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TNY263-268 PI-2643-030701CLOCKOSCILLATORSOURCESRQDCMAXBYPASS(BP) + - VILIMITFAULTPRESENTCURRENT LIMITCOMPARATORENABLELEADINGEDGEBLANKINGTHERMALSHUTDOWN+ - REGULATORBYPASS PINUNDER-VOLTAGETENABLE/ UNDER- VOLTAGE(EN/UV) Q240 μA50 μALINE UNDER-VOLTAGERESETAUTO- RESTARTCOUNTERJITTERCURRENTLIMIT STATEMACHINE5.8 V4.8 V(S) DRAIN(D) 5.8 V1.0 V + V1.0 V6.3 V Figure 2. Functional Block Diagram. Pin Functional Description DRAIN (D) Pin: Power MOSFET drain connection. Provides internal operating current for both start-up and steady-state operation. BYPASS (BP) Pin: Connection point for a 0.1 μF external bypass capacitor for the internally generated 5.8 V supply. ENABLE/UNDER-VOLTAGE (EN/UV) Pin: This pin has dual functions: enable input and line under-voltage sense. During normal operation, switching of the power MOSFET is controlled by this pin. MOSFET switching is terminated when a current greater than 240 μA is drawn from this pin. This pin also senses line under-voltage conditions through an external resistor connected to the DC line voltage. If there is no external resistor connected to this pin, TinySwitch-II detects its absence and disables the line undervoltage function. PI-2685-101600EN/UVDSSS (HV RTN) S (HV RTN)BPP Package (DIP-8B) G Package (SMD-8B) 8571423 Figure 3. Pin Configuration. SOURCE (S) Pin: Control circuit common, internally connected to output MOSFET source. SOURCE (HV RTN) Pin: Output MOSFET source connection for high voltage return. 2 G 4/05 TNY263-268 TinySwitch-II Functional Description TinySwitch-II combines a high voltage power MOSFET switch with a power supply controller in one device. Unlike conventional PWM (pulse width modulator) controllers, TinySwitch-II uses a simple ON/OFF control to regulate the output voltage. The TinySwitch-II controller consists of an oscillator, enable circuit (sense and logic), current limit state machine, 5.8 V regulator, BYPASS pin under-voltage circuit, over- temperature protection 更多：https://www.bmcx.com/ , current limit circuit, leading edge blanking and a 700 V power MOSFET. TinySwitch-II incorporates additional circuitry for line under-voltage sense, auto-restart and frequency jitter. Figure 2 shows the functional block diagram with the most important features. Oscillator The typical oscillator frequency is internally set to an average of 132 kHz. Two signals are generated from the oscillator: the maximum duty cycle signal (DCMAX) and the clock signal that indicates the beginning of each cycle. The TinySwitch-II oscillator incorporates circuitry that introduces a small amount of frequency jitter, typically 8 kHz peak-to-peak, to minimize EMI emission. The modulation rate of the frequency jitter is set to 1 kHz to optimize EMI reduction for both average and quasi-peak emissions. The frequency jitter should be measured with the oscilloscope triggered at the falling edge of the DRAIN waveform. The waveform in Figure 4 illustrates the frequency jitter of the TinySwitch-II. Enable Input and Current Limit State Machine The enable input circuit at the EN/UV pin consists of a low impedance source follower output set at 1.0 V. The current through the source follower is limited to 240 μA. When the current out of this pin exceeds 240 μA, a low logic level (disable) is generated at the output of the enable circuit. This enable circuit output is sampled at the beginning of each cycle on the rising edge of the clock signal. If high, the power MOSFET is turned on for that cycle (enabled). If low, the power MOSFET remains off (disabled). Since the sampling is done only at the beginning of each cycle, subsequent changes in the EN/UV pin voltage or current during the remainder of the cycle are ignored.