User's Manual

System Overview and Functional Block Descriptions
1322x-LPB Reference Manual, Rev. 1.1
Freescale Semiconductor 3-11
3.8 User Interfaces
This section provides a summary of the user interfaces.
3.8.1 LEDs, Switches, and Reset
For application interface the 1322x-LPB provides:
• Two red LEDs (D1 and D2)are driven by the MCU and controlled by the software application.
• Two pushbuttons (SW1 and SW2) are connected to the MCU GPIO for software application. Only
SW1 has interrupt generation capability, and can be used as an input for low power wake-up.
• Jumper J17 provides a hardware reset capability. Shorting Pin 1 to Pin 2 causes the hardware reset
input to be held low and resets the MC13224/225.
3.8.2 ADC Voltage References
When using the ADC input channels ADC2 and ADC3 (through J2), consider;
• The ADC high voltage reference ADC2_VREFH is tied to SW_VCC through a resistor. This
reference is not absolute and will move as VCC decreases with battery operation.
• A fixed voltage reference for ADC1_VREFH is provided (see Figure 3-12).
— The fixed voltage is 1.5 VDC.
— The LM285M (U17) is programmed via R120 and R121 to provide a constant reference
— The reference can be enabled via jumper J18. This number can also be used to measure current
to the reference circuit.
— This reference is useful for battery operation where a known, fixed high reference voltage for
the ADC is required.
Figure 3-12. ADC Voltage 1.5 VDC Voltage Reference
R1
10K
SW_VCC
1
2
J18
HDR_1X2
R120
120K
1%
R121
24.9K
1%
TP106
1.5V
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
U17
LM285M
ADC1_VREFH