M61558FP

Rev.1.0, Sep.19.2003, page 14 of 17

LPF circuit

The output LPF circuit must have characteristics in accord with the signal-frequency band and characteristic impedance

value of the speaker that constitutes the load. The simplest example is a second-order Butterworth filter in an LC

configuration.

Damping circuit

When the speaker is removed, the frequency characteristics of the low-pass filter may lead to problems of high-band

characteristics such as peaking. Accordingly, a high-band damping circuit should be installed in parallel with the

speaker. (Take the allowable power, etc., of the damping resistor into consideration.)

Zener diode for surge protection

Ringing, etc., occurs during the high-speed switching operation of this IC. During short-circuit, connection to ground or

VDD of load, very large surge voltages are generated. When the surge voltage exceeds the voltage tolerance of the

transistors (step-down voltage between source and drain, etc.), the IC may be damaged. We recommend that you

prevent damage to this IC by connecting a Zener diode for surge protection to the output pins (select a Zener voltage

slightly below 35 V).

Precautions on wiring for the protective circuits

PRVD (pin 18) is wired to the protective detection circuits.

Use as short a wiring run as is possible to connect this pin to a point on the VD power-supply line near the VD pin.

This point should not be readily affected by variation in voltages due to power supply and the operating conditions.

Please take care because this may affect the characteristics of the protective circuits or damage the IC.

Measures against EMI

Please note the need to reduce the levels of unwanted radiation components produced by high-speed switching

operation. For example, apply countermeasures such as raising the order of the output LPF circuit, or attaching a

capacitor with a value of about 1000 pF to the speaker pin.

Single-ended operation

This IC is for bridge-tied load (BTL) operation, but single-ended operation for an independent half-bridge configuration

is possible. In this case, note that performance changes (e.g. 30 W x 1 ch. becomes 7.5 W x 2 ch). Also, other parts of

the IC are designed on the specific assumption of BTL operation, so sufficient evaluation and examination is required.

Pop noise when turning the power supply on and off

One simple countermeasure against pop noise is to ensure that VD (power-stage power-supply voltage ) is only turned

on and off while VDD (power-supply voltage of the pre-driver stage) is applied. If this measure is ignored, pop noise

may occur when the power supply is turned on or off.

We also recommend operation under the condition VDD < VD. Consider turning the power supply on and off in the

following sequence.