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R0603-DNP Datasheet(PDF) 3 Page - Texas Instruments |
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R0603-DNP Datasheet(HTML) 3 Page - Texas Instruments |
3 / 12 page L PVDD PVDD I = I VBAT 0.8 æ ö ´ ç ÷ ´ è ø L BOOST VBAT (PVDD VBAT) L = I PVDD ´ - ´ ´ f www.ti.com Operation NOTE: The TPA2025D1 has an auto pass-through mode. Under normal operation (EN = HIGH), the boost converter automatically turns off if no audio signal is present at one of the inputs (IN+ or IN-). 2.2 Boost Settings The default voltage for the boost converter is 5.9 V (unloaded) and cannot be changed. If no audio signal is present, the boost converter is automatically disabled. Once the audio signal is present at IN+ and IN-, the boost converter enables automatically, when the output signal exceeds 2 V PEAK. 2.2.1 Boost Terms The following is a list of terms and definitions: C MIN Minimum boost capacitance required for a given ripple voltage on PVOUT (PVDD) L Boost inductor f boost Switching frequency of the boost converter I PVDD Current pulled by the class-D amplifier from the boost converter I PVDD Current pulled by the class-D amplifier from the boost converter I L Current through the boost inductor. PVDD (PVOUT) Supply voltage for the class-D amplifier (Voltage generated by the boost converter output) VBAT (VDD) Supply voltage to the TPA2025D1 (Supply voltage to the EVM). ΔI L Ripple current through the inductor. ΔV Ripple voltage on PVOUT (PVDD) due to capacitance 2.2.2 Changing the Boost Inductor Working inductance decreases as inductor current increases. If the drop in working inductance is severe enough, it may cause the boost converter to become unstable, or cause the TPA2025D1 to reach its current limit at a lower output power than expected. Inductor vendors specify currents at which inductor values decrease by a specific percentage. This can vary by 10% to 35%. Inductance is also affected by dc current and temperature. Inductor current rating is determined by the requirements of the load. The inductance is determined by two factors: the minimum value required for stability and the maximum ripple current permitted in the application. Use Equation 1 to determine the required current rating. Equation 1 shows the approximate relationship between the average inductor current, I L, to the load current, load voltage, and input voltage (IPVDD, PVOUT, and VBAT, respectively.) Insert I PVDD, PVDD, and VBAT into Equation 1 to solve for IL. The inductor must maintain at least 90% of its initial inductance value at this current. (1) The minimum working inductance is 1.3 μH. A lower value may cause instability. Ripple current, ΔI L, is peak-to-peak variation in inductor current. Smaller ripple current reduces core losses in the inductor as well as the potential for EMI. Use Equation 2 to determine the value of the inductor, L. Equation 2 shows the relationships among inductance L, VBAT, PVDD, the switching frequency, f boost, and ΔI L. Insert the maximum acceptable ripple current into Equation 2 to solve for L. (2) 3 SLOU310 – September 2011 TPA2025D1 Audio Power Amplifier Evaluation Module Submit Documentation Feedback Copyright © 2011, Texas Instruments Incorporated |
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