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LM53603-Q1: Design suggestions

Sky Kao
Intellectual 320 points
Part Number: LM53603-Q1
Other Parts Discussed in Thread: LM53603, LMQ66410-Q1

Tool/software:

In the design of the LM53603 EVM, Vin has three 10uF capacitors, and Vout has three 22uF capacitors. Due to limited PCBA space and my application requirements (Vin=9V, Vout=3.3V, Imax=300mA), is it possible to remove two of the 10uF capacitors on Vin and two of the 22uF capacitors on Vout?

  • 0
    TI__Genius 16855 points

    Hi Sky,

    The datasheet recommends a minimum of 15 uF of effective capacitance on input (section 9.2.1.2.3). It also recommends a minimum of 42 uF of effective capacitance for output (section 9.2.1.2.2). Providing less than these in your application may result in an unstable design and will require further bench testing to validate if these reductions in output capacitance/input capacitance still produce acceptable characteristics (load transient requirements, stability). You may be able to utilize the feed-forward capacitor to further optimize these characteristics, but TI does not guarantee performance from applications with lower input and output capacitances than those listed in the datasheet.

    I have begun a webench design to help you get started with evaluating if your modifications are feasible: https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=051D6D1F1E9D1F18 This should help you simulate if your key care-abouts (phase margin, output ripple, crossover freq) and determine if they are acceptable for your design.

    Should you find that this device is still too difficult to fit in your system, I can recommend the LMQ66410-Q1. It has a much smaller footprint due to the inclusion of integrated input bypass caps and a smaller package footprint, while still being able to support your power requirements.

    Thank you,

    Joshua Austria