LV8731V
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20
Current Limit Reference Voltage Setting Function
By setting a current limit, this IC automatically exercises
short braking control to ensure that when the motor current
has reached this limit, the current will not exceed it.
• Current Limit Control Time Chart
Figure 17. Current Limit Control Time Chart
fchop
CHARGE
SLOW
Current Mode
Coil Current
Set Current
Forced Charge
section
The limit current is set as calculated on the basis of the
voltage input to the VREF pin and the resistance between the
RF pin and GND using the formula given below.
Ilimit + (VREF ń 5) ń RF resistance
(eq. 4)
The voltage applied to the VREF pin can be switched to
any of the four setting levels depending on the statuses of the
two inputs, ATT1 and ATT2.
• Function for Attenuating VREF Input Voltage
ATT1 ATT2 Current Setting Reference Voltage Attenuation Ratio
Low Low 100%
High Low 80%
Low High 50%
High High 20%
The formula used to calculate the output current when
using the function for attenuating the VREF input voltage is
given below.
Ilimit + (VREF ń 5) (attenuation ratio) ń RF resistance
(eq. 5)
Example: At VREF of 1.5 V, a reference voltage setting
of 100% [(ATT1, ATT2) = (L, L)] and an RF resistance of
0.3 Ω, the output current is set as shown below.
Ilimit + 1.5 V ń 5 100% ń 0.3 + 1.0 A
If, in this state, (ATT1, ATT2) has been set to (H, H), Ilimit
will be as follows :
Ilimit + 1.0 A 20% + 200 mA
