Data Sheet

ADP5075

Rev. B | Page 15 of 19

Loop Compensation

The ADP5075 uses external components to compensate the

regulator loop, allowing the optimization of the loop dynamics

for a given application. It is recommended to use the ADIsimPower

tool to calculate compensation components.

The inverting converter, produces an undesirable right half

plane zero in the regulation feedback loop. This feedback loop

requires compensating the regulator such that the crossover

frequency occurs well below the frequency of the right half plane

zero. The right half plane zero frequency is determined by the

following equation:

Duty

L1

π

Duty)

(

R

(RHP)

f

2

LOAD

Z

×

×

−

=

2

1

where:

divided by the load current.

















+

+

+

=

DIODE

NEG

IN

DIODE

NEG

V

|

|V

V

V

|

|V

Duty

(D1).

To stabilize the regulator, ensure that the regulator crossover

frequency is less than or equal to one-tenth of the right half

plane zero frequency.

The regulator loop gain is

OUT

CS

COMP

OUT

M

NEG

IN

IN

NEG

FB

VL

Z

G

Z

||

R

G

V

V

V

|

|V

V

A

×

×

×

×

×

+

×

=

|)

|

2

(

where:

to GND.

current divided by the voltage at COMP), which is internally

set by the ADP5075 and is 6.25 A/V.

capacitor.

To determine the crossover frequency, it is important to note

Therefore, when solving for the crossover frequency, the equation

(by definition of the crossover frequency) is simplified to

1

2

1

|)

|

2

(

=

×

×

×

×

×

×

×

+

×

=

OUT

C

CS

C

M

NEG

IN

IN

NEG

FB

VL

C

f

π

G

R

G

V

V

V

|

|V

V

A

CS

M

IN

FB

NEG

IN

NEG

OUT

C

C

G

G

V

V

V

(V

|

|V

C

f

π

R

×

×

×

×

+

×

×

×

×

=

|)

|

2

(

2

IN

NEG

IN

NEG

OUT

C

C

V

V

V

V

C

f

R

|)

|

2

(

(

|

|

4188

×

+

×

×

×

×

=

For better accuracy, it is recommended to use the value of

After the compensation resistor is known, set the zero formed

C

C

C

R

f

π

C

×

×

=

2

ERROR

AMPLIFIER

REF

FB

COMP

Figure 26. Compensation Components

introduced by the ESR of the output capacitor. For low ESR

from the design.

C

OUT

B

R

C

ESR

C

×

=

adjusted by observing the load transient response of the ADP5075.