LTC1285IS8 Linear Technology, LTC1285IS8 Datasheet - Page 13

• Manufacturer Part Number: LTC1285IS8
• Description: IC A/D CONV SAMPLING 12BIT 8SOIC
• Manufacturer: Linear Technology

Specifications of LTC1285IS8

• Number Of Bits: 12
• Sampling Rate (per Second): 7.5k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 480µW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATION INFORMATION
Transfer Curve
The LTC1285/LTC1288 are permanently configured for
unipolar only. The input span and code assignment for
this conversion type are shown in the following figures.
Operation with D
The LTC1288 can be operated with D
together. This eliminates one of the lines required to
communicate to the microprocessor (MPU). Data is trans-
mitted in both directions on a single wire. The processor
pin connected to this data line should be configurable as
1 1 1 1 1 1 1 1 1 1 1 0
0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1
(D
IN
1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 0
0 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0
/D
DATA
OUT
CLK
•
•
•
CS
OUTPUT CODE
)
•
•
•
IN
U
and D
Transfer Curve
Output Code
INPUT VOLTAGE
U
V
V
OUT
REF
REF
MPU CONTROLS DATA LINE AND SENDS
1LSB =
1LSB
0V
– 1LSB
– 2LSB
•
•
•
Tied Together
4TH RISING CLK AND BEFORE THE 4TH FALLING CLK
START
MUX ADDRESS TO LTC1288
Figure 3. LTC1288 Operation with D
1
V
4096
PROCESSOR MUST RELEASE DATA LINE AFTER
REF
W
INPUT VOLTAGE
(V
REF
IN
4.99878V
4.99756V
0.00122V
SGL/DIFF
= 5.000V)
0V
and D
•
•
•
LTC1285/88 • AI05
2
U
OUT
LTC1285/88 • AI04
ODD/SIGN
tied
V
3
IN
MSBF BIT LATCHED
either an input or an output. The LTC1288 will take control
of the data line and drive it low on the 4th falling CLK edge
after the start bit is received (see Figure 3). Therefore the
processor port line must be switched to an input before
this happens to avoid a conflict.
In the Typical Applications section, there is an example of
interfacing the LTC1288 with D
the Intel 8051 MPU.
ACHIEVING MICROPOWER PERFORMANCE
With typical operating currents of 160 A and automatic
shutdown between conversions, the LTC1285/LTC1288
achieves extremely low power consumption over a wide
range of sample rates (see Figure 4). The auto-shutdown
allows the supply curve to drop with reduced sample rate.
BY LTC1288
Figure 4. Automatic Power Shutdown Between Conversions
Allows Power Consumption to Drop with Sample Rate
IN
MSBF
and D
4
1000
100
10
OUT
1
0.1
Tied Together
T
V
V
f
CLK
A
CC
REF
LTC1288 TAKES CONTROL OF DATA LINE
ON 4TH FALLING CLK
= 25°C
= 2.7V
= 120kHz
= 2.5V
LTC1288 CONTROLS DATA LINE AND SENDS
SAMPLE FREQUENCY (kHz)
1
A/D RESULT BACK TO MPU
LTC1285/LTC1288
B11
IN
10
and D
LTC1285/88 • F04
B10
OUT
100
tied together to
• • •
LTC1285/88 F03
13