33899 Datasheet, PDF (21/26 Pages) Freescale Semiconductor, Inc – Programmable H-Bridge Power IC

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Fault Detection During ON State
While the H-Bridge circuit is in operation (i.e., when a high
side MOSFET is ON), the 33899 is capable of detecting both
shorts to VIGNP and shorts to ground. A short will cause the
appropriate MOSFETs to current limit. The current limit is
active for numerous retry periods until an over-temperature
condition is reached, at which time all outputs are turned
OFF.
All ON-state faults must be present for a period of time that
exceeds the fault time before the 33899 will consider them
valid. Once they are valid, they are latched until the SPI has
reported these faults to the microcontroller via the DO pin and
a logic [1] is written to the FLTCLR bit.
In order for the user to be certain that all detectable ON-
state faults have been reported, a minimum ON time is
required for the low side MOSFET. For example, if the PWM
frequency is 11kHz, ON-state fault detection would not be
guaranteed for duty cycles of less than 11%.
Thermal Shutdown
The H-Bridge has thermal protection circuitry. A thermal
fault sets the thermal shutdown bits (and any other faults that
may be present at that time) and latches off. The H-Bridge will
remain disabled until the microprocessor sets the FLTCLR bit
(refer to Table 8, page 22).
Analog Integrated Circuit Device Data
Freescale Semiconductor
33899
21