Document
NOT RECOMMENDED FOR NEW DESIGNS
SG6848x1 — Low Cost, Green-Mode PWM Controller for Flyback Converters
SG6848x1
Low-Cost, Green-Mode PWM Controller for Flyback Converters
Features
Green-Mode PWM Controller Low Startup Current: 5 μA Low Operating Current: 3 mA Programmable PWM Frequency Peak-Current-Mode Operation Leading-Edge Blanking Built-in Synchronized Slope Compensation Cycle-by-Cycle Current Limiting Constant Output Power Limit Gate Output Voltage Clamped at 15 V Small SSOT-6 Package
Applications
General-purpose switched-mode power supplies (SMPS) and flyback power converters, such as:
Battery chargers for cellular phones, cordless phones,
PDAs, digital cameras, and power tools
Power adapters for ink jet printers, video game
consoles, and portable audio players
Open-frame SMPS for TV/DVD standby and auxiliary
supplies, home appliances, and consumer electronics
Replacements for linear transformers and RCC SMPS PC 5 V Standby Power
Description
This highly integrated PWM controller provides several enhancements to meet the low standby-power needs of low-power SMPS. To minimize standby power consumption, the proprietary Green Mode provides offtime modulation to continuously decrease PWM frequency under light-load conditions. Green Mode enables the power supply to meet even strict power conservation requirements.
The BiCMOS fabrication process enables reducing the startup current to 5 μA and the operating current to 3 mA. As a result, a large startup resistance can be used. Built-in synchronized slope compensation ensures the stability of peak-current-mode control. Proprietary internal compensation provides a constant output power limit over a universal AC input range (90 VAC to 264 VAC). Cycle-by-cycle current limiting ensures safe operation during short-circuits.
To protect the external power MOSFET from damage by supply over voltage, the SG6848X1 output driver is clamped at 15 V. The SG6848X1 controllers can be used to improve the performance and reduce the production cost of power supplies. The SG6848X1 can replace linear and RCC power supplies. It is available in DIP-8 and SSOT-6 packages.
Ordering Information
Part Number
Operating Temperature Range
Package
SG6848TZ1
-40 to +105°C
6-Lead, SUPERSOT™-6, JEDEC MO-193, 1.6 mm Wide
SG6848DZ1
-40 to +105°C
8-Lead, MDIP, JEDEC MS-001, .300" Wide, Two Dap
SG6848DY1
-40 to +105°C
8-Lead, MDIP, JEDEC MS-001, .300" Wide, Two Dap
Packing Method
Tape & Reel
Tube
Tube
© 2007 Fairchild Semiconductor Corporation SG6848x1 • Rev. 2, Feb-2020
www.fairchildsemi.com
SG6848x1 — Low-Cost, Green-Mode PWM Controller for Flyback Converters
Application Diagram
NOT RECOMMENDED FOR NEW DESIGNS
Figure 1. Typical Application
Internal Block Diagram
© 2007 Fairchild Semiconductor Corporation SG6848x1 • Rev. 2, Feb-2020
Figure 2. Functional Block Diagram
2
www.fairchildsemi.com
SG6848x1 — Low-Cost, Green-Mode PWM Controller for Flyback Converters
Marking Information
NOT RECOMMENDED FOR NEW DESIGNS
XXX: AAH=SG6848x1 TT : Die Run Code
. . . : Year Code
- - - : Week Code
*Marking for SG6848TZ1 (Pb-free)
T: D=DIP P: Z= Lead Free + RoHS Compatible
Null=Regular Package XXXXXXXX: Wafer Lot Y: Year WW: Week V: Assembly Location
*Marking for SG6848DZ1 (Pb-free)
DZXXYYTTTT 6848 TPM
F- Fairchild Logo Z- Plant Code X- 1-Digit Year Code Y- 1-Digit Week Code TT: 2-Digit Die Run Code T: Package Type (D=DIP) P: Z: Pb-free, Y: Green Package
M: Manufacture Flow Code
*Marking for SG6848DY1 (Green Compound) Figure 3. Top Mark
© 2007 Fairchild Semiconductor Corporation
SG6848x1 • Rev. 2, Feb-2020
3
www.fairchildsemi.com
SG6848x1 — Low-Cost, Green-Mode PWM Controller for Flyback Converters
Pin Configurations
NOT RECOMMENDED FOR NEW DESIGNS
Figure 4. SSOT-6 Pin Configuration
Figure 5. DIP-8 Pin Configuration
Pin Definitions
DIP Pin #
1 2 3 4
5
6 7 8
SSOT Pin #
Name
Description
6
GATE The totem-pole output driver for driving the power MOSFET
5
VDD Power supply
NC No connection
Current sense. This pin senses the voltage across a resistor. When the voltage reaches 4 SENSE the internal threshold, PWM output is disabled. This activates over-current protection.
This pin also provides current amplitude information for current-mode control.
A resistor connected from the RI pin to ground generates a constant current source
used to charge an internal capacitor and determine the switching frequency. Increasing
3
RI the resistance reduces the amplitude of the current source and the switching frequency.
A 95 kΩ resistor, RI, results in a 50 μA constant current, II, and a 70 kHz switching frequency.
NC No connection
Feedback. The FB pin provides the output voltage regulation signal. It provides
2
FB feedback to the internal PWM comparator, so that the PWM comparator can control the
duty cycle.
1
GND Ground
© 2007 Fairchild Semiconductor Corporation
SG6848x1 • R.