LTC1283 Datasheet, PDF (22/24 Pages) Linear Technology – 3V Single Chip 10-Bit Data Acquisition System

LTC1283
TYPICAL APPLICATI S
A “Quick Look” Circuit for the LTC1283
3V
4.7µF
CHO
V_CC
CH1
ACLK
f
CH2
SCLK
CH3
D_IN
CH4
D_OUT
LTC1283
CH5
CS
CH6
REF⁺
V_IN
CH7
REF^–
COM
V^–
DGND
AGND
SNEAK-A-BIT^TM
TO
OSCILLOSCOPE
The LTC1283’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 10-bit + sign word is returned to memory
inside the MPU. The MC68HC05C4 was chosen as an
example; however, any processor could be used.
f/64
CLK
V_DD
EN
RESET
Q1
Q4
Q2 CD4520 Q3
Q3
Q2
Q4
Q1
RESET
EN
V_SS
CLK
CLOCK IN
500kHz MAX
0.1µF
LTC1283 • TA03
Two 10-bit unipolar conversions are performed: the first
over a 0V to 3V span and the second over a 0V to – 3V span
(by reversing the polarity of the inputs). The sign of the
input is determined by which of the two spans contain it.
Then the resulting number (ranging from – 1023 to 1023
decimal) is converted to 2’s complement notation and
stored in RAM.
SNEAK-A-BIT Circuit
10µF 1MHz
CLOCK
3V
OTHER
CHANNELS
OR
SNEAK-A-BIT
INPUTS
V_IN
–3V TO 3V
CHO
V_CC
CH1
ACLK
CH2
SCLK
CH3
D_IN
CH4
D_OUT
LTC1283
CH5
CS
CH6
REF⁺
CH7
REF^–
COM
V^–
DGND
AGND
MC68HC05C4
SCK
MOSI
MISO
CO
LTC1283 • TA05
0.1µF
–3V
SNEAK-A-BIT is a trademark of Linear Technology Corp.
SNEAK-A-BIT Code
D_OUT from LTC1283 in MC68HC05C4
SIGN
LOCATION $77 B10 B9 B8 B7 B6 B5 B4 B3
LSB
LOCATION $87 B2 B1 B0
FILLED WITH 0’s
LTC1283 • TA07
D_IN Words for LTC1283
D_{IN 1}
MUX ADDR.
(ODD/SIGN)
0 0 11
MSBF
UNI
WORD
LENGTH
1111
D_{IN 2} 0 1 1 1 1 1 1 1
D_{IN 3} 0 0 1 1 1 1 1 1
LTC1283 • TA08
22