SG6846B Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – Highly Integrated Green-Mode PWM Controller

October 2008
SG6846B
Highly Integrated Green-Mode PWM Controller
Features
ƒ Low Startup Current: 8µA
ƒ Low Operating Current: 3.7mA
ƒ Peak-Current Mode Operation with Cycle-by-cycle
Current Limiting
ƒ PWM Frequency Continuously Decreasing with
Burst Mode at Light Loads
ƒ VDD Over Voltage Protection (OVP)
ƒ AC Input Brownout Protection with Hysteresis
ƒ Constant Output Power Limit (Full AC Input Range)
ƒ Internal Latch Circuit for OVP, OTP, and OCP
(BLSY, BLSZ)
ƒ Two-level OCP Delay with 200ms
ƒ Programmable PWM Frequency with Frequency
Hopping
ƒ OCP Threshold is 2/3 Peak Current Limit
ƒ Soft Startup Time: 5ms
Applications
General-purpose switch-mode power supplies and
flyback power converters, including:
ƒ Power Adapters
ƒ Open-frame SMPS
ƒ 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
VFB is larger than around 1.6V, PWM pulses out. This
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
latches itself (BLSY version) or restarts after VDD
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
hysteresis and VDD over-voltage protection. For over-
temperature protection, an external NTC thermistor can
be applied to sense the ambient temperature. When
OCP, VDD OVP, or OTP are activated, an internal latch
circuit is used to latch-off the controller. The latch resets
when VDD supply is removed.
SG6846B is available in 8-pin SOP package.
Ordering Information
Part
Operating
OCP
Number Temperature Range Latch
SG6846BLSY
-40 to +105°C
Yes
SG6846BLSZ
-40 to +105°C
Yes
SG6846BCSY
-40 to +105°C
No
SG6846BCSZ
-40 to +105°C
No
Eco
Status
Green
RoHS
Green
RoHS
Package
Packing
Method
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
SG6846B • Rev. 1.3.3
www.fairchildsemi.com