SG6846G_09 Datasheet, PDF (1/14 Pages) Fairchild Semiconductor – Highly Integrated Green-Mode PWM Controller

June 2009
SG6846G
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
ƒ Two-Level OCP Delay: 500ms
ƒ Programmable PWM Frequency with
Frequency Hopping
ƒ OCP Threshold is Half Peak Current Limit
ƒ Feedback Open-Loop Protection with 500ms Delay
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
A highly integrated PWM controller, SG6846G provides
several features to enhance the performance of flyback
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, which
completely shuts off PWM output. Output restarts just
before the supply voltage drops below the UVLO lower
limit. This green-mode function enables power supplies
to meet international power conservation requirements.
The SG6846G is designed for SMPS with surge-current
output, 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 500ms, SG6846G shuts down immediately.
SG6846G also integrates a frequency-hopping function
internally, which helps reduce EMI emission of a power
supply with minimum line filters. The built-in
synchronized slope compensation provides proprietary
internal compensation for constant output power limit
over a universal AC input range. The gate output is
clamped at 18V to protect the external MOSFET from
over-voltage damage.
Other protection functions 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 latches off the
controller. The latch resets when VDD supply is removed.
SG6846G is available in an 8-pin SOP package.
Ordering Information
Part
Operating
OCP
Number Temperature Range Latch
SG6846GLSY
-40 to +105°C
Yes
Eco
Status
Green
Package
Packing
Method
8-Pin Small Outline Package (SOP) Tape & Reel
For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
SG6846G • Rev. 1.0.2
www.fairchildsemi.com