Greetings, What is a good way to control the power to a memory module. One of the memory modules (4MB FIFO) that I intend to use consumes 14mA in standby mode, which is one order of magnitude of what I want. Is there a way to turn off power to components and use something in the order of uA instead of mA when not in use?
Thanks,
A
If there is no STBY pin ( I assume there isn't) a mosfet in the ground line will do it....
Were you able to do that ? Can you tell me the method / link for this ?
Karthik Balaguru
It is possible to control by using a transistor in the ground line or i the supply line.
But there are more considerations. What you have to be careful of is wha the other inputs to the memory are doing. I know from experience (man years ago, so technology may have changed a bit) that if you switch th supply side, each input acts as if it is shorted to the ground pin (or ar connected via an internal diode), so it will load every signal that is o the device. You need to be able to set these signals to a logic low (i this case, perhaps a logic high if you are switching the ground) and kee them there while the memory is powered down. If you need the contro signals for other devices while the memory is powered down, you will nee a way to separate the control signal. 30 years ago, I used the CMO CD4050, powered from the same supply as the memory. Its inputs ar floating gates and will tolerate signals beyond the supply rails. Today suppose you could use a voltage level translator.
Actually continuing with the idea, you also need to investigate what th outputs of the memory are going to do in power down- they could also en up loading any signal they are connected to. If memory serves i was usin an open collector data bus on the memory.
-Aubrey
In one case where I wanted to disconnect and power down a component, I simply interposed tristate buffers between the device and the MPU bus. You have to do this on both the inputs and outputs of the device.
There are also bidirectional bus switch packages that might be easier to implement.
Mark Borgerson
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