SG6846C Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – Highly Integrated Green-Mode PWM Controller

May 2008
SG6846C
Highly Integrated Green-Mode PWM Controller
Features
ƒ Low Start-up 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: 110ms
ƒ Programmable PWM Frequency with
Frequency Hopping
ƒ OCP Threshold is Half Peak Current Limit
ƒ Feedback Open-loop Protection with 110ms Delay
ƒ Soft Start-up 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, SG6846C 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 SG6846C 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 110ms, SG6846C shuts down immediately.
SG6846C also integrates 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.
SG6846C is available in 8-pin SOP and DIP packages.
Ordering Information
Part Number
SG6846CLSZ
SG6846CLDZ
Operating Temperature Range
-20 to +85°C
-20 to +85°C
OCP Latch
Package
Yes
8-Pin Small Outline Package (SOP)
Yes
8-Pin Dual Inline Package (DIP)
All standard Fairchild Semiconductor products are RoHS compliant and many are also “GREEN” or going green.
For Fairchild’s definition of “green” please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2007 Fairchild Semiconductor Corporation
SG6846C • Rev. 1.1.2
www.fairchildsemi.com