Specification

[AP1034]
016003455-E-01 - 12 - 2016/06

FS : PWM Chopper Frequency Select Terminal
By inputting “H” to the FS input, it is possible to drive the PWM chopper frequency in 77kHz (typ). By
inputting “L” or connecting GND, PWM chopper frequency becomes 39kHz (typ).
Please decide the setting of the FS input “50us” before than the ENABLEB input is set to "L".
Table 8. Settings of PWM chopper frequency select terminal
FS
Condition
L
f
CP
=39kHz(typ)
H
f
CP
=77kHz(typ)
10.2
PWM Constant Current Control

Setting of the Output Current
The frequency of the internal OSC circuit is used to drive a stepper motor in PWM constant current controlling.
The maximum current value (Setting Current = Trip Current) is determined by a sense resistance (R
IS
) for
sensing current and the input voltage to the VREF pin (V
REF
).
Iload (100%) [A]= (V
REF
/8) / R
IS
VREF : PWM constant current setting voltage
RIS : H-Bridge sense resistor
VREF damping ratio : 1/8
Calculation example1：VREF=2.5V, RIS=0.2ohm
Iload (100%)[A] = (2.5 / 8) / 0.2ohm = 1.56A
In the figure below, area shaded in gray is the range of recommended sense resistance value.
Figure 8. Recommended Sense Resistor