LinkSwitch-XT Design Guide:The LinkSwitch-XT family is designed for low power adapters
and chargers (cell/cordless phones, PDAs, digital cameras,
portable audio etc), as well as auxiliary supplies employed
in applications such as white goods. The ICs combine a high
voltage power MOSFET switch with an ON/OFF controller
in one device. It is completely self-powered from the DRAIN
pin, has a jittered switching frequency for low EMI and is fully
fault protected. Auto-restart limits device and circuit dissipation
during overload, output short circuit and open loop conditions
while hysteretic over-temperature protection disables the
internal MOSFET during thermal faults. EcoSmart? technology
enables designs to easily attain <150 mW no-load consumption.
LinkSwitch-XT is ideal for linear charger replacement circuits
because of its low cost and also because it can meet the efficiency
standards set forth by the California Energy Commission (CEC).
LinkSwitch-XT is designed to operate without the need for a
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primary-side clamp circuit (Clampless?) for output powers
below 2 W (and up to 2.5 W with a bias winding) and thus
dramatically reduces component count and total system cost.
Figure 1 shows a LinkSwitch-XT based 2 W power supply
without a primary-side clamp.