lb11691 Sanyo Semiconductor Corporation, lb11691 Datasheet - Page 14

• Manufacturer Part Number: lb11691
• Description: Pre-driver Ic For Brushless Motor Drive In Electric Bicycles
• Manufacturer: Sanyo Semiconductor Corporation

7. Low-voltage protective circuit
8. RES circuit
The low-voltage protective circuit performs detection using the voltage applied to the LVS pin and turns OFF all drive
outputs when the voltage drops below the operating voltage (3.85Vtyp). The circuit has hysteresis to prevent repetition
of ON/OFF near the protected operating voltage. The output is not recovered when the voltage does not rise by about
0.5V above the operating voltage. In the protection operation, the RES pin voltage
becomes “L” too.
The protection operating voltage is based on the 5V system detection level. To raise the
detection level, connect Zener diode in series to the LVS pin and shift the detection
level (detection voltage = 3.85Vtyp+Vz). The LVS pin inrush current at detection is
about 62μA. If it is necessary to stabilize rise of the Zener diode voltage and to suppress
fluctuation of the Zener voltage, insert a resistor between LVS pin and GND to increase
the diode current. The detection voltage may also be raised, without using Zener diode,
by resistive potential division. When connection as shown in the right is made ;
With R1 = 13kΩ and R2 = 2.2kΩ, the detection voltage becomes about 28V while the
cancellation voltage becomes about 32V. Pay due attention when raising R2 because
the error of detection voltage may increase because of temperature and variance.
When the protective circuit is not to be used, do not open the LVS pin (output OFF
when this is opened) and apply the voltage on an inoperative level.
Apply initial reset with the RES pin to ensure stable operation at power ON. Initial reset includes the following
operations :
Normally, connect a resistor and capacitor between RES and V5 pins and between
these pins and GND respectively and set the reset time. Use a 2.7kΩ or more
resistor. Set so that the time constant becomes R × C ≥ 1m (0.1μF or more if this is
10kΩ). If the charge of a capacitor connected to EI + or FV pin must be completely
discharged, set the reset time by taking into account the discharge time of these
pins. It is also recommended to set the reset time longer than the time necessary for
stabilization of the VB voltage at power ON.
In addition to initial reset, reset may be applied when the control voltage is low as
shown in Fig. 1 in the right. In this case, all drive outputs can be turned OFF when
the control voltage becomes about 0.67V(1.27V - V BE ). The reset cancellation
voltage is about 0.9V (0.67V+0.23V). If only the control voltage is 0% duty (1.2V
or less), the motor is braked when driven in the reverse direction. This is an
effective application when braking is not necessary during reverse drive. If the
control voltage cannot be decreased to 1V or less, application as shown in Fig. 3
may be used.
Heat detection with thermistor may also be considered to prevent thermal
breakdown of output FET. Connect as shown in Fig. 2 in the right and adjust the
external resistance, and the protective operation can be done. Fig. 4 shows a
combination of this application with thermistor and an application shown in Fig. 3.
Detection voltage ≈ ((3.85 ÷ R2) + 62μA) × (R1+R2)
Cancellation voltage ≈ ((4.35 ÷ R2) + 70μA) × (R1+R2)
• All drive outputs OFF
• EI + pin voltage at “L”
• FV pin voltage at “L”
Fig.3
RES
Control voltage (1V to 4V)
10kΩ
47kΩ
EI +
LB11691
RES
Fig.4
To V5 pin
RES pin
Control voltage (1V to 4V)
Fig.1
Fig.2
To V5 pin
power supply
power supply
10kΩ
47kΩ
To detectiom
To detectiom
RES pin
Thermistor
EI +
LVS pin
LVS pin
To control voltage
To V5 pin
No.A0879-14/21
EI + pin
V Z
R1
R2