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5. Forward/backward changeover The motor rotation can be changed over with the F/R pin. Following cautions should be observed when F/R changeover is to be made while the motor is running: . The circuit incorporates a measure against the through current at a time of changeover. However it is necessary to take an appropriate measure to prevent the voltage from exceeding the rated voltage (35 V) because ofrising ofthe VM voltage at changeover (instantaneous return ofthe motor current to the power supply). When this is a problem, increase the capacitance of a capacitor between VM and GND. . When the motor current after changeover is the current limit or more, the lower Tr is turned OFF. But the upper Tr enters the short-brake condition, and the current determined from the motor counter-electromotive voltage and coil resistance flows. It is necessary to prevent this current from exceeding the rated current (3.5 A). (F/R changeover at high rotation speed is dangerous.) 6. Brake operation Brake operation is made through setting ofthe BR pin to the "L" level. This operation consists ofa short-brake operation in which all oflower outputs are turned OFF while all of upper outputs are turned ON. While the brake is operating, current limiting and motor lock protection circuits are not operative. Apply brake only when the current during operation does not exceed the rated current (3.5 A). The circuit incorporates a measure against the through current at a time ofchangeover. However it is necessary to take an appropriate measure to prevent the voltage from exceeding the rated voltage (35 V) because ofrising of the VM voltage at changeover (instantaneous return ofthe motor current to the power supply). When this is a problem, increase the capacitance of a capacitor between VM and GND. 7. Motor lock protection circuit A motor lock protection circuit is incorporated for protection ofIC and motor when the motor is locked. The lower output Tr is turned OFF when the Hall input signal is not switched for a certain period in the motor drive condition. The time is set by means of a capacity of a capacitor connected to the CSD pin. Time setting of about 3.5 sec is possible for the capacitance of 10 UF. (Variance30%) Set time (s)0.35 x C (UF) Due care must be taken on any leakage current in the capacitor used because it may adversely affect error ofthe set time, etc. To cancel the motor lock protection condition, one of following steps must be taken: . Stop mode . Maintaining the output duty 0% condition through input ofPWMIN or TOC for more than the period oftPWM x 8. (tPWM: IC internal PWM oscillation period) . Power must be applied again (in the stop condition). Connect the CSD pin to GND when the motor lock protection circuit is not to be used. The motor lock protection active period at restart becomes shorter than the setting when the stop time to cancel motor lock protection is shorter because the charge ofcapacitor cannot be fully discharged. Therefore, it is necessary to provide a certain allowance to the stop period while referring to the following formula as a guideline. Stop time(ms 15 x C (yF) 8. Circuit for low-voltage protection This circuit detects the voltage applied to the Vcc pin. When this voltage drops below the operation voltage (see the electric characteristics), the lower side output is turned OFF. To prevent repetition of output ON/OFF near the protection activation voltage, the hysteresis is provided. Accordingly, the output is not recovered unless the voltage rises by about 0.5 V above the activation voltage. 9. HP output For the HP output, the composite signal of three phases ofHall element signal is output. This is an open collector output. This can be used for the motor rotation detection signal, etc.