LV8804V Sanyo Semiconductor Corporation, LV8804V Datasheet - Page 7

• Manufacturer Part Number: LV8804V
• Description: PC and Server Fan Motor Driver
• Manufacturer: Sanyo Semiconductor Corporation

LV8804V Functional Description
1 Control Characteristics
The current flowing to the motor and the control characteristics are determined by adjusting the resistance of the RF
resistor.
By connecting a resistor with a resistance of 0.25Ω between the RF pin and GND, the limit current is set at a motor current
of 1A, and the control characteristics shown in the diagram above are achieved.
By increasing the RF resistance, the limit current is reduced; conversely, by reducing the RF resistance, the limit current is
increased.
Since I O max. is 1.2A, the RF resistance must be set in such a way that the current flowing to the motor does not exceed
this maximum value.
By varying the CTL voltage between 1V and 3V, the current flowing to the output is limited.
PWM control is exercised within the voltage range above (1V to 3V) to control the motor speed.
When the CTL voltage is less than 1V, the current limiter value determined by the RF resistance is reached, and the motor
speed is limited.
When the CTL voltage is greater than 3V, PWM is reduced to 0%, and the motor stops. (However, the motor does not stop
if the minimum speed has been set.)
The minimum speed can be set by resistor-dividing the REG voltage (5V) to create a voltage of 1V to 3V, and inputting
this voltage to the MINSP pin.
If the minimum speed is not going to be set, the MINSP pin and CTL pin (pin 8) must be short-circuited.
2. Timing at Startup (soft start)
SOFTS pin
V CC pin
CTL pin
0.5A
IRF
1A
0V
When RF = 0.25Ω
Soft start
1V
Stop
Stop
2V
Full speed
The gradient and limit current are determined by the resistance of the RF pin.
The gradient changes in accordance with the capacitance of the SOFTST pin.
(The higher the capacitance, the steeper the gradient.)
Full speed
3V
LV8804V
Minimum speed
This minimum speed is determined by the MINSP pin voltage.
4V
VCTL
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