Richtek R7731GE Schematic [ru]

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R7731

Burst Triple Mode PWM Flyback Controller

General Description

The R7731 is a high performance, low cost, low start-up current, current mode PWM controller with burst triple mode to support green mode power saving operation. The R7731 integrates functions of Soft-Start, Under Voltage Lockout (UVLO), Leading Edge Blanking (LEB), Over Temperature Protection (OTP), internal slope compensation. It provides the users a superior AC/DC power application of higher efficiency, low external component counts and lower cost solution.

To protect the external power MOSFET from being damaged by supply over voltage, the R7731 output driver is clamped at 12V. Furthermore, R7731 features fruitful protections like OLP (Over Load Protection) ,OVP (Over Voltage Protection) to eliminate the external protection circuits and provide reliable operation. R7731 is available in SOT-23-6 and DIP-8 packages.

Features

zVery Low Start-Up Current (<30μA)

z10/14V UVLO

zSoft-Start Function

zCurrent Mode Control

zJittering Switching Frequency

zInternal Leading Edge Blanking

zBuilt-in Slope Compensation

zBurst Triple Mode PWM for Green-Mode

zCycle-by-Cycle Current Limiting

zFeedback Open Protection

zOutput Over Voltage Protection

zOver Temperature Protection

zOver Load Protection

zSoft Driving for Reducing EMI

zHigh Noise Immunity

zOpto Coupler Short Protection

zRoHS Compliant and Halogen Free

Applications

zAdaptor and Battery Charger

zATX Standby Power

zSet Top Boxes (STB)

zDVDand CD(R)

zTV/Monitor Standby Power

zPC Peripherals

Typical Application Circuit

VO+ AC Mains

(90V to 265V)

VO-

RT

VDD

 

R7731

COMP

 

GATE

GND

CS

DS7731-03 March 2011

www.richtek.com

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R7731

Ordering Information

R7731

Package Type

E : SOT-23-6

N : DIP-8

Lead Plating System

G : Green (Halogen Free and Pb Free)

Note :

Richtek products are :

`RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

`Suitable for use in SnPb or Pb-free soldering processes.

Marking Information

For marking information, contact our sales representative directly or through a Richtek distributor located in your area.

Pin Configurations

(TOP VIEW)

 

 

GATE

 

 

VDD CS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

 

 

 

 

5

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GND COMP RT

 

 

 

 

 

SOT-23-6

 

 

 

 

 

 

GND COMP NC

 

 

RT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8

 

 

 

7

 

 

6

 

 

5

 

 

 

 

 

 

 

 

 

2

 

 

3

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GATE VDD

 

NC

 

 

 

CS

DIP-8

www.richtek.com

DS7731-03 March 2011

2

Richtek R7731GE Schematic

R7731

Function Block Diagram

 

 

 

 

OVP +

VDD

 

 

 

 

POR

-

27V

 

 

Shutdown

OTP

 

 

 

 

Logic

 

 

+

 

 

 

 

 

 

 

Brown out

 

 

 

UVLO

-

14V/10V

sensing

 

 

 

 

 

 

COMP open

 

Counter

 

 

Bias &

 

 

 

 

sensing

 

 

 

 

Bandgap

OLP

 

 

Jittering Oscillator

 

 

Constant

SS

 

 

 

 

RT

 

 

Dmax

 

 

Power

 

 

 

 

 

 

 

 

 

 

 

Soft

 

 

 

 

S

 

Driver

 

 

 

 

 

 

 

 

 

-

 

Q

GATE

COMP

 

 

-

R

 

 

 

 

 

+

 

 

 

 

 

 

PWM

 

 

 

CS

Slope

comparator

 

 

 

 

 

 

 

 

Ramp

 

 

 

 

COMP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Burst

 

VBURL

LEB

X3

 

 

Triple Mode

 

VBURH

 

 

 

 

VDD

 

 

 

 

 

 

 

 

 

 

 

 

GND

Functional Pin Description

Pin No.

