NCV8877

www.onsemi.com

14

Table 2. OTA COMPENSATION TRANSFER FUNCTION AND COMPENSATION VALUES

Desired OTA Gain at Cross−over

10

desired_G

fc_gain_db

20

Desired Phase Boost at Cross−

q

(fc)

180

°

p *

90

°

p

180

°

Select OTA Compensation Zero to

Coincide with Modulator Pole at

w

p1e

2

p

Resulting OTA High Frequency

V

OUT

1

)

2

1

)

1

2

pf

1

2

V

OUT

V

ref

V

OUT

Low Frequency Zero (

1

2

R

R

1

*

1

* 4

R

R

2

C

1

High Frequency Zero (

1

2

R

R

1

)

1

* 4

R

R

2

C

1

Low Frequency Pole (

1

2

R

R

1

*

1

* 4

R

R

2

C

1

High Frequency Pole (

1

2

R

R

1

)

1

* 4

R

R

2

C

1

−G

0_OTA

1

) j

2

pf

w

z1e

1

w

p1e

1

) j

2

pf

w

z2e

1

w

p2e

The open−loop−response in closed−loop form to verify the gain/phase margins may be obtained from the following

expressions.

T(f)

+ G