STCC05-B Datasheet, PDF (9/13 Pages) STMicroelectronics – HOME APPLIANCE CONTROL CIRCUIT

STCC05-B
■ STCC05 POWER PERFORMANCE VERSUS ITS THERMAL CAPABILITY
Figure 11: Driver current sum versus regulator
current at T_AMB = 85°C for V_PS = 12, 14, 16, 18V
Figure 12: Driver current sum versus regulator
current at T_AMB = 70°C for V_PS = 12, 14, 16, 18V
Σ I_M(A)
0.35
Σ I_M(A)
0.35
0.3
V_PS=12V
0.3
V_PS=12V & 14V
0.25
0.2
T_AMB =85°C
0.15
0.1
0
0.01
0.02
V_PS=14V
V_PS=16V
V_PS=18V
0.03
0.04
I_DD(A)
0.05
0.25
0.2
T_AMB =70°C
0.15
0.1
0
0.01
0.02
0.03
V_PS=16V
V_PS=18V
I_DD(A)
0.04
0.05
The main heat sources of the circuit during operation are the voltage regulator and the relay coil drivers.
Depending of the power supply voltage V_PS, the ambient temperature T_AMB, and the thermal of resistance
of the package R_th(j-a), the sum of all the coil driver currents ΣI_M is linked to the output regulator current
I_DD. In order to avoid spurious thermal shutdown of the system, it is advised to respect this relationship as
shown on figures 7 and 8.
■ EXTENSION OF THE REGULATOR CURRENT CAPABILITY
The output current capability of the STCC05 voltage regulator can be increased in a cost effective manner
by adding an external ballast transistor and two biasing resistors. With such a circuit, the output voltage
regulation remains at 5V 5%, and the current limitation is still active.
Such a topology generates also power losses in the external power transistor especially when the supply
voltage V_PS is high or the regulator is in current limiting mode. Therefore it is advised to use a package
with a suitable thermal resistance (R_{th j-a}).
An example is proposed in the following figure doubling the regulator current capability of the solution to
100mA while producing a current limitation typically at 110mA.
Figure 13: Circuit diagram to extend the
STCC05 regulator current to 100mA
Figure 14: Application diagram of the buzzer
drive
V_PS
R_E
27Ω ½W
Q₁
BD136
R_B
20 Ω ¼W
STCC05
5V-50mA
Regulator
VDD
V_PS
EN_BZ
IN_BZ
10 kΩ
V_IN
R_OH = 1kΩ
BZ₂
R_BZ= 1kΩ
BZ₁
R_S= 560 Ω
C_S= 47 µF
■ FLOATING BUZZER OPERATION
The sound produced by the buzzer is controlled by the frequency of the square signal applied to the IN_BZ
input pin.
The external R_S C_S network connected to the BZ₂ output pin produces a soft sound by smoothing the
buzzer supplying envelope at power up and power down. Contrary to basic drivers, which directly apply
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