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TPS63021DSJT Datasheet(PDF) 16 Page  Texas Instruments 


TPS63021DSJT Datasheet(HTML) 16 Page  Texas Instruments 
16 / 24 page OUT OUT IN1 OUT IN1 I V (V  V ) I1 = + 0.8 2 x V x f x L OUT OUT IN2 x OUT IN2 IN2 OUT V x I V (V  V ) I2 = + 0.8 x V 2 x V x f x L H F × L × 10 = C OUT TPS63020 TPS63021 SLVS916 – APRIL 2010 www.ti.com maximum input voltage. In Equation 3 the minimum inductance, L2, for boost mode operation is calculated. The recommended minimum inductor value is either L1 or L2, whichever is higher. As an example, a suitable inductor for generating 3.3V from a LiIon battery with a battery voltage range from 2.5V up to 4.2V is 1.5mH. The recommended inductor value range is between 1.5mH and 4.7mH. This means that at high voltage conversion rates, higher inductor values offer better performance. With the chosen inductance value, the peak current for the inductor in steady state operation can be calculated. Equation 4 shows how to calculate the peak current I1 in step down mode operation and Equation 5 shows how to calculate the peak current I2 in boost mode operation. (4) (5) In both equations, f is the minimum switching frequency. VIN2 is the minimum input voltage. The critical current value for selecting the right inductor is the higher value of I1 and I2 . Consideration must be given to the load transients and error conditions that can cause higher inductor currents. This must be taken into account when selecting an appropriate inductor. The following inductor series from different suppliers have been used with TPS6302x converters: Table 2. List of Inductors VENDOR INDUCTOR SERIES Coilcraft XFL4020 Toko FDV0530S CAPACITOR SELECTION Input Capacitor At least a 10mF input capacitor is recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit. A ceramic capacitor placed as close as possible to the VIN and PGND pins of the IC is recommended. Bypass Capacitor To make sure that the internal control circuits are supplied with a stable low noise supply voltage, a capacitor can be connected between VINA and GND. Using a ceramic capacitor with a value of 0.1mF is recommended. The value of this capacitor should not be higher than 0.22mF. If no capacitor is used at VINA, VINA should be connected directly to VIN. Output Capacitor For the output capacitor, use of small ceramic capacitors placed as close as possible to the VOUT and PGND pins of the IC is recommended. If, for any reason, the application requires the use of large capacitors which can not be placed close to the IC, use a smaller ceramic capacitor in parallel to the large capacitor. The small capacitor should be placed as close as possible to the VOUT and PGND pins of the IC. To get an estimate of the recommended minimum output capacitance, Equation 6 can be used. (6) A capacitor with a value in the range of the calculated minimum should be used. This is required to maintain control loop stability. There are no additional requirements regarding minimum ESR. There is also no upper limit for the output capacitance value. Larger capacitors will cause lower output voltage ripple as well as lower output voltage drop during load transients. 16 Submit Documentation Feedback Copyright © 2010, Texas Instruments Incorporated Product Folder Link(s): TPS63020 TPS63021 
