LB11692JH

No.A0333-9/12

LB11692JH Overview

1. Output Drive Circuit

The LB11692JH uses a direct PWM drive technique. Since the motor speed can be controlled by holding the supply

voltage constant and changing the output duty, the power supply design can be simplified compared to designs used

with techniques that vary the supply voltage (such as PAM drive). The low side output transistor is switched with a

pulse-width modulated signal and the drive output is adjusted by changing the duty. The LB11692JH includes built-

in output diodes for the regenerative currents that occur when the PWM signal is off and during phase switching.

2. Power Supply Stabilization

Since the LB11692JH uses a control method based on PWM switching, the power supply lines are susceptible to

disruption. Electrolytic capacitors with an adequate capacitance for stabilization must be connected between VCC

and ground. If diodes are inserted in the power supply lines to prevent destruction of the equipment if the power

supply is connected in reverse, the power supply lines will be particularly susceptible to disruption. In this case, even

larger capacitors must be used. The connected electrolytic capacitors must be located as close as possible to the IC

pins (VCC, VM, and GND2). If the electrolytic capacitors cannot be attached close to the pins due to problems with

the heat sink or other issues, ceramic capacitors of about 0.1µF must be attached close to the pins.

3. VREG Pin

At the same time as being the 5V regulator output, the VREG pin is also the power supply for the IC internal control

circuits. Therefore, a capacitor of at least 0.1µF must be connected between the VREG pin and ground to stabilize the

control circuit power supply. The ground side of the connected capacitor must be connected to the GND1 pin with as

short a line as possible.

4. FC Pin

The capacitor connected to the FC pin is required to correct the control loop's frequency characteristics.

(It should be about 0.1

µF.)

5. VD Pin

The VD pin supplies the low side output transistor drive current (a maximum of about 0.1A).

The IC internal power consumption is suppressed by connecting a resistor between the VCC and VD pins and

dividing power consumption due to the low side output transistor drive current with that resistor. Although the IC

internal power consumption due to the drive current can be reduced by lowering the VD pin voltage, a voltage of at

least 4V must be assured at the VD pin. Use a resistor in the range from about 50

Ω (0.5W) to about 100Ω (1W)

between the VCC and VD pins when the LB11692JH is used with VCC = 24V.

6. Hall Effect Sensor Input Signals

Signals with amplitudes greater than 80mVp-p are required for the Hall effect sensor inputs. If possible, we

recommend providing signal amplitudes in excess of 100mVp-p to minimize the effects of noise. Add capacitors

across the Hall inputs (between the + and - sides of each input) if the output waveforms are disrupted by noise during

phase switching.

7. Current Limiter Circuit

The current limiter circuit limits the peak value of the output current to a current determined by the equation I =

VRF/Rf (where VRF = 0.5V (typical), Rf = current detection resistor value). When the limiter operates, it suppresses

the current by PWM control of the low side output transistor at the PWM frequency determined by the external

capacitor connected to the PWM pin, in particular, by reducing the on duty.