908E626_12 Datasheet, PDF (26/43 Pages) Freescale Semiconductor, Inc – Integrated Stepper Motor Driver with Embedded MCU and LIN Serial Communication

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
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
Coil Current
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 0.1 kHz to 20 kHz.
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 , for current limit
values). The low side MOSFET switches on again if a rising
edge on the FGEN input was detected (Figure 13).
H-Bridge low side
MOSFET will be switched
off if select current limit is
reached.
Half-bridge
Low Side Output
H-Bridge low side
MOSFET will be turned on
with each rising edge of
the FGEN input.
t (µs)
FGEN Input
(MCU PWM
Signal)
t (µs)
908E626
26
Minimum 50 µs
Figure 13. Half-bridge Current Limitation
t (µs)
Analog Integrated Circuit Device Data
Freescale Semiconductor