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| 型號(hào)： | 2184LPSTJ |
| 英文描述： | Interface IC |
| 中文描述： | 接口IC |
| 文件頁(yè)數(shù)： | 3/5頁(yè) |
| 文件大?。?/td> | 89K |
| 代理商： | 2184LPSTJ |
Troubleshooting Micro Power Off Mode on élan
TM
SC300/élanSC310 Microcontrollers and Evaluation Boards
3
soon afterwards. If ROMCS occurs in a reasonable
amount of time, then focus on the software
instructions being read by the CPU.
I
Check to make sure that the élanSC300
microcontroller is configured for the desired bus
mode (that is, Full/Maximum ISA, Internal LCD, or
Local Bus) by reading bits 5 and 6 in the Memory
Configuration 1 Register (Index 66h). Refer to
page 68 in the élanSC300 microcontroller data
sheet for a description of how to configure the bus
mode at reset. Note that the timing diagram in
Figure 8 is only for the purposes of demonstrating
when the processor samples the CFG0–CFG1 bits
and is not intended to imply timing sequence
requirements for VCC, RESIN, and IORESET.
These timing requirements are specified on pages
99–101 of the data sheet.
I
If you are having problems with high current in
Micro Power Off mode, then refer to the next section
in this application note for the description of a
known problem with high current on the élanSC300
microcontroller evaluation board. If you are
experiencing a different problem with higher than
expected current, then isolate the VCC power input
that is drawing the current to the élanSC300
microcontroller’s internal power planes. Next, check
the voltage level on each individual signal powered
by (VCCIO) or clamped to (VCC Clamp) that power
plane to determine if that plane is being
back-powered by one or more pins. If you leave
DRAM powered up, then you must also either leave
VMEM powered up or make sure that the
élanSC300 microcontroller’s DRAM control signals
are held at 0 V.
I
If you are still unable to solve your problem, then
you should attempt to isolate the problem. How
many boards and élanSC300 microcontroller chips
are having the problem Could the problem be
isolated to a single board or chip instead of the
design Again, which power pin(s) are drawing
current and which Loop Filters are active What is
the bus mode configuration What is the DRAM
configuration
HIGH CURRENT PROBLEM IN MICRO
POWER OFF MODE ON THE éLANSC300
EVALUATION BOARD
Although this problem is described in reference to the
evaluation board, the information contained here can
also be correlated to other customer-specific
applications if similar symptoms appear.
The problem is defined by a high-current consumption
on the VCC Core and Analog VCC inputs to the
élanSC300 microcontroller, when the VCC core
typically draws between 29 mA and 30 mA and the
AVCC approximately draws between 2
μ
A and 2.5
μ
A.
The normal Micro Power Off mode power consumption
is approximately 4
μ
A for VCC (core) and 19.8
μ
A for
AVCC (see Typical Power Numbers on page 82 of the
élanSC300 microcontroller data sheet). The
élanSC300 evaluation board has exhibited this
problem under three conditions:
1. At initial power-on
2. After pressing the Micro Power Off mode button
twice in a very tight window of time
3. After entering Micro Power Off mode normally and
then pressing the RESET button
I
The initial power-on demonstrates this problem
because the evaluation board powers up in Micro
Power Off mode, with RESIN going High after
approximately 1 s and IORESET kept Low by the
logic until switch SW5 (the Micro Power Off mode
button) is pressed. This is shown on page D-20
(schematic sheet #19) of the élanSC300 and
élanSC310 evaluation board manuals. This does
not allow the microcontroller to power up into
High-Speed mode and properly initialize itself. A
detailed description is provided on page 59 of the
élanSC300 microcontroller data sheet, part of
which states, "The system should not be powered
up directly into Micro Power Off mode. The system
must be allowed to fully power up into High Speed
mode upon initial power application of any power
source."
In the absence of any violation in the power-on tim-
ing specifications, the only external anomaly (other
than the high-current consumption on the VCC core
and Analog VCC) is that the Loop Filters are pow-
ered on to within a general approximation of their
normal operating voltage of between 1 V and 1.6 V.
This is the only external indication that represents
the state of whether or not the internal PLLs are
powered up and running. The conclusion that can
be drawn here is that if the élanSC300 microcon-
troller is not properly initialized and the PLLs are
powered up while in this undefined state, then the
microcontroller will draw an abnormally high level of
current. Because this is documented in the data
sheet, this should be considered a problem unique
to the evaluation board design.
I
The second occurrence of this high-current
condition happens after the élanSC300
microcontroller is properly initialized in High-Speed
mode and then taken into a normal Micro Power Off
mode.
While the chip is in the Micro Power Off mode, if you
press the Micro Power Off mode button twice in a
very tight window of time (approximately between
400 ms and 500 ms), then it is possible to end up in
Micro Power Off mode with the high-current prob-
lem.
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