LB11823M Datasheet, PDF (17/19 Pages) Sanyo Semicon Device – Direct PWM Drive Brushless Motor Predriver for OA Products

LB11823M
9. Motor lock protection circuit
A motor lock protection circuit is incorporated for protection of IC and motor when the motor is locked. When the
Hall input signal is not changed for a certain period with the motor driving, the one-side output (UH, VH, WH) is
turned OFF. The time is set by means of a capacity of a capacitor connected to the CSD pin.
Set time (s) ^.=. 154 × C (µF)
Addition of a 0.01 µF capacitor causes a protection time of about 1.54 seconds. (Drive is turned OFF when one cycle
of Hall input signal is longer than this time period.) The time to be set must have a sufficient allowance so that the
protection is not activated at a normal motor startup. Select the capacitor of 4700 pF or more. The protection circuit is
not activated when braking. To cancel the restriction protection condition, one of following steps must be taken:
• Stop mode (10 µs or more)
• Maintaining the output duty 0% condition through input of VCTL or PWMIN for more than the period of tCSD × 2.
(tCSD (s) ^.=. 0.5 × C (µF).
When the 0.01 µF capacitor is added, maintaining for about 10 ms or more is necessary.)
• Re-application of power supply
The CSD pin acts also as an initial reset pulse generation pin and causes reset of the logic circuit when connected with
GND. Accordingly, the motor drive condition can not be obtained. When this pin is not to be used, a resistor of about
150 kΩ and a capacitor of about 4700 pF must be connected to GND in parallel. When the restriction protection circuit
is not used, following functions are also invalid:
• Protection circuit for the reverse mode
• Overheat protection circuit
10. Protection circuit at reverse
This circuit becomes effective when the REVSEL pin is set to the L level. When this protection is not necessary, either
connect it to the VREG pin or keep it open.
When this circuit is effective, all outputs are OFF (all of UL, VL, WL, UH, VH, and WH OFF) when the drive is OFF
(output duty 0%). If the condition is switched rapidly from the output drive condition to the drive OFF condition, the
current flowing through the motor is returned to the power supply (the coil current flows through output upper and
lower diodes to power supply). If this current causes a trouble, such as rise of the supply voltage, etc., it is necessary to
reduce the duty in steps, instead of shutting of the drive suddenly.
Reverse condition is detected according to the input sequence of Hall signals (IN1, IN2, and IN3). When using this
protection circuit, it is necessary to connect the Hall device with motor while considering the Hall input sequence. (See
the three-phase logic truth table.) Reversing is judged when the Hall input is reversed by more than 120 degrees in the
electrical angle. The drive is not shut OFF immediately after judgment of reverse, but the drive is continued for a
certain period (equal to the motor lock protection set time) after drive start. If the reversing condition continues for a
certain period (equal to the set time of motor lock protection), the drive is shut OFF (all OFF).
When the motor is reversing before it is driven, the drive is continued for a certain period (equal to the set time of
motor lock protection). If the motor does not return to forward rotation within this period, the drive is shut OFF (all
OFF).
To cancel the protection, one of following steps must be taken:
• Stop mode (10 µs or more)
•
Maintaining the output duty 0% condition
(tCSD(s) ^.=. 0.5 × C (µF). When the 0.01 µF
through input of V_CTL or PWMIN for more than the period of tCSD
capacitor is added, maintaining for about 10 ms or more is necessary.)
×
2.
• Re-application of power supply
11. Overheat protection circuit
One-side output (UH, VH,WH) is turned OFF when the junction temperature (Tj) exceeds a specified temperature
(TSD). Since the minimum variation of TSD is 125°C, thermal design must be made so that Tj = 125°C is not
exceeded except in the case of abnormality. Accordingly, Pdmax when Tj(max) = 125°C is 0.72 W (Ta = 25°C).
When the motor lock protection is not to be used by inserting in parallel the resistor of about 150kΩ and capacitor of
about 4700pF between the CSD pin and GND, this overheat protection circuit does not function.
In this case, Tj(max) = 150°C, so that Pdmax = 0.9W (Ta = 25°C)
No. 7106-17/19