TOP209

Use a Kelvin connection to the SOURCE pin for the CONTROL pin bypass capacitor 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.

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_C power supply be 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 autorestart cycle period (see the I_C vs. Drain Voltage 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 (VC_(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.

For additional applications information regarding the TOPSwitch family, refer to AN-14 in the 1996-97 Data Book and Design Guide or on our Web site.

The TOP209/210 implements all functions necessary for an off-line switched mode control system: high voltage N-channel power MOSFET with controlled turn-on gate driver, voltage mode PWM controller with integrated oscillator, high voltage start-up bias circuit, bandgap derived reference, bias shunt regulator/error amplifier for loop compensation and fault protection circuitry. Compared to discrete MOSFET and controller or self oscillating (RCC) switching converter solutions, a TOPSwitch integrated circuit can reduce total cost, component count, size, weight and at the same time increase efficiency and system reliability. The TOP209/210 are intended for 100/110/230 VAC off-line Power Supply applications in the 0 to 8 W (0 to 5 W universal) range.