CR6848

Novel Low Cost Green-Power PWM Controller

Features
z Low Cost, PWM&PFM&CRM universal AC input
z Low Start-up Current (about 10µA) z Cycle-by-cycle current limiting
z Low Operating Current (about 2mA) z Clamped gate output voltage 16.5V
z Current Mode Operation z Over voltage protect 26.7V
z Under Voltage Lockout (UVLO) z High-Voltage CMOS Process with ESD
z Built-in Synchronized Slope z SOT-23-6L、SOP-8 & DIP-8 Pb-Free
Compensation Packaging
z Programmable PWM Frequency z Compatible with SG5701 & SG5848 &
z Leading edge Blanking on Sense input LD7535 &OB22632/63
z Constant output power limiting for

Applications
z Switching AC/DC Adaptor z Open Frame Switching Power Supply
z Battery Charger z 384X Replacement

General Description
The CR6848 is a highly integrated low cost edge blanking circuit on current sense input
current mode PWM controller, which is ideal could remove the signal glitch due to
for small power current mode of offline snubber circuit diode reverse recovery and
AC-DC fly-back converter applications. thus greatly reduces the external
Making use of external resistors, the IC component count and system cost in the
changes the operating frequency and design. Pulse-by-pulse current limiting
automatically enters the PFM/CRM under ensures safe operation even during
light-load/zero-load conditions. This can short-circuit.
minimize standby power consumption and The CR6848 offers more protection like
achieve green-power functions. With a very OVP (Over Voltage Protection) and OCP
low start-up current, the CR6848 could use (Over current protection). The CR6848’s
a large value start-up resistor (1.5Mohm). output driver is clamped to maximum 16.5V
Built-in synchronized slope compensation to protect the power MOSFET. Excellent
enhances the stability of the system and EMI performance is achieved soft switching
avoids sub-harmonic oscillation. Dynamic control at the totem pole gate driver output.
peak limiting circuit minimizes output power CR6848 is offered in SOT-23-6, SOP-8 and
change caused by delay time of the system DIP-8 packages.
over a universal AC input range. Leading

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CR6848

CR68XX Series

Part PWM
Package Description
Number Frequency
PWM&PFM&CRM 、 Current Mode 、 Slope
External DIP-8、SOP8 Compensation Leading-edge Blanking 、 Gate
CR6848
Adjustable SOT-23-6L Clamped、Over-voltage Protection、Over-current
Protection、 Soft Drive.
External DIP-8、SOP8 With All Functions of CR6848 、 Gate soft
CR6850
Adjustable SOT-23-6L Clamped
With All Functions of CR6850、Frequency jitter、
External DIP-8、SOP8
CR6851 Soft start、Sense Fault Protect、OLP、SCP、
Adjustable SOT-23-6L
OTP

TYPICAL APPLICATION

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CR6848

Pin Assignment

Pin Descriptions

Name Description
GND GND Pin
FB Analog Input. Voltage feedback pin (same as the COMP pin in UC384X),
This pin is to program the switching frequency. By connecting a resistor
RI
to ground to set the switching frequency.
SEN Current sense pin, connect to sense the MOSFET current.
VDD Supply voltage pin.
GATE Gate output to drive the external power MOSFET.

Block Diagram

Simplified Internal Circuit Architecture

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CR6848

Absolute Maximum Ratings

Symbol Parameter Rating Unit
VDD Supply voltage Pin Voltage 40 V
IOVP VDD OVP maximal enter current 20 mA
VFB Input Voltage to FB Pin -0.3 to 6V V
VSEN Input Voltage to SEN Pin -0.3 to 6V V
PD Power Dissipation 300 mW
ESD Capability, HBM Model 2000 V
ESD Capability, Machine Model 200 V
20 second
220 ℃
Lead Temperature SOT-23-6L
TL
(Soldering) 10 second
260 ℃
DIP-8
TSTG Storage Temperature Range -55 to + 150 ℃

RECOMMENDED OPERATION CONDITION

Symbol Parameter Min ~ Max Unit
VDD VDD Supply Voltage 11~20 V
RI RI PIN Resistor Value 58~120 K ohm
TOA Operation Ambient Temperature -20~85 ℃
PO Output Power 0~60 W
FPWM Frequency of PWM 48~100 kHz

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CR6848

Electrical Characteristics (Ta=25°C unless otherwise noted, VDD = 15V.)

