LTC1290BI LINER [Linear Technology], LTC1290BI Datasheet - Page 24

• Manufacturer Part Number: LTC1290BI
• Description: Single Chip 12-Bit Data Acquisition System
• Manufacturer: LINER [Linear Technology]

LTC1290
larger current limiting resistors. Use 1N4148 diode clamps
from the MUX inputs to V
resistor will not allow the maximum clock speeds to be
used or if an unknown source is used to drive the LTC1290
MUX inputs.
How the various power supplies to the LTC1290 are
applied can also lead to overvoltage conditions. For single
supply operation (i.e., unipolar mode), if V
not tied together, then V
REF
from REF
For dual supplies (bipolar mode) placing two Schottky
diodes from V
A “Quick Look” Circuit for the LTC1290
Users can get a quick look at the function and timing of the
LTC1290 by using the following simple circuit. REF
D
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 1/128 the clock
rate by the CD4520 and D
pins are tied to a ground plane. The output data from the
D
to trigger on the falling edge of CS.
24
A
TYPICAL
IN
OUT
PPLICATI
+
are tied to V
. If this sequence cannot be met, connecting a diode
pin can be viewed on an oscilloscope which is set up
+
to V
CC
A
CC
and V
O
PPLICATI
CC
LTC1290
is recommended (see Figure 21).
U
selecting a 5V input span, CH7 as a
S
–
REF
V
to ground (Figure 23) will prevent
CC
Figure 21
CC
CC
+
I FOR ATIO
OUT
should be turned on first, then
and V
U
20
14
outputs the data. All other
O
1N4148
–
if the value of the series
U
W
S
CC
22 F
1290 F21
5V
V
REF
and REF
U
+
+
and
are
power supply reversal from occuring when an input source
is applied to the analog MUX before power is applied to the
device. Power supply reversal occurs, for example, if the
input is pulled below V
below ground which could cause the device not to power
up properly. Likewise, if the input is pulled above V
V
are present on the MUX, the Schottky diodes are not
required if V
Because a unique input protection structure is used on the
digital input pins, the signal levels on these pins can
exceed the device V
V
IN
–
will be pulled a diode drop above ground. If no inputs
22 F
CHO
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
DGND
LTC1290
A “Quick Look” Circuit for the LTC1290
–
Figure 22. Power Supply Reversal
DGND
is applied first, then V
AGND
ACLK
SCLK
D
REF
REF
V
OUT
LTC1290
D
CS
V
CC
IN
+
–
–
OSCILLOSCOPE
CC
AGND
V
V
CC
without damaging the device.
TO
–
–
then V
f
f/128
CC
CLOCK IN
2MHz MAX
CLK
EN
Q1
Q2
Q3
Q4
RESET
V
1N5817
1N5817
SS
will pull a diode drop
CC
CD4520
.
RESET
V
CLK
DD
Q4
Q3
Q2
Q1
EN
22 F
0.1 F
1290 F22
5V
–5V
5V
CC
then
0.1 F
1290 TA02