Operation description

VIPER37

26/35

Doc ID 022218 Rev 1

8.10

Feedback and overload protection (OLP)

The device is a current mode converter: the feedback pin controls the PWM operation,

controls the burst mode, and actives the overload protection.

Figure 30 and Figure 31 show

the internal current mode structure.

sensed and converted into voltage that is applied to the non-inverting pin of the PWM

comparator.

This voltage is compared with the one on the feedback pin through a voltage divider on a

cycle-by-cycle basis. When these two voltages are equal, the PWM logic orders the switch-

In case of overload, the feedback pin increases in reaction to this event and when it goes

the OCP comparator, see

Figure 2.

the converter itself.

To avoid this event, the appropriate feedback network must be selected according to the

output load. Moreover, the feedback network fixes the compensation loop stability.

Figure 30

and

Figure 31 show the two different feedback networks.

Equation 5

In

as well as being necessary to activate the overload protection.

Table 11.

CONT pin configurations

Function / component

(1)

1.

See

Figure 16

No

No

OVP

≥ 80 kΩ

See

Equation 4

Yes

See

Figure 16

See

Equation 4

Yes

T

OLP

delay

–

C

FB

V

FBolp

V

FBlin

–

I

FB

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×

=