Features: · Linearly Decreasing PWM Frequency
· Green-Mode under Light-Load and Zero-Load
Conditions
· Constant Voltage (CV) and Constant Current (CC)
· No Secondary Feedback
· Low Startup Current (5uA)
· Low Operating Current (3.6mA)
· Leading-Edge Blanking
· Constant Power Limit
· Universal AC Input Range
· Synchronized Slope Compensation
· 150°C OTP Sensor with Hysteresis
· VDD Over Voltage Clamping
· Cycle-by-Cycle Current Limiting
· Under Voltage Lockout (UVLO)
· Fixed PWM Frequency (65kHz/100kHz)
· Gate Output Maximum Voltage Clamped at 16.7V
· Small SOT-26 PackageApplication· 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 other auxiliary supplies, home appliances, consumer electronics, and PC 5V standby-power.
· Replacements for linear transformers and RCC SMPS.
Pinout
Specifications
|
Symbol |
Parameter |
Value |
Unit |
| VDD |
DC Supply Voltage*
Zener Clamp
Zener Current |
25
30
10 |
V
V
mA |
| VFB |
FB Pin Input Voltage |
-0.3 to 7 |
V |
| VSENSE |
Sense Pin Input Voltage |
-0.3 to 7 |
V |
| PD |
Power Dissipation |
300 |
mW |
| RJA |
Thermal Resistance (Junction to Air) |
SOT-26
DIP-8 |
243.3
113.0 |
°C/W |
| RJC |
Thermal Resistance (Junction to Case) |
SOT-26
DIP-8 |
115
67.1 |
°C/W |
| TJ |
Operating Junction Temperature |
150 |
°C |
| TSTG |
Storage Temperature Range |
-55 to +150 |
°C |
| TL |
Lead Temperature (Soldering) |
20 sec SOT-26
10 sec DIP-8 |
220
260 |
°C |
| |
ESD Capability, Human Body Model |
3.0 |
KV |
| |
ESD Capability, Machine Model |
300 |
V |
*All voltage values, except differential voltages, are given with respect to the network ground terminal.DescriptionThis highly integrated PWM controller provides several features to enhance the performance of low power flyback converters. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. This green-mode function enables the power supply to easily meet international power conservation requirements. The supply voltage VDD is also used for feedback compensation, to regulate the output voltage without requiring a conventional TL431 and a photo-coupler.Another advantage of the SG6849 is that the typical startup current is only 5uA, while the typical operating current can be as low as 3.6mA. A large startup resistance could be used to achieve even higher power conversion efficiency. Built-in synchronized slope compensation maintains the stability of peak current-mode control.Proprietary internal compensation ensures constant output power limiting over a universal range of AC input voltages, from 90VAC to 264VAC.The SG6849 provides many protection functions. Pulse-by-pulse current limiting ensures a constant output current, even if a short circuit occurs. Also, the internal protection circuit will disable PWM output, if VDD exceeds 22.7V. The gate output is clamped at 16.7V to protect the power MOS from over-voltage damage. The built-in over temperature protection (OTP) function will shutdown the controller at 150°C with a 20°C hysteresis. The SG6849 is designed to provide a low-cost total solution for flyback converters. It is available in a small footprint, 6-pin, SOT-26 package.
SG6849 Data Sheet
