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KnowledgeBase
296 Posts |
 Posted - 26 Feb 2002 : 16:42:28
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Q: I am testing sleep mode power on my Graphics Client [or Graphics Master] evaluation system. When I disconnect and reconnect the 5V power, my system resets. What am I doing wrong?
There are two ways to supply backup power to the Graphics Client (section 4.1.1 of the Graphics Client User's Manual).
- Connect a permanent 5-12V supply to J5.6 ("Vperm"). This supply is usually a battery but can also be a "permanent" or "uninterruptible" power source. Set JP5 to 1-2
- (see below)
Connect a 3V battery to J3. Set JP5 to 2-3.
In each case, when main power fails, the system will go to sleep, relying on one of those backup power sources to power the real-time clock and DRAM.
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ADS Knowledge Base |
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akidder
1519 Posts |
Posted - 13 Mar 2002 : 17:34:37
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The 3V battery input is not recommended for powering system while asleep.
We are recommending that developers not use the "3V battery" input on the Graphics Client Plus and Graphics Master in new designs. That voltage must remain roughly between 3.0 and 3.2V for normal operation, which typically is too narrow a range for chemical batteries to maintain.
Background:
The GC Plus and GMaster include an electronic switch that selects between the 3V battery input and the 3.3V derived from Vperm/5V (see JP5). The switch is set up such that if the 3.3-Vperm voltage falls below the 3V battery input, the system goes to sleep and begins drawing power from the 3V battery. This also occurs if the 3V battery input rises higher than the 3.3-Vperm voltage. Furthermore, the backup voltage should not fall below 3V, as the DRAM will not be able to maintain itself.
We have found that the 3V battery input is not a practical backup power solution. Upcoming designs will likely reconfigure use of the 3V battery input.
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Drew Kidder
ADS Technology Transfer
Title edited by akidder on 27Mar02 |
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gesslingd
2 Posts |
Posted - 26 Mar 2002 : 11:42:58
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We had decided to use the 3V backup voltage input on Graphics Master. We are using a voltage regulator with adequate accuracy to maintain the voltage at the specified value. So we should be OK. Right?
What do you mean by "reconfiguring" this input? We certainly want our circuit to work correctly with future Graphics Masters. |
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akidder
1519 Posts |
Posted - 27 Mar 2002 : 15:28:51
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Hi Don:
The way you're using the 3V battery input will work. However, it sounds like you're doing the same thing as the Vperm input already does: Vperm runs through a linear regulator to supply sleep current. We recommend using the Vperm input for new designs.
The GMaster and GC Plus are headed in the direction of using the J3 input to power a real-time clock circuit instead of the sleep power circuit. However, future revisions will most likely be backward compatible, allowing you to continue to supply backup power to the system through the 3V input. Please note that this is advance information and is subject to change.
We'll update the title of the response above from "...not recommended for new designs" to "...not recommended for powering system while asleep" to emphasize that future changes will still support this input.
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Drew Kidder
ADS Technology Transfer |
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Supplying backup power to GC+/GMaster
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