33887 Datasheet, PDF (24/37 Pages) Freescale Semiconductor, Inc – 5.0 A H-Bridge with Load Current Feedback

FUNCTIONAL DEVICE OPERATION
PROTECTION AND DIAGNOSTIC FEATURES
PROTECTION AND DIAGNOSTIC FEATURES
SHORT CIRCUIT PROTECTION
If an output short circuit condition is detected, the power
outputs tri-state (latch-OFF) independent of the input (IN1
and IN2) states, and the fault status output flag is SET logic
LOW. If the D1 input changes from logic HIGH to logic LOW,
or if the D2 input changes from logic LOW to logic HIGH, the
output bridge will become operational again and the fault
status flag will be reset (cleared) to a logic HIGH state.
The output stage will always switch into the mode defined
by the input pins (IN1, IN2, D1, and D2), provided the device
junction temperature is within the specified operating
temperature range.
ACTIVE CURRENT LIMITING
The maximum current flow under normal operating
conditions is internally limited to I_LIM (5.2 A to 7.8 A). When
the maximum current value is reached, the output stages are
tri-stated for a fixed time (t _a) of 20 µs typical. Depending on
the time constant associated with the load characteristics, the
current decreases during the tri-state duration until the next
output ON cycle occurs (see Figures 11 and 14, page 13 and
page 15, respectively).
The current limiting threshold value is dependent upon the
device junction temperature. When -40°C ≤ T_J ≤ 160°C, I_LIM
is between 5.2 A to 7.8 A. When T_J exceeds 160°C, the I_LIM
current decreases linearly down to 4.0 A typical at 175°C.
Above 175°C the device overtemperature circuit detects T_LIM
and overtemperature shutdown occurs (see Figure 9,
page 12). This feature allows the device to remain
operational for a longer time but at a regressing output
performance level at junction temperatures above 160°C.
Output Avalanche Protection
An inductive fly-back event, namely when the outputs are
suddenly disabled and V+ is lost, could result in electrical
overstress of the drivers. To prevent this the V+ input to the
33887 should not exceed the maximum rating during a fly-
back condition. This may be done with either a zener clamp
and/or an appropriately valued input capacitor with
sufficiently low ESR.
OVERTEMPERATURE SHUTDOWN AND
HYSTERESIS
If an overtemperature condition occurs, the power outputs
are tri-stated (latched-OFF) and the fault status flag is SET to
logic LOW.
To reset from this condition, D1 must change from logic
HIGH to logic LOW, or D2 must change from logic LOW to
logic HIGH. When reset, the output stage switches ON again,
provided that the junction temperature is now below the
overtemperature threshold limit minus the hysteresis.
Note Resetting from the fault condition will clear the fault
status flag.
33887
24
Analog Integrated Circuit Device Data
Freescale Semiconductor