908E626_09 Datasheet, PDF (26/44 Pages) Freescale Semiconductor, Inc – Integrated Stepper Motor Driver with Embedded MCU and LIN Serial Communication

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
HBx_L — Low Side On / Off Bits
These read / write bits turn on the low side MOSFETs.
Reset clears the HBx_L bits.
• 1 = Low side MOSFET turned on for half-bridge output
x.
• 0 = Low side MOSFET turned off for half-bridge output
x.
HBx_H — High Side On/Off Bits
These read / write bits turn on the high side MOSFETs.
Reset clears the HBx_H bits.
• 1 = High side MOSFET turned on for half-bridge output
x.
• 0 = High side MOSFET turned on for half-bridge output
x.
HALF-BRIDGE CURRENT LIMITATION
Each low side MOSFET offers a current limit or constant
current feature. This features is realized by a pulse width
modulation on the low side MOSFET. The pulse width
modulation on the outputs is controlled by the FGEN input
and the load characteristics. The FGEN input provides the
PWM frequency, whereas the duty cycle is controlled by the
load characteristics.
The recommended frequency range for the FGEN and the
PWM is 0.1kHz to 20kHz.
Functionality
Each low side MOSFET switches off if a current above the
selected current limit was detected. The 908E626 offers five
different current limits (refer to Table 8, page 30, for current
limit values). The low side MOSFET switches on again if a
rising edge on the FGEN input was detected (Figure 13).
908E626
26
Analog Integrated Circuit Device Data
Freescale Semiconductor