ML4819CP_NL Fairchild Semiconductor, ML4819CP_NL Datasheet - Page 13

• Manufacturer Part Number: ML4819CP_NL
• Manufacturer: Fairchild Semiconductor

Specifications of ML4819CP_NL

• Start-up Supply Current: 600uA
• Operating Supply Voltage (max): 35V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Package Type: PDIP
• Pin Count: 20
• Mounting: Through Hole
• Lead Free Status / RoHS Status: Compliant

CONSTRUCTION AND LAYOUT TIPS
High frequency power circuits require special care during
breadboard construction and layout. Double sided printed
circuit boards with ground plane on one side are highly
recommended. All critical switching leads (power FET,
output diode, IC output and ground leads, bypass
capacitors) should be kept as small as possible. This is to
minimize both the transmission and pickup of switching
noise.
There are two kinds of noise coupling; inductive and
capacitive. As the name implies inductive coupling is
due to fast changing (high di/dt) circulating switching
currents. The main source is the loop formed by Q1, D6,
and
C3–C4. Therefore this loop should be as small as possible,
and the above capacitors should be good, high frequency
types.
The second form of noise coupling is due to fast changing
voltages (high dv/dt). The main source in this case is the
drain of the power FET. The radiated noise in this case can
be minimized by insulating the drain of the FET from the
heatsink and then tying the heatsink to the source of the
FET with a high frequency capacitor.
The IC has two ground pins named PWR GND and Signal
GND. These two pins should be connected together with a
very short lead at the printed circuit board exit point. In
general grounding is very important and ground loops
should be avoided. Star grounding schemes are preferred.
REV. 1.0 10/10/2000
COMP.
SLOPE
I
RSC
Figure 15. Voltage Mode Configuration
2
+
+
+
–
–
–
1V
DUTY CYCLE
+
–
OSC
OSC
0.7V
I
SENSE
PWM B
I
LIM
C
B
T
20
11
7
9
8
FROM U2, R15
R23, C14
C6
FROM
R
V
V
REF
R13
R14
ML4819
13