October 2008

© 2008 Fairchild Semiconductor Corporation

www.fairchildsemi.com

SG6846B • Rev. 1.3.3

SG6846B

Highly Integrated Green-Mode PWM Controller

Features

Low Startup Current: 8µA

Low Operating Current: 3.7mA

Peak-Current Mode Operation with Cycle-by-cycle

Current Limiting

PWM Frequency Continuously Decreasing with

Burst Mode at Light Loads

AC Input Brownout Protection with Hysteresis

Constant Output Power Limit (Full AC Input Range)

Internal Latch Circuit for OVP, OTP, and OCP

(BLSY, BLSZ)

Two-level OCP Delay with 200ms

Programmable PWM Frequency with Frequency

Hopping

OCP Threshold is 2/3 Peak Current Limit

Soft Startup Time: 5ms

Applications

General-purpose switch-mode power supplies and

flyback power converters, including:

Power Adapters

Open-frame SMPS

SMPS with Surge-current Output, such as for

Printers, Scanners, Motor Drivers

Description

The highly integrated PWM controller, SG6846B,

provides several features to enhance the performance

of fly-back converters. To minimize standby power

consumption,

a

proprietary

green-mode

function

provides off-time modulation to continuously decrease

the switching frequency under light-load conditions.

Under zero-load conditions, the power supply enters

burst-mode. This completely shuts off PWM output. If

green-mode function enables power supplies to meet

international power conservation requirements.

The SG6846B is designed for SMPS with surge-current

output. It is incorporated with a two-level OCP function.

Besides, the cycle-by-cycle current limiting, if the

switching current is higher than OCP threshold and

lasts for 200ms, SG6846B stops gate immediately and

charges up to 16.5V (BCSY version). SG6846B also

integrates frequency-hopping function internally. The

frequency hopping function helps reduce EMI emission

of a power supply with minimum line filters. It has built-

in

synchronized

slope

compensation,

proprietary

internal compensation for constant output power limit

over universal AC input range. The gate output is

clamped at 18V to protect the external MOSFET from

over-voltage damage.

Protection include: AC input brownout protection with

temperature protection, an external NTC thermistor can

be applied to sense the ambient temperature. When

circuit is used to latch-off the controller. The latch resets

SG6846B is available in 8-pin SOP package.

Ordering Information

Part

Number

Operating

Temperature Range

OCP

Latch

Eco

Status

Package

Packing

Method

SG6846BLSY

-40 to +105°C

Yes

Green

8-Pin Small Outline Package (SOP)

Tape & Reel

SG6846BLSZ

-40 to +105°C

Yes

RoHS

8-Pin Small Outline Package (SOP)

Tape & Reel

SG6846BCSY

-40 to +105°C

No

Green

8-Pin Small Outline Package (SOP)

Tape & Reel

SG6846BCSZ

-40 to +105°C

No

RoHS

8-Pin Small Outline Package (SOP)

Tape & Reel