IC FOR PROXIMITY DETECTOR
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
V
CC
Output Voltage
U
Q
Output Current
I
QL
Junction Temperature
T
J
Power Dissipation at
T
amb
= 25°C
Derate for
T
amb
> 25°C
Storage Temperature Range
T
st
Operating Temperature Range
T
amb
T
amb
35V
32V
20mA
150°C
P
D
= 600mW
1/R
Θ
= 5mW/°C
– 55...125°C
– 25...85°C (V
CC
= 15V to 35V)
– 20...85°C (V
CC
= 4.75V to 35V)
AM 313
FUNCTIONAL DESCRIPTION
The proximity detection is based on the amplitude attenuation of an
LC–oscillator
which depends
on the distance to a metal object.
The signal from the oscillator is rectified and filtered, then detected by a Schmitt–Trigger which
switches the outputs
Q
(for close switch operation) and
Q
(for open switch operation).
An additional LED output shows the on-state of the detection. The LED is blanked in the case of
short circuit. To protect the circuit from overload, the outputs are disconnected and retested
periodically. The limitation of the output current is set by the resistor
R
m
.
The temperature compensation to adapt the oscillator voltage to different types of external LC
resonators is performed by connecting a resistor between pins 7 (VREF) and 2 (RK).
The circuit has a power–on–delay which is adjusted with
CABT.
Within this delay, the outputs
Q
and
Q
are set to high level.
FUNCTIONAL DIAGRAMS
V
CC
VREF
7
14
VCC
3
LED
11
R
m
Z
2
10
9
R
K
2
1
AM313
R
H
15
Q
Q
T
D
1
Output
Z
1
C
R
Ground
L
16
C
OSC
R
D
6
5
4
8
R
S
D
2
Figure 2
analog microelectronics
April 2005
3/4
AME [ ANALOG MICROELECTRONICS ]
