Document
CR6842
Green-Power PWM Controller with Freq. Jittering
Features
z z z www.DataSheet4U.com z z z z z z z z Low Cost, Green-Power Burst-Mode PWM Very Low Start-up Current ( about 7.5µA) Low Operating Current ( about 3.0mA) Current Mode Operation Under Voltage Lockout (UVLO) VDD Over Voltage Protection(OVP) programmable over-temperature protection Internal Latch Circuit(OTP,OVP) Built-in soft start with 1ms Built-in Frequency jitter for better EMI Signature Soft Clamped gate output voltage 16.5V z z z z z z z z z z VDD over voltage protect 25.5V Cycle-by-cycle current limiting Sense Fault Protection Output SCP (Short circuit Protection) Built-in Synchronized Slope Compensation
Leading-edge blanking on Sense input
Programmable PWM Frequency High-Voltage CMOS Process with ESD DIP-8 & SOP-8 Pb-Free Package Compatible with SG6842J&LD7552&OB2269
Applications
z z Power Adaptor Battery Charger Adapter z z Open Frame Switching Power Supply LCD Monitor
General Description
The CR6842 is a low startup current , low cost, current mode PWM controller with Green-Power & burst-mode power-saving operation. The integrated functions such as the leading-edge blanking of the current sensing, internal slope compensation provide the users a high efficiency, low external component counts, and low cost solution for AC/DC power applications. The special Green-Power function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. And under zero-load conditions, the power supply enters burst-mode to further reduce power consumption by shutting off PWM output. When the output of power supply is short or over loaded, the FB voltage will increase ,and if the FB voltage is higher than 5.2V for longer than 56msec the PWM output will be turned off. A external NTC resistor connected from pin RT to ground can be applied to over-temperature protection. Pulse by pulse current limit ensures a constant output current even under short circuit. PWM output will be disabled as long as VDD exceeds a threshold. When internal latch circuit is used to latch-off the controller, the latch will be reset when the power supply VDD is disabled.
Dec.2006
V 1.3
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Chengdu Chip-Rail Tech.Co.,Ltd
CR6842
Pin Assignment & Description
1 2 3 4
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GND FB VIN RI GATE VDD SENSE RT
8 7 6 5
Name GND FB VIN RI RT SENSE VDD GATE
Description GND Pin
Voltage feedback pin. The PWM duty cycle is determined by FB and Sense. This pin is pulled high to the rectified line input through a large resistor for start-up. This pin is also used to detect line voltage to compensate for constant output power limit for universal AC input. By connecting a resistor to ground to set the switching freq.. Increasing the resistor will reduce the switching freq.. An NTC resistor is connected from this pin to ground for over-temperature protection. Current sense pin, The sensed voltage is used for current-mode control and pulse-by-pulse current limiting. Power supply voltage pin. Gate drive output to drive the external MOSFET.A soft driving waveform is implemented
to improve EMI.
Typical Application Circuit
From bridge rectifier
From auxiliary winding
1 2 3 4
GND FB VIN RI
GATE VDD SENSE RT
8 7 6
Rs
5
NTC
Dec.2006
V 1.3
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Chengdu Chip-Rail Tech.Co.,Ltd
CR6842
Block Diagram
RI VIN
0.9V Current Reference VDD
Soft Driver
GATE
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RT
OTP
PWM LATCH
Internal BIAS
OSC
S R
Blanking Circuit
SENSE
Slope Compensation
VDD
UVLO
OVP Burst Mode Controller Green Mode Controller
56ms Debounce
FB
5.2V
GND
Absolute Maximum Ratings
Symbol VDD VFB VSense PD Parameter Supply voltage Pin Voltage Input Voltage to FB Pin Input Voltage to SENSE Pin Power Dissipation ESD Capability, HBM Model ESD Capability, Machine Model TL TSTG Lead Temperature(Soldering)
Storage Temperature Range
Rating 40 -0.3 to 6V -0.3 to 6V 1000 2000 200 DIP-8£¨ 10sec£© SOP-8£¨ 10sec£© 260 230
Unit V V V mW V V ¡æ ¡æ ¡æ
-55 to + 150
Dec.2006
V 1.3
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Chengdu Chip-Rail Tech.Co.,Ltd
CR6842
Electrical Characteristics (Ta=27°C unless otherwise noted, VDD = 15V.)
Symbol Parameter Supply Voltage (VDD Pin) IST Startup Current
ISS VTH(ON) VTH(OFF) Operating Current
Conditions
VDD=17 VFB= VSENSE = 0V VDD=15 ---
Min.
Typ.
7.5 3.0
Max.
30 5 17.0 11.2 25.0 13.0
Unit µA
mA V V V V
Start Threshold Voltage Min. Operating Voltage VDD Over Voltage www.DataSheet4U.com VDD-OVP Protection(Latch off) VDD Low-Threshold Voltage VDD-th-g to Exit Green-OFF Mode Voltage Feedback (FB Pin) IFB Short Circuit Current VFB Open Loop Voltage Current Sensing (SEN Pin) Threshold voltage for current VTH limit TPD Delay to Output ZCS Input Impedance Bnk Leading Edge Blanking Time Oscillator (RI Pin) FOSC Frequency in nominal mode FOSC-green Frequency in green mode Beginning of frequency VN reducing at FB Voltage End of frequency reducing at VG FB voltage Frequency Temp. Stability
16.0 10.4 23.0 11.0
16.5 10.8 24.5 12.0
VFB=0V VFB=Open
1.42 6.00
mA V
IVIN =.