Analog Integrated Circuit Device Data



Freescale Semiconductor

40

BC3770

6.1.2.6

PCB Layout Considerations

The device contains a high-frequency switching converter. Therefore, the PCB layout is a very important design practice to ensure a

satisfactory performance. The following provides some guidelines.

1. The power loop is composed of the inductor, the input and output capacitor, the LX pin and the PGND pin. It is important to make

the power loop as small as possible and the connecting traces among them should be direct, short and wide. They should be

placed as close as possible to their respective the IC pins.

2. The switching node of the converter, the LX pin, and the traces connected to this node are very noisy. This trace keeps other noise

sensitive traces separated.

3. The GND and PGND should connect to the power ground plane at only one point, to minimize the effects of power ground currents.

Also, battery ground should connect directly to the power ground plane.

4. Connect the BATREG pin directly to the + terminal on the battery cell and connect the BATSNSN pin directly to the – terminal on

5. One bypass capacitor for PMID should be placed as close to the pin and power ground as possible.

Figure 24 is an example layout for some key components.

Figure 24. Key Component Layout Example