SG6846B Fairchild Semiconductor, SG6846B Datasheet

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SG6846B

Manufacturer Part Number
SG6846B
Description
The highly integrated PWM controller, SG6846B, provides several features to enhance the performance of fly-back converters
Manufacturer
Fairchild Semiconductor
Datasheet

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© 2008 Fairchild Semiconductor Corporation
SG6846B • Rev. 1.3.4
SG6846B
Highly Integrated Green-Mode PWM Controller
Features
Applications
General-purpose switch-mode power supplies and
flyback power converters, including:
Ordering Information
SG6846BLSY
SG6846BLSZ
SG6846BCSY
SG6846BCSZ
Number
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
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
V
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
Power Adapters
Open-frame SMPS
SMPS with Surge-current Output, such as for
Printers, Scanners, Motor Drivers
Part
DD
Over Voltage Protection (OVP)
Temperature Range
-40 to +105°C
-40 to +105°C
-40 to +105°C
-40 to +105°C
Operating
Latch
OCP
Yes
Yes
No
No
Status
Green
Green
RoHS
RoHS
Eco
Description
The highly integrated PWM controller, SG6846B,
provides several features to enhance the performance
of fly-back converters. To minimize standby power
consumption,
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
V
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 V
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
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 V
temperature protection, an external NTC thermistor can
be applied to sense the ambient temperature. When
OCP, V
circuit is used to latch-off the controller. The latch resets
when V
SG6846B is available in 8-pin SOP package.
FB
is larger than around 1.6V, PWM pulses out. This
synchronized
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
8-Pin Small Outline Package (SOP)
DD
DD
supply is removed.
OVP, or OTP are activated, an internal latch
a
Package
DD
proprietary
slope
over-voltage protection. For over-
compensation,
green-mode
October 2008
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
www.fairchildsemi.com
Packing
Method
proprietary
function
DD

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SG6846B Summary of contents

Page 1

... PWM pulses out. This FB green-mode function enables power supplies to meet international power conservation requirements. The SG6846B 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 ...

Page 2

... AC input Filter N VIN Block Diagram 0.9V/0.7V VIN 3 V -TH-G DD VDD 7 UVLO 16.5V/10.5V 23. 1.05V © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3 VDD GATE 8 SENSE 6 GND SG6846B Figure 1. Typical Application Over Power Compersation 0.895-0.065 Internal BIAS ...

Page 3

... Marking Information SG6846BFTP XXXXXXXXYWWV ※ Marking for SG6846BLSZ (Pb-free) SG6846BCSZ (Pb-free) ※ Marking for SG6846BLSY (Green-compound) SG6846BCSY (Green-compound) © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3 OCP Latch OCP auto-recovery SOP Lead Free + ROHS Compatible Null = regular package XXXXXXXX: Wafer Lot Y: Year ...

Page 4

... 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 200ms, SG6846B turns off immediately. This two-level OCP feature is especially suitable for SMPS with surge current output open-circuit failure occurs in the feedback loop, the internal protection circuit disables PWM output as long as V The totem-pole output driver for the power MOSFET ...

Page 5

... 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 © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 Parameter <50°C SOP A SOP Parameter 5 Min ...

Page 6

... STH3V-2/3 t Delay Time for Over-Current Protection D-OCP t Output Short Circuit Protection delay time D-Short t SS-65KHz Period During Soft Start Time t SS-130KHz © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 Test Condition for Short-Circuit DD V – 0.16V DD-ON GATE Open R = 26kΩ ...

Page 7

... Frequency Variation vs Frequency Variation vs. Temperature f DT Deviation © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3 Timing = 200ms OCP Figure 6. SG6846B OCP/SCP Logic Flow Diagram (Continued) Test Condition Center Frequency R = 26kΩ Jitter Range Center Frequency R = 13kΩ Jitter Range ...

Page 8

... 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 © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 (Continued) Test Condition V = 15V 12V GATE = 1nF GATE = 1nF V = 20V DD ( 26kΩ ...

Page 9

... Temperature (℃ ) Figure 11. OCP Threshold Voltage for Current Limit (V ) vs. Temperature STH1V-2/3 © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3 Temperature DD- Figure 8 ...

Page 10

... Temperature PW M Turn-on Threshold Voltage (V 0.925 0.920 0.915 0.910 0.905 -40 -25 - Temperature ( ℃ ) Figure 17. PWM Turn-on Threshold Voltage (V vs. Temperature © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 (Continued Temperature OSC 8 7.2 8 7.0 8 6.8 8 6.6 8 6 110 125 - Figure 14 ...

Page 11

... Over-Temperature Protection (OTP) An external NTC thermistor can be connected from the RT pin to GND. The impedance of the NTC decreases at high temperatures. When the voltage of the RT pin drops below 1.05V, the SG6846B is turned off. For protection-mode options, see Ordering Information. the resistance and the switching ...

Page 12

... Good placement and layout practices should be followed. Avoid long PCB traces and component leads. Compensation and filter components should be located near the SG6846B. © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 (Continued) Slope compensation 12 Figure 19 ...

Page 13

... 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% © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 BD1 LF2 CX2 R12 ...

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/. © 2008 Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 5.00 4.80 A 3.81 ...

Page 15

... Fairchild Semiconductor Corporation SG6846B • Rev. 1.3.4 15 www.fairchildsemi.com ...

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