Texas Instruments TPS65020 Power Management IC - Toradex

TPS65020SLVS607C –SEPTEMBER 2005–REVISED SEPTEMBER 2011www.ti.comLDO_CTRL. Register Address: 08h (read/write)Default Value: 23hLDO_CTRL B7 B6 B5 B4 B3 B2 B1 B0Bit name andfunctionEquation 4 calculates the maximum inductor current under static load conditions. The saturation current of theinductor should be rated higher than the maximum inductor current as calculated with Equation 4. This is neededbecause during heavy load transient the inductor current rises above the value calculated under Equation 4.1 VoutI Vout VinL L ƒ(4)I Lmax I outmax I L2LDO2_2 LDO2_1 LDO2_0 LDO1_2 LDO1_1 LDO1_0Default 0 1 0 0 1 1Default valueloaded by:UVLO UVLO UVLO UVLO UVLO UVLORead/Write R/W R/W R/W R/W R/W R/WThe LDO_CTRL registers can be used to set the output voltage of LDO1 and LDO2.LDO1 OUTPUTLDO1_2 LDO1_1 LDO1_0 LDO2_2 LDO2_1 LDO2_0VOLTAGELDO2 OUTPUTVOLTAGE0 0 0 1 V 0 0 0 1 V0 0 1 1.05 V 0 0 1 1.05 V0 1 0 1.1 V 0 1 0 1.1 V0 1 1 1.3 V 0 1 1 1.3 V1 0 0 1.8 V 1 0 0 1.8 V1 0 1 2.5 V 1 0 1 2.5 V1 1 0 3 V 1 1 0 3 V1 1 1 3.3 V 1 1 1 3.3 VDESIGN PROCEDUREInductor Selection for the DC-DC ConvertersEach of the converters in the TPS65020 typically use a 3.3 μH output inductor. Larger or smaller inductor valuesare used to optimize the performance of the device for specific operation conditions. The selected inductor has tobe rated for its dc resistance and saturation current. The dc resistance of the inductance influences directly theefficiency of the converter. Therefore, an inductor with lowest dc resistance should be selected for highestefficiency.For a fast transient response, a 2.2-μH inductor in combination with a 22-μF output capacitor is recommended.with:f = Switching Frequency (1.5 MHz typical)L = Inductor ValueΔI L = Peak-to-Peak inductor ripple currentI LMAX = Maximum Inductor currentThe highest inductor current occurs at maximum Vin.Open core inductors have a soft saturation characteristic, and they can usually handle higher inductor currentsversus a comparable shielded inductor.A more conservative approach is to select the inductor current rating just for the maximum switch current of theTPS65020 (2 A for the VDCDC1 and VDCDC2 converters, and 1.3 A for the VDCDC3 converter). The corematerial from inductor to inductor differs and has an impact on the efficiency especially at high switchingfrequencies.38 Submit Documentation Feedback Copyright © 2005–2011, Texas Instruments IncorporatedProduct Folder Link(s) : TPS65020(5)