TB6608FNG Datasheet, PDF (14/30 Pages) Toshiba Semiconductor – Stepping Motor Driver IC

TB6608FNG
Chopper Control
Turning on the power (chop on) causes a current to flow into the coils. Once the VRF voltage reaches Vref, it is
detected by the comparator and the power is turned off (chop off).
The off timer/counter counts the number of falling edges of the internal CK signal, which is derived from the OSC
signal, and generates the motor-driving PWM signal based on the turn-off time of four CK cycles.
OSC
Internal CK
Off timer counter
Generate PWM
Upper limit:
Vref/R_NF
Coil current
chop on
off
on
off
on
off
on
The upper limit of the current across the motor coil (i.e., the peak current in each excitation mode), I (Limit), can
be calculated as follows:
I (Limit) = Vref/RNF
Vref equals to 0.125 V when TQ is Low, while it equals to 0.5 V when TQ is High.
RNF is the value of resistors used for output current detection. One of those resistors is connected between RFA
and GND, and the other is connected between RFB and GND.
Timing chart may be simplified for the sake of brevity.
14
2014-10-01