ADP2325ACPZ-R7 datasheet(21/32 Pages) AD

21 / 32 page

Data Sheet

ADP2325

Rev. 0 | Page 21 of 32

The ADP2325 uses adaptive slope compensation in the current

loop to prevent subharmonic oscillations when the duty cycle is

larger than 50%. The internal slope compensation limits the min-

imum inductor value.

For a duty cycle that is larger than 50%, the minimum inductor

value is determined by the following equation:



OUT







The inductor peak current is calculated by

OUT

PEAK







The saturation current of the inductor must be larger than the

peak inductor current. For the ferrite core inductors with a

quick saturation characteristic, the saturation current rating of the

inductor should be higher than the current-limit threshold of the

switch to prevent the inductor from entering saturation.

The rms current of the inductor can be calculated by

OUT

RMS







Shielded ferrite core materials are recommended for low core

loss and low EMI.

Table 9. Recommended Inductors

Vendor

Part No.

Value

(μH)

ISAT

(A)

IRMS

(A)

DCR

(mΩ)

Sumida

CDRH105RNP-0R8N

0.8

13.5

9.5

4.3

CDRH105RNP-1R5N

1.5

10.5

8.3

5.8

CDRH105RNP-2R2N

2.2

9.25

7.5

7.2

CDRH105RNP-3R3N

3.3

7.8

6.5

10.4

CDRH105RNP-4R7N

4.7

6.4

6.1

12.3

CDRH105RNP-6R8N

6.8

5.4

Coilcraft

MSS1048-152NL

1.5

10.5

10.8

5.1

MSS1048-222NL

2.2

8.4

9.78

7.2

MSS1048-332NL

3.3

7.38

7.22

10.1

MSS1048-472NL

4.7

6.46

6.9

11.4

MSS1048-682NL

6.8

5.94

6.01

15.4

Wurth

Elektronik

7447797110

1.1

7.6

7447797180

1.8

13.3

7.3

7447797300

3.0

10.5

7.0

7447797470

4.7

8.0

5.8

7447797620

6.2

7.5

5.5

OUTPUT CAPACITOR SELECTION

The output capacitor selection affects both the output voltage

ripple and the loop dynamics of the regulator. For example,

during load step transient on the output, when the load is sud-

denly increased, the output capacitor supplies the load until the

control loop can ramp up the inductor current, which causes an

undershoot of the output voltage. Use the following equation to

calculate the output capacitance that is required to meet the voltage

droop requirement:



OUT_UV

OUT

STEP

OUT_UV















where:

ΔISTEP is the load step.

ΔVOUT_UV is the allowable undershoot on the output voltage.

KUV

is a factor, typically setting KUV = 2.

Another example is when a load is suddenly removed from the

output and the energy stored in the inductor rushes into the

output capacitor, which causes the output to overshoot. The

output capacitance required to meet the overshoot requirement

can be calculated using the following equation:



OUT

STEP

OUT_OV















where:

ΔVOUT_OV is the allowable overshoot on the output voltage.

KOV

is a factor, typically setting KOV = 2.

The output ripple is determined by the ESR of the output

capacitor and its capacitance value. Use the following equation to

select a capacitor that can meet the output ripple requirements:

OUT_RIPPLE









OUT_RIPPLE

ESR





where:

ΔVOUT_RIPPLE is the allowable output voltage ripple.

RESR

is the equivalent series resistance of the output capacitor.

Select the largest output capacitance given by COUT_UV, COUT_OV,

and COUT_RIPPLE to meet both load transient and output ripple

performance.

The selected output capacitor voltage rating must be greater

than the output voltage. The minimum rms current rating of

the output capacitor is determined by the following equation:

rms

OUT





ADP2325ACPZ-R7 数据表(PDF) 21 Page - Analog Devices

ADP2325ACPZ-R7 数据表(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

数据表下载

链接网址

ADP2325ACPZ-R7 数据表(PDF) 21 Page - Analog Devices

ADP2325ACPZ-R7 数据表(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

数据表 下载

链接网址

数据表下载