LTC1290 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1290' PDF : 28 Pages View PDF
LTC1290
TYPICAL APPLICATI S
SNEAK-A-BITTM
The LTC1290’s unique ability to software select the polar-
ity of the differential inputs and the output word length is
used to achieve one more bit of resolution. Using the
circuit below with two conversions and some software, a
2’s complement 12-bit + sign word is returned to memory
inside the MPU. The MC68HC05C4 was chosen as an
example, however, any processor could be used.
Two 12-bit unipolar conversions are performed: the first
over a 0V to 5V span and the second over a 0V to – 5V span
(by reversing the polarity of the inputs). The sign of the
input is determined by which of the two spans contained
it. Then the resulting number (ranging from –4095 to
+4095 decimal) is converted to 2’s complement notation
and stored in RAM.
SNEAK-A-BIT Circuit
9V LT1021-5
22µF
OTHER CHANNELS
OR SNEAK-A-BIT
INPUTS
VIN
–5V TO 5V
CHO
VCC
CH1
ACLK
CH2
SCLK
CH3
DIN
CH4
DOUT
LTC1290
CH5
CS
CH6
REF+
CH7
REF–
COM
V–
DGND
AGND
2MHz
CLOCK
MC68HC05C4
SCLK
MOSI
MISO
CO
1290 TA04
0.1µF
–5V
5V
VIN
(+) CH6
(–) CH7
1ST CONVERSION 0V
VIN
(–) CH6
(+) CH7
2ND CONVERSION
SNEAK-A-BIT
VIN
5V
1ST CONVERSION
4096 STEPS
SOFTWARE
0V
0V
2ND CONVERSION
4096 STEPS
–5V
–5V
8191
STEPS
1290 TA05
SNEAK-A-BIT is a trademark of Linear Technology Corp.
1290fe
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