ML4818CS Micro Linear, ML4818CS Datasheet - Page 9

• Manufacturer Part Number: ML4818CS
• Description: Phase Modulation/Soft Switching Controller
• Manufacturer: Micro Linear

UNDER-VOLTAGE LOCKOUT
On power up, when V
little current (1.1mA typ.) and V
rises above 16V, the IC becomes active and V
enabled and will stay in that condition until V
below 10.2V. (see Figure 12).
THERMAL INFORMATION
The ML4818 is offered in a Power DIP package. This
package features improved thermal conduction through
the leadframe. Much of the heat is conducted through the
center 4 grounded leads. Thermal dissipation can be
improved with this package by using copper area on the
board to function as a heat sink. Increasing this area can
reduce the
power handling capability of the package. Additional
improvement may be obtained by using an external heat
sink (available from Staver).
POWER
DOWN
Figure 13. Supply Current vs. Temperature ( C).
70
68
66
64
62
60
58
56
54
52
50
–75
Figure 12. Under-Voltage Lockout and
INHIBIT
OUTPUTS
JA
(see figures 14 and 15), increasing the
–25
Reference Circuits.
CC
+
–
25
TEMPERATURE
is below 16V, the IC draws very
9V
REF
75
INTERNAL
is disabled. When V
BIAS
+
–
4V
125
TO LOGIC
CIRCUITS
REF
CC
falls
is
175
5V
V
V
24
20
REF
CC
CC
I
APPLICATIONS
The application circuit shown in Figure 16 features the
ML4818 in a primary-side controlled voltage mode
application with voltage feed-forward. Input voltage is
rectified 120VAC (nominal). Feed-forward is provided by
the RAMP pin via the resistor connected to the high
voltage input. Current is sensed through sense transformer
T4.
50
40
30
20
Figure 14. PC Board Copper Area Used as a Heat Sink.
0
Figure 15.
0.2
I
0.4
I : HEAT SINK DIMENSION (INCHES)
0.6
JA
as a Function of I (see figure 15).
0.8
1
2
3
4
5
6
7
8
9
10
11
12
1
0.555"
1.2
24
23
22
21
20
19
18
17
16
15
14
13
1.4
1.6
ML4818
1.8
I
2
9
I