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TOP267VG Datasheet(PDF) 4 Page - Power Integrations, Inc. |
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TOP267VG Datasheet(HTML) 4 Page - Power Integrations, Inc. |
4 / 40 page Rev. E 08/12 4 TOP264-271 www.powerint.com PI-5665-110609 CONTROL Current CONTROL Current CONTROL Current ICOFF IC03 IC02 IC01 IB ICD1 100 78 55 25 132 66 30 Slope = PWM Gain Auto-Restart Variable Frequency Mode Low Frequency Mode Multi-Cycle Modulation Jitter Full Frequency Mode TOP264-271 Functional Description Like TOPSwitch-HX, TOP264-271 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 6. 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 shut- down, the TOP264-271 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 have been used to implement some of the new functions. These terminals can be connected to the SOURCE pin to operate the TOP264-271 in a TOPSwitch- like three terminal mode. However, even in this three terminal mode, the TOP264-271 offers many transparent features that do not require any external components: 1. 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. 2. A maximum duty cycle (DC MAX) of 78% allows smaller input storage capacitor, lower input voltage requirement and/or higher power capability. 3. Multi-mode operation optimizes and improves the power supply efficiency over the entire load range while maintaining good cross regulation in multi-output supplies. 4. Switching frequency of 132 kHz reduces the transformer size with no noticeable impact on EMI. 5. Frequency jittering reduces EMI in the full frequency mode at high-load condition. 6. Hysteretic over-temperature shutdown ensures thermal fault protection. 7. Packages with omitted pins and lead forming provide large drain creepage distance. 8. Reduction of the auto-restart duty cycle and frequency to improve the protection of the power supply and load during open-loop fault, short-circuit, or loss of regulation. 9. Tighter tolerances on I2f power coefficient, current limit reduction, PWM gain and thermal shutdown threshold. The VOLTAGE-MONITOR (V) pin is usually used for line sensing by connecting a 4 M W resistor from this pin to the rectified DC high-voltage bus to implement line overvoltage (OV), under- voltage (UV) and dual-slope line feed-forward with DC MAX reduction. In this mode, the value of the resistor determines the OV/UV thresholds and the DC MAX is reduced linearly with a dual slope to improve line ripple rejection. In addition, it also provides another threshold to implement the latched and Figure 6. Control Pin Characteristics (Multi-Mode Operation). X DC Input Voltage + - D S C CONTROL V RIL RLS 12 k Ω 4 M Ω VUV = IUV × RLS + VV (IV = IUV) VOV = IOV × RLS + VV (IV = IOV) For RLS = 4 MΩ DCMAX@100 VDC = 76% DCMAX@375 VDC = 41% For RIL = 12 kΩ ILIMIT = 61% See Figure 37 for other resistor values (RIL) to select different ILIMIT values. V UV = 102.8 VDC V OV = 451 VDC Figure 5. Package Line-Sense and Externally Set Current Limit. |
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