SG6846C Fairchild Semiconductor, SG6846C Datasheet

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SG6846C

Manufacturer Part Number
SG6846C
Description
The highly integrated PWM controller, SG6846C provides several features to enhance the performance of flyback converters
Manufacturer
Fairchild Semiconductor
Datasheet

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© 2007 Fairchild Semiconductor Corporation
SG6846C • Rev. 1.1.2
SG6846C
Highly Integrated Green-Mode PWM Controller
Features
Applications
General-purpose switch mode power supplies and
flyback power converters, including:
Ordering Information
SG6846CLSZ
SG6846CLDZ
Part Number
Low Start-up 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
V
AC Input Brownout Protection with Hysteresis
Constant Output Power Limit (Full AC Input Range)
Internal Latch Circuit for OVP, OTP, and OCP
Two-level OCP Delay: 110ms
Programmable PWM Frequency with
Frequency Hopping
OCP Threshold is Half Peak Current Limit
Feedback Open-loop Protection with 110ms Delay
Soft Start-up Time: 5ms
Power Adapters
Open-frame SMPS
SMPS with Surge-current Output, such as for
Printers, Scanners, Motor Drivers
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.
DD
Over-Voltage Protection (OVP)
Operating Temperature Range
-20 to +85°C
-20 to +85°C
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
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
protection. For over-temperature protection, an external
NTC thermistor can be applied to sense the ambient
temperature. When OCP, V
activated, an internal latch circuit latches off the
controller. The latch resets when V
SG6846C is available in 8-pin SOP and DIP packages.
OCP Latch
Yes
Yes
with
with
minimum
8-Pin Small Outline Package (SOP)
8-Pin Dual Inline Package (DIP)
hysteresis
line
Package
DD
and
DD
filters.
OVP, or OTP are
supply is removed.
V
DD
May 2008
The
www.fairchildsemi.com
over-voltage
built-in

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SG6846C Summary of contents

Page 1

... For over-temperature protection, an external NTC thermistor can be applied to sense the ambient temperature. When OCP, V activated, an internal latch circuit latches off the controller. The latch resets when V SG6846C is available in 8-pin SOP and DIP packages. OCP Latch -20 to +85°C Yes -20 to +85°C ...

Page 2

... Typical Application Block Diagram 0.9V/0.7V VIN 3 V -TH-G DD VDD 7 UVLO 16.5V/10.5V 23. 1.05V © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 Figure 1. Typical Application Over Power Compensation 1.18-0. Internal BIAS Latch Debounce OCP Delay 1 GND Figure 2. Block Diagram VDD Soft ...

Page 3

... Current sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting. If the switching current is higher than OCP threshold and lasts for 110ms, SG6846C turns off immediately. This two-level OCP feature is especially suitable for SMPS with surge current output. ...

Page 4

... The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings. Symbol T Operating Ambient Temperature A © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 Parameter DIP <50°C A SOP DIP SOP ...

Page 5

... OCP Threshold Voltage for Current Limit STH1V-1/2 V OCP Threshold Voltage for Current Limit STH3V-1/2 t Delay Time for Over-Current Protection D-OCP t SS-65KHz Period During Start up Time t SS-130KHz © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 Test Condition Min. 15.5 9 – 0.16V DD-ON GATE Open 22 26kΩ 60 ...

Page 6

... FB Voltage at f FB-G OSC-G S Slope for Green-Mode Modulation G f Frequency Variation vs Frequency Variation vs. Temperature f DT Deviation © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 (Continued) Test Condition Center Frequency R = 26kΩ Jitter Range Center Frequency R = 13kΩ Jitter Range ...

Page 7

... Operating Range NOR I RI Maximum R Value for Protection MAX I RI Minimum R Value for Protection MIN I Note: 1. The relationship between R © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 (Continued) Test Condition V = 15V 12V GATE = 1nF GATE = 1nF V = 20V DD ( 26kΩ ...

Page 8

... VIN=1V) vs Temperature 0.60 0.58 0.56 0.54 0.52 0.50 -40 -25 - Temperature (℃ ) Figure 10. OCP Threshold Voltage for Current Limit ( 1V) vs. Temperature STH1V 1/2 IN © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1 11.5 11.0 10.5 10.0 9.5 9 110 125 -40 ) Figure 7. Turn-off Threshold Voltage (V DD- erat ure 4.0 3.5 3.0 2 ...

Page 9

... urn hres olt perat u re 0.910 0.905 0.900 0.895 0.890 -40 -25 - perat u re (℃ ) Figure 16. PWM Turn-on Threshold Voltage (V vs. Temperature © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 (Continued perat ure 87.0 86.8 86.6 86.4 86.2 86 110 125 -40 ) Figure 13 ...

Page 10

... This green-mode function dramatically consumption under light-load and zero-load conditions. Power supplies using the SG6846C can meet even the most restrictive international regulations regarding standby power consumption. Oscillator Operation A resistor connected from the RI pin to GND generates a reference current source, inside the SG6846C, used to determine the PWM frequency ...

Page 11

... Good placement and layout practices should be followed. Avoid long PCB traces and component leads. Compensation and filter components should be located near the SG6846C. © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 (Continued) Slope compensation 11 Figure 18 ...

Page 12

... R6 330Ω +/-1% R19 102KΩ +/-1% R14 0Ω22 +/-5% R16, R17 1W 20Ω +/-5% R11 20KΩ +/-5% R12 100KΩ +/-5% R20 887KΩ +/-1% R22 10KΩ +/-1% © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 BD1 LF2 CX2 R12 ...

Page 13

... Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1 Figure 20 ...

Page 14

... Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ © 2007 Fairchild Semiconductor Corporation SG6846C • Rev. 1.1 ...

Page 15

... Fairchild Semiconductor Corporation SG6846C • Rev. 1.1.2 15 www.fairchildsemi.com ...

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