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TOP224Y Datasheet(PDF) 8 Page - Power Integrations, Inc.
POWERINT [Power Integrations, Inc.]
TOP224Y Datasheet(HTML) 8 Page - Power Integrations, Inc.
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Key Application Considerations
• Keep the SOURCE pin length very short. 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 9.
• Minimize peak voltage and ringing on the DRAIN voltage
at turn-off. Use a Zener or TVS Zener diode to clamp the
drain voltage below the breakdown voltage rating of
TOPSwitch under all conditions, including start-up and
The maximum recommended clamp Zener
voltage for the TOP2XX series is 200 V and the
corresponding maximum reflected output voltage on the
primary is 135 V. Please see Step 4: AN-16 in the 1996-97
Data Book and Design Guide or on our Web site.
• The transformer should be designed such that the rate of
change of drain current due to transformer saturation is
within the absolute maximum specification (
in 100 ns
before turn off as shown in Figure 13). As a guideline, for
most common transformer cores, this can be achieved by
maintaining the Peak Flux Density (at maximum I
current) below 4200 Gauss (420 mT). The transformer
spreadsheets Rev. 2.1 (or later) for continuous and Rev.1.0
(or later) for discontinuous conduction mode provide the
• Do not plug TOPSwitch into a “hot” IC socket during test.
External CONTROL pin capacitance may be charged to
excessive voltage and cause TOPSwitch damage.
• While performing TOPSwitch device tests, do not exceed
maximum CONTROL pin voltage of 9 V or maximum
CONTROL pin current of 100 mA.
• 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. To avoid this problem when doing
bench evaluations, it is recommended that the V
supply be turned on before the DRAIN voltage is applied.
TOPSwitch can also be reset by shorting the CONTROL
pin to the SOURCE pin momentarily.
• CONTROL pin currents during auto-restart operation are
much lower at low input voltages (< 36 V) which increases
the auto-restart cycle time (see the I
vs. DRAIN Voltage
• Short interruptions of AC power may cause TOPSwitch to
enter the 8-count auto-restart cycle before starting again.
This is because the input energy storage capacitors are not
completely discharged and the CONTROL pin capacitance
has not discharged below the internal power-up reset
• 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.
ReplacingTOPSwitch with TOPSwitch-II
There is no external latching shutdown function in
TOPSwitch-II. Otherwise, the functionality of the
TOPSwitch-II devices is same as that of the TOPSwitch family.
However, before considering TOPSwitch-II as a 'drop in'
replacement in an existing TOPSwitch design, the design
should be verified as described below.
The new TOPSwitch-II family offers more power capability
than the original TOPSwitch family for the same MOSFET
Therefore, the original TOPSwitch design must be
reviewed to make sure that the selected TOPSwitch-II
replacement device and other primary components are not over
stressed under abnormal conditions.
The following verification steps are recommended:
• Check the transformer design to make sure that it meets the
specification as outlined in the General Guidelines
• Thermal: Higher power capability of the TOPSwitch-II
would in many instances allow use of a smaller MOSFET
device (higher R
) for reduced cost. This may affect
TOPSwitch power dissipation and power supply efficiency.
Therefore thermal performance of the power supply must
be verified with the selected TOPSwitch-II device.
• Clamp Voltage: Reflected and Clamp voltages should be
verified not to exceed recommended maximums for the
TOP2XX Series: 135 V Reflected/200 V Clamp. Please
see Step 4: AN-16 in the Data Book and Design Guide and
readme.txt file attached to the transformer design
• Agency Approval: Migrating to TOPSwitch-II may require
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