Symbol Parameter Conditions Min. Typ. Max. Unit

Supply Voltage (VDD Pin)
IST Startup Current 10 µA
VFB=0V 2.8 mA
ISS Operating Current VFB=3V 2.3 mA

VFB=Open 1.46 mA
VDDON Turn-on Threshold Voltage 16.1 V
VDDOFF Turn-off Threshold Voltage 11.1 V

VDCLAMP VDD Clamp Voltage IVDD=20mA 26.7 V

Voltage Feedback (FB Pin)

IFB Short Circuit Current VFB=0V 2.8 mA
VFB Open Loop Voltage VFB=Open 4.8 V
IPFM Enter PFM, FB current 0.92 mA
ICRM Enter CRM, FB current 1.5 mA

Current Sensing (SEN Pin)

VTH_L Minimum Voltage Lever 0.83 0.87 V
VTH_H Maximum Voltage Lever 1.0 1.05 V
TPD Delay to Output 300 ns
RCS Input Impedance 50 KΩ

Oscillator (RI Pin)

FOSC Normal Frequency RI=100Kohm 53 58 63 KHz
FPFM PFM Frequency RI=100Kohm 11.6 KHZ
DCMAX Maximum Duty Cycle RI=100Kohm 75 %

ΔFTEMP Frequency Temp. Stability -30-85℃ 5 %

TBLANK Leading-Edge Blanking Time 300 nS

GATE Drive Output (GATE Pin)

VOL Output Low Level VDD=15V, IO=20mA 1 V
VOH Output High Level VDD=15V, IO=20mA 8 V
TR Rising Time CL=1000pF 450 ns

TF Falling Time CL=1000pF 130 ns

VGCLAMP Output Clamp Voltage VDD=20V 16.5 V

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CR6848

TYPICAL CHARACTERISTICS

VDD startup Current VS Temperature VDD startup Current VS Temperature

VDD (OFF) VS Temperature VDD Operation Current VS Temperature

OVP VS Temperature PWM frequency VS Temperature

Duty cycle VS Temperature

FOSC VS FB Current
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CR6848

FOSC VS RI pin resistor

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CR6848

OPERATION DESCRIPTION
Current Model suggested operating frequency range of
Compared to voltage model control, CR6848 is within 48KHz to 100KHz.
current model control has a current Green Power Operation
feedback loop. When the voltage of the The power dissipation of switching mode
sense resistor peak current of the primary power supply is very important in zero load
winding reaches the internal setting value or light load condition. The major dissipation
VTH, comparator reverse, register reset and result from conduction loss、switching loss
power MOSFET cut-off. So that to detect and consume of the control circuit. However,
and modulate the peak current cycle by all of them related to the switching
cycle could control the output of the power frequency. There are many difference
supply. The current feedback has a good topologies has been implemented in
linear modulation rate and a fast input and different chip. The basic operation theory of
output dynamic impact avoid the pole that all these approaches intended to reduce the
the output filter inductance brings and the switching frequency under light-load or
second class system descends to first class no-load condition.
and so it widens the frequency range and CR6848`s green power function adapts
optimizes overload protection and short PWM、PFM and CRM combining modulation.
circuit protection. When RI resistor is 100k, the PWM
Startup Current and Under Voltage frequency is 58kHz in medium or heavy load
Lockout operation. Through modifying the pulse
The startup current of CR6848 is set to be width, CR6848 could control output voltage.
very low so that a large value startup The current of FB pin increases when the
resistor can therefore be used to minimize load is in light condition and the internal
the power loss. For AC to DC adaptor with mode controller enters PFM&PWM when
universal input range design, a 1.5 MΩ, 1/8 the feedback current is over 0.92mA. The
W startup resistor and a 10uF/25V VDD operation frequency of oscillator is to
hold capacitor could be used. descend gradually. The invariable frequency
The turn-on and turn-off threshold of the of oscillator is 11.6kHz when the feedback
CR6848 is designed to 16.1V/11.1V. During current is over 1.05mA. To decrease the
startup, the hold-up capacitor must be standby consumption of the power supply ,
charge to 16.1V through the startup resistor. Chip-Rail introduces the Cycle Reset Mode
The hysteresis is implemented to prevent technology；If the feedback current were
the shutdown from the voltage dip during over 1.1mA, mode controller of CR6848
startup. would reset internal register all the time and
Internal Bias and OSC Operation cut off the gate pin, while the output voltage
A resistor connected between RI pin and is lower than the set value, it would set
GND pin set the internal constant current register, gate pin operating again. Although
source to charge or discharge the internal the frequency of the internal OSC is
fixed cap. The charge time and discharge invariable, the register would reset some
time determine the internal clock speed and pulses so that the practical frequency is
the switching frequency. Increasing the decreased at the gate pin.
resistance will reduce the value of the input
current and reduce the switching frequency.
The relationship between RI pin and PWM
switching frequency follows the below
equation within the RI allowed range.
5800
FOSC = (kHz )
RI ( KΩ)
For example, a 100kΩ resistor RI could
generate a 50uA constant current and a
58kHz PWM switching frequency. The CR6848 Green-Power Function

