C8051F930-DK
Rev. 0.5
21
8. Frequently Asked Questions
1.
Should power be turned off when switching between one-cell and two-cell mode?
Yes, power must be turned off by placing SW5 in the OFF position when switching between one-cell and two-
cell mode. Switching between modes while power is on may result in increased power consumption and
possible damage to low voltage transistors.
2.
I have placed the MCU in Sleep Mode. Why is the supply current greater than 1 µA?
This can be caused by a number of factors. Check the following:
a. Verify that the USB Debug Adapter is not connected to the device. When connected, it can draw
approximately 2–5 µA from the VDD/DC+ supply net.
b. Verify that the P1.5 and P1.6 LEDs are turned off in software (P1.5 and P1.6 set to logic HIGH).
Alternatively, the P1.5 and P1.6 LEDs can be disabled by removing the corresponding shorting blocks
from J8.
c. Verify that the VDD/DC+ Power LED is disabled (remove shorting block from J5).
d. Verify that the shorting block on J15 does not connect the potentiometer negative terminal to GND, since
this would result in continuous current of ~ 300 µA. The shorting block may be removed, or configured to
enable the potentiometer when P1.4 is set to logic LOW. When the potentiometer enable is under
software control, be sure to set P1.4 to logic HIGH prior to placing the device in Sleep Mode.
e. Verify that J7, J13, and J14 do not have shorting blocks installed.
3.
I have been measuring the sleep mode current using the “µA” setting on my multimeter. Why am I no
longer able to connect to the IDE?
When most multimeters are placed in “µA” mode, a large resistance is placed in series with the power supply.
This “current limiting” resistor prevents the MCU from starting up. To measure current during startup, make sure
that the multimeter is configured to its “mA” setting.
Alternatively, a shorting block can be placed on J17 to ensure that the multimeter does not limit current during
startup.
4.
Where can I find a schematic of the C8051F930 Target Board?
A target board schematic can be found in the C8051F930-DK User’s Guide which is available on the
Development Tools CD and is installed in the following folder (by default):
C:\SiLabs\MCU\Documentation\UsersGuides
5.
Which power LED should I use to determine if the MCU is powered?
The VDD/DC+ LED (DS5) should be used to determine if the MCU is powered. If you have applied power to the
board, but the VDD/DC+ LED is not turning on, check the following:
a. Verify that the correct power source (J10, J11) is selected.
b. Verify that J17 has a shorting block.
c. Verify that SW5 is in the ON position.
d. Verify that J5 has a shorting block installed.
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