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SPX2731U-3.3 Datasheet(PDF) 4 Page - Sipex Corporation |
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SPX2731U-3.3 Datasheet(HTML) 4 Page - Sipex Corporation |
4 / 9 page Rev. 12/7/00 SPX2730/31/32/33 APPLICATION HINTS The SPX2730/31/32/33 incorporates protection against over- current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. However, the use of an output capacitor is required in order to insure the stability and the performances. Thermal Consideration Although the SPX2730/31/32/33 offers limiting circuitry for overload conditions, it is necessary not to exceed the maximum junction temperature, and therefore to be careful about thermal resistance. The heat flow will follow the lowest resistance path, which is the Junction-to-case thermal resistance. In order to insure the best thermal flow of the component, a proper mounting is required. Note that the case of the device is electrically connected to the output. The case has to be electrically isolated, a thermally conductive spacer can be used. However do not forget to consider its contribution to thermal resistance. Assuming: VIN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 50 °C/W, θHeatsink Case= 6°C/W, θHeatsink Case = 0.5°C/W, θ JC = 3°C/W Power dissipation under this condition PD = (VIN – VOUT) * IOUT = 7.5W Junction Temperature TJ = TA + PD * ( θCase – HS + θ HS θ JC) For the Control Section TJ = 50 + 7.5*(0.5 + 6=3) = 121.25 °C 121.25 °C < TJ (max) for the Control & Power Sections. In both case reliable operation is insured by adequate junction temperature. Capacitor Requirements The output capacitor is needed for stability and to minimize the output noise. The required value of the capacitor varies with the load. However, a minimum value of 10 µF Aluminum will guarantee stability over load. A tantalum capacitor is recommended for a fast load transient response If the power source has high AC impedance, a 0.1 µF capacitor between input & ground is recommended. This capacitor should have good characteristics up to 250 kHz. Minimum Load Current To ensure a proper behavior of the regulator at light load, a minimum load of 10mA for SPX2730/31/32/33 is required. Adjustable Regulator Design SPX2732/33are adjustable regulators and maybe programmed for any value between 1.25V and 16V using two resistors. The relation between the resistors is given by: R1=R2 (VOUT/1.240 –1) Resistors have a large value up to 1m Ω in order to reduce the current consumption. This might be interesting in the case of widely varying load currents. Error Flag SPX2731/33 features an error indicating either an over current fault or a low input voltage. This flag pulls low when such a problem occurs and may sink 10mA. It is inoperative during thermal shutdown. Enable Input SPX2731/32 features enable input allowing turning ON & OFF the device. EN has been designed to be compatible with TTL/CMOS logic. When the regulator is ON, the current flowing through this pin is approximately 20 µA. SPX2730 Fig.1 Basic Fixed Output Regulator VOUT V IN SPX2732/33 Fig. 2 Adjustable Output Voltage Regulator VOUT V IN 1 2 3 4 5 R 2 R 1 For best results, the total series resistance should be small enough to pass the minimum regulator load current V OUT = VREF X [ 1 + (R1/R2) ] |
Similar Part No. - SPX2731U-3.3 |
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Similar Description - SPX2731U-3.3 |
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