Technical Note

6/8

BD6387xEFV Series

www.rohm.com

2012.02 - Rev.A

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

○Over Current Protection (OCP)

This IC has a built in over current protection circuit as a provision against destruction when the motor outputs are

shorted each other or VCC-motor output or motor output-GND is shorted. This circuit latches the motor output to OPEN

condition when the regulated threshold current flows for 4

μs (Typ.). It returns with power reactivation or a reset of the

PS terminal. The over current protection circuit’s only aim is to prevent the destruction of the IC from irregular situations

such as motor output shorts, and is not meant to be used as protection or security for the set. Therefore, sets should

not be designed to take into account this circuit’s functions. After OCP operating, if irregular situations continues and

the return by power reactivation or a reset of the PS terminal is carried out repeatly, then OCP operates repeatly and

the IC may generate heat or otherwise deteriorate. When the L value of the wiring is great due to the wiring being long,

after the over current has flowed and the output terminal voltage jumps up and the absolute maximum values may be

exceeded and as a result, there is a possibility of destruction. Also, when current which is over the output current rating

and under the OCP detection current flows, the IC can heat up to over Tjmax=150℃ and can deteriorate, so current

which exceeds the output rating should not be applied.

○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.

○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 4

μs (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.

○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.

●Usage Notes

(1) Absolute maximum ratings

An excess in the absolute maximum ratings, such as supply voltage, temperature range of operating conditions, etc., can

break down the devices, thus making impossible to identify breaking mode, such as a short circuit or an open circuit. If

any over rated values will expect to exceed the absolute maximum ratings, consider adding circuit protection devices,

such as fuses.

(2) Connecting the power supply connector backward

Connecting of the power supply in reverse polarity can damage IC. Take precautions when connecting the power supply

lines. An external direction diode can be added.

(3) Power supply Lines

Design PCB layout pattern to provide low impedance GND and supply lines. To obtain a low noise ground and supply line,

separate the ground section and supply lines of the digital and analog blocks. Furthermore, for all power supply terminals

to ICs, connect a capacitor between the power supply and the GND terminal. When applying electrolytic capacitors in the

circuit, not that capacitance characteristic values are reduced at low temperatures.

(4) GND Potential

The potential of GND pin must be minimum potential in all operating conditions.

(5) Metal on the backside (Define the side where product markings are printed as front)

The metal on the backside is shorted with the backside of IC chip therefore it should be connected to GND. Be aware that

there is a possibility of malfunction or destruction if it is shorted with any potential other than GND.

(6) Thermal design

Use a thermal design that allows for a sufficient margin in light of the power dissipation (Pd) in actual operating conditions.

Users should be aware that these products have been designed to expose their frames at the back of the package, and

should be used with suitable heat dissipation treatment in this area to improve dissipation. As large a dissipation pattern

should be taken as possible, not only on the front of the baseboard but also on the back surface. It is important to

consider actual usage conditions and to take as large a dissipation pattern as possible.