L4990

D97IN511A

DC

VREF

R

START

3

12

8

4

11

Figure 40. Protection against overvol-

tage/feedback disconnection (not

latched)

D97IN512A

PGND

L4990

OPTIONAL

VREF

SGND

DIS

ISEN

I

4

14

13

12

11

R

2

2.5

1-

R

2

•

Figure 41. Device shutdown on overcurrent

D97IN513

PGND

L4990

OUT

SGND

ISEN

Lp

R

6

R·Lp

RSENSE

RSENSE

13

10

12

11

80

÷ 400V

DC

Figure 42. Constant power in pulse-by-pulse current limitation (flyback discontinuous)

REFERENCES

[1] Efficient active Clamp for Off-line Applications using L4990 and L6380 (N.Tricomi, G. Gattavari,

C. Adragna, PCIM96 - NURBERG).

[2] 25W Off-Line Autoranging Battery Charger with L4990 (AN889)

[3] 300W Secondary Controlled Two-Switch Forward Converter with L4990 (AN890)

[4] SMPS with L4990 for Multisync Monitors (AN891)

[5] High performance VRM using L4990A, for Pentium Pro

® processor (AN908).

L4990

DC

10K

COMP

3

6

12

13

SGND

ISEN

D97IN570A

Figure 43. Voltage mode operation.

L4990 - L4990A

21/24