908E425 Datasheet, PDF (28/49 Pages) Freescale Semiconductor, Inc – Integrated Quad Half H-Bridge with Power Supply, Embedded MCU, and LIN Serial Communication

FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
HxEN
HxF
Three-Terminal Hall-Effect Sensor
Vs
Sense
Hx
Out
Circuitry
V
GND
GND
Figure 15. Hall-Effect Sensor Input Pin Connected to Three-Pin Hall-Effect Sensor
INTERRUPTS
The Hall-effect sensor input pins are interrupt capable.
How and when an interrupt occurs is dependent on the
operating mode, RUN or Stop.
RUN MODE
In RUN mode the Hall-effect sensor input pin interrupt flag
(HPF) will be set if a state change on the hallflags (HxF) is
detected. The interrupt is maskable with the HPIE bit in the
Interrupt Mask Register. Before enabling the interrupt, the
flag should be cleared in order to prevent a wrong interrupt.
STOP MODE
In STOP mode the Hall-effect sensor input pins are
disabled independent of the state of the HxEN flags.
CYCLIC WAKE-UP
The Hall-effect sensor inputs can be used to wake up the
system. This wake-up function is provided by the cyclic check
wake-up feature of the AWD (Autonomous Watchdog).
If the cyclic check wake-up feature is enabled (AWDCC bit
is set), the AWD switches on the enabled Hall-effect sensor
pins periodically. To ensure that the Hall-effect sensor current
is stabilized after switching on, the inputs are sensed after
~40 µs. If a 1 is detected (I_{Hall sensor} > I_HSCT) and the
interrupt mask bit HPIE is set, an interrupt is performed. This
wakes up the MCU and starts the main voltage regulator.
The wake-up function via this input is available when all
three conditions exist:
• The two-pin Hall-effect sensor input is enabled
(HxEN = 1)
• The cyclic wake-up of the AWD is enabled (AWDCC =
1); see Figure 16
• The Hall-effect sensor input pin interrupt is enabled
(HPIE = 1)
908E425
28
Analog Integrated Circuit Device Data
Freescale Semiconductor