MC34151 MC33151
LAYOUT CONSIDERATIONS
High frequency printed circuit layout techniques are
optimum drive performance, it is recommended that the initial
circuit design contains dual power supply bypass capacitors
imperative to prevent excessive output ringing and
overshoot. Do not attempt to construct the driver circuit
on wire–wrap or plug–in prototype boards. When driving
large capacitive loads, the printed circuit board must contain
a low inductance ground plane to minimize the voltage spikes
induced by the high ground ripple currents. All high current
loops should be kept as short as possible using heavy copper
runs to provide a low impedance high frequency path. For
connected with short leads as close to the V
pin and
CC
ground as the layout will permit. Suggested capacitors are a
low inductance 0.1 µF ceramic in parallel with a 4.7 µF
tantalum. Additional bypass capacitors may be required
depending upon Drive Output loading and circuit layout.
Proper printed circuit board layout is extremely critical
and cannot be over emphasized.
Figure 18. Enhanced System Performance with
Common Switching Regulators
Figure 19. MOSFET Parasitic Oscillations
V
CC
0.1
V
47
in
6
+
–
5.7V
V
in
+
+
+
+
+
+
+
R
g
7
5
2
D
1
TL494
or
TL594
1N5819
4
Series gate resistor R may be needed to damp high frequency parasitic
g
3
oscillations caused by the MOSFET input capacitance and any series
wiring inductance in the gate–source circuit. R will decrease the
g
MOSFET switching speed. Schottky diode D can reduce the driver’s
1
power dissipation due to excessive ringing, by preventing the output pin
from being driven below ground.
The MC34151 greatly enhances the drive capabilities of common switching
regulators and CMOS/TTL logic devices.
Figure 20. Direct Transformer Drive
Figure 21. Isolated MOSFET Drive
+
+
7
Isolation
Boundary
+
4 X
1N5819
+
1N
5819
+
5
3
3
Output Schottky diodes are recommended when driving inductive loads at
high frequencies. The diodes reduce the driver’s power dissipation by
preventing the output pins from being driven above V
and below ground.
CC
7
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA ]
