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TPS51513RHBT Datasheet(PDF) 22 Page - Texas Instruments |
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TPS51513RHBT Datasheet(HTML) 22 Page - Texas Instruments |
22 / 39 page ![]() CS(eff ) CS DROOP M L L R A R G R - ´ = ´ SLEW SLEW SLEW K V R SR ´ = IMON IMON IMON CS V R K V = ´ ( ) CS MAX CS eff V R I = ´ CS CSINT IMON IMON2 IMON 8 V A R R V ´ ´ ´ = TPS51513 SLUS956A – JUNE 2009 – REVISED FEBRUARY 2010 www.ti.com Step Seven: Set the load line. The load line is set by the droop resistor knowing RL-L and RCS_Eff. (15) RDROOP = 5.23 kΩ. Step Eight: Select the DROOP capacitor. The DROOP capacitor is used to provide high-frequency filtering of the voltage loop. Use values under 100 pF. A higher value provides less jitter for steady-state operation, but slows down the transient response. Step Nine: Calculate RSLEW. RSLEW sets both slew rates: 1. Sleep exit slew rate. 2. Soft-start and soft-stop exit rate is 1/8 of the sleep exit rate Set the sleep rate to 6 mV/ms to allow 20% for tolerances. From Equation 3): (16) In this case, RSLEW is terminated to GND. KSLEW = 1.25x10 9 and V SLEW = 0.45 V. For a slew rate (SR) of 6 mV/ms nominal, 5 mV/mS minimum, RSLEW = 90.9 kΩ. Step Ten: Calculate IMON resistors. From Equation 6, (17) And, where • VCS = 29.8 mV • KIMON = 2mA/mV (18) The IMONC pin is connected to 3.3 V; to allow for tolerances, a full scale value of 3.1 V (VIMON) is desired. Then, RIMON = 47.5 kΩ. In order to increase the accuracy of the current monitor overtemperature the IMON2 pin is provided to match the temperature coefficients of two critical resistors in the circuit. Connect a resistor from IMON2 to VREF. After determining the full-scale voltage on the IMON output (VIMON) and selecting RIMON, the value of RIMON2 resistor is from Equation 7: where • ACSINT = 6 • RIMON2 = 24.3kΩ (19) 22 Submit Documentation Feedback Copyright © 2009–2010, Texas Instruments Incorporated Product Folder Link(s) :TPS51513 |
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