GBWP, –85dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 15mA/amplifier,
0.95nV/√Hz.
LT6203: 100MHz GBWP, –80dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 3mA/amplifier,
1.9nV/√Hz.
LT6600: Amplifier/Filter Differential In/Out with 10MHz
Cutoff Frequency.
®
P-P
P-P
1630: Dual 30MHz Rail-to-Rail Voltage FB Amplifier.
into 1kΩ, V
into 1kΩ, V
S
S
= 5V), making the part excellent for AC
= 5V), making the part excellent for AC
VOL
VOL
LTC2351-12
, 1.5mV offset and
, 500µV offset and
13
V
V
235112f
= 1,
= 1,