LB11948T Datasheet, PDF (11/12 Pages) Sanyo Semicon Device – Monolithic Digital IC PWM Constant Current Control 1-2 Phase Excitation Stepping Motor Driver

LB11948T
Usage Notes
Simplified Formulas for Determining Resistor and Capacitor Values
The formulas for setting the rise time (T1) and the fall time (T2) for the RC oscillator are shown below.
T1 ≈ 0.44C⋅ R (s)
T2 ≈ 0.72⋅ (C⋅R⋅100)/(R + 1000) (s)
Set the oscillator frequency using the simplified formulas shown above.
Note that the T2 triangle wave fall time is the noise canceller circuit operating time.
R C circuit waveform
T1 T2
Setting the Constant Current Level
The reference voltage VREF1 and VREF2 can be set by voltage dividing the 1 V regulator output.
The output current is set by the voltage applied to the VREF pins and the resistors RE connected between the E1 and
E2 pins and ground.
The output current is set according to the following equation: I_O = VREF/Re (A)
VREF voltage operating range: 0 to 1 V
E1 pin voltage range: 0 to 1 V
Notes on the VREF Pins
• Since the VREF pins are the input pins for the reference voltage used to set the current, applications must be
designed so that noise that could influence circuit operation does not occur at these pins.
Notes on the Ground Pins
Since this IC switches large currents, the following notes on ground lines must be observed.
• The PCB pattern lines in areas that handle large currents must be as wide as possible so as to have low impedances,
and must be kept as far as possible from the small signal systems.
• The ground terminals on the sensing resistors Re connected to the E pins (E1 and E2) must be connected as close as
possible to the IC GND (pin 21), PGND (pin 22), or DGND (pins 5 and 26) pins as possible.
• The capacitors between V_CC and ground and between V_BB and ground must be as close as possible to the
corresponding V_CC and V_BB pin in the pattern.
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