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TOP250YN-TL Datasheet(PDF) 11 Page - Power Integrations, Inc. |
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TOP250YN-TL Datasheet(HTML) 11 Page - Power Integrations, Inc. |
11 / 52 page TOP242-250 11 M 12/04 DC MAX reduction, the vertical axis represents the magnitude of the DC MAX. Line feed-forward with DCMAX reduction lowers maximum duty cycle from 78% at I L(DC) (+60 µA typical) to 38% at I OV (+225 µA). EXTERNAL CURRENT LIMIT (X) Pin Operation (Y, R and F Packages) When current is drawn out of the EXTERNAL CURRENT LIMIT pin, it works as a voltage source of approximately 1.3 V up to a maximum current of -240 µA (typical). At -240 µA, it turns into a constant current source (refer to Figure 12a). There are two functions available through the use of the EXTERNAL CURRENT LIMIT pin: external current limit and remote ON/OFF. Connecting the EXTERNALCURRENT LIMIT pin and SOURCE pin disables the two functions. In high efficiency applications, this pin can be used to reduce the current limit externally to a value close to the operating peak current by connecting the pin to the SOURCE pin through a resistor. The pin can also be used for remote ON/OFF. Table 2 shows several possible combinations using this pin. See Figure 11 for a description of the functions where the horizontal axis (left hand side) represents the EXTERNAL CURRENT LIMIT pin current. The meaning of the vertical axes varies with function. For those that control the ON/OFF states of the output such as remote ON/OFF, the vertical axis represents the enable/disable states of the output. For external current limit, the vertical axis represents the magnitude of the I LIMIT. Please see graphs in the Typical Performance Characteristics section for the current limit programming range and the selection of appropriate resistor value. MULTI-FUNCTION (M) Pin Operation (P and G Packages) The LINE-SENSE and EXTERNAL CURRENT LIMIT pin functions are combined to a single MULTI-FUNCTION pin for P and G packages. The comparator with a 1 V threshold at the LINE-SENSE pin is removed in this case as shown in Figure 2b. All of the other functions are kept intact. However, since some of the functions require opposite polarity of input current(MULTI-FUNCTIONpin),theyaremutuallyexclusive. Forexample,linesensingfeaturescannotbeusedsimultaneously with external current limit setting. When current is fed into the MULTI-FUNCTION pin, it works as a voltage source of approximately 2.6 V up to a maximum current of +400 µA (typical). At +400 µA, this pin turns into a constant current sink. When current is drawn out of the MULTI-FUNCTION pin, it works as a voltage source of approximately 1.3 V up to a maximum current of -240 µA (typical). At -240 µA, it turns into a constant current source. Refer to Figure 12b. There are a total of five functions available through the use of the MULTI-FUNCTION pin: OV, UV, line feed-forward with DC MAX reduction, external current limit and remote ON/OFF. A short circuit between the MULTI-FUNCTION pin and SOURCE pin disables all five functions and forces TOPSwitch-GX to operate in a simple three terminal mode like TOPSwitch-II. The MULTI-FUNCTION pin is typically used for line sensing by connecting a resistor from this pin to the rectified DC high voltage bus to implement OV, UV and DC MAX reduction with line voltage. In this mode, the value of the resistor determines the line OV/UV thresholds, and the DC MAX is reduced linearly with increasing rectified DC high voltage starting from just above the UV threshold. External current limit programming is implemented by connecting the MULTI-FUNCTIONpintotheSOURCEpinthrougharesistor. However, this function is not necessary in most applications since the internal current limit of the P and G package devices has been reduced, compared to the Y, R and F package devices, to match the thermal dissipation capability of the P and G packages. It is therefore recommended that the MULTI- FUNCTION pin is used for line sensing as described above and not for external current limit reduction. The same pin can also Table 3. Typcial MULTI-FUNCTION Pin Configurations. MULTI-FUNCTION PIN TABLE* Figure Number 30 31 32 33 34 35 36 37 38 39 40 Three Terminal Operation ✓ Under-Voltage ✓ ✓ ✓ Overvoltage ✓ ✓ ✓ Line Feed-Forward (DC MAX) ✓ ✓ Overload Power Limiting ✓ External Current Limit ✓ ✓ ✓ ✓ Remote ON/OFF ✓ ✓ ✓ ✓ ✓ *This table is only a partial list of many LINE-SENSE and EXTERNAL CURRENT LIMIT pin configurations that are possible. |
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