SM3320-BATT-EV-NOPB Datasheet, PDF (11/21 Pages) Texas Instruments – AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference Design

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Microcontroller Functions
13 Microcontroller Functions
The charge profile is implemented in the current design using a PIC16F722 microcontroller.
13.1 Normal Operation
The flowchart in Figure 16 details the operation of the microcontroller needed to achieve the desired
charging pattern.
Modification to this flowchart can easily be done and programmed to include:
• Modified threshold depending on temperature (if battery temperature information available).
• Timer to maintain high voltage threshold for a certain time before switching to floating charge to
maximize energy stored in the battery.
• Pulse charging during the float charge period.
The microcontroller is programmed using a 10 pin CLE-105 connector (J5). The connections are:
• 1: NC (Not Connected)
• 2: PGD/ICSPDAT
• 3: GND
• 4: PGC/ICSPCLK
• 5: NC
• 6: GND
• 7: +5Vdc
• 8: MCLR!
• 9: GND
• 10: NC
Refer to the Microchip website for proper programming/debugging of the PIC16F family microcontrollers.
13.2 Start-Up Operation
At start-up, the microcontroller needs to assess the PV and battery voltage to verify proper connection and
values.
If the values are within the specified range (correct panel and battery voltage), the microcontroller enables
the charge by releasing the RESET line of the SM72442 chip. If needed, the start-up circuit is turned on
by setting RB5 to ‘1’ (5V) (If the microcontroller used in the application is running below 5V, a level shifting
circuit will be necessary).
Once current begins to flow in the battery the start-up circuit can be released.
While the start-up circuit is enabled, the panel current and voltage are not available through I2C. The
corresponding registers can be read but will not contain the correct values.
13.3 Safety Feature
The microcontroller is programmed by default to stop charging the battery if the output voltage is above
14.5V or below 8V.
SNOSB76C – December 2010 – Revised May 2013
AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference
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