LT1424-5 Linear Technology, LT1424-5 Datasheet - Page 13

• Manufacturer Part Number: LT1424-5
• Description: Isolated Flyback Switching Regulator with 5V Output
• Manufacturer: Linear Technology

APPLICATIONS
In further contrast to traditional current mode switchers,
V
The dynamic nature of the clamped feedback amplifier
forms an effective track/hold type response, whereby the
V
“held” during the subsequent “switch ON” portion of the
next cycle. This action naturally holds the V
stable during the current comparator sense action (cur-
rent mode switching).
PCB LAYOUT CONSIDERATIONS
For maximum efficiency, switch rise and fall times are
made as short as practical. To prevent radiation and high
frequency resonance problems, proper layout of the com-
ponents connected to the IC is essential, especially the
C
C
pin ripple is generally not an issue with the LT1424-5.
voltage changes during the flyback pulse, but is then
U
INFORMATION
U
V
IN
W
CIRCULATING
FREQUENCY
PATH
HIGH
U
C
voltage
•
Figure 1
•
power paths (primary and secondary). B field (magnetic)
radiation is minimized by keeping output diode, switch pin
and output bypass capacitor leads as short as possible. E
field radiation is kept low by minimizing the length and
area of all traces connected to the switch pin. A ground
plane should always be used under the switcher circuitry
to prevent interplane coupling.
The high speed switching current paths are shown sche-
matically in Figure 1. Minimum lead length in these paths
are essential to ensure clean switching and minimal EMI.
The path containing the input capacitor, transformer pri-
mary, output switch, the path containing the transformer
secondary, output diode and output capacitor are the only
ones containing nanosecond rise and fall times. Keep
these paths as short as possible.
CIRCULATING
FREQUENCY
PATH
HIGH
ISOLATED
LOAD
F
1424-5 F01
V
OUT
LT1424-5
13