SLUUCB5E June   2020  – July 2022 BQ25792 , BQ25798

 

  1.   BQ25792EVM, BQ25798BKUPEVM and BQ25798EVM (BMS034) Evaluation Module
  2. 1Introduction
    1. 1.1 EVM Features
    2. 1.2 I/O Descriptions
    3. 1.3 Recommended Operating Conditions
  3. 2Test Setup and Results
    1. 2.1 Equipment
    2. 2.2 Equipment Setup
    3. 2.3 Software Setup
      1. 2.3.1 BQSTUDIO using EV2400
      2. 2.3.2 TI Charger GUI for USB2ANY
    4. 2.4 Test Procedure
      1. 2.4.1 Initial Settings
      2. 2.4.2 Communication Verification
      3. 2.4.3 Charge Mode Verification
      4. 2.4.4 OTG Mode Verification
  4. 3PCB Layout Guidelines
  5. 4Board Layout, Schematic and Bill of Materials
    1. 4.1 BMS034 Board Layout
    2. 4.2 BQ2579XEVM (BMS034) Schematics
    3. 4.3 Bill of Materials
  6. 5Revision History

3 PCB Layout Guidelines

Careful placement of components is critical in order for the charger to meet specifications. The items below are listed in order of placement priority.

  1. Place high frequency decoupling capacitors for PMID and SYS (C3 and C18 on the EVM) as close possible to their respective pins and ground pin on the same layer as the charger IC (in other words, no vias) in order to have the smallest current loop.
  2. Place bulk capacitors for PMID and SYS as close possible to their respective pins and the charger's ground pin on the same layer as the charger IC on the same layer as the charger IC (in other words, no vias).
  3. Place the REGN capacitor (C35) to ground and BTST capacitors (C6 and C8) to SW as close as possible to their respective pins only using vias for 1 side of each component if necessary.
  4. Place high frequency decoupling capacitors for VBUS and BAT pins as close as possible to their respective pins. Use at least 2 vias per capacitor terminal if required.
  5. Place bulk capacitors for VBUS and BAT pins as close as possible to their respective pins. Use at least 2 vias per capacitor terminal if required.
  6. Place the inductor close to SW1 and SW2 pins. It is acceptable to use multiple vias to make these connections as the vias are only adding small amounts of inductance and resistance to an inductor.
  7. While this EVM has analog ground (AGND) and power ground (PGND) planes that connect close to the charge GND pin, two grounds not required. Resistors and capacitors used for setting sensitive nodes (for example, ILIM, TS) can use one common ground plane but with their ground terminals connected away from high current ground return paths containing switching noise.

Note that this EVM has test points and jumpers requiring traces out to the PCB edges. Routing these traces required some PCB layout compromises for less critical components than those listed in the first six items above.