Data Sheet

ADP2386

Rev. A | Page 17 of 24

The selected output capacitor voltage rating must be greater

than the output voltage. The rms current rating of the output

capacitor must be larger than the value that is calculated by

using the following equation:

12

L

I

∆

PROGRAMMING THE INPUT VOLTAGE UVLO

The ADP2386 has a precision enable input that can be used to

program the UVLO threshold of the input voltage (see Figure 31).

EN

EN CMP

ADP2386

1.17V

4µA

1µA

PVIN

Figure 31. Programming the Input Voltage UVLO

μA

1

V

17

.

1

μA

5

V

07

.

1

V

17

.

1

V

07

.

1

_

_

×

−

×

×

−

×

FALLING

IN

RISING

IN

V

V

V

17

.

1

μA

5

V

17

.

1

_

_

_

−

×

−

×

EN

TOP

RISING

IN

EN

TOP

R

V

R

where:

COMPENSATION DESIGN

For peak current-mode control, the power stage can be simplified

as a voltage controlled current source supplying current to the

output capacitor and load resistor. It is composed of one domain

pole and a zero that is contributed by the output capacitor ESR.

The control-to-output transfer function is based on the following:

)

(

)

(

s

V

s

V

COMP

OUT













×

×

+













×

×

+

P

Z

f

s

f

s

π

π

2

1

2

1

OUT

ESR

C

R

×

×

×

π

2

1

OUT

ESR

C

R

R

×

+

×

×

)

(

2

1

π

where:

R is the load resistance.

The ADP2386 uses a transconductance amplifier for the error

amplifier and to compensate the system. Figure 32 shows the

simplified, peak current-mode control, small signal circuit.

R

+

–

g

m

–

+

Figure 32. Simplified Peak Current Mode Control, Small Signal Circuit

The closed-loop transfer equation is as follows:

×

+

−

×

+

CP

C

m

TOP

BOT

BOT

C

C

g

R

R

R

1

()

(1

)

CC

VD

CCCP

C

CP

RC

s

Gs

RC

C

ss

CC

+

××

×

××

×+

×

+

capacitor applications:

VI

m

C

OUT

OUT

A

g

f

C

V

×

×

×

×

×

×

V

6

.

0

2

π

C

OUT

ESR

R

C

R

R

×

+

)

(

the ESR of the output capacitor.

C

OUT

ESR

R

C

R

×

ADIsimPOWER DESIGN TOOL

The ADP2386 is supported by the ADIsimPower™ design tool

set. ADIsimPower is a collection of tools that produce complete

power designs that are optimized for a specific design goal. The

tools enable the user to generate a full schematic and bill of

materials and calculate performance in minutes. ADIsimPower

can optimize designs for cost, area, efficiency, and part count,

while taking into consideration the operating conditions and

limitations of the IC and all real external components. For more

information about theADIsimPower design tools, refer to

www.analog.com/ADIsimPower. The tool set is available from

this website, and users can request an unpopulated board.