LDC0851 Datasheet, PDF (11/39 Pages) Texas Instruments – Differential Inductive Switch

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LDC0851
SNOSCZ7A – DECEMBER 2015 – REVISED JANUARY 2016
8.3 Feature Description
8.3.1 Basic Operation Mode
The LDC0851 is configured for Basic Operation mode when the ADJ pin is tied to ground. Two identical coils
should be used for LSENSE and LREF. The switching point occurs when the inductances of both coils are equal.
Basic Operation mode can be used for a wide variety of applications including event counting or proximity
sensing. An example showing gear tooth counting can be found in section Event Counting.
For proximity sensing the switching point can be set by placing a conductive target at a fixed distance from the
reference coil as shown in Figure 17. The output will switch when a conductive target approaches LSENSE and
reaches the same distance set by the fixed reference target. For reliable and repeatable switching it is
recommended to place the reference target at a distance less than 40% of the coil diameter from the reference
coil.
Output High
(LS > LR)
LS (Inductance)
LR (Inductance)
Target Distance
’
Output Low
(LS < LR)
0
dswitch = d
Movable
Metal Target
Sense
Coil
Fixed
Reference
Sensor
Cap
Reference
Coil
Switching distance set
by Reference Target
LSENSE
LCOM
LREF
Differential
LDC Core
Inductance
Converter
Inductance
Converter
+
±
Mode Select
0: Basic Operation
1 ± 15: Threshold Adjust
ADJ
Offset
4-bit ADC
LDC0851
LS
+
LR _±
OUTPUT
VDD
Power
EN
Management
GND
VDD
CBYP
Figure 17. Basic Operation Mode Diagram for Distance Sensing With Reference Target
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