11

LT1160/LT1162

+

+

IN TOP

IN BOTTOM

BOOST

T GATE DR

T GATE FB

T SOURCE

B GATE DR

B GATE FB

LT1160

HV

1160 F02

12V

REF PWM

OUT A

OUT A

Figure 2. Adding Synchronous Switching to a Step-Down Switching Regulator

Motor Drive Applications

In applications where rotation is always in the same

direction, a single LT1160 controlling a half-bridge can be

used to drive a DC motor. One end of the motor may be

connected either to supply or to ground as seen on Figure

3. A motor in this configuration is controlled by its inputs

which give three alternatives: run, free running stop (coast-

ing) and fast stop (“plugging” braking, with the motor

shorted by one of the MOSFETs).

To drive a DC motor in both directions the LT1162 can be

used to drive an H-bridge output stage. In this configura-

tion the motor can be made to run clockwise, counter-

clockwise, stop rapidly (“plugging” braking) or free run

(coast) to a stop. A very rapid stop may be achieved by

reversing the current, though this requires more careful

design to stop the motor dead. In practice a closed-loop

control system with tachometric feedback is usually

necessary.

The motor speed in these examples can be controlled by

switching the drivers with pulse width modulated square

waves. This approach is particularly suitable for micro-

computers/DSP control loops.

Figure 3. Driving a Supply Referenced Motor

BOOST

T GATE DR

T GATE FB

T SOURCE

B GATE DR

B GATE FB

PGND

LT1160

12V

1160 F03

HV

+

IN TOP

IN BOTTOM