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CR6848

Internal Synchronized Slop primary wind inductance. V IN ranges from

Compensation 85VAC to 264VAC. To guarantee the output
Although there are more advantages of the power is a constant for universal input AC
current mode control than conventional voltage, there is a dynamic peak limit circuit
voltage mode control, there are still several to compensate the system delay T that the
drawbacks of peak-sensing current-mode system delay brings on.
converter. Especially the open loop
instability when it operates in higher than
Leading-edge Blanking (LEB)
50% of the duty-cycle. CR6848 is introduced
Each time the power MOSFET is switched
an internal slope compensation adding
on, a turn-on spike will inevitably occur at
voltage ramp to the current sense input
the sense pin, which would disturb the
voltage for PWM generation to solve this
internal signal from the sampling of the
problem. It improves the close loop stability
RSENSE. There is a 300n sec leading edge
greatly at CCM, prevents the sub-harmonic
blanking time built in to avoid the effect of
oscillation and thus reduces the output
the turn-on spike and the power MOSFET
ripple voltage.
cannot be switched off during this time. So
DUTY that the conventional external RC filtering on
VSLOP = 0.33 × = 0.4389 × DUTY
DUTYMAX sense input is no longer required.

Current Sensing & Dynamic peak

limiting
The current flowing by the power MOSFET
comes in to being a voltage VSENSE on the
sense pin cycle by cycle, which compares to Over Voltage Protection (OVP)
the internal reference voltage, controls the There is a 26.7V over-voltage protection
reverse of the internal register, limits the circuit in the CR6848 to improve the
peak current IMAX of the primary of the credibility and extend the life of the chip. The
1 GATE is to shutdown immediately when the
transformer. The energy E = × L × I MAX
2
voltage of the VDD is over 26.7V and the
2 voltage of VDD is to descend rapidly.
deposited by the transformer. So adjusting
the RSENSE can set the Max output power of Gate Driver & Soft Clamped
the power supple mode. The current flowing CR6848’ output designs a totem pole to
by the power MOSFET has an extra value drive a periphery power MOSFET. The dead
V IN time is introduced to minimize the transfixion
∆I = × TD due to the system delay T current when the output is drove. The
LP
NMOS is shut off when the other NMOS is
that the current detected from the sense pin turned on. The clamp technology is
to power MOSFET cut off in the CR6848 introduced to protect the periphery power
(Among these, VIN is the primary winding MOSFET from breaking down.
voltage of the transformer and LP is the

