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TNY287DG-TL Datasheet(PDF) 10 Page - Power Integrations, Inc. |
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TNY287DG-TL Datasheet(HTML) 10 Page - Power Integrations, Inc. |
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10 / 26 page  Rev. A 09/12 10 TNY284-290 www.powerint.com capacitor to be effective as a high frequency filter, the capacitor should be located as close as possible to the SOURCE and BYPASS/MULTI-FUNCTIONAL pins of the device. For best performance of the OVP function, it is recommended that a relatively high bias winding voltage is used, in the range of 15 V - 30 V. This minimizes the error voltage on the bias winding due to leakage inductance and also ensures adequate voltage during no-load operation from which to supply the BYPASS/MULTI-FUNCTIONAL pin for reduced no-load consumption. Selecting the Zener diode voltage to be approximately 6 V above the bias winding voltage (28 V for 22 V bias winding) gives good OVP performance for most designs, but can be adjusted to compensate for variations in leakage inductance. Adding additional filtering can be achieved by inserting a low value (10 W to 47 W) resistor in series with the bias winding diode and/or the OVP Zener as shown by R7 and R3 in Figure 16. The resistor in series with the OVP Zener also limits the maximum current into the BYPASS/MULTI-FUNCTIONAL pin. Reducing No-load Consumption As TinySwitch-4 is self-powered from the BYPASS/MULTI- FUNCTIONAL pin capacitor, there is no need for an auxiliary or bias winding to be provided on the transformer for this purpose. Typical no-load consumption when self-powered is <150 mW at 265 VAC input. The addition of a bias winding can reduce this down to <50 mW by supplying the TinySwitch-4 from the lower bias voltage and inhibiting the internal high-voltage current source. To achieve this, select the value of the resistor (R8 in Figure 16) to provide the data sheet DRAIN supply current. In practice, due to the reduction of the bias voltage at low load, start with a value equal to 40% greater than the data sheet maximum current, and then increase the value of the resistor to give the lowest no-load consumption. Audible Noise The cycle skipping mode of operation used in TinySwitch-4 can generate audio frequency components in the transformer. To limit this audible noise generation the transformer should be designed such that the peak core flux density is below 3000 Gauss (300 mT). Following this guideline and using the standard transformer production technique of dip varnishing practically eliminates audible noise. Vacuum impregnation of the transformer should not be used due to the high primary capacitance and increased losses that result. Higher flux densities are possible, however careful evaluation of the audible noise performance should be made using production transformer samples before approving the design. Ceramic capacitors that use dielectrics such as Z5U, when used in clamp circuits, may also generate audio noise. If this is the case, try replacing them with a capacitor having a different dielectric or construction, for example a film type. TinySwitch-4 Layout Considerations Layout See Figure 17 for a recommended circuit board layout for TinySwitch-4. Single Point Grounding Use a single point ground connection from the input filter capacitor to the area of copper connected to the SOURCE pins. Bypass Capacitor (C BP) The BYPASS/MULTI-FUNCTIONAL pin capacitor must be located directly adjacent to the BYPASS/MULTI-FUNCTIONAL and SOURCE pins. If a 0.1 μF bypass capacitor has been selected it should be a high frequency ceramic type (e.g. with X7R dielectric). It must be placed directly between the ENABLE and SOURCE pins to filter external noise entering the BYPASS pin. If a 1 μF or 10 μF bypass capacitor was selected then an additional 0.1 μF capacitor should be added across BYPASS and SOURCE pins to provide noise filtering (see Figure 17). ENABLE/UNDERVOLTAGE Pin Keep traces connected to the ENABLE/UNDERVOLTAGE pin short and, as far as is practical, away from all other traces and nodes above source potential including, but not limited to, the bypass, drain and bias supply diode anode nodes. Primary Loop Area The area of the primary loop that connects the input filter capacitor, transformer primary and TinySwitch-4 should be kept as small as possible. Primary Clamp Circuit A clamp is used to limit peak voltage on the DRAIN pin at turn-off. This can be achieved by using an RCD clamp or a Zener (~200 V) and diode clamp across the primary winding. To reduce EMI, minimize the loop from the clamp components to the transformer and TinySwitch-4. Thermal Considerations The SOURCE pins are internally connected to the IC lead frame and provide the main path to remove heat from the device. Therefore all the SOURCE pins should be connected to a copper area underneath the TinySwitch-4 to act not only as a single point ground, but also as a heat sink. As this area is connected to the quiet source node, this area should be maximized for good heat sinking. Similarly for axial output diodes, maximize the PCB area connected to the cathode. Peak Output Power Table Product 230 VAC ± 15% 85-265 VAC I LIMIT-1 I LIMIT I LIMIT+1 I LIMIT-1 I LIMIT I LIMIT+1 TNY284P 9.1 W 10.9 W 9.1 W 7.1 W 8.5 W 7.1 W TNY285P 10.8 W 12 W 15.1 W 8.4 W 9.3 W 11.8 W TNY286P 11.8 W 15.3 W 19.4 W 9.2 W 11.9 W 15.1 W TNY287P 15.1 W 19.6 W 23.7 W 11.8 W 15.3 W 18.5 W TNY288P 19.4 W 24 W 28 W 15.1 W 18.6 W 21.8 W TNY289P 23.7 W 28.4 W 32.2 W 18.5 W 22 W 25.2 W TNY290P 28 W 32.7 W 36.6 W 21.8 W 25.4 W 28.5 W Table 3. Minimum Practical Power at Three Selectable Current Limit Levels. |
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