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

1V SYNCHRONOUS BOOST CONVERTER

SLUS242B – JANUARY 1999 – REVISED JUNE 2001

7

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APPLICATION INFORMATION

A detailed block diagram of the UCC3941 is shown in Figure 1. Unique control circuitry provides high-efficiency

power conversion for both light and heavy loads by transitioning between discontinuous and continuous

conduction based on load conditions. Figure 2 depicts converter waveforms for the application circuit shown

in Figure 3. A single 22-

µH inductor provides the energy pulses required for a highly efficient 3.3-V converter

at up to 500 mW output power.

UDG–98146

4

5

2

3

8

1

6

6

7

SD

PLIM

VGD

VIN

SW

VOUT

FB

(UCC3941–ADJ

ONLY)

PGND

SGND

(UCC3941–3/–5

ONLY)

5 Ω

VGD

* 3.3 V FOR UCC3941–3

5.0 V FOR UCC3941–5

1.25 V FOR UCC3941–ADJ

VGD

** 8.7 V FOR UCC3941–3

9.6 V FOR UCC3941–5/–ADJ

VGD

*** 7.7 V FOR UCC3941–3

8.8 V FOR UCC3941–5/–ADJ

FROM

SD

5V

1.1 A

MAX

CURRENT

LIMIT

50 mV

VIN

VIN

SD

50 mV

MAXIMUM

200 kHz

STARTUP

OSCILLATOR

AND CONTROL

VGD

VGD

VGD ZERO

DETECT

VOUT ZERO

DETECT

ANTI–RINGING

SWITCH

1.7 µS

OFF TIME

CONTROLLER

RECTIFIER

CONTROL

FROM SD

CLK

DQ

L1

RQ

SD

BOOST

LATCH

ON TIME

CONTROLLER

T

11 µSEC

VIN

VSAT

*

**

***

THERMAL

SHUTDOWN

R

Q

SD

+

+

+

+

+

+

+

NOTE: Switches are shown in the logic low state; external RPLIM = 6.2 Ω

Figure 1. 1–V Synchronous Boost