Technical Note

5/8

BD63843EFV, BD63847EFV

www.rohm.com

2012.02 - Rev.A

© 2012 ROHM Co., Ltd. All rights reserved.

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Under Voltage Lock Out (UVLO)

This IC has a built-in under voltage lock out function to prevent false operation such as IC output during power supply under

voltage. When the applied voltage to the VCC terminal goes under 15V (Typ.), the motor output is set to OPEN. This

switching voltage has a 1V (Typ.) hysteresis to prevent false operation by noise etc. Please be aware that this circuit does

not operate during power save mode. Also, the electrical angle is reset when the UVLO circuit operates during CLK-IN drive

mode.

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Over Voltage Lock Out (OVLO)

This IC has a built-in over voltage lock out function to protect the IC output and the motor during power supply over voltage.

When the applied voltage to the VCC terminal goes over 32V (Typ.), the motor output is set to OPEN. This switching

voltage has a 1V (Typ.) hysteresis and a 4µs (Typ.) mask time to prevent false operation by noise etc. Although this over

voltage locked out circuit is built-in, there is a possibility of destruction if the absolute maximum value for power supply

voltage is exceeded, therefore the absolute maximum value should not be exceeded. Please be aware that this circuit does

not operate during power save mode.

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Ghost Supply Prevention (protects against malfunction when power supply is disconnected)

If a signal (logic input, VREF, MTH) is input when there is no power supplied to this IC, there is a function which prevents

the false operation by voltage supplied via the electrostatic destruction prevention diode from these input terminals to the

VCC to this IC or to another IC’s power supply. Therefore, there is no malfunction of the circuit even when voltage is

supplied to these input terminals while there is no power supply.

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Thermal derating curve

HTSSOP-B28 has exposed metal on the back, and it is possible to dissipate heat from a through hole in the back. Also, the

back of board as well as the surfaces has large areas of copper foil heat dissipation patterns, greatly increasing power

dissipation. The back metal is shorted with the back side of the IC chip, being a GND potential, therefore there is a

possibility for malfunction if it is shorted with any potential other than GND, which should be avoided. Also, it is

recommended that the back metal is soldered onto the GND to short. Please note that it has been assumed that this

product will be used in the condition of this back metal performed heat dissipation treatment for increasing heat dissipation

efficiency.

Fig.2 HTSSOP-B28 Thermal derating curve

Ambient temperature:Ta[C]

1.0

100

125

0

4.70W

4

3.30W

3

1.85W

2

1.45W

1

2.0

3.0

4.0

5.0

Measurement machine：TH156（Kuwano Electric）

Measurement condition：ROHM board

Board size：70mm*70mm*1.6mm

(With through holes on the board)

The exposed metal of the backside is connected to the board with solder.

Board①：1-layer board (Copper foil on the back 0mm)

Board②：2-layer board (Copper foil on the back 15mm*15mm)

Board③：2-layer board (Copper foil on the back 70mm*70mm)

Board④：4-layer board (Copper foil on the back 70mm*70mm)

50

25

85

75

150