|
|
本帖最后由 超級狗 于 2014-2-18 14:46 编辑
, b9 ~2 t' A; E+ @ j8 o% G) ^
1 H" J& n. L3 R' f. B不一定是這個問題，但您可以參考一下！" e V; }. a7 {7 N
; z& z. ~9 h, ]在我們的設計上，也許不會像這份設計建議中的那麼怕死，用到 22uF 的電容，但至少是 1uF ~ 10uF + 100nF，原理圖中 SD Card 插槽電源只用了 2 個 10nF。
0 U3 n3 x# M3 Q3 ]" U5 h' U \6 c- V G/ Y
SD/MMC Power Supply- V5 A, v: `8 w; k5 V
SD/MMC cards provide a relatively low power storage solution for embedded controllers however implementers often do not pay enough attention to the peak power requirements and inrush currents and may encounter situations where the embedded system resets when an SD/MMC card is inserted or the SD/MMC card may stop talking to the Microcontroller. The power supply circuitry must be able to deal with the momentary inrush current when a card is inserted. This inrush current can be of the order of 200mA. Generally this is handled using large value power supply filter capacitors before and after the voltage regulator. Ignoring the requirements for other components of an embedded system, typical values for the power supply input capacitor are in the range of 220uF to 470uF. Lower value capacitors than have low ESR (Effective Series Resistance) could be use used. A typical value for the filter capacitor after the regulator is 47uF tantalum capacitor.
: t" k# c% v/ X" P# X& t
* p6 n% v% {' U hIn situations where the SD/MMC card socket is not located in close proximity to the regulator filter capacitors, an additional 22uF tantalum capacitor should be placed as close as practical to the SD/MMC card socket between power pin and ground pin of the socket. A 100nF power supply decoupling capacitor should be placed as close as practical to the SD/MMC card socket between power pin and ground pin of the socket.6 ~9 L0 z% V8 z$ O5 c2 K) }
8 Q# o/ v( y4 _( r
 |
|
/1 
发表于 2014-2-18 09:23
QQ好友和群
QQ空间
腾讯微博
腾讯朋友
微信
收藏
支持！
反对！
发表于 2014-2-18 14:43
楼主
