CR6842
CR6842
Green-Power PWM Controller Features
z Low Cost, Green-Power Burst-Mode PWM
z Very Low Start-up Current ( about 6μA)
z Low Operating Current ( about 3mA)
z Current
Mode
Operation
z Under Voltage Lockout (UVLO)
z VDD Over Voltage Protection(OVP)
z programmable
over-temperature
protection z Internal
Latch
Circuit(OTP,OVP)
z Built-in soft start with 1ms
z Built-in Frequency jitter for better EMI Signature z Soft Clamped gate output voltage 16.5V z VDD over voltage protect 25.5V
z Cycle-by-cycle
current
limiting
z Sense Fault Protection
z Output SCP (Short circuit Protection)
z Built-in Synchronized Slope Compensation z Leading-edge blanking on Sense input z Programmable PWM Frequency
z High-Voltage CMOS Process with ESD
z DIP-8 & SOP-8 Pb-Free Package
z Compatible with SG6842J&LD7552
Applications
z Power
Adaptor
z Battery Charger Adapter z Open Frame Switching Power Supply z 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.
Aug.2006 V 1.1 1/4
Pin Assignment & Description
Name Description
GND GND
Pin
FB Voltage feedback pin. The PWM duty cycle is determined by FB and Sense.
VIN 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.
RI By connecting a resistor to ground to set the switching freq.. Increasing the resistor will reduce the switching freq..
RT An NTC resistor is connected from this pin to ground for over-temperature protection.
SENSE Current sense pin, The sensed voltage is used for current-mode control and pulse-by-pulse current limiting.
VDD Power supply voltage pin.
GATE Gate drive output to drive the external MOSFET.A soft driving waveform is implemented to improve EMI.
Typical Application Circuit
Aug.2006 V 1.1 2/4
Block Diagram
Absolute Maximum Ratings
Symbol Parameter Rating Unit V DD Supply voltage Pin V oltage 40 V V FB Input V oltage to FB Pin -0.3 to 6V V V Sense Input V oltage to SENSE Pin -0.3 to 6V V P D Power Dissipation 1000 mW ESD Capability, HBM Model 2000 V
ESD Capability, Machine Model 200 V
T L Lead Temperature(Soldering) DIP-8(10sec)
260 ℃
T STG Storage Temperature Range-55 to + 150 ℃
Aug.2006 V 1.1 3/4
Aug.2006 V 1.1 4/4
Electrical Characteristics (Ta=27°C unless otherwise noted, V DD = 15V.)
Symbol Parameter Conditions Min.Typ.Max. Unit Supply Voltage (V DD Pin)
I ST Startup Current
VDD=17
5.6
30
μA
I SS Operating Current
V FB = V SENSE = 0V VDD=15 3.5 5 mA
V TH(ON) Start Threshold Voltage -- 17.618.619.6 V
V TH(OFF)
Min. Operating Voltage -- 10.111.112.1 V VDD-OVP VDD Over Voltage
Protection(Latch off)
26.427.428.4 V
VDD-th-g VDD Low-Threshold Voltage to Exit Green-OFF Mode
12 12.513 V
Voltage Feedback (FB Pin)
I FB Short Circuit Current V FB =
0V 1.5 mA V FB Open Loop Voltage V FB =Open 5.88 V Current Sensing (SEN Pin)
V TH Threshold voltage for current limit
I VIN =0
0.660.9 V
T PD Delay to Output 100 200 nsec Z CS Input Impedance 12 K ? B nk Leading Edge Blanking Time 260 360 460 nsec Oscillator (RI Pin) F OSC Frequency in nominal mode RI=26K ? 63 68 73 KHz F OSC-green Frequency in green mode RI=26 K ? 33.336 38.5 KHz
V N Beginning of frequency reducing at FB Voltage
VDD=15V
1.9
2.1 2.3 V
V G End of frequency reducing at FB voltage
VDD=15V
1.4 1.6 1.8 V G
Frequency Temp. Stability -30-85℃ 5.0 % GATE Drive Output (GATE Pin) V OL
Output Low Level
V DD =12V,
I O =50mA 1.6 V V OH
Output High Level
V DD =12V, I O =50mA
6.7 V
T R Rising Time VDD=15V,C L =
1nF 150 203 350 ns T F Falling Time VDD=13V,C L =
1nF 30 74 90 ns DC MAX Maximum Duty Cycle
80 92 95 Over-Temperature Protection Section
I RT Output current of pin RT RI=26K ? 64 68 76
μA V OTP Threshold voltage for over-temperature protection. 1.015 1.053 1.115 V RI Section RI NOR RI Operating Range 15.5 36 K ? RI MAX Max RI value for Protection 216 K ? RI MIN 6 K ?