Pin Name

Pin Function

SOT-23-6

DIP8

 

 

1

8

GND

Ground.

2

7

COMP

Comparator Input Pin. By connecting a photo-coupler to this pin, the peak

current set point is adjusted accordingly to the output power requirement.

 

 

 

3

5

RT

Set the switching frequency by connecting a resistor to GND.

4

4

CS

Primary Current Sense Pin.

5

2

VDD

IC Power Supply Pin.

6

1

GATE

Gate driver output to drive the external MOSFET.

--

3, 6

NC

No Internal Connection.

 

 

 

 

DS7731-03 March 2011

www.richtek.com

3

R7731

Absolute Maximum Ratings (Note 1)

z Supply Input Voltage, VDD -------------------------------------------------------------------------------------------

30V

z GATE Pin ----------------------------------------------------------------------------------------------------------------

20V

z FB, RT, COMP, CS Pin ----------------------------------------------------------------------------------------------

6.5V

z IDD -------------------------------------------------------------------------------------------------------------------------

10mA

z Power Dissipation, PD @ TA = 25°C

 

SOT-23-6 ----------------------------------------------------------------------------------------------------------------

0.4W

DIP-8 ---------------------------------------------------------------------------------------------------------------------

0.714W

z Package Thermal Resistance (Note 2)

 

z SOT-23-6, θJA -----------------------------------------------------------------------------------------------------------

250°C/W

z DIP-8, θJA ----------------------------------------------------------------------------------------------------------------

140°C/W

z Junction Temperature -------------------------------------------------------------------------------------------------

150°C

z Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------

260°C

z Storage Temperature Range ----------------------------------------------------------------------------------------

−65°C to 150°C

z ESD Susceptibility (Note 3)

 

HBM (Human Body Mode) ------------------------------------------------------------------------------------------

4kV

MM (Machine Mode) --------------------------------------------------------------------------------------------------

250V

Recommended Operating Conditions

(Note 4)

z Supply Input Voltage, VDD -------------------------------------------------------------------------------------------

12V to 25V

z Operating Frequency -------------------------------------------------------------------------------------------------

50k to 130kHz

z Junction Temperature Range ----------------------------------------------------------------------------------------

−40°C to 125°C

z Ambient Temperature Range ----------------------------------------------------------------------------------------

−40°C to 85°C

Electrical Characteristics

(VDD = 15V, RT = 100kΩ, TA = 25°C, unless otherwise specified)

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

VDD Section

 

 

 

 

 

 

VDD Over Voltage Protection Level

VOVP

 

25.5

27

28.5

V

On Threshold Voltage

VTH_ON

 

13

14

15

V

VDD On/Off Hysteresis

VDD_hys

 

3

4

5

V

Start-Up Current

IDD-ST

VDD = VTH_ON – 0.1V

--

20

30

μA

Operating Current

IDD-OP

VDD = 15V, RT = 100kΩ,

--

1.1

2.2

mA

GATE = Open, VCOMP = 2.5V

 

 

 

 

 

 

VDD Hold Up Mode Hysteresis

VDD_hys

VCOMP < 1.6V

--

11.5

--

V

Ending Level

 

 

 

 

 

 

VDD Hold Up Mode Entry Level

VDD_Low

VCOMP < 1.6V

--

11

--

V

VDD Clamp Voltage

VDD_Clamp

 

--

29

--

V

Oscillator Section (RT pin)

 

 

 

 

 

 

Normal PWM Frequency

fOSC

RT = 100kΩ

60

65

70

kHz

Frequency Jittering Range

 

 

--

± 4

--

%

Maximum Duty Cycle

DMAX

 

70

75

80

%

 

 

 

 

 

To be continued

 

 

 

 

 

 

 

www.richtek.com

 

 

 

DS7731-03 March 2011

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