User's Manual

System Overview and Functional Block Descriptions
1322x-LPB Reference Manual, Rev. 1.1
3-10 Freescale Semiconductor
• SW_VCC is provided on the J2 GPIO Pin Header
• SW_VCC also powers U17 the voltage reference for ADC operation.
Figure 3-11. Switched VCC for Peripheral Devices
3.7.2 Measuring Current
The 1322x-LPB provides three primary points for current measurement:
• Total current to the board - reference Figure 3-11. R68 can be removed and current can be
measured between TP29 and TP47.
• Total current to the MC13224/225 - reference Figure 3-7. R65 can be removed and current can be
measured through jumper J16.
• ADC voltage reference current - reference Figure 3-12. Voltage reference U17 is enabled via J18;
current can be measured through this jumper.
3.7.3 Other Low Power Considerations
When designing low power operation, consider:
• Indicator LEDs D1 and D2 are connected to ground not VCC, so as to not put GPIO high during
low lower mode.
• The GPIO connector (J2) provides access and connectivity to the MC13224/225
— SW_VCC is provided.
— No peripheral device should pull a GPIO high during low power mode
— Signal SWITCH1 is connected to KBI_4 and can be used as a wake-up interrupt to the
MC13224/225. See the CRM chapter of the
MC13224/225 Reference Manual.
— Signal SWITCH2 is connected to KBI_0 and can be used as a wake-up signal from the
MC13224/225 to an external device. See the CRM chapter of the
MC13224/225 Reference
Manual
.
• The UART1 connector (J3) provides direct access to the MC13224/225 GPIO. If low power mode
is enabled and UART1 is connected to an external device, extraneous high leakage current can
occur if any of the UART1 signals is driven high.
KBI_3
SW_VCC
TP32
R68
0R
TP47
VCCTP29
C56
4.7uF
Q2
FDV302
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