LTC1090CJ View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1090CJ' PDF : 28 Pages View PDF
LTC1090
TYPICAL APPLICATIO
A “Quick Look” Circuit for the LTC1090
Users can get a quick look at the function and timing of the
LTC1090 by using the following simple circuit. REF+ and
DIN are tied to VCC selecting a 5V input span, CH7 as a
single ended input, unipolar mode, MSB first format and
16-bit word length. ACLK and SCLK are tied together and
driven by an external clock. CS is driven at 1/64 the clock
rate by the CD4520 and DOUT outputs the data. All other
pins are tied to a ground plane. The output data from the
DOUT pin can be viewed on an oscilloscope which is set up
to trigger on the falling edge of CS.
A “Quick Look” Circuit for the LTC1090
5V
4.7µF
f/64
CH0
VCC
CH1
ACLK
CLK
VDD
0.1
CH2
SCLK
f
EN
RESET
CH3
DIN
CH4
DOUT
LTC1090
CH5
CS
Q1
Q4
Q2
Q3
LTC1090
Q3
Q2
CH6
VIN
CH7
REF +
REF –
COM
V–
DGND
AGND
Q4
Q1
RESET
EN
VSS
CLK
SNEAK-A-BITTM
The LTC1090’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.
Two 10-bit unipolar conversions are performed: the first
over a 0 to 5V span and the second over a 0 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 –1023 to 1023
decimal) is converted to 2’s complement notation and
stored in RAM.
Scope Trace of LTC1090 “Quick Look” Circuit
Showing A/D Output of 0101010101 (155HEX)
CS
DOUT
TO OSCILLOSCOPE
CLOCK IN
1MHz MAX
LTC1090 • TA03
DEGLITCHER
MSB
LSB
FILLS
TIME
(B9)
(B0)
ZERO
SNEAK-A-BIT Circuit
9V
LT1021-5
10µF
OTHER CHANNELS
OR SNEAK-A-BIT
INPUTS
VIN
– 5V TO 5V
CH0
VCC
CH1
ACLK
CH2
SCLK
CH3
DIN
CH4
DOUT
LTC1090
CH5
CS
CH6
REF +
CH7
REF –
COM
V–
DGND
AGND
SNEAK-A-BIT is a trademark of Linear Technology Corp.
0.1µF
– 5V
2MHz
CLOCK
MC68HC05C4
SCK
MOSI
MISO
CO
LTC1090 • TA04
1090fc
23
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