STK416-090-E

No. A1621-11/12

A protection application circuit of STK416-100sr consists of each block of (1)-(4).

(1)Stand-by control circuit part

(2)Load short detection part

(3)Latch-up circuit part

(4)DC voltage protection part

1) Stand-by control circuit part

About #17 pin reference voltage VST.

<1> Operation mode

The SW transistor of pre-driver IC is turned on at VST

≥ 2.5V, and the amplifier becomes operation mode.

ex) at VST (min) = 2.5V

VST = (*2)

× IST + 0.6V → 2.5V=4.7kΩ × IST + 0.6V, I1 ≈ 0.40mA

<2> Stand-by mode

The SW transistor of pre-driver IC is turned off at VST

≤ 0.6V (typ 0V), and the amplifier becomes stand-by

mode.

ex) at VST = 0.6V

VST = (*2)

× IST+0.6V → 0.6V = 4.7kΩ × IST + 0.6V, I1 ≈ 0mA

(*1) Resistance for restriction

Please set R1 for the voltage (VST) of the stand-by terminal to become ratings (+2.5V to 5.5V (typ 3.0V)).

(*2) Please supply the stand-by control voltage by the microcomputer etc.

(*3) The limitation resistance is built into hybrid IC internal (#17pin) and 4.7k

Ω is built into.

2) Load short detection part

Please refer to the attached paper (RL short protect explanation) for the operation explanation.

TR1 (or TR2) doesn't move by normal operation. Because, Point.B - Point.C

< 0.6V.

Therefore load short detection part doesn't operate.

But, when a load short-circuited, TR1 (or TR2) operate (Point.B - Point.C

> 0.6V), and an electric current ‘I2’ flows.

3) Latch-up circuit part

When I2 was supplied to latch-up circuit, TR3 operate.

VST becomes stand-by mode (0V) when TR3 operates (I3 flows), the power amplifier is protected.

Stand-by mode is maintained when once TR3 operates because TR3 and TR4 compose the thyristor.

It is necessary to make the Stand-by control voltage (*2) L (0V) once to release stand-by mode and to make the

power amplifier operate again.

After, when stand-by control (*2) is returned to H (ex, +5V), it operates again.

(*4) I3 is changed depending on the power-supply voltage (-VCC).

Please set resistance (R2) to become I1 < I3 by the following calculation types.

I1

≤ I3=VCC/R2

4) DC offset protection part

DC offset protection works at applying VDC (+), VDC (-)

≈ 0.5V (typ) to ‘OUT CH1’ or ‘OUT Ch2’, then HIC will

shutdown (stand-by mode).

It is necessary to make the stand-by control voltage (*2) L (0V) once to release stand-by mode.

The power amplifier operates again after stand-by control (*2) return to H (ex, +5V).

Please set the protection level by the resistance of ‘82k

Ω’.

Moreover, please set the time constant by ‘22

μ//22μ’ so as not to mis-detect it when the audio signal is output.