LTC1402IGN Linear Technology, LTC1402IGN Datasheet - Page 14

• Manufacturer Part Number: LTC1402IGN
• Description: IC ADC 12BIT 2.2MSPS SHDN 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC1402IGN

• Number Of Bits: 12
• Sampling Rate (per Second): 2.2M
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 150mW
• Voltage Supply Source: Analog and Digital, Dual ±
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
LTC1402
more than 0.25 inch long to the common reference. You
may also choose to tie AGND2 (Pin 6) directly to a solid
analog ground plane and eliminate all the 10 F capacitors
at this pin. The external reference source needs to have
enough output drive current for the 2k load at each ADC.
FULL-SCALE AND OFFSET ADJUSTMENT
Figure 9 shows the ideal input/output characteristics for
the LTC1402 in bipolar mode and unipolar mode. Figure
10a shows the components required for full-scale error
adjustment. Figure 10b includes the components for off-
set and full-scale adjustment.
Adjustment in Bipolar Mode with Pin 8 Held High
The code transitions occur midway between successive
integer LSB values (i.e., – FS + 0.5LSB, – FS + 1.5LSB, – FS
+ 2.5LSB,...FS – 2.5LSB, FS – 1.5LSB). The output at D
is two’s complement binary with 1LSB = FS – (– FS)/4096
= 4.096V/4096 = 1.0mV. In applications where absolute
accuracy is important, offset and full-scale errors can be
adjusted to zero. Offset error must be adjusted before full-
scale error. In Figure 10b, zero offset is achieved by
adjusting the offset applied to the A
offset error, apply – 0.5mV (i.e., – 0.5LSB) to A
adjust the offset at the A
code flickers between 0000 0000 0000 and 1111 1111
1111. For full-scale adjustment in Figures 10a and 10b,
apply an input voltage of 2.0465V (FS – 1.5LSB) to A
and adjust R5 until the output code flickers between 0111
1111 1110 and 0111 1111 1111.
14
011...111
011...110
011...101
100...010
100...001
100...000
Figure 9. LTC1402 Transfer Characteristic
– (FS – 1LSB)
U
INPUT VOLTAGE (V)
IN
INFORMATION
–
U
input using R8 until the output
W
FS – 1LSB
IN
–
1402 F09
input. For zero
111...111
111...110
111...101
000...010
000...001
000...000
U
IN
+
and
OUT
IN
+
Adjustment in Unipolar Mode with Pin 8 Held Low
The code transitions occur midway between successive
integer LSB values (i.e., – FS + 0.5LSB, – FS + 1.5LSB,
D
1.0mV. In applications where absolute accuracy is impor-
tant, offset and full-scale errors can be adjusted to zero.
Offset error must be adjusted before full-scale error. In
Figure 10b, zero offset is achieved by adjusting the offset
applied to the A
– 0.5mV (i.e., – 0.5LSB) to A
A
ANALOG INPUT
FULL-SCALE
– FS + 2.5LSB,...FS – 2.5LSB, FS – 1.5LSB). The output at
ANALOG INPUT
OFFSET
IN
OUT
0V TO 4.096V
0V TO 4.096V
OR 2.048V
OR 2.048V
–
ADJ
input using R8 until the output code flickers between
ADJ
is binary with 1LSB = FS/4096 = 4.096V/4096 =
10k
R8
Figure 10b. Offset and Full-Scale Adjustment
Circuits with 10LSB Range
500
Figure 10a. Full-Scale Adjustment Circuit with
5V
500
R5
10LSB Range
R5
51
51
R1
R3
7.5k
R7
51
51
R4
470k
R1
R3
R4
470k
IN
5V
–
R2
39k
R6
24k
R2
24k
10 F
10 F
input. For zero offset error apply
3
4
5
7
6
6
3
4
5
7
AGND2
A
A
V
GAIN
A
A
V
GAIN
AGND2
IN
IN
REF
IN
IN
REF
+
–
+
–
IN
+
and adjust the offset at the
REFERENCE
S/H
REFERENCE
S/H
64k
64k
64k
64k
AMP
AMP
2.048V
2.048V
REFERENCE
REFERENCE
BANGAP
BANGAP
LTC1402
LTC1402
1402 F010a
1402 F010b