7

UCC1913

UCC2913

UCC3913

1

2

LINEAR

CURRENT

AMPLIFIER

PL

7

OUT

IMAX

V

DD

50

Ω

8

V

DD

6

SENSE

5

VSS

4

CT

ON-TIME

CONTROL

3

VDD

UVLO

5.0V

REF

LOGIC

SUPPLY

9.5V SHUNT REGULATOR

20

µA

1=

UNDERVOLTAGE

SOURCE

ONLY

SD/FLT

V

DD

CSS

R2

VSS

C

VDD

R1

R

VDD

R

T

OUTPUT

R

S

C

T

VSS

FAULT=

50mV

DISABLE

Figure 6. Typical application diagram.

maximum current that the UCC1913 will allow through

the transistor, M1, and it can be shown that during

startup with an output capacitor the power MOSFET, M1,

can be modeled as a constant current source of value

I

V

R

MAX

IMAX

SENSE

=

Given this information, calculation of the startup time is

now possible via the following:

Current Source Load:

T

CVSS

II

START

OUT

MAX

LOAD

=

•

−

Resistive Load:

TC

R

n

IR

IR

VSS

START

OUT

OUT

MAX

OUT

MAX

OUT

=•

•

•

•−













UCC1913 must be addressed and component values de-

rived. Assuming the user chooses to limit the maximum

allowable average power that will be associated with the

easily determined by the following:

APPLICATION INFORMATION (cont.)

UDG-99002