BC3770 Datasheet, PDF (40/45 Pages) Freescale Semiconductor, Inc – 2.0 A Switch-Mode Charger

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
the battery cell, to regulate the V_{BAT_REG} battery regulation voltage as close to the target as possible.
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
Analog Integrated Circuit Device Data
Freescale Semiconductor
BC3770
40