8

4

2

1

R2

R1

C

+

-

Error

Amplifier

R

R

Internal

Bias

Oscillator

1.0mA

2R

R

5

+

-

+

-

+

-

+

-

7

6

5

3

+

-

R

S

Q

Q1

Comp/ Latch

1.0V

Figure 14. Adjustable buffered reduction of clamp level with soft-start

+

-

+

-

+

-

+

-

7

7

6

5

3

5

R

1.0V

+

-

R

S

Q

SENSEFET

D

G

M

K

S

Power Ground to

Input Source Retum

Control Circuitry Ground

Comp/ Latch

Figure 15. Current sensing power mosfet

For proper operation during over current

conditions, a reduction of the Ipk(max)

clamp level must be implemented.

Refer to Figures 11 and 12.

1/4W

V=

clamp

1.67

(

+ 1)

R2

R1

I=

PK(max)

where: 0

V

1.0V

clamp

t

= -ln [ 1-

]

softstart

C

V

clamp

RS

V

C

3V

clamp

R1 + R2

R1 + R2

V

5=

PIN

If= SENSEFET= MTP10N10M

= 200

Then :

R

S

V

5= 0.075 l

PIN

PK

R I

R

S PK

DS(on)

RR

DS(on) +

S

13

MPSA63