Semiconductor Group 1
TCA 505 BG
Besides its basic functions (oscillator, demodulator and threshold switch), the bipolar
monolithic IC TCA 505 B includes a number of useful extra functions that enable high-grade,
inductive proximity switches to be designed for an attractive price/performance ratio and with
space savings.
Compared to earlier ICs for inductive proximity switches temperature drift, noise immunity and
the switching frequency of the IC have been improved.
TCA 505 BG
Bipolar IC
PG-DSO-16-1
Pb-free lead plating; RoHS compliant
Features
●Wide supply voltage of 3.1 to 4.5 V
and 4 to 40 V
●Low current consumption of less than 0.8 mA
●Integrated output stage for up to 60 mA
output current
●Short-circuit and overload protection of output
stages and external components
●Temperature response of the IC compensates
that of the coil
●High noise immunity
●High switching frequencies up to 5 kHz
●Useful extra functions
●Suitable for two-wire AC proximity switches
●Temperature range – 40 to 110 ˚C
TCA 505 BGQ67000-A8341PG-DSO-16-1 (SMD)
Type Ordering Code Package
TCA 505 B Q67000-A8342 Chip
IC for Inductive Proximity Switches
with Short-Circuit Protection
02.05
Semiconductor Group 2
TCA 505 BG
TCA 505 BG
Pin Definitions and Functions
Pin Symbol Function
1 LC Oscillator
2 RDi Distance
3 N.C. Not connected
4 CIIntegrating capacitance
5 RHy Hysteresis
6 SC Short-circuit detector
7 GND Ground
8 Q4 Output
9 Q3 Output
10 Q2 Output
11 Q1 Output
12 VSSupply voltage
13 VREF Reference voltage
14 B Base Output Transistors
15 CDTurn-ON delay / Short-circuit delay
16 VTTwo-wire regulator
Pin Configurations
(top view)
Semiconductor Group 3
TCA 505 BG
Functional Description and Application
Operation Schematic
Block Diagram
Semiconductor Group 4
TCA 505 BG
Functional Description
This circuit is used to design inductive proximity switches. The resonant circuit of the LC
oscillator is implemented with an open half-pot ferrite and a capacitor in parallel (pin LC). If a
metallic target is moved closer to the open side of the half-pot ferrite, energy is drawn from the
resonant circuit and the amplitude of the oscillation is reduced accordingly. This change in
amplitude is transmitted to a threshold switch by means of a demodulator and triggers the
outputs (see operation schematic).
By means of an external distance resistor on the oscillator (pin RDi) it is possible to set the
switching distance within wide limits, the optimal distances being 0.1 to 0.6 of the diameter of
the half-pot ferrite, although both of these parameters can be exceeded. The circuit also
enables the setting of a path hysteresis by switching of the external distance resistor via pin
RHy (see application circuit 1).
There are two antiphase output stages (Q1 / Q2 and Q3 / Q4) for max. 50 mA. The output
transistors are driven in a floating state thus providing the user with optimal flexibility for
evaluation of the output signals. It is therefore possible to use the output transistors either as
emitter follower, open-collector, as a current source or in push-pull operation. When pin B is
connected to VREF, Q2 and Q4 can be used between 0 V and VREF. The maximum base voltage
of the output transistors can be set on pin B. If B is connected to VREF, any constant current up
to 50 mA can be set on the outputs by means of resistors on Q2 or Q4 (see application
circuits 2 and 3).
Q1 through Q4 and also additional external output transistors can be protected against
destruction by short-circuit or overload. This is the purpose of pin SC which turns off the output
transistors periodically in the presence of overload.
By means of a capacitor on CD it is possible to set the response delay and the turn-OFF time
of short-circuit protection. The same capacitor also defines the turn-ON delay of the output
stages when the supply voltage is applied, whereby the output stages are inhibited during
buildup of the oscillator. Finally CD produces a turn-OFF delay of the output stages to prevent
the turn-ON delay from running its full length at brief voltage dips on VS.
A switching regulator is incorporated for the voltage supply of the circuit when it is used as a
two-wire AC proximity switch, and this is activated when pin VT is connected to VS. The circuit
has a stabilized voltage of approx. 2.9 V that is brought out on pin VREF.
Supply-voltage range: The operating range in normal operation is between 4 and 40 V. If pin
VREF is connected to VS, the circuit is operating between 3.1 and 4.5 V. In this case, however,
VREF is no longer internally stabilized, i.e. the analog IC functions depend on the operating
voltage.
