LV11961HA Datasheet, PDF (13/14 Pages) ON Semiconductor – Single-phase FAN Motor Driver

LV11961HA
*4 < Hall signal input >
To defend signals against the noise, it is necessary to wire as short as possile from hall sensor to each pin
and to conect the capacitor between IN1 and IN2, as shown in Fig.1. Value from 1,000pF to 10,000pF is
recommended for C5 in Fig.1. But its value should be selected in consideration with the actual motor
action.
The amplitude of each hall signal must be more than 60mVp-p because of the sensitivity of inner circuit.
*5 < Capacitor to adjust the PWM frequency >
The oscillation for PWM control is generated by connecting a capacitor between CPWM pin and GND.
The frequency of this oscillation is calculated as below;
  ^fCPWM

1_
2 C₂ 
I _CPWM
V_CPH  V_CPL
In the case C₂=100[pF];
  f _{CPWM 100 pF}

1
2

100
E
25.0E ^6
12 _{ 2.15}

0.62
 81.70 kHz
This is the result which is calculated by typical values of each electrical characteristic in this IC. Actually,
there is variability which is defined by min/max in electrical characteristics. In addition, there may be some
difference between calculated value and actual value because of a parasitic capacitance on the board
and so on.
Therefore, the value of C2 should be settled with actual operation, in view of those factors.
*6 < Input to VTH pin >
VTH pin needs to be input DC signal which is from 0V to VREG.
If the external control signal is the pulse type, it should be flatten by the filter and be shifted to suitable
level, shown in Fig.1, to input to VTH pin.
In the case that the high duty of PWM signal input in Fig.1 is D [%], VTH input level flatten by the filter is
calculated apprpximately as below;
VTH
 V_REG




R₁
R₂


R₂
R₃

R₃

R₁

R₂
R₁  R₃
 R₃  R₁

R₂


D
100



This calculation is justified by the condition that Rds of MN1 << R3. So, a large value of resistor should be
selected to R3.
But, too large value of R1 – R3 and R4 causes the instability because of the effect of input impedance at
VTH pin.
The recommendation value of R1 – R3 and R4 is from 4.7k[ohm] to 47k[ohm].
The cut-off frequency fc by C3 and R4 is calculated as below;
f_c

2
1
 C₃

R₄
The actual value of C3 or R4 is better to select more than 50 times the above calculation value to be flatten
thoroughly. Furthermore, it is better to do it by the value of C3 because of the effect of input impedance at
VTH pin.
To compensate for disconnection of PWM input, it is recommended that the gate of the FET is pulled up to
REG with a resistor as R5 shown in Fig.1.
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