LTC1290 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1290' PDF : 28 Pages View PDF
LTC1290
APPLICATI S I FOR ATIO
1k
VIN
CH0
VCC
LTC1290
DGND
V–
AGND
5V
22µF
–5V
0.1µF
1290 F20
Figure 20. Overvoltage Protection for MUX
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 VCC and REF+ are
not tied together, then VCC should be turned on first, then
REF+. If this sequence cannot be met, connecting a diode
from REF+ to VCC is recommended (see Figure 21).
For dual supplies (bipolar mode) placing two Schottky
diodes from VCC and V– to ground (Figure 23) will prevent
power supply reversal from occurring 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– then VCC will pull
a diode drop below ground which could cause the device
not to power up properly. Likewise, if the input is pulled
above VCC then V– will be pulled a diode drop above
ground. If no inputs are present on the MUX, the Schottky
diodes are not required if V– is applied first, then VCC.
Because a unique input protection structure is used on the
digital input pins, the signal levels on these pins can
exceed the device VCC without damaging the device.
20
VCC
LTC1290
1N4148
5V
22µF
REF+ 14
VREF
1290 F21
Figure 21
VCC
LTC1290
DGND
V–
AGND
1N5817
5V
22µF
1N5817
–5V
0.1µF
1290 F22
Figure 22. Power Supply Reversal
1290fe
25
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