SM3320-BATT-EV-NOPB Datasheet, PDF (9/21 Pages) Texas Instruments – AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference Design

www.ti.com
Output Current Regulation
10 Output Current Regulation
Current regulation is enforced by a comparator (U11A). The current setting can be switched from a low
current limit to a high current limit with a bit set by the microcontroller. When microcontroller pin RC5 (pin
number 16) is set to high impedance, the high current limit is set. When pin RC5 is set to 0V, the low
current limit is set.
In this design, the high current limit is set to 9A and the low current limit to 0.5A.
11 Voltage Regulation
Voltage regulation with the SM72442 is performed internally. The initial output voltage setting is set
through pin A0 (0-5V). The output voltage set point can then be changed through the I2C communication
interface by setting the register 0x03 bits 20:29 to the required voltage set point and bit 46 to 1.
Figure 13 shows the system performing voltage regulation on the battery at 13.5V.
In addition to the voltage regulation, a comparator (U11B) will reset the SM72442 and cause the DC/DC
converter to shutdown if the output voltage increases beyond the values set by R71 and R72. When the
negative input of the comparator reaches over 5V, the SM72442 controller will be reset. The default value
corresponds to 14.6V battery voltage.
Reg3[29:20]
R₅₁ + R₅₂ + R₅₃
V_setpoint =
1024
x VDDA x
R₅₃
(1)
Figure 13. Charging Waveforms During Float
SNOSB76C – December 2010 – Revised May 2013
AN-2121 SolarMagic™ SM3320-BATT-EV Charge Controller Reference
9
Submit Documentation Feedback
Design
Copyright © 2010–2013, Texas Instruments Incorporated