Semiconductor Group 5
TCA 505 BG
Circuit Diagram (simplified)
Semiconductor Group 6
TCA 505 BG
Pin Functions
Pin 1; LC
The resonant circuit of the proximity switch is connected between LC and ground.
Pin 2; RDi
A resistor between this pin and ground sets the current in the oscillator circuit. The greater the
value of the resistor, the smaller is the current feed from the oscillator into the resonant circuit
and the greater therefore is the switching distance. The greater the Q of the resonant circuit,
the greater is the value of the distance resistor necessary for setting a certain switching
distance.
Pin 4; CI
C
I can remain open; if high noise immunity is to be achieved however, this pin should be
provided with a series RC element (RI,CI). If pin CD is not used, a correctly dimensioned RC
element on this pin will also prevent any erroneous pulses on the output when the supply
voltage is turned on (see application circuit 1).
Pin 5; RHy
Depending on the status of the circuit, RHy will be high-impedance or low-impedance to ground
(open collector). If the distance resistance (see RDi) is split into two resistors RDi and RHy, a
distance hysteresis can be set by means of RHy. If series hysteresis is applied, RHy is connected
in series with RDi or shorted. If parallel hysteresis is applied, RHy is connected in parallel with RDi
or made high-impedance (see application circuit 1).
Pin 6; SC
SC serves for short-circuit sensing in the output circuit that is to be protected. The current can
be sensed referred to ground or VS. The current sensing is made by a dedicated resistor in the
output circuit. For a voltage drop≥ 0.3 V acrossVS and SC or across ground and SC, all outputs
are turned off after the turn-OFF delay (brief glitches on the outputs or the charging of line
capacitances therefore do not trigger the short-circuit protection). After a pause about 200
times the turn-off delay, the outputs turn-ON again. If the short-circuit is still present, the turn-
OFF cycle will start up anew.
Semiconductor Group 7
TCA 505 BG
Both the internal output stages and externally connected output stages can be protected
against sustained short-circuits or overload.
A limiting of the output current is an externally connected output stage during the turn-off delay
must be ensured. Normally the current limiting by the β of the output transistor is sufficient,
meaning that no further circuit devices are called for (see application circuits). The outputs
Q1 to Q4 are already internally protected against overcurrent so that, in the case of a short-
circuit, the current will not exceed 250 mA.
In order to prevent thermal overloads, the current-conducting output is to be connected to pin
SC (see application circuit 4).
Pins 8, 9, 10, 11; Outputs Q1, Q2, Q3, Q4
Q1 is the open collector, Q2 the open emitter of one output transistor, Q3 the open collector
and Q4 the open emitter of the second output transistor in antiphase with the first output
transistor (see operation schematic). Q1 and Q3 or Q2 and Q4 can be connected in parallel
as required. The function of the outputs is ensured when the emitter potential of the output
transistors (Q2, Q4) is between 0 V and the voltage on pin B. If B is not connected, the
operating range of Q2 and Q4 extends to approx. VS– 2 V. For current setting on the outputs,
see pin B.
Pin 12; VS
Outputs Q1 through Q4 are inhibited as long as the voltage on VS is below approx. 3.6 V. They
are enabled between approx. 3.6 and 4 V, the basic function of the circuit is then ensured.
During the turn-ON and turn-OFF of VS there are consequently no undesirable static states.
The operating data and characteristics apply upwards from 4 V. See pin CD for the avoidance
of erroneous pulses during oscillator buildup.
Pin 13; VREF
The internal stabilized voltage of the IC of approx. 2.9 V appears on this pin. A capacitor can
be connected between VREF and ground to improve the noise immunity of the overall circuit
function. If VREF is connected to VS, it is possible to operate the circuit in a supply- voltage range
of 3.1 through 4.5 V. In this case VREF is no longer stabilized. The analog functions of the circuit
e.g. switching distance, however, are then dependent on the supply voltage.
Semiconductor Group 8
TCA 505 BG
Pin 14; B
This pin serves for limiting the base voltage of the internal output-stage transistors. If this pin
is connected to VREF for example, it is possible to set a constant output current (IQ=VREF /
external resistor) that is independent of the supply voltage by means of an external resistor
across Q2 (or Q4) and ground (watch out for power dissipation!).
Pin 15; CD
A capacitor on this pin delays the activation of the outputs after the supply voltage is applied
(turn-ON delay). In this way erroneous pulses are prevented on the output during buildup of
the oscillator.
