STK4067

No. 4376-3/8

STK4067 Design Data

(1) The Protection Circuits

a) Overvoltage Protector

delivers no output. The overvoltage protection circuit is set for a functional range from 18 to 28 V; 100%

operation at 28 V. For this reason, you should be careful not to exceed the 18 V limit in quiescent mode and keep

in mind AC line regulations when setting using a transformer power supply for designs such as home stereo

systems. Exceeding 18 V activates the overvoltage protector and results in the generation of abnormal sounds.

b) Thermal Shutdown

The thermal shutdown protection circuit is designed to first detect abnormal temperature rises which occur during

abnormal operation (such as load shorts) and then prevent damage to the IC by limiting the input signal; thereby

preventing a further rise in the temperature. The thermal shutdown protector is set to activate at substrate

temperature of 135°C with a complete shutdown by switching to an off-state if temperatures rise to 175°C. Under

normal application, the IC is equipped with a heat sink and the temperature never reaches a level resulting in a

complete off-state switch and saturation occurs at a specific temperature. For example, when a short occurs with

an IC mounted 4.5°C/W heat sink, saturation is achieved at approximately 160°C. At this point, Tj exceeds its

maximum rating of 170°C. As previously mentioned, this circuit is designed to protect the IC from damage

sustained in a short period of time and you should note that the protection circuit will not protect the IC if

abnormal temperature rises occur over a long period of time.

(2) Precautions

a) Excessive Input

If a 1 V or greater (f = 1 kHz.rms) overinput is applied to the input pin, the DC balance of the input channel for

the input monolithic amplifier is disrupted and output is cut off. In addition, DC voltage is generated on the

output pins and causes damage to the speakers. Proper caution should be displayed in preventing input above this

voltage.

b) Parasitic Oscillation

The STK4067 performs phase compensation using 2.2

Ω and 0.47µF between V

such conditions, the power supply line must be in a close proximity to the bootstrap pins for the inverting and

non-inverting amplifiers. If the power line is too long, parasitic oscillation is likely to occur at low temperatures.

If such a problem arises, add a 0.1µF rated condenser between the ground and the head of the power supply line

in order to lower the impedance.

c) Power Supply Voltage Inverse Application

The STK4067 is not equipped with a built-in power supply voltage inversion protection circuit. If the possibility

exists, one should be externally connected.

d) Power Off

1, install a resistor rated for 100

Ω or greater in series with pin 1, or you may place a diode between pin 10 and pin

1.

(3) Application Circuits

a) The under frequency band may be magnified, for applications using a booster amplifier or woofer driver

b) L1 = 3 µH and R3 = 4.7

Ω are for anti-oscillation applications against capacity loads. We recommend the use of

this coil and resistor with the most compatible amplifier sets connected to general use speakers. This coil is not

necessary when the load capacity is low using a chosen speaker connected to a radio-cassette player or active

speaker.