LTC1400 LINER [Linear Technology], LTC1400 Datasheet - Page 9

• Manufacturer Part Number: LTC1400
• Description: Complete SO-8, 12-Bit, 400ksps ADC with Shutdown
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
Figure 5 shows the IMD performance at a 100kHz input.
Peak Harmonic or Spurious Noise
The peak harmonic or spurious noise is the largest spectral
component excluding the input signal and DC. This value
is expressed in decibels relative to the RMS value of a full-
scale input signal.
Full Power and Full Linear Bandwidth
The full power bandwidth is the input frequency at which
the amplitude of the reconstructed fundamental is reduced
by 3dB for a full-scale input signal.
The full linear bandwidth is the input frequency at which
the S/(N + D) has dropped to 68dB (11 effective bits). The
LTC1400 has been designed to optimize input bandwidth,
allowing the ADC to undersample input signals with fre-
quencies above the converter’s Nyquist Frequency. The
noise floor stays very low at high frequencies; S/(N + D)
becomes dominated by distortion at frequencies far be-
yond Nyquist.
Driving the Analog Input
The analog input of the LTC1400 is easy to drive. It draws
only one small current spike while charging the sample-
and-hold capacitor at the end of a conversion. During
conversion, the analog input draws only a small leakage
current. The only requirement is that the amplifier driving
the analog input must settle after the small current spike
before the next conversion starts. Any op amp that settles
Figure 5. Intermodulation Distortion Plot in Bipolar Mode
–100
–110
–120
–10
–20
–30
–40
–50
– 60
–70
–90
–80
0
0
f
fa = 99.512kHz
fb = 102.441kHz
SAMPLE
fb – fa
20
2fa + fb
2fa – fb
40
2fb + fa
U
= 400kHz
60
FREQUENCY (kHz)
3fb
80 100
INFORMATION
U
fa fb
120
3fa
2fb – fa
140
fa + fb
W
160
2fb
LTC1400 • F05
2fa
180
200
U
in 200ns to small load current transient will allow maxi-
mum speed operation. If a slower op amp is used, more
settling time can be provided by increasing the time
between conversions. Suitable devices capable of driving
the ADC’s A
op amps.
LTC1400 comes with a built-in unipolar/bipolar detection
circuit. If V
circuitry will automatically switch to bipolar mode.
The following list is a summary of the op amps that are
suitable for driving the LTC1400, more detailed informa-
tion is available in the Linear Technology databooks and
the LinearView
LT 1215/LT1216: Dual and quad 23MHz, 50V/ s single
supply op amps. Single 5V to 15V supplies, 6.6mA
specifications, 90ns settling to 0.5LSB.
LT1223: 100MHz video current feedback amplifier. 5V
to 15V supplies, 6mA supply current. Low distortion up
to and above 400kHz. Low noise. Good for AC applica-
tions.
LT1227: 140MHz video current feedback amplifier. 5V
to 15V supplies, 10mA supply current. Lowest distor-
tion at frequencies above 400kHz. Low noise. Best for AC
applications.
LT1229/LT1230: Dual and quad 100MHz current feedback
amplifiers. 2V to 15V supplies, 6mA supply current
each amplifier. Low noise. Good AC specs.
LT1360: 37MHz voltage feedback amplifier. 5V to 15V
supplies. 3.8mA supply current. Good AC and DC specs.
70ns settling to 0.5LSB.
LT1363: 50MHz, 450V/ s op amps. 5V to 15V sup-
plies. 6.3mA supply current. Good AC and DC specs. 60ns
settling to 0.5LSB.
LT1364/LT1365: Dual and quad 50MHz, 450V/ s op amps.
fier. 60ns settling to 0.5LSB.
Internal Reference
The LTC1400 has an on-chip, temperature compensated,
curvature corrected, bandgap reference, which is factory
5V to 15V supplies, 6.3mA supply current per ampli-
SS
IN
potential is forced below GND, the internal
input include the LT
TM
CD-ROM.
®
1360 and the LT1363
LTC1400
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