If VS falls to less than 3.6 to 4 V, the outputs are not inhibited until after a turn-OFF delay time,
this also being determined by CD. In this way the delayed turn-ON operation described above
is suppressed if there are just short glitches (voltage dips) on VS. This is of particular advantage
for large core diameters, because in such cases a relativity long turn-ON delay has to be
selected and the delayed twin-on operation would otherwise be activated each time there was
a brief voltage dip.
The capacitor CD also sets the turn-off delay and the pause duration in short-circuit operation.
The sample / pause ratio is approx. 1:200 (see pin SC).
If these functions can be dispensed with, CD can remain open.
Pin 16; VT
If this pin is connected to + VS, the supply voltage of the IC (when used as a two-wire proximity
switch) can be generated by switching the outputs. The quiescent current can then be kept low.
This mode is primarily suitable for AC switches with power supply by phase-control.
The switching of the outputs is made in a VS range of 6 to 8 V. At 8 V the outputs are turned
on, until VS falls to 6 V. At 6 V the outputs are inhibited, until VS again reaches 8 V. In this mode
VS should not exceed 14 V or fall below 4 V.
Semiconductor Group 9
TCA 505 BG
Absolute Maximum Ratings
TA = – 40 to 110 ˚C
Parameter Symbol Limit Values Unit Test Condition
Supply voltage VS– 0.3 42 V
Output voltages
B open
B connected
VQ1;VQ3
VQ2;VQ4
VQ2;VQ4
– 1
– 1
– 1
41
VS + 1
VB
V
V
V
VQ2;VQ4 ≤VS
VQ2;VQ1;VQ4
<VQ3
Output currents IQ1;IQ3
–IQ2; – IQ4 0
060
60 mA
mA does not apply to
shortcircuit
Voltage on VTVT– 0.3 14 V
Current on VREF –IREF 0 100 µA
Voltage on SC VSC 0VSV
Current from RDi –IRDi 02mA
Current to RHys IRHy 02mA
Voltage on B VSB – 0.3 VSV
Storage temperature Tstg – 55 110 ˚C
Thermal resistance
(system - air) Rth SA110K/WPG-DSO-16-1
Junction temperature Tj
Tj110
150 ˚C
˚C max. 70.000 h
Capacitor CV50 nF applies to short-
circuit at the
TCA 505 B only
Operating Range
min. max.
Supply voltage VS4
3.1 40
4.5 V
VVREF = VS
Ambient temperature TA– 40 110 ˚C
Distance and
Hysteresis resistance
RDi and RHy in series
RDi and RHy parallel
RDi
RHy
RDi/RHy
300
0
300
Ω
Ω
Output voltage on
Q2, Q4
B open
B connected VQ2;VQ4
VQ2;VQ4 – 0.3
– 0.3 VS – 2
VBV
V
Only the circuitry provided for passive components may be connected to pins LC, RDi,CI,CD
Semiconductor Group 10
TCA 505 BG
Characteristics
4 V ≤VS≤ 40 V; TA = – 40 to 110 ˚C
Parameter Symbol
min. typ. max.
Unit Test
Circuit
Power Supply (VS)
Oscillator (LC, RDi)
Demodulator, Threshold Switch (CI,RHy)
Reference Voltage (VREF); Base Output Transistors
Current consumption
Normal mode (S1 = S2 = OFF)
Two-wire operation
S1 = ON, S2 = OFF
4 V ≤VS≤ 12 V
IS
IS550
625 740
840 µA
µA1
1
Turn-ON threshold
(outputs active)
S1 = OFF
VTON1 3.64 4 V 1
Turn-OFF threshold
(outputs disabled)
S1 = OFF
VTOFF1 3.0 3.6 V 1
Hysteresis VTON1 – VTOFF1
S1 = OFF ∆VHy1 40 mV 1
Oscillator frequency fOSC 3 MHz 1
Oscillator amplitude AOSC 0.8 Vpp 1
Threshold on CIVCI 2V1
Hysteresis on CIVHyCI 0.8 V 1
Current in CIICI 7µA1
Current from CI–ICI 6µA1
Switching frequency
CI < 50 pF fS5 kHz 1
(L = 70 µH)
Reference voltage
IREF = 0 to 100 µAVREF 2.65 2.9 3.10 V
Offset voltage VB = VQ2,4
VB = VREF;IQ2,4 = 5 mA VOB 110 155 mV 1
Limit Values
Semiconductor Group 11
TCA 505 BG
Characteristics (cont’d)
4 V ≤VS≤ 40 V; TA = – 40 to 110 ˚C
Parameter Symbol
min. typ. max.
