BLE18PS080SN1 datasheet(25/36 Pages) TI

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A feedforward capacitor (CFF) is not required for proper operation, but can further improve output noise.

However, care must be taken in choosing the CFF, since the power good (PG) function may not be valid with a

large CFF during start-up, and can cause spurious triggering of the PG pin during a large load transient. The

noise performance with various CFF is shown in Figure 6-29. Refer to the Pros and Cons Using a Feedforward

Capacitor with a Low Dropout Regulator Application Report for a discussion of the pros and cons of using a

feedforward capacitor.

8.2.2.2.7 NR/SS Capacitor Selection

As described in Section 7.3.8, the NR/SS cap affects both the total noise and the soft-start time. The

recommended value for a 5-ms soft-start time and good noise performance is 470 nF. The maximum NR/SS cap

is 3.3 μF for a start-up time of 35 ms. Values greater than 1 μF have minimal improvement in noise performance.

Use Equation 9 and Equation 10 to calculate the soft-start time based on desired soft-start time or the chosen

capacitor value.

*0.8

( )

NRSS

(9)

( )

0.8

NRSS

(10)

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SLVSFP4 – AUGUST 2020

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BLE18PS080SN1 数据表(PDF) 25 Page - Texas Instruments