LTC1403 Linear Technology, LTC1403 Datasheet - Page 11

• Manufacturer Part Number: LTC1403
• Description: Serial 12-Bit/14-Bit/ 2.8Msps Sampling ADCs with Shutdown
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
INPUT SPAN VERSUS REFERENCE VOLTAGE
The differential input range has a unipolar voltage span
that equals the difference between the voltage at the
reference buffer output V
ground (Exposed Pad Ground). The differential input
range of the ADC is 0V to 2.5V when using the internal
reference. The internal ADC is referenced to these two
nodes. This relationship also holds true with an external
reference.
DIFFERENTIAL INPUTS
The LTC1403/LTC1403A has a unique differential sample-
and-hold circuit that allows inputs from ground to V
The ADC will always convert the unipolar difference of
A
IN
+
– A
IN
–
–100
–120
–20
–40
–60
–80
, independent of the common mode voltage at
0
100
1k
U
CMRR vs Frequency
10k
FREQUENCY (Hz)
REF
Figure 3
U
100k
at Pin 3, and the voltage at the
1M
W
10M 100M
1403A F03
U
DD
.
the inputs. The common mode rejection holds up at
extremely high frequencies, see Figure 3. The only require-
ment is that both inputs not go below ground or exceed
V
nonlinearity errors (DNL) are largely independent of the
common mode voltage. However, the offset error will
vary. The change in offset error is typically less than 0.1%
of the common mode voltage.
Figure 4 shows the ideal input/output characteristics for
the LTC1403/LTC1403A. The code transitions occur mid-
way between successive integer LSB values (i.e., 0.5LSB,
1.5LSB, 2.5LSB, FS – 1.5LSB). The output code is natural
binary with 1LSB = 2.5V/16384 = 153 V for the LTC1403A,
and 1LSB = 2.5V/4096 = 610 V for the LTC1403. The
LTC1403A has 1LSB RMS of random white noise.
DD
. Integral nonlinearity errors (INL) and differential
111...111
111...110
111...101
000...010
000...001
000...000
0
LTC1403/LTC1403A Transfer
LTC1403/LTC1403A
INPUT VOLTAGE (V)
Characteristic
Figure 4
FS – 1LSB
1403A F05
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1403af