ADP2389 datasheet(18/23 Pages) AD

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ADP2389/ADP2390

Data Sheet

According to the calculations for COUT_RIPPLE, COUT_OV, and

COUT_UV, the output capacitance must be greater than 332 µF and

the ESR of the output capacitor must be less than 3.78 mΩ. It is

recommended that five 100 µF, X5R, 6.3 V ceramic capacitors

be used, such as the GRM32ER60J107ME20 from Murata, with

an ESR of 2 mΩ.

COMPENSATION COMPONENTS

For better load transient and stability performance, set the cross

frequency, fC, to fSW/10. In this case, fSW is running at 500 kHz;

therefore, set fC to 50 kHz.

The 100 µF ceramic output capacitors have a derated value of

62 µF.

Ω

A/V

μS

500

kHz

μF

2 π

(

)

1623

μF

002

Ω

μF

002

Ω

Choose the following standard components: RC = 20 kΩ, CC =

1500 pF, and CCP = 33 pF.

SOFT START TIME PROGRAM

The soft start feature ramps up the output voltage in a controlled

manner, eliminating output voltage overshoot during soft start,

and limiting the inrush current. Set the soft start time to 4 ms.

4 ms 3.4 μA 22.67 nF

0.6 V

××

Choose a standard component value of CSS = 22 nF.

INPUT CAPACITOR SELECTION

Place a minimum 10 µF ceramic capacitor near the PVIN pin.

In this application, one 10 µF, X5R, 25 V ceramic capacitor is

recommended.

SCHEMATIC FOR DESIGN EXAMPLE

Figure 32. Schematic for Design Example

BST

COMP

PGOOD

GND

VREG

ILIM

FTW

0.68µH

CVREG

1µF

121kΩ

PGND

PVIN

VIN

CIN

10µF

25V

VIN = 12V

CBST

0.1µF

COUT1

100µF

6.3V

COUT2

100µF

6.3V

COUT3

100µF

6.3V

COUT4

100µF

6.3V

COUT5

100µF

6.3V

VOUT = 1.2V

RTOP

10kΩ

RBOT

10kΩ

1500pF

20kΩ

CSS

22nF

CCP

33pF

ADP2389/

ADP2390

Rev. 0 | Page 18 of 23

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