TOP222G-TL データシートの表示（PDF） - Power Integrations, Inc

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TOP222G-TL

Three-Terminal Off-Line PWM Switch

Power Integrations, Inc 

TOP221-227

Key Application Considerations

General Guidelines

• 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

overload. 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 (∆ID 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 ILIMIT

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

necessary information.

• 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 VC power

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

C

Characteristic curve).

• 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

voltage.

• 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

RDS(ON). 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

∆ID specification as outlined in the General Guidelines

section above.

• 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

DS(ON)

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

spreadsheets.

• Agency Approval: Migrating to TOPSwitch-II may require

agency re-approval.

8

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7/01

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