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CR6848

PACKAGE DEMENSIONS
DIP-8L

Dimensions

Millimeters Inches
Symbol
Min. Typ. Max. Min. Typ. Max.
A 5.334 0.210
A1 0.381 0.015
A2 3.175 3.302 3.429 0.125 0.130 0.135
b 1.524 0.060
b1 0.457 0.018
D 9.017 9.271 10.160 0.355 0.365 0.400
E 7.620 0.300
E1 6.223 6.350 6.477 0.245 0.250 0.255
e 2.540 0.100
L 2.921 3.302 3.810 0.115 0.130 0.150
eB 8.509 9.017 9.525 0.335 0.355 0.375
θ˚ 0˚ 7˚ 15˚ 0˚ 7˚ 15˚

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CR6848

SOT-23-6L

Dimensions In Millimeters Dimensions In Inches

Symbol
Min Max Min Max
A 0.700 1.000 0.028 0.039
A1 0.000 0.100 0.000 0.004
B 1.397 1.803 0.055 0.071
b 0.300 0.559 0.012 0.022
C 2.591 3.000 0.102 0.118
D 2.692 3.099 0.106 0.122
e 0.838 1.041 0.033 0.041
H 0.080 0.254 0.003 0.010
L 0.300 0.610 0.012 0.024

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CR6848

SOP-8L

Dimensions DISCLAIMERS
Millimeter Inch
Symbol
Min. Typ. Max. Min. Typ. Max.
A 1.346 1.752 0.053 0.069
A1 0.101 0.254 0.004 0.010
b 0.406 0.016
c 0.203 0.008
D 4.648 4.978 0.183 0.196
E 3.810 3.987 0.150 0.157
e 1.016 1.270 1.524 0.040 0.050 0.060
0.381X45 0.015X45
F ° °
H 5.791 6.197 0.228 0.244
L 0.406 1.270 0.016 0.050
θ˚ 0° 8° 0° 8°

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CR6848

REFERENCE CIRCUIT 1

CR6848 drives a periphery Power MOSFET.

5V/6A 30W Power Supply

Quantity Part Number Description Quantity Part Number Description

1 C1 102/1000V 1 F1 0.25A
1 C2 103/1000V 1 L1 10uH
1 C3 104 1 R1 20R
1 C4 33uF/400V 2 R2、R3 1K
1 C5 223/1000V 1 R4 100K
1 C7 103/1000V 1 R5 100K/0.5W
1 C8 102/100V 1 R6 47R
2 C6、C7 1000 uF/25V 1 R7 1.5M
1 C8 104 1 R8 0R51
1 BD1 KBL406 1 R9 20R
1 D1 FR107 2 R11、R12 3.3K
1 D2 1N4007 1 U1 CR6848
1 D3 Y2010D 1 U2 PC817
1 D4 LED 1 U3 TL431
1 T1 20mH 1 Q1 2N60
1 T2 EI-22

Notice: Q1 is a Power MOSFET

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CR6848

REFERENCE CIRCUIT 2
CR6848 drives a periphery Power BJT（5V/3A 15W Power Supply）

Quantity Part Number Description Quantity Part Number Description

2 C1、C2 104/400V 1 R2 100K

1 C3 472 1 R3 100K/0.5W
1 C4 102 1 R4 1K
1 C5 33uF/400V 1 R5 1.5M
1 C6 10uF/50V 2 R6、R7 220R/1W
1 C7 103/1000V 1 R8 220R
1 C8 102/100V 1 R9 20K
1 C9 223/1000V 2 R10、R11 20R
2 C10、C11 220uF/16V 1 R12 1R2/1W
1 C12 1.0uF/16V 1 R13 20K
5 D1、D2、D3、
D4、D5 1N4007 1 R14 2K2
2 D6、D7 1N4148 1 U1 CR6848
1 D8 18V 1 U2 PC817
1 D9 SB560 1 U3 TL431
2 D10、D11 FR107 1 U4 LM358
1 T1 20mH 1 Q1 13003
1 T2 EI-22 1 Q2 9013
1 F1 0.25A
Notice: Q1 is a Power BJT

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