UCC2941-3, UCC2941-5, UCC2941-ADJ, UCC3941-3, UCC3941-5, UCC3941-ADJ

1V SYNCHRONOUS BOOST CONVERTER

SLUS242B – JANUARY 1999 – REVISED JUNE 2001

3

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Terminal Functions

TERMINAL

NO.

NAME

UCC2941–3

UCC2941–5

UCC3941–3

UCC3941–5

UCC2941–ADJ

UCC3941–ADJ

I/O

DESCRIPTION

FB

–

6

I

Feedback control pin used in the UCC3941–ADJ version only. The internal

reference for this comparator is 1.25V and external resistors provide the gain to

the output voltage.

PGND

7

7

–

Power ground of the IC. The inductor charging current flows through this pin. For

the UCC3941–ADJ signal ground and power ground lines are tied to a common

pin.

PLIM

5

5

I

Peak current limit

SGND

6

–

–

Signal ground of the IC. For the UCC3941–ADJ signal ground and power ground

lines are tied to a common pin

SD

4

4

I

Shutdown pin

SW

8

8

I

Inductor connection

VGD

2

2

O

Gate drive supply

VIN

3

3

I

Input voltage to supply the IC during startup. After the output is running the IC

draws power from VOUT or VGD

VOUT

1

1

O

Main output voltage

detailed description

peak limit (PLIM)

The PLIM pin is programmed to set the maximum input power for the converter. For example a 1-A current limit

at 1 V would have a 333-mA limit at 3 V input keeping the input power constant at 1 W. The peak current at

VIN = 1 V is programmed to 1.5 A (1.5 W) when this pin is grounded. The power limit is given by:

PL

W +

11.8

n

R

PL )

6.7

) V

IN

0.26

converter. The peak current limit is given by:

I

PK(A) +

11.8

n

V

IN

R

PL )

6.7

) 0.26

Constant power gives several advantages over constant current such as lower output ripple.

shutdown (SD)

When the SD pin is open, the built-in 7-

µA current source pulls up on the pin and programs the IC to go into

shutdown mode. This pin requires an open circuit for shutdown and does not operate correctly when driven to

a logic level high with TTL or CMOS logic. When this pin is connected to ground, (either directly or with a

transistor) the IC is enabled and both output voltages regulate.

(1)

(2)