) J* {/ F7 L1 v5 x7 J* \8 Y& x4 @之所以會用到 560Ω 這麼大的電阻,個人的推測如下:; u8 T( Q. T' ?$ w
根據 Ramtron 的 Application Note 說,如果你用的 Backup Battery 是一次電池(不可充電),則逆向的倒灌電流 UL 有規定(避免充電充到爆炸)。以 3.3V 或 5V 的 VREG 電壓,Ramtron 建議要串 2 個 1.3KΩ 的電阻。(Ramtron 的 IC 已內建,請參考下列附圖及原文): f+ [2 h; c5 Z j4 k
5 w6 b8 w8 t, p
UL Compliance; o* o* D+ I4 Z
Users of primary batteries (non-rechargeable) need assurance that the charging circuit has low reverse current when off and that it also has a protective resistor in series with the battery. This limits the charge current in the event that a malfunction in the charging circuit that would cause excessive battery current. The circuit diagram below shows two 1.3K ohm resistors in series with the P-ch current source. There are no other elements in the path to the VBAK pin. . N/ {& }( a# G: b. g 7 U6 Y9 c* w. T4 V此線路應該是大家在「天下文章一大抄」之後,誤把 560Ω 的電阻值也給抄進去了!