JAJSU64A April 2024 – August 2024 TPS7H4011-SP
PRODMIX
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The input supply to the TPS7H4011 must be well regulated with sufficient capacitor bypassing for proper electrical performance. While a minimum ceramic capacitor of at least 4.7µF effective capacitance near the PVIN and VIN inputs is required, additional bulk capacitance is generally required to handle the high input currents. Similar to the output capacitor selection, when selecting the input capacitors, care should be taken to select capacitors with a sufficient voltage rating, temperature rating, and consideration of any effective capacitance changes due to DC bias effects. The capacitor must also have a ripple current rating greater than the maximum input current ripple as calculated using Equation 18. For this design, ICINrms is calculated to be 5.4A.
The minimum input capacitance can then be calculated by using Equation 19 and selecting a maximum desired input ripple voltage, ∆VINdesired. For this design, a 20mV input voltage ripple maximum is used, resulting in a minimum input capacitance of 300µF.
Note, however, that Equation 19 does not include the effects of ESR on the input ripple voltage. Therefore, additional capacitance is utilized. Specifically, 7x100µF Tantalum capacitors are used along with 2x22µF, 1x10µF, 1x4.7µF, and 3x0.1µF ceramic capacitors are selected for a total input capacitance of 759µF.