AN7198Z 데이터 시트보기 (PDF) - Panasonic Corporation

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AN7198Z

Dual 20 W BTL Power IC for Car Audio

Panasonic Corporation 

AN7198Z

ICs for Audio Common Use

s Technical Information (continued)

3. Application note (continued)

12) Precautions on misuse (continued)

(1) Destruction mode for the AN7198Z/99Z

The AN7198Z/99Z are the power ICs with high breakdown withstanding voltage but it has been found that

the destruction occurs under special conditions.

• GND-open short-circuit to ground.

Short-circuit the output terminal to the GND terminal of power supply when GND terminal of the IC is open,

or a short-circuiting is made to GND when the GND terminal of the IC is over 0.7 V higher than the short-

circuited output terminal.

At that time, if VCC = 16 V or more and a voltage is also applied to STB terminal, then the destruction occurs.

• The plus and minus side output terminals are short-circuited to power supply at the same time.

Ιf short-circuit to power supply occurs on both the plus and minus side output terminals at the same time with

a short-circuit resistor which does not actuate the protection circuit, the power GND terminal current may

exceed 10 A and the wire melts down since the current exceeds the capacity of Au wire.

• VCC − GND reverse connection

Parasitic device is created everywhere and the circuit destruction takes place.

4. Countermeasure for shock noise of the AN7198Z

Points of shock noise prevention

Plus and minus output of the BTL amp. is not changed suddenly by STB-on/off and Mute-on/off.

1) Standby pin to off (pin 5 VSTB = 5 V → 0 V) (Standby state → Operating state)

(1) Ripple filter pin (pin 12) becomes on gradually (Charge up to VCC) when VSTB = 0 V → 5V.

Current source and reference voltage are on instantaneously.

(2) Output D range suppression circuit is incorporated which limits the dynamic range of output to 0 V < VOUT

< VRF − 3 VBE when the ripple filter pin voltage is less than 6.8 V.

DC voltage change of input circuit causes steep DC voltage change of output pin and that generates shock noise.

This steep DC voltage change can be suppressed by the above mentioned circuit.

Voltage of the mute pin (pin 7) makes high forcedly in the inside circuit.

(3) Input mute is on when the ripple filter pin voltage VRF is less than 6.8 V.

This prevents the shock noise which is inputted from the pre-stage of power amp.

Also, mute is on in order to prevent the abnormal sound which is generated by clipping of waveform.

(Output is clipped due to narrow D range at start up)

(4) DC voltage of output pin changes with 1/2 voltage of the ripple filter pin.

Steep changes of output pin voltage is suppressed by start up gradually of the ripple filter pin.

(5) Output waveform of each plus and minus output at power supply on changes as same by symmetric placement

of inverting and non-inverting amplifier which consist of BTL amp.

VSTB-on

3 VBE Clamp-off

Output D-range RF

Reference

Mute-off

12

voltage

10

constant on

current source

VOUT without D-range

suppression circuit

8

VOUT

6

4

2

0

Mute-on

t

Image figure of output waveform, RF-pin waveform has exponential characteristics in actually.

18

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