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RC5061 数据表(PDF) 16 Page - Fairchild Semiconductor |
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RC5061 数据表(HTML) 16 Page - Fairchild Semiconductor |
16 / 18 page RC5061 PRODUCT SPECIFICATION 16 REV. 1.0.0 7/6/00 Appendix Worst-Case Formulae for the Calculation of Cout, R7, and Cin (Circuit of Figure 1 only) The following formulae design the RC5061 for worst-case operation, including initial tolerance and temperature depen- dence of all of the IC parameters (initial setpoint, reference tolerance and tempco, active droop tolerance, current sensor gain), the initial tolerance and temperature dependence of the MOSFET, and the ESR of the capacitors. The following information must be provided: VT+, the value of the positive transient voltage limit; |VT-|, the absolute value of the negative transient voltage limit; IO, the maximum output current; Vnom, the nominal output voltage; Vin, the input voltage (typically 5V); ESR, the ESR of the ouput caps, per cap (44m Ω for the Sanyo parts shown in this datsheet); RD, the on-resistance of the MOSFET (10mΩ for the FDB7030); ∆R D, the tolerance of the current sensor (usually about 67% for MOSFET sensing, including temperature). Irms, the rms current rating of the input caps (2A for the sanyo parts shown in this datasheet.) The value of R7 must be ≤ 8.3KΩ. If a greater value is calcu- lated, RD must be reduced. Number of capacitors needed fo Cout = the greater of: Example: Suppose that the transient limits are ±134mV, cur- rent I is 14.2A, and the nominal voltage is 2.000V, using MOSFET current sensing and the usual caps. We have VT+ = |VT-| = 0.134, IO = 14.2, Vnom = 2.000, and ∆RD = 0.67. We calculate: Since X > Y, we choose X, and round up to find we need 5 capacitors for COUT. 2 Irms Vin Vnom Vin Vnom * IO Cin – = 50 * 10 -6 IO* RD * (1 + ∆RD) * 1.10 R7 = VT- ESR * IO ESR * IO X= 18 * R5 * 1.1 14400 * IO * RD Y or VT+ –0.004 * Vnom + = 2 5 2.000 5 2.000 * 14.2 Cin 2 3.47 ⇒ 4 caps = – = = = 5.2K Ω 50 * 10-6 14.2 * 0.010 * (1 + 0.67) * 1.0 R5 4.28 18 * 10400 * 1.1 14400 * 14.2 * 0.020 0.134 – 0.004 * 2.000 0.044 * 14.2 Y = + = 4.66 0.134 0.044 * 14.2 X = = |
类似零件编号 - RC5061 |
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类似说明 - RC5061 |
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