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TOP257PN Datasheet(PDF) 7 Page - Power Integrations, Inc. |
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TOP257PN Datasheet(HTML) 7 Page - Power Integrations, Inc. |
7 / 48 page Rev. F 01/09 7 TOP252-262 www.powerint.com PI-4713-021308 DC Input Voltage + - DM S C For R IL = 12 k I LIMIT = 61% CONTROL RIL See Figure 55b for other resistor values (R IL) to select different I LIMIT values. For R IL = 19 k I LIMIT = 37% Figure 8. P/G Package Externally Set Current Limit. reduction, output overvoltage protection (OVP), external current limit adjustment, remote ON/OFF and device reset. A connection to SOURCE pin disables all functions on this pin and makes TOPSwitch-HX operate in simple three terminal mode (like TOPSwitch-II). FREQUENCY (F) Pin (TOP254-258Y, and all E and L packages): Input pin for selecting switching frequency 132 kHz if connected to SOURCE pin and 66 kHz if connected to CONTROL pin. The switching frequency is internally set for fixed 66 kHz operation in the P, G, M package and TOP259YN, TOP260YN and TOP261YN. SIGNAL GROUND (G) Pin (TOP259YN, TOP260YN & TOP261YN only): Return for C pin capacitor and X pin resistor. SOURCE (S) Pin: Output MOSFET source connection for high voltage power return. Primary side control circuit common and reference point. TOPSwitch-HX Family Functional Description Like TOPSwitch-GX, TOPSwitch-HX is an integrated switched mode power supply chip that converts a current at the control input to a duty cycle at the open drain output of a high voltage power MOSFET. During normal operation the duty cycle of the power MOSFET decreases linearly with increasing CONTROL pin current as shown in Figure 9. In addition to the three terminal TOPSwitch features, such as the high voltage start-up, the cycle-by-cycle current limiting, loop compensation circuitry, auto-restart and thermal shutdown, the TOPSwitch-HX incorporates many additional functions that reduce system cost, increase power supply performance and design flexibility. A patented high voltage CMOS technology allows both the high-voltage power MOSFET and all the low voltage control circuitry to be cost effectively integrated onto a single monolithic chip. Three terminals, FREQUENCY, VOLTAGE-MONITOR, and EXTERNAL CURRENT LIMIT (available in Y and E/L packages), two terminals, VOLTAGE-MONITOR and EXTERNAL CURRENT LIMIT (available in M package) or one terminal MULTI-FUNCTION (available in P and G package) have been used to implement some of the new functions. These terminals can be connected to the SOURCE pin to operate the TOPSwitch-HX in a TOPSwitch-like three terminal mode. However, even in this three terminal mode, the TOPSwitch-HX offers many transparent features that do not require any external components: A fully integrated 17 ms soft-start significantly reduces or eliminates output overshoot in most applications by sweeping both current limit and frequency from low to high to limit the peak currents and voltages during start-up. A maximum duty cycle (DC MAX) of 78% allows smaller input storage capacitor, lower input voltage requirement and/or higher power capability. Multi-mode operation optimizes and improves the power supply efficiency over the entire load range while maintaining good cross regulation in multi-output supplies. 1. 2. 3. Figure 9. Control Pin Characteristics (Multi-Mode Operation). PI-4645-041107 CONTROL Current CONTROL Current CONTROL Current I COFF I C03 I C02 I C01 I B I CD1 100 78 55 25 132 66 30 Slope = PWM Gain (constant over load range) Auto-Restart Variable Frequency Mode Low Frequency Mode Multi-Cycle Modulation Jitter Full Frequency Mode |
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