LV8136VGEVB Datasheet, PDF (18/19 Pages) –

Description of LV8136V
LV8136V
1. Current Limiter Circuit
The current limiter circuit limits the output current peak value to a level determined by the equation I = VRF/Rf (where
VRF = 0.25V typ, Rf is the value of the current detection resistor). The current limiter operates by reducing the output
on duty to suppress the current.
The current limiter circuit detects the reverse recovery current of the diode due to PWM operation. To assure that the
current limiting function does not malfunction, its operation has a delay of approx. 1μs. If the motor coils have a low
resistance or a low inductance, current fluctuation at startup (when there is no back electromotive force in the motor)
will be rapid. The delay in this circuit means that at such times the current limiter circuit may operate at a point well
above the set current. Application must take this increase in the current due to the delay into account when the current
limiter value is set.
2. Power Saving Circuit (CTL pin)
This IC goes into the power saving mode that stops operation of all the circuits to reduce the power consumption. If the
HB pin is used for the Hall element bias and the output block, the current consumption in the power-saving mode is
zero.
3. Hall Input Signal
Signals with an amplitude in excess of the hysteresis is required for the Hall inputs. However, considering the influence
of noise and phase displacement, an amplitude of over 100mV is desirable.
If noise disrupts the output waveform (at phase change), this must be prevented by inserting capacitors or other devices
across the Hall inputs. The constraint protection circuit uses the Hall inputs to discriminate the motor constraint state.
Although the circuit is designed to tolerate a certain amount of noise, care is required.
If all three phases of the Hall input signal go to the same input state (HHH or LLL), the outputs are all set to the off
state.
If the outputs from a Hall IC are used, fixing one side of the inputs (either the + or –side) at a voltage within the
common-mode input voltage range (0.3V to VREG-1.7V) allows the other input side to be used as an input over the 0V
to VREG range.
4. Constraint Protection Circuit
This IC goes into the power saving mode that stops operation of all the circuits to reduce the power consumption. If the
HB pin is used for the Hall element bias and the output block, the current consumption in the power-saving mode is
zero.
This IC provides an on-chip constraint protection circuit to protect the IC itself and the motor when the motor is
constrained.
If the Hall input signals do not change for over a fixed period when the motor is in operation, this circuit operates. Also,
the upper-side output transistor is turned off while the constraint protection circuit is operating. This time is determined
by the capacitance of the capacitor connected to the CSD pin.
Set time (in seconds) ≈ 90 × C (μF)
If a 0.022μF capacitor is used, the protection time will be about 2.0 seconds.
The set time must be selected to have an adequate margin with respect to the motor startup time
Conditions to clear the constraint protection state :
CTL pin when a low-level voltage is input → Release protection and reset count
When TSD protection is detected
→ Stop count
5. Power Supply Stabilization
Since this IC adopts a switching drive technique, the power-supply line level can be disrupted easily. Thus capacitors
large enough to stabilize the power supply voltage must be inserted between the VCC pins and ground. If the
electrolytic capacitors cannot be connected close to their corresponding pins, ceramic capacitors of about 0.1μF must
be connected near these pins.
If diodes are inserted in the power-supply line to prevent destruction of the device when the power supply is connected
with reverse polarity, the power supply line levels will be even more easily disrupted, and even larger capacitors must
be used.
No.A2005-18/19