Chip-Rail CR6850S, CR6850T Schematics
Novel Low Cost Green-Power PWM Controller
Features
z Low Cost, PWM&PFM&CRM (Cycle
Reset Mode)
z Low Start-up Current (about 8µA)
z Low Operating Current (about 2mA)
z Current Mode Operation
z Under Voltage Lockout (UVLO)
z Built-in Synchronized Slope
Compensation
z Programmable PWM Frequency
z Audio Noise Free Operation
z
Leading edge Blanking on Sense input
Applications
z Switching AC/DC Adaptor
z Battery Charger
General Description
The CR6850 is a highly integrated low cost
current mode PWM controller, which is ideal
for small power current mode of offline
AC-DC fly-back converter applications.
Making use of external resistors, the IC
changes the operating frequency and
automatically enters the PFM/CRM (Cycle
Reset Mode) under light-load/zero-load
conditions. This can minimize standby
power consumption and achieve
green-power functions. With a very low
start-up current, the CR6850 could use a
large value start-up resistor (2Mohm).
Built-in synchronized slope compensation
enhances the stability of the system and
avoids sub-harmonic oscillation. Dynamic
peak limiting circuit minimizes output power
change caused by delay time of the system
CR6850
z Constant output power limiting for
universal AC input
z Cycle-by-cycle current limiting
z Soft clamped gate output voltage 16.8V
z Over voltage protect 25.5V
z High-Voltage CMOS Process with ESD
z SOT-23-6L、SOP8 & DIP-8 Pb-Free
Packaging
z
Compatible with SG5701 & SG5848 &
LD7535 & OB2262/63
z Open Frame Switching Power Supply
z 384X Replacement
over a universal AC input range. Leading
edge blanking circuit on current sense input
could remove the signal glitch due to
snubber circuit diode reverse recovery and
thus greatly reduces the external
component count and system cost in the
design. Pulse-by-pulse current limiting
ensures safe operation even during
short-circuit.
The CR6850 offers more protection like
OVP (Over Voltage Protection) and OCP
(Over current protection). The CR6850’s
output driver is soft clamped to maximum
16.8V to protect the power MOSFET.
Excellent EMI performance is achieved soft
switching control at the totem pole gate
driver output. CR6850 is offered in
SOT-23-6, SOT-8 and DIP-8 packages.
Dec, 2006 V1.5 1/15
TEL:0755-25311262 FAX:0755-25311968
web:www.kingkeyelec.com
CR6850
CR68XX Series
Part
Number
CR6848
CR6850
CR6851
PWM
Frequency
External
Adjustable
External
Adjustable
External
Adjustable
DIP-8、SOP8
SOT-23-6L
DIP-8、SOP8
SOT-23-6L
DIP-8、SOP8
SOT-23-6L
TYPICAL APPLICATION
Package Description
PWM&PF&CRM 、 Current Mode 、 Slope
Compensation Leading-edge Blanking 、 Gate
Clamped、Over-voltage Protection、Over-current
Protection、 Soft Drive.
With All Functions of CR6848 、 Gate soft
Clamped
With All Functions of CR6850、Frequency jitter、
Soft start、Sense Fault Protect、OLP、SCP、
OTP
Pin Assignment
Pin Descriptions
Name Description
GND GND Pin
FB
RI
SEN
VDD Supply voltage pin.
GATE
Analog Input. Voltage feedback pin (same as the COMP pin in UC384X),
This pin is to program the switching frequency. By connecting a resistor
to ground to set the switching frequency.
Current sense pin, connect to sense the MOSFET current.
Totem output to drive the external Power MOSFET.
Dec, 2006 V1.5 2/15
TEL:0755-25311262 FAX:0755-25311968
web:www.kingkeyelec.com
CR6850
Block Diagram
Simplified Internal Circuit Architecture
Absolute Maximum Ratings
Symbol Parameter Rating Unit
V
DD
I
OVP
V
FB
V
SEN
P
D
ESD
T
L
T
STG
Supply voltage Pin Voltage 40 V
VDD OVP maximal enter current 20 mA
Input Voltage to FB Pin -0.3 to 6V V
Input Voltage to SEN Pin -0.3 to 6V V
Power Dissipation 300 mW
ESD Capability, HBM Model 2500 V
ESD Capability, Machine Model 250 V
Lead Temperature
(Soldering)
Storage Temperature Range -55 to + 150
20second
SOT-23-6L
10second
DIP-8
220
260
℃
℃
℃
RECOMMENDED OPERATION CONDITION
Symbol Parameter Min ~ Max Unit
VDD VDD Supply Voltage 11~20 V
RI RI PIN Resistor Value 65~130 K ohm
TOA Operation Ambient Temperature -20~85
PO Output Power 0~60 W
F
PWM
Frequency of PWM 50~100 kHz
℃
Dec, 2006 V1.5 3/15
TEL:0755-25311262 FAX:0755-25311968
web:www.kingkeyelec.com
CR6850
Electrical Characteristics (Ta=25°C unless otherwise noted, VDD = 15V.)
Symbol Parameter Conditions Min. Typ. Max. Unit
Supply Voltage (VDD Pin)
I
ST
Startup Current 8
µA
VFB=0V 2.9 mA
I
VDD
VDD
VD
SS
CLAMP
Operating Current
Turn-on Threshold Voltage 15.3 V
ON
Turn-off Threshold Voltage 9.8 V
OFF
VDD Clamp Voltage I
VFB=3V 1.9 mA
=Open 1.44 mA
V
FB
=20mA 25.5 V
VDD
Voltage Feedback (FB Pin)
IFB Short Circuit Current VFB=0V 1.68 mA
VFB Open Loop Voltage VFB=Open 4.7 V
I
Enter PFM&PWM, FB current 1.2 mA
PFM
I
CRM
Enter CRM, FB current 1.5 mA
V
PFM Threshold V
PFM
FB
1.15 V
Current Sensing (SEN Pin)
V
V
TH_L
TH_H
Minimum Voltage Lever 0.55 0.65 0.75 V
Maximum Voltage Lever 0.75 0.85 0.95 V
TPD Delay to Output 300 ns
RCS Input Impedance
50 KΩ
Oscillator (RI Pin)
F
Normal Frequency RI=100Kohm 60 65 70 KHz
OSC
F
PFM Frequency RI=100Kohm 20.6 KHZ
PFM
DC
Maximum Duty Cycle RI=100Kohm 77 %
MAX
ΔF
T
Frequency Temp. Stability
TEMP
Leading-Edge Blanking Time 300 nS
BLANK
-30-85
℃
5 %
GATE Drive Output (GATE Pin)
V
OL
V
OH
Output Low Level VDD=15V, IO=20mA 1 V
Output High Level VDD=15V, IO=20mA 8 V
VG
T
T
CLAMP
Rising Time
R
Falling Time CL=1000pF 120 ns
F
CL=1000pF 420 ns
Output Clamp Voltage VDD=20V 16.8 17.8 V
Dec, 2006 V1.5 4/15
TEL:0755-25311262 FAX:0755-25311968
web:www.kingkeyelec.com
CR6850
TYPICAL CHARACTERISTICS
VDD startup Current VS Temperature
VDD Operation Current VS Temperature
VDD (OFF) VS Temperature
PWM frequency VS Temperature
VDD (ON) VS Temperature
Dec, 2006 V1.5 5/15
TEL:0755-25311262 FAX:0755-25311968
web:www.kingkeyelec.com
Duty cycle VS Temperature
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