LB11691H Datasheet, PDF (13/21 Pages) Sanyo Semicon Device – Monolithic digital IC Pre-Driver IC for Brushless Motor Drive in Electric Bicycles

LB11691H
4. Control method
The output duty is determined from comparison between the PWM oscillation waveform and TOC pin voltage. The
duty becomes 0% when the TOC pin voltage is about 1.2V or less and 100% when the pin voltage is about 3.0V or
more.
Normally, the integrating amplifier is used as a full return amplifier (EI- pin
and TOC pin connected) and the control voltage is entered to EI+ pin. (The
Control voltage
TOC
output duty increases with increasing EI+ pin voltage.) At resetting with the
RES pin, the EI+ pin is lowered approximately to the GND voltage by IC
-
EI-
internal TR (for capacitor discharge). Therefore, always enter the voltage via
resistor, instead of direct connection of the low-impedance power. Also
EI+
+
connect a pull-down resistor between the EI+ pin and GND to prevent the
motor from being driven when the control voltage is open. When the control
voltage contains noise or in order to suppress sudden fluctuation of the control
voltage, connect a capacitor between the EI+ pin and GND to remove the
To FV pin
noise. The operating voltage range of control input can be widened by
entering the voltage divided by the resistor into the EI+ pin, as shown in the
TOC
figure right.
To perform control while keeping the rotation speed constant to a certain
degree under load fluctuation, the speed control circuit with FV pin output
Control voltage
EI-
may be formed as shown in the right. Select a 25kΩ or more resistance to be
EI+
-
+
inserted between FV and EI- pins. Select the return capacitor capacity so that
the TOC pin voltage is sufficiently stable at low speed.
5. Charge pump circuit
The voltage is raised by the charge pump circuit, generating the gate voltage of upper output FET. The voltage is raised
by a capacitor CP connected between CP1 and CP2 pins, accumulating the charge in the capacitor CB between VB and
VCC pins. The capacitance value of CP and CB must always have the following relationship :
CB ≥ 4 × CP
CP capacitor charge and discharge are made on the basis of PWM cycle. Though the VB power supply current capacity
increases with increasing capacity of the CP capacitor, excessively large capacity may cause faulty charge/discharge
operation. The VB voltage becomes more stable when the CB capacitor capacity is larger, but excessively large
capacity causes longer time of VB voltage generation at a time of power ON. Set the capacity of CP and CB by
referring to the table below.
When the VCC voltage decreases below 20V, the current capacity of VB power supply deteriorates suddenly, causing
drop of VB voltage. Therefore, due care must be taken when designing.
VCC voltage
CP
24V
0.1μF
36V
6800pF
CB
1μF
0.47μF
6. Hall input signal
Connect the Hall IC output to the Hall input. As an about 10kΩ pull-up
12V
resistor is incorporated for the 5V regulator, it is normally not necessary to Hall IC
connect the pull-up resistor externally. If the Hall IC with built-in pull-up
5V _LB11690
resistor is used, it is enough to use the Hall IC power supply with 5V. If the
Hall IC power supply is to be used with 12V, it is necessary to add the
IN
pull-down resistor or voltage clamp Zener diode to prevent application of
voltage of 5V or more to the Hall input.
The input is a comparator input with about 0.9V hysteresis width. If the
noise presents problem, connect a noise removing capacitor between the
input and GND.
When three inputs of Hall input signal are in the same input condition, both upper and lower outputs are turned OFF.
No.8314-13/21