LMD18200QML Datasheet, PDF (11/18 Pages) Texas Instruments – 2.4A, 55V H-Bridge

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FIGURE 6. Bootstrap Circuitry
INTERNAL PROTECTION DIODES
A major consideration when switching current through induc-
tive loads is protection of the switching power devices from
the large voltage transients that occur. Each of the four
switches in the LMD18200 have a built-in protection diode to
clamp transient voltages exceeding the positive supply or
ground to a safe diode voltage drop across the switch.
The reverse recovery characteristics of these diodes, once
the transient has subsided, is important. These diodes must
come out of conduction quickly and the power switches must
be able to conduct the additional reverse recovery current of
the diodes. The reverse recovery time of the diodes protecting
the sourcing power devices is typically only 70 ns with a re-
verse recovery current of 1A when tested with a full 6A of
forward current through the diode. For the sinking devices the
recovery time is typically 100 ns with 4A of reverse current
under the same conditions.
Typical Applications
FIXED OFF-TIME CONTROL
This circuit controls the current through the motor by applying
an average voltage equal to zero to the motor terminals for a
fixed period of time, whenever the current through the motor
exceeds the commanded current. This action causes the mo-
tor current to vary slightly about an externally controlled av-
erage level. The duration of the Off-period is adjusted by the
resistor and capacitor combination of the LM555. In this circuit
the Sign/Magnitude mode of operation is implemented (see
Types of PWM Signals).
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FIGURE 7. Fixed Off-Time Control
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