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BQ25887EVM: BQ25887 EVM Design

Babu Vishwanath Hemath Kumar
Prodigy 230 points
Part Number: BQ25887EVM
Other Parts Discussed in Thread: BQ25887,

Hi, 

My name is Babu, I am designing the PCB with BQ25887 IC. Regarding the component selection of capacitor and resistors, if we see in the evaluation module datasheet the different packages of components are used for example some components have 0402 and 0603 package. I would like to know whether we have to follow the same package as mentioned in the BOM datasheet of BQ25887 or can we increase the package size of the component?

If you recommend to use the same package size, could you tell me the reason for using the small size SMD components in the evaluation module?

  • +1
    TI__Genius 10175 points

    Hi Babu,

    The specific footprints/packages of the components do not have to be the same as the BQ25887EVM, so long as the value of the component characteristics correct. We do recommend using similar package sizes as it allows the component to be placed as close as possible to the IC. Placing components as close to the IC can greatly improve EMI performance and overall device performance.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 230 points

    Thanks for your reply Ospina and I apologize for the late reply, I have a doubt that in the datasheet you mentioned that place 10nf Capacitor to VBUS as close as possible to IC but you have placed that capacitor far away from the IC, can I know the reason for this?

    In the SNS pin you have used many capacitors like 2.2uF, 1uF and more but in the datasheet of BQ25887 you just mentioned to use 44uF capacitor, Can I know the reason for this too?

  • +1 in reply to Babu Vishwanath Hemath Kumar
    TI__Genius 10175 points

    Hi Babu,

    The datasheet requires a 44uF capacitor on the SNS pin to function, however to reduce ringing in the switch node additional capacitors like those seen are recommended. These can help minimize EMI and keep spike voltages to a minimum. These capacitors are given the highest priority. The VBUS capacitor is important to keep as close as possible to the IC but it has a lower priority to other capacitors, which must be placed closer. You can read about the capacitor placement priority here, along with recommended components and component values. Please note, for the BQ25887 there is a type where the SNS pin is referred to as the SYS pin. 

    Best Regards,

    Juan Ospina