SM3320-BATT-EV-NOPB Datasheet, PDF (6/21 Pages) Texas Instruments – AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference Design

Programmable Modes/Gain Settings
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Figure 7. Boost Gate Drive Signals From SM72442
Figure 8. Switch Nodes in Boost Mode
6 Programmable Modes/Gain Settings
The voltage dividers for the output voltage sensing are set to ensure high resolution of the output voltage
while providing a safe voltage (<5V) for the SM72442 and microcontroller.
The default resistor setting in this reference design sets a full scale of 30V.
The programmable modes of the SM72442 used in this design are as follows:
• VADC2 = 5V (50% of 4sec in BB)
• VADC6 = 5V (startup at 0mA)
• VADC0 = 0V. This value provides an initial output voltage limit of 19V. However, this limit will be
modified by the microcontroller through I2C before the controller begins supplying the battery.
• VADC4 = 5V. Current limiting will be done externally so the max current limit can be set at full scale.
7 Current Sense Gains and Offset
The gain of the current sensing circuit depends on the application. In our system it was set with a gain of
0.44 V/Amps. The gain is set by a pull-down resistor at the output of IOUT (12) and IIN (3) pins of the
SM72295 as stated in the data sheet of the device.
6
AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference
SNOSB76C – December 2010 – Revised May 2013
Design
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