LB11650H Datasheet, PDF (4/6 Pages) Sanyo Semicon Device – PWM Input Forward/Reverse Motor Driver

LB11650H
High/Low Short Protection Function
This function turns the outputs off to prevent destruction of the IC if a problem such as an output pin being shorted to
VM or ground occurs and excessive current flows in the output transistors.
When an excessive current flows in an output transistor, a potential will occur across either the high side or the low side
current sense resistor. If that value exceeds the current detection threshold voltage, the capacitor connected to the C pin
starts to charge. Then, when the C pin voltage is charged to the output off threshold voltage, the output transistors are
turned off.
To restart the IC once it has gone to the output off state, either set the ST pin to the low level, or temporarily cut the V_CC
power supply, and then reapply power.
The overcurrent detection current setting can be set to an arbitrary level with the resistor inserted between VM and VHS
for current flowing in the high side output transistor, and with the resistor inserted between VLS and ground for current
flowing in the low side output transistor.
When the resistor connected to VHS or VLS pin is R (Ω), the detected current I (A) will be as follows.
I (A) = 0.5 (V) / R (Ω)
For example, if R is 0.5 Ω, the detected current I will be 1 A.
This function is not an output current limiter function.
The detection current described above has the meaning that the short-circuit protection circuit begins to operate when a
current in excess of the detection current flows in the outputs. Therefore, if an output pin is shorted to VM or ground, the
maximum possible overcurrent that the output transistors are capable of will flow until the mask time set with the filter
circuit has elapsed. Designers must exert great care in designing the mask time setting.
Filter Circuit
To prevent the overcurrent protection and thermal shutdown circuits from operating incorrectly due to noise, the
LB11650 includes a circuit that sets a mask time so that when an abnormality is detected, it only turns the outputs off if
that state continues for a certain length of time.
When the capacitor connected between the C pin and ground is C (pF), the mask time T (µs) will be as follows.
T (µs) = 2.6 × 10^–2 × C (pF)
For example, if C is 50 pF, the mask time T will be 1.3 µs.
Low Side Transistor Drive Current Switching Pin
Since the lower side output transistor drive current is created from V_CC, if the V_CC power supply level is reduced, the
drive current will also be reduced. Therefore, the LB11650 is provided with a pin for switching the drive current so that
the LB11650 can provide the same drive current when used with 3.3 V specifications as it does when used with 5 V
specifications.
When V_CC = 5 V: Leave the R pin open.
When V_CC = 3.3 V: Short the R pin to V_CC.
No. 7676-4/6