Technical Note

15/16

BD5426EFS

www.rohm.com

2009.06 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

●Notes on Usage

1. About absolute maximum ratings

If an applied voltage or an operating temperature exceeds an absolute maximum rating, it may cause destruction of a

device. A result of destruction, whether it is short mode or open mode, is not predictable. Therefore, provide a physical

safety measure such as fuse, against a special mode that may violate conditions of absolute maximum ratings.

2. About power supply line

As return of current regenerated by back EMF of output coil happens, take steps such as putting capacitor between

power supply and GND as a electric pathway for the regenerated current. Be sure that there is no problem with each

property such as emptied capacity at lower temperature regarding electrolytic capacitor to decide capacity value. If the

connected power supply does not have sufficient current absorption capacity, regenerative current will cause the voltage

on the power supply line to rise, which combined with the product and its peripheral circuitry may exceed the absolute

maximum ratings. It is recommended to implement a physical safety measure such as the insertion of a voltage clamp

diode between the power supply and GND pins.

3. Potential of GND (11, 12, 33, 34, and 43 pins)

Potential of the GND terminal must be the lowest under any operating conditions.

4. About thermal design

Perform thermal design with sufficient margins, in consideration of maximum power dissipation Pd under actual operating

conditions. This product has an exposed frame on the back of the package, and it is assumed that the frame is used with

measures to improve efficiency of heat dissipation. In addition to front surface of board, provide a heat dissipation pattern

as widely as possible on the back also.

A class-D power amplifier has heat dissipation efficiency far higher than that of conventional analog power amplifier and

generates less heat. However, extra attention must be paid in thermal design so that a power dissipation Pdiss should

not exceed the maximum power dissipation Pd.

Maximum power dissipation



W

θ

Ta

-

T

Pd

a

j

jmax



Tjmax: Maximum temperature junction = 150[℃]

Ta: Operating ambient temperature [℃]

θja: Package thermal resistance [℃/W]

Po: Output power [W]

η: Efficiency

Power dissipation



W

1

-

η

1

P

P

O

diss























5. About operations in strong electric field

Note that the device may malfunction in a strong electric field.

6. Thermal shutdown (TSD) circuit

This product is provided with a built-in thermal shutdown circuit. When the thermal shutdown circuit operates, the output

transistors are placed under open status. The thermal shutdown circuit is primarily intended to shut down the IC avoiding

thermal runaway under abnormal conditions with a chip temperature exceeding Tjmax = 150℃, and is not intended to

protect and secure an electrical appliance. Accordingly, do not use this circuit function to protect a customer's electrical

appliance.

7. About shorting between pins and installation failure

Be careful about direction and displacement of an LSI when installing it onto the board. Faulty installation may destroy

the LSI when the device is energized. In addition, a foreign matter getting inbetween LSI pins, pins and power supply,

and pins and GND may cause shorting and destruction of the LSI.

8. About power supply startup and shutdown

When starting up a power supply, be sure to place the MUTEX pin (pin 20) at “L” level. When shutting down a power

supply also, be sure to place the pin at “L” level. Those processes reduce pop noises generated upon turning on and off

the power supply. In addition, all power supply pins must be started up and shut down at the same time.

9. About WARNING output pin (pin 18) and ERROR output pin (pin 19)

A WARNING flag is output from the WARNING output pin upon operation of the high-temperature protection function and

under-voltage protection function. And an ERROR flag is output from the ERROR output pin upon operation of VCC/GND

shorting protection function and speaker DC voltage applying protection function. These flags are the function which the

condition of this product is shown in. The use which aimed at the protection except for this product is prohibition.

10. About N.C. pins (pins 21 and 22)

The N.C. (Non connection) pins are not connected with an internal circuit. Leave the pins open or connect them to GND.