SAMA5D2 Typical Application Example

A detailed implementation of the previously mentioned solution is presented in Figure . This board uses the USB port to charge the Li-Ion battery through the MCP73871, which also supplies the load current for the PMIC.

The charge current is established using a single resistor connected to the PROG1 pin, while the charge termination current is set using the resistor connected to the PROG3 pin. The MCP73871 device continuously monitors battery temperature during a charge cycle by measuring the voltage between the THERM pin and Ground. Once a voltage outside the threshold is detected during a charge cycle, the MCP73871 immediately suspends the charge cycle. The MCP73871 suspends charging by turning off the charge pass transistor and holding the timer value. The charge cycle resumes when the voltage at the THERM pin returns to within the normal range. The configuration pins of the MCP73871 are controlled by the MPU, which determine when to charge the battery, limit the input current, or enable the safety timer, based on the status of the battery charge management controller.

At the PMIC level, the SELV2 and SELV3 pins are meant to program the default settings of some rails that must be activated during the power-up sequence, but whose voltage values are application-dependent. These are Buck2 and Buck3; the first is dedicated to DDRx/LPDDRx power, while the latter is dedicated to core power. In this example, SAMA5D2 has a LPDDR2 memory connected.

Once the MCP73871 supplies power to the PMIC, there are two options to initiate a valid start-up event for the PMIC: either by pressing the button connected to the nSTRT pin, or by a decision of the MPU to generate a Low-to-High transition on the PWRHLD pin.

The default power channel sequencing is built-in according to the requirements of the MPU. A dedicated pin (LPM) facilitates the transition to Low-Power modes and the implementation of Backup mode with DDR in self-refresh (Hibernate mode).