LB11948T_10 Datasheet, PDF (11/13 Pages) Sanyo Semicon Device – PWM Constant Current Control 1-2 Phase Excitation Stepping Motor Driver

LB11948T
Usage Notes
(1) Simple Formulas for Determining Resister and Capacitor Values
The formula for setting the rising time (T1) and the falling time (T2) for the RC oscillator are shown below. (Refer to
Fig. 1)
T2
V2
V1
T1
Fig. 1
Formulas
Oscillation period T = T1+T2 (sec)
Threshold voltages V1 = ((VCC - Vset1) × 10.7k/48.7k) + Vset1 (V)
V2 = ((VCC - Vset2) × 42.7k/80.7k) + Vset2 (V)
Vset1 : VCE voltage of transistor for internal comparator hysteresis = 0.05V
Vset2 : VCE voltage of reference resistance switching transistor of oscillation circuit = 0.1V
When charging : T1 = -C × R × ln {(VCC - V2)/(VCC - V1)} (sec)
When discharging : T2 = -C × Rin × ln (V1/V2) (sec)
Rin : Internal discharge resistance of the CR pin1.3kΩ
C : External capacitor
R : External resistor
Oscillation frequency Fc = 1/T (Hz)
The T2 fall time serves as the noise canceling time (Tn). This time is a forced-on time for the output, and the output is
not turned off even when the E pin voltage is higher than the sense voltage that has been preset by VREF.
No.7947-11/13