Unit Test
Circuit
Two-Wire Regulator (VT)
Limit Values
Turn-ON, Turn-OFF and Short-Circuit Delay (CD)
Outputs (Q1, Q2, Q3, Q4)
Shortcircuit Detector (SC)
Turn-ON threshold
(outputs active) S1 = ON VTON2 6.7 8 9.3 V 1
Turn-ON threshold
(outputs disabled) S1 = ON VTOFF2 5.0 6 7.0 V 1
Hysteresis VTON2 – VTOFF2, S1 = ON ∆Hy 21.6 2 2.4 V 1
Turn-ON delay S1 = OFF tDON 0.49 0.65 0.82 ms/nF 2
Turn-OFF delay S1 = OFF;
VS≥ 3.6 V tVA 17.0 25 34.0 µs/nF 2
Shortcircuit turn-off delay
S1 = OFF tSC 1.70 2.5 3.40 µs/nF 2
Shortcircuit pause S1 = OFF tP0.36 0.5 0.65 ms/nF 2
Residual voltage
Q1-Q2, Q3-Q4
SQ2 0-1 = ON, SQ4 0-1 = ON
S1 = OFF
IQ = 5 mA
IQ = 60 mA
IQ = 60 mA
VQRes
VQR
VQR
VQR VS – 2.2
0.10
0.5
VS –1.8
0.14
0.99 V
V
V
1
1
1
Reverse current on Q1, 3 IQR 10 µA
Residual current on Q2, 4*)
Q2, 4 conducting but Q1, 3 open IQres 50 µA1
In case of short-circuit output current IQSC 300 500 mA 1
Trigger level ref. to VS, S1 = OFF VSCS 0.255 0.3 0.345 V 1
Trigger current S1 = OFF ISCS 30 µA1
Trigger level ref. to ground S1 = OFF VSCO 0.255 0.3 0.345 V 1
Trigger current S1 = OFF – ISCO 6µA1
Semiconductor Group 12
TCA 505 BG
Diagrams
Temperature Response of Switching Point
Resistor RLC is set in each case so that the TCA 505 B just switches from D2 to D1. In this way
the TCA 505 B, together with a suitably dimensioned resonant circuit, can form a proximity
switch that exhibits a very good temperature coefficient (±2.5 %) over the entire temperature
range and without any kind of extra external wiring.
Semiconductor Group 13
TCA 505 BG
Diagrams
Reference Voltage versus
Junction Temperature Tj
Current Consumption versus
Junction Temperature Tj
Switching Amplitude versus
Frequency f
Semiconductor Group 14
TCA 505 BG
Test Circuit 1
Test Circuit 2
Semiconductor Group 15
TCA 505 BG
Application Circuit 1
Input Circuitry (Use of pins LC, RDi,RHy,CI)
For explanation see under "Pin Function"
Semiconductor Group 16
TCA 505 BG
Application Circuit 2
Output Circuitry (Use of pins VREF, B, SC, Q1 through Q4, CD)
P-switch, short-circuit-proof, LED indicator, configurable as normally closed or
normally open
For dimensioning of CDsee characteristics. CD is usually between 1 and 10 nF. Filtering of
VREF is for noise immunity. CREF can be 10 nF for example.
Short-circuit-current sampling: RSC =
Constant base current: 1) RQ=
0.3 V
max. load current
2.9 V – VLED
max. base current
1) When IQ > 10 mA, a resistor RREF on pin VREF will improve the constant current operation.
Semiconductor Group 17
TCA 505 BG
Application Circuit 3
Output Circuitry (Use of pins VREF, B, SC, Q1 through Q4, CD)
N-switch, short-circuit-proof, LED indicator, configurable as normally closed or
normally open
For dimensioning of CDsee characteristics.CD is usually between 1 and 10 nF. Filtering of
VREF is for noise immunity. CREF can be 10 nF for example. RREF serves for discharging residual
current of outputs Q2, 4.
Short-circuit-current sampling: RSC =
Constant base current: 1) RQ=
0.3 V
max. load current
2 V
max. base current + IRR
1) When IQ > 10 mA, a resistor RREF on pin VREF will improve the constant current operation.
Semiconductor Group 18
TCA 505 BG
Application Circuit 4
Output Circuitry (Use of pins SC, Q1 to Q4, CD)
P-switch, short-circuit-proof, configurable as normally closed or normally open
During the sampling time, the short-circuit current within the IC is limited to a maximum of 250
mA. For dimensioning of CV,see characteristics.CD is usually between 1 and 10 nF.
Short-circuit-current sampling: RSC =0.3 V
max. load current
