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ST5R50MTR 数据表(PDF) 10 Page - STMicroelectronics |
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ST5R50MTR 数据表(HTML) 10 Page - STMicroelectronics |
10 / 15 page ST5R00 SERIES 10/15 Figure 30: No Load Input Current vs Temperature Figure 31: No Load Input Current vs Temperature APPLICATION INFORMATION PC LAYOUT AND GROUNDING HINTS The ST5R00 high frequency operation makes PC layout important for minimizing ground bounce and noise. Place external components as close as possible to the device pins. Take care to the Supply Voltage Source connections that have to be very close to the Input of the application. Set the Output Load as close as possible to the output capacitor. If possible, use a Star ground connection with the centre point on the Device Ground pin. To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the ICs ground pin directly to the ground plane. Remember that the LX Switching Current flows through the Ground pin, so, in order to minimize the series resistance that may cause power dissipation and decrease of the Efficiency conversion, the Ground pattern has to be as large as possible. INDUCTOR SELECTION An inductor value of 47µH performs well in most ST5R00 applications. However, the inductance value is not critical, and the ST5R00 will work with inductors in the 33µH to 120µH. Smaller inductance values typically offer a smaller physical size for a given series resistance, allowing the smallest overall circuit dimensions. However, due to higher peak inductor currents, the output voltage ripple (Ipeak x output filter capacitors ESR) also tends to be higher. Circuits using larger inductance values exhibit higher output current capability and larger physical dimensions for a given series resistance. In order to obtain the best application performances the inductor must respect the following condition: - The DC resistance has to be as little as possible, a good value is <0.25 Ω. This choice will reduce the lost power as heat in the windings. - The inductor core must not saturate at the forecast maximum LX current. This is mainly a function of the Input Voltage, Inductor value and Output Current. However, it is generally acceptable to bias the inductor into saturation by as much as 20%, although this will slightly reduce efficiency. In order to calculate this parameter we have to distinguish two cases: 1) When a light load is applied on the output (discontinuous mode operation) the inductor core must not saturate at ILX(max)= (VIN x TON)/L. 2) For heavy load (continuos mode operation) the inductor core must not saturate at ILX(max)= (IOUT x T)/TOFF(min) + (VIN x TON)/2L Where: VIN is the Input Voltage, Ton is the switch on period (typ. 5ms), L is the inductance value, IOUT is the maximum forecast Output Current, T = TON+TOFF(min) and TOFF(min) is the minimum switch off period (typ. 1.7µs), - Choose an inductance value in the 47µH to 82µH range. - For application sensitive to Electromagnetic Interference (EMI), a pot core inductor is recommended. |
类似零件编号 - ST5R50MTR |
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类似说明 - ST5R50MTR |
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