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TPS709 output cap and stability

Bell Ye
Intellectual 1135 points
Other Parts Discussed in Thread: TPS709

Hi L&S team,

Our customer has some concern about the TPS709, would you kindly help look into this?

The TPS709 devices are stable with output capacitors with an effective capacitance of 2.0 μF or greater for output voltages below 1.5 V. For output voltages equal or greater than 1.5 V, the minimum effective capacitance for stability is 1.5 µF. The maximum capacitance for stability is 47 µF. The equivalent series resistance (ESR) of the output capacitor must be between 0 Ω and 0.2 Ω for stability.

1. Could you kindly show me the transfer formula of the feedback loop inside the LDO?

2. What's the minimum Cout for stability?

Best regards,

Bell

  • 0
    TI__Guru 55940 points
    Hi Bell,

    There are many factors that affect the feedback loop (load current, temperature, etc). Over simplifying the feedback loop can lead to issues depending on specific application factors. As a result, we provide information in the Input and Output Capacitor section of the datasheet to help customers know what the minimum requirements are for the capacitors.

    The minimum Cout required by TPS709 will depend on the application; however, in general we recommend that at least a 2.2uF capacitor be used.

    Very Respectfully,
    Ryan