Layout and Bill of Materials
9
Layout and Bill of Materials
9.1
bq5122x Traces
The bq5122x device pins traces can be classified as follows:
•
Signal/Sensing Traces
TS/CTRL, SDA, SCL, LPRB2/PD_DET, LPRB1/WPG ,COMM, CHG, ILIM, AD, AD_EN, FOD, TMEM,
CM_ILIM, VO_REG, VIREG, LPRB_EN/TERM.
Make sure these trace are not being interfered by the noisy traces.
•
Noisy Traces
AC1, AC2, BOOT, COMM
Make sure to isolated these traces from other traces, you can use ground plan.
•
Power Traces
AC1, AC2, OUT, CLAMP, PGND
Make sure to use the right width for the right current rating.
9.2
Layout Guidelines
•
The traces from the input connector to the inputs of the bq5122x IC pin should be as wide as possible
to minimize the impedance in the lines. Otherwise, a voltage drop and thermal issue will be caused.
•
Keep the trace resistance as low as possible on AC1, AC2, and OUT.
•
Use the appropriate current rating traces (width) on the AC, OUT, CLAMP and GND.
•
The PCB should have a ground plane (return) connected directly to the return of all components
through vias (At least two vias per capacitor for power-stage capacitors, one via per capacitor for
small-signal components).
•
The dissipation of heat path is important. Adding internal layers increases the thermal performance.
Multiple vias in the PGND pulls of the IC is recommended to decrease the thermal resistance in the
board and allow much easier thermal dissipation through inner layer and power ground layers.
•
The via interconnect is important and must be optimized near the power pad of the IC and the GND.
•
2-oz copper or greater is recommended
•
For high-current applications, the balls for the power paths should be connected to as much copper in
the board as possible. This allows better thermal performance because the board conducts heat away
from the IC.
•
It is always a good practice to place high frequency bypass capacitors next to RECT and OUT.
9.3
Printed-Circuit Board Layout Example
The primary concerns when doing a layout for a custom receiver PCB are as follows:
•
AC1 and AC2, GND return trace resistance
•
OUT trace resistance
•
GND connection
•
Copper weight
≥
2 oz
For a 1-A fast charge current application, the current rating for each net is as follows:
•
AC1 = AC2 = 1.2 A
•
BOOT1 = BOOT2 = 1 A
•
RECT = 10 mA
•
OUT = 1 A
•
COMM1 = COMM2 = 300 mA
•
CLAMP1 = CLAMP2 = 500 mA
•
ILIM = 10 mA
18
Dual Mode (WPC and PMA) Integrated Wireless Receiver Power Supply
SLUUAX6B – February 2014 – Revised June 2014
Copyright © 2014, Texas Instruments Incorporated
