TOP414 Power Integrations Inc., TOP414 Datasheet - Page 7

• Manufacturer Part Number: TOP414
• Description: Three-terminal DC to DC PWM Switch
• Manufacturer: Power Integrations Inc.

Key Application Issues
Use a Kelvin connection to the SOURCE pin for the CONTROL
pin bypass capacitor. Use single point grounding techniques at
the SOURCE pin as shown in Figure 8. Use a ceramic high
frequency decoupling capacitor to bypass noise transients which
might appear on the CONTROL pin. The TOP412 and TOP414
have an over current latching shutdown feature. Failure to use
a high frequency decoupling capacitor may allow incidental
noise to accidentally trigger this feature.
Limit peak voltage and ringing on the DRAIN voltage at turn-
off to a safe value. Use a Zener or TVS Zener diode to clamp
the DRAIN voltage.
Do not plug the TOPSwitch device into a “hot” IC socket during
test. External CONTROL pin capacitance may deliver a surge
current sufficient to trigger the shutdown latch which turns the
TOPSwitch off.
Figure 8. Recommended TOPSwitch Layout.
Bias/Feedback
auto-restart/bypass capacitor C5
and/or compensation network
Input
Kelvin-connected
Bias/Feedback
Return
SOURCE
CONTROL
CONTROL pin transient
decoupling capacitor
G PACKAGE
TOP VIEW
Under some conditions, externally provided bias or supply
current driven into the CONTROL pin can hold the TOPSwitch
in one of the 8 auto-restart cycles indefinitely and prevent
starting. Shorting the CONTROL pin to the SOURCE pin will
reset the TOPSwitch. To avoid this problem when doing bench
evaluations, it is recommended that the V
turned on before the DRAIN voltage is applied.
CONTROL pin currents during auto-restart operation are much
lower at low input voltages (< 20 V) which increases the auto-
restart cycle period (see the I
curve).
In some cases, minimum loading may be necessary to keep a
lightly loaded or unloaded output voltage within the desired
range due to the minimum ON-time.
For additional applications information regarding the TOPSwitch
family, refer to Web site, www.powerint.com.
DRAIN
SOURCE
High Voltage
Return
C
vs. Drain Voltage Characteristic
TOP412/414
C
power supply be
PI-2210-102798
4/99
A
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