8.3.4.4 On-State Diagnostics (OLA) - SPI Variant Only
Device state: ACTIVE - high-side
recirculation
Mechanism and threshold: On-state
diagnostics (OLA) can detect an open load detection in the ACTIVE state during high-side
recirculation. This includes high-side load connected directly to VM or through a
high-side FET on the other half-bridge. During a PWM switching transition, the inductive
load current re-circulates into VM through the HS body diode when the LS FET is turned
OFF. The device looks for a voltage spike on OUTx above VM during the brief dead time,
before the HS FET is turned ON. To observe the voltage spike, this load current needs to
be higher than the pull down current (IPD_OLA) on the output asserted by the
FET driver. Absence of this voltage spike for "3" consecutive re-circulation switching
cycles indicates a loss of load inductance or increase in load resistance and is
detected as an OLA fault.
Action:
nFAULT pin is asserted low
Output - normal function
maintained
IPROPI pin - normal function
maintained
Reaction configurable between latch
setting and retry setting. In retry setting, OLA fault is automatically cleared with the
detection of "3" consecutive voltage spikes during re-circulation switching
cycles.
This monitoring is optional and can be disabled.
Note:
OLA is not supported for low-side loads (low-side recirculation).
CLR_FAULT command can clear this fault (recorded in the STATUS1 register) only if the direction commanded is aligned with
direction during which the fault was detected.