TC78B002FNG
2013-10-17
21
10. Lock protection
It monitors the motor rotation by the hall signal and operates when the zero cross of the hall signal can not be
detected for certain time (T
ON
) or more. When lock protection operates, the upper output transistor is turned off
for 1ms(typ) and then all output power transistors are turned off. The motor drive resumes certain time (T
OFF
)
after the lock protection operates.
T
ON
= 0.4s (typ)
T
OFF
= 4s (typ)
FG is outputted by the hall signal even while the lock protection is operating.
In case the zero cross of the hall signal is detected twice in re-startup, the lock protection is cleared and the
RDO signal outputs low again.
11. Quick Start
During T
OFF
of lock protection, lock protection is cleared when the voltage of VSP pin is set to V
AD(L)
or less.
When V
AD(L)
or more is applied to the VSP pin again, the motor restarts operating quickly without waiting for
the end of the T
OFF
term.
Because the voltage of VSP pin is detected through A/D circuit, the voltage of VSP pin should be kept at V
AD(L)
or less for VSP response time (T
VSP
) or more in order to clear the lock protection.
Quick start is disabled when the minimum of the duty is configured by applying the voltage of V
AD(L)
or more
to VMI pin.
HP-HM
FG
OUT2
OUT1
OFF (Hi-Z)
RDO
T
ON
T
OFF
T
ON
OFF (Hi-Z)
OFF (Hi-Z)
OFF (Hi-Z)
L
L
20us
20us
HP-HM
FG
OUT2
OUT1
RDO
T
ON
T
OFF
VSP
0.5V
OFF (Hi-Z)
OFF (Hi-Z)
L
20us
1ms
1ms
1ms
0.55V
