LTC1288IS8 Linear Technology, LTC1288IS8 Datasheet - Page 15

• Manufacturer Part Number: LTC1288IS8
• Description: IC A/D CONV SAMPLING 12BIT 8SOIC
• Manufacturer: Linear Technology

Specifications of LTC1288IS8

• Number Of Bits: 12
• Sampling Rate (per Second): 6.6k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 630µW
• 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
of Maximum Clock Rate vs Supply Voltage). If the maxi-
mum clock frequency is used, care must be taken to
ensure that the device converts correctly.
Mixed Supplies
It is possible to have a microprocessor running off a 5V
supply and communicate with the LTC1285/LTC1288
operating on a 3V supply. The inputs of CS, CLK and D
of the LTC1285/LTC1288 have no problem to take a
voltage swing from 0V to 5V. With the LTC1285 operating
on a 3V supply, the output of D
0V and 3V. The 3V output level is higher enough to trip a
TTL input of the MPU. Figure 6 shows a 3V powered
LTC1285 interfacing a 5V system.
COMMON-MODE RANGE
DIFFERENTIAL INPUTS
Figure 6. Interfacing a 3V Powered LTC1285 to a 5V System
0V TO 3V
"+" INPUT
"–" INPUT
3V
D
CLK
OUT
D
CS
IN
V
+IN
–IN
GND
REF
U
LTC1285
D
U
CLK
V
OUT
CS
CC
3V
OUT
4.7 F
Figure 7. LTC1288 “+” and “–” Input Settling Windows
W
may only go between
START
P1.4
P1.3
P1.2
(e.g. 8051)
MPU
U
LTC1285/88 • F06
SGL/DIFF
IN
5V
BOARD LAYOUT CONSIDERATIONS
Grounding and Bypassing
The LTC1285/LTC1288 are easy to use if some care is
taken. They should be used with an analog ground plane
and single point grounding techniques. The GND pin
should be tied directly to the ground plane.
The V
a 10 F tantalum capacitor with leads as short as possible.
If the power supply is clean, the LTC1285/LTC1288 can
also operate with smaller 1 F or less surface mount or
ceramic bypass capacitors. All analog inputs should be
referenced directly to the single point ground. Digital
inputs and outputs should be shielded from and/or routed
away from the reference and analog circuitry.
SAMPLE-AND-HOLD
Both the LTC1285 and the LTC1288 provide a built-in
sample-and-hold (S&H) function to acquire signals. The
S&H of the LTC1285 acquires input signals from “+” input
relative to “–” input during the t
However, the S&H of the LTC1288 can sample input
signals in the single-ended mode or in the differential
inputs during the t
1ST BIT TEST "–" INPUT MUST
SAMPLE
SETTLE DURING THIS TIME
CC
SETTLE DURING
"+" INPUT MUST
THIS TIME
pin should be bypassed to the ground plane with
t
SMPL
MSBF
HOLD
SMPL
LTC1285/LTC1288
time (see Figure 7).
t
CONV
DON’T CARE
SMPL
LTC1285/88 • F07
B11
time (see Figure 1).
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