The VBAT pin acts as a device power supply pin, used to power up some of the internal analog blocks within the device. This pin also acts as a voltage sense pin when the device is configured to sense the supply voltage on the VBAT pin. This pin is used for various battery monitoring decisions like voltage limiting, brown-out detection, boost turn-on, and more, especially in VBAT1S mode.

The following guidelines need to be taken into account while routing the VBAT pin on to the PCB:

• The VBAT pin carries a current up to 10mA. The trace routed to this pin can be narrower compared to the previously mentioned pins.
• The VBAT pin needs to be routed to the power source through a trace that is independent of the high current path used to route to the SW inductor.
• The VBAT pin needs to be decoupled to GND with a capacitor of value ≥ 1µF, that is placed as close to the device as possible. Using a 0201 package capacitor for lower ESL and ESR is recommended.
• The bottom plate of the capacitor, if connected to GND through the ground plane of the PCB, needs to be connected using multiple vias to minimize parasitic inductance to the GND pin.

Figure 3-11 Placement of Decoupling Capacitor Near the VBAT Pin

Figure 3-12 Routing of Power Source to VBAT Pin