ML4411/ML4411A
+5V
R1
VCC2
4
1K
1/6
IC1
TO ML4411
PIN 16
16K
1/6
IC1
ML4411
PIN 17
–
INHIBIT N3
A6
D1
P3
C1
5
P
+
D2
R2
ML4411A ONLY
Q2
1/6
IC1
TO ML4411
PIN 18
C2
Figure 13. Alternate cross-conduction prevention for
ML4411A
Figure 11. Analog Start-up Circuit
In Condition 2 above, the P-Channel MOSFET is pulled up
inside the ML4411 with a 16Ký resistor. If the current
through C(CGp) is greater than V Þ 16K when the
TH
N-FET turns on, the P-FET could turn on simultaneously,
causing cross-conduction. Adding R1 as shown in Figure
14 eliminates this. The size of R1 will depend on the fall
time of the phase voltage, and the size of the C(DGp). D1
may be needed for high power applications to limit the
negative current pulled (through C(DGn)) out of the
substrate diode in the ML4411 when P-FET turns off.
–
A1
TO ML4411
PIN 20
+
R3
C3
R4
+12V
VCC2
–
R5
TO ML4411
PIN 28
A1
+
R1
R6
RG(P)
P
C(DGp)
C(DGn)
SYMBOL VALUE
SYMBOL
R4
VALUE
100Ký
50Ký
50Ký
3.3µF
A1
LM358
74HC14
IN4148
1Mý
N
IC1
D1, D2
R1
R5
RG(N)
D1
R6
C1
R2
1Mý
C2
3.3µF
R3
100Ký
C3
0.47µF
Figure 14. Causes of Cross-conduction
Adding a series damping resistor to the N-FET gate (RGn)
will slow the fall time. The damping resistor should be
low enough to:
Figure 12. Analog Speed Control
1. When transitioning from mode 0 to mode A (see table
1) P3 goes from on to off at the same time N3 goes
from off to on. If the P3 turns off slowly and N3 turns
on quickly, cross-conduction may occur. This condition
has been prevented inside the IC on the ML4411A
through the addition of comparator A6 on the P3
output (Figure 9). This comparator may cause an
oscillation when the N3 switches on due to the
capacitive coupling effect described below pulling the
P3 pin below VCC2-1.4V. To avoid this, use the circuit
in Figure 13.
Avoid turning on the N-Channel gate when the PNP
turns on via the same mechanism outlined in condition
2 above
Not severely increase the switching losses in the N-FET
UNIPOLAR OPERATION
Unipolar mode offers the potential advantage of lower
motor drive cost by only requiring the use of 3 transistors
to drive the motor. The ML4411 will operate in unipolar
mode (Figure 15) provided the following precautions are
taken:
2. When the MOSFET in the same phase switches on gate
current flows due to capacitive coupling of current
through the MOSFET’s drain to gate capacitance. This
could cause the device that was off to be turned on.
1. The IC supplies should not exceed 12V + 10%.
2. The phase pins on the IC should not exceed the
supply voltage.
11
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
