Technical Note
9/14
BD67929EFV
www.rohm.com
2010.12 - Rev.
© 2010 ROHM Co., Ltd. All rights reserved.
●Protection Circuits
○Thermal Shutdown (TSD)
This IC has a built-in thermal shutdown circuit for thermal protection. When the IC's chip temperature rises above 175℃
(Typ.), the motor output becomes OPEN. Also, when the temperature returns to under 150℃(Typ.), it automatically
returns to normal operation. However, even when TSD is in operation, if heat is continued to be added externally, heat
overdrive can lead to destruction.
○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 pr motor output-GND is shorted. This circuit latches the motor output to OPEN condition
when the regulated threshold current flows for 4µs (Typ.). It returns with power reactivation or a reset of the SS 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 repeatedly, then OCP operates repeatedly 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 V
CC
terminal does 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 SS=HI 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 33V (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 SS=HI mode.
○Restricted protection circuit
This IC has a built-in restricted protection circuit for the provision against restriction of the motor. This circuit sets PD to H
for decreasing the torque when FG signal does not change over for certain time. It returns by re-charging the power
supply or resetting by SS terminal. The length of the time for detecting the motor lock will be able to set by the value of
the capacitor which is connected to PROCLK terminal.
When motor is locked by some reason, Pd is changed to H and the motor torque is decreased. The time that is until
detecting the lock is set by the value of capacitor which is connected to PROCLK terminal.
The period of PROCLK = C×200k[s]
The detecting time to lock = the period of PROCLK×96 count
= C×200k[s]×96 count
ex.) When C=0.1µF, T= 1.92 [s]. The declination of 1 count may occur by the timing of the count.
○Non input CLK protection circuit
This IC has a built-in non input CLK protection circuit for the provision against breaking of CLK. This circuit sets the motor
output open when CLK signal does not change over for certain time. It returns by re-changing the power supply or
resetting by SS terminal. The length of the time for detecting the state of non input CLK will be able to set by the value of
the capacitor which is connected to PROCLK terminal.
The period of PROCLK = C×200k[s]
The detecting time to lock T = The period of PROCLK×3count
= C×200k[s]×3count
ex.) When C=0.1µF, T= 80 [ms]. The declination of 1 count may occur by the timing of the count.
