LTC1400 LINER [Linear Technology], LTC1400 Datasheet - Page 10

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

APPLICATIONS
LTC1400
10
trimmed to 2.42V. It is internally connected to the DAC and
is available at Pin 3 to provide up to 1mA of current to an
external load. For minimum code transition noise, the
reference output should be decoupled with a capacitor to
filter wideband noise from the reference (10 F tantalum in
parallel with a 0.1 F ceramic). The V
with a DAC or other means to provide input span adjust-
ment in bipolar mode. The V
least 2.45V to prevent conflict with the internal reference.
The reference should not be driven to more than 5V.
Figure 6 shows an LT 1306 op amp driving the reference
pin. Figure 7 shows a typical reference, the LT1019A-5
connected to the LTC1360. This will provide an improved
drift (equal to the maximum 5ppm/ C of the LT1019A-5)
and a 4.231V full scale. If V
2.42V, the REFRDY bit in the serial data output will be
forced to low.
INPUT RANGE 4.231V
0.846V
INPUT RANGE
(= 0.846V
REF(OUT)
Figure 6. Driving the V
Figure 7. Supplying a 5V Reference Voltage to the
LTC1400 with the LT1019A-5
REF
)
+
–
LT1360
LT1019A-5
U
GND
10V
V
IN
V
OUT
INFORMATION
V
U
REF
REF(OUT)
REF
with the LT1360 Op Amp
REF
pin must be driven to at
2.45V
3
3
10 F
10 F
W
is forced lower than
REF
pin can be driven
A
V
GND
A
V
GND
REF
REF
IN
IN
LTC1400
LTC1400
–5V
–5V
V
V
V
U
V
5V
5V
CC
SS
CC
SS
LTC1400 • F06
LTC1400 • F07
UNIPOLAR / BIPOLAR OPERATION AND ADJUSTMENT
Figure 8 shows the ideal input/output characteristics for
the LTC1400. The code transitions occur midway between
successive integer LSB values (i.e., 0.5LSB, 1.5LSB,
2.5LSB, … FS – 1.5LSB). The output code is natural binary
with 1LSB = 4.096/4096 = 1mV. Figure 9 shows the
input/output transfer characteristics for the bipolar mode
in two’s complement format.
Unipolar Offset and Full-Scale Error Adjustments
In applications where absolute accuracy is important,
offset and full-scale errors can be adjusted to zero. Figure
10a shows the extra components required for full-scale
Figure 8. LTC1400 Unipolar Transfer Characteristics
Figure 9. LTC1400 Bipolar Transfer Characteristics
011...111
011...110
000...001
000...000
111...111
111...110
100...001
100...000
111...111
111...110
111...101
111...100
000...011
000...010
000...001
000...000
0V
–FS/2
UNIPOLAR
ZERO
1LSB = FS
LSB
1
4096
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
=
4.096
BIPOLAR
4096
LSB
–1
ZERO
0V
LSB
1
FS/2 – 1LSB
FS – 1LSB
LTC11400 • F09
LTC1400 • F08