Richtek RT8562GQW Schematic [ru]

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Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area.
DS8562-01 April 2011
General Description
The RT8562 is a 40V 8-channel LED driver capable of delivering 30mA to each channel with 10 LEDs (3.6V per diode), total of 80 LEDs with one driver. The RT8562 is a current mode boost converter opearated at 1MHz, wide VIN range covers from 6V to 24V and the on-chip current switch is rated at 2.5A.
The PWM output voltage loop regulates the LED pins to 0.6V with an auto-adjustment circuit allowing voltage mismatches between LED strings. The RT8562 automatically detects and disconnects any unconnected and/or broken strings during operation from PWM loop to prevent VOUT from over voltage.
The 1.5% matched LEDcurrents on all channels are simply programmed with a resistor or a current sink. Both analog dimming and digitally controlled PWM dimming are supported by RT8562. Analog dimming is linearly controlled by an external voltage. Avery high contrast ratio true digital PWM dimming can be achieved by driving PWM pin with a PWM signal.
Other protecting features include programmable output over voltage protection, LED curren limit, PWM switch current limit and thermal shutdown.
The RT8562 is packaged with a tiny footprint package of WQFN-24L 4x4 packages.

RT8562

High Voltage 8 Channel LED Driver

Features

z High Voltage : VIN up to 24V, VOUT up to 40V, Driving up to 80 x 3.6V LEDs (10 each channel)

z Channel Current Programmabe 10mA to 30mA and

Matched to 1.5%

z Current Mode PWM 1MHz Boost Converter z Easy Analog and Digital Dimming Control z Programmable Soft Start

z Automatic Detecting Unconnected and/or Broken

Channel

z Programmable Over Voltage Protection z Disconnects LED in Shutdown

z Providing High Accuracy Digital Dimming by PWM

Signal

z VIN Under Voltage Lockout

z Over Temperature Protection

z Current Limiting Protection

z Small 24-Lead WQFN Package

z RoHS Compliant and Halogen Free

Applications

z UMPC and Notebook Computer Backlight

z GPS, Portable DVD Backlight

z Desk Lights and Room Lighting

Pin Configurations

(TOP VIEW)

Ordering Information

 

VDC

VIN

COMP

NC

LX2

LX1

 

 

RT8562

 

 

 

 

Package Type

 

 

 

 

 

 

 

 

 

 

 

24

23

22

21

20

19

 

 

 

 

 

 

 

 

 

 

 

 

 

QW : WQFN-24L 4x4 (W-Type)

EN

1

 

 

 

 

 

18

PGND2

 

 

 

 

 

 

 

 

 

Lead Plating System

NC

2

 

 

 

 

 

17

PGND1

 

SS

3

 

 

 

 

 

16

OVP

 

G : Green (Halogen Free and Pb Free)

 

GND

 

 

Note :

NC

4

 

 

 

15

CH1

 

 

 

 

 

 

Richtek products are :

GND

5

 

 

 

 

 

14

CH2

 

 

 

 

 

25

 

` RoHS compliant and compatible with the current require-

PWM

6

 

 

 

 

13

CH3

 

 

 

 

 

 

7

8

9

10

11

12

 

 

ments of IPC/JEDEC J-STD-020.

 

 

 

 

CH8

CH7

CH6

CH5

ISET

CH4

 

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WQFN-24L 4x4

 

 

www.richtek.com

1

RT8562

Typical Application Circuit

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

L

 

 

D1

 

 

 

40V MAX

 

 

VIN

 

 

 

10µH

 

 

 

 

 

 

 

 

6V to 24V

 

C1

 

 

 

 

 

C5

 

 

 

 

 

 

R4

 

 

 

 

 

 

 

 

 

 

 

10µF

RT8562

 

 

 

10µF

:

:

:

 

 

 

10

 

 

 

 

 

 

:

10 LED String

 

 

 

 

23 VIN

LX1

19

 

 

:

:

... :

:

 

 

C6

 

R7

 

:

:

:

:

 

 

 

 

 

 

LX2

20

C7

:

:

:

:

 

 

 

1µF

R5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15

 

 

 

 

 

 

 

 

 

5V

1k

1 EN

CH1

 

 

 

 

 

 

 

 

 

R6 1k

 

6 PWM

CH2

14

 

...

 

 

 

 

 

 

 

 

 

8

 

 

 

 

 

 

PWM Signal

 

 

CH7

 

 

 

 

 

 

 

 

22 COMP

 

 

 

 

 

 

 

 

 

 

 

CH8

7

 

 

R2

 

 

 

 

R1

 

 

 

24

 

16

 

 

 

 

 

 

 

 

 

VDC

OVP

 

 

 

VOUT

 

 

1.8k

 

 

 

 

 

 

 

 

 

 

C2

C3

 

 

3 SS

ISET

11

 

 

R3

 

 

 

 

4.7µF

 

 

GND

 

 

RISET

 

 

 

 

 

3.9nF

 

C4

 

 

 

 

 

 

 

 

 

 

 

0.1µF

 

5, Exposed Pad (25)

4.75k

 

 

 

 

 

 

 

 

 

 

 

 

 

ILED (mA) =

20 x 4.75

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RISET (kΩ)

 

 

 

 

 

 

Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

L

 

 

D1

 

 

 

40V MAX

 

 

VIN

 

 

 

10µH

 

 

 

 

 

 

 

 

6V to 24V

 

C1

 

 

 

 

 

C5

 

 

 

 

 

 

R4

 

 

 

 

 

 

 

 

 

 

 

10µF

RT8562

 

 

 

10µF

:

:

:

 

 

 

10

 

 

 

 

 

 

:

10 LED String

 

 

 

 

23 VIN

LX1

19

 

 

:

:

... :

:

 

 

 

 

 

 

:

:

:

:

 

 

 

C6

 

 

 

LX2

20

R7

C7

:

:

:

:

 

 

 

1µF

R5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15

 

 

 

 

 

 

 

 

 

5V

1k

1 EN

CH1

 

 

 

 

 

 

 

Analog

R6 1k

 

6 PWM

CH2

14

 

...

 

 

 

 

 

 

 

8

 

 

 

 

 

 

 

 

CH7

 

 

 

 

 

 

Dimming

 

 

22 COMP

 

 

 

 

 

 

 

 

 

 

 

CH8

7

 

 

R2

 

 

 

 

R1

 

 

 

24

 

16

 

 

 

 

 

 

 

 

 

VDC

OVP

 

 

 

VOUT

 

 

1.8k

 

 

 

 

 

 

 

 

 

 

C2

C3

 

 

3 SS

ISET

11

 

 

R3

 

 

 

 

4.7µF

 

 

GND

 

 

RISET

 

 

 

 

 

3.9nF

 

C4

 

 

 

 

 

 

 

 

 

 

 

 

 

5, Exposed Pad (25)

4.75k

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILED (mA) =

20 x 4.75

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RISET (kΩ)

 

 

 

 

Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control

www.richtek.com

DS8562-01 April 2011

2

Richtek RT8562GQW Schematic

RT8562

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

L

 

 

D1

 

 

 

40V MAX

 

VIN

 

 

 

10µH

 

 

 

 

 

 

 

 

4V to 36V

C7

C1

 

 

 

 

 

 

C5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1µF

10µF

RT8562

 

 

 

 

10µF

:

:

:

 

 

R4

 

 

 

19

 

 

:

10 LED String

 

 

 

 

LX1

 

 

:

:

... :

:

VAVDD

10

 

23

VIN

 

R7

 

:

:

:

:

 

6V to 24V

 

C6

 

LX2

20

C8

:

:

:

:

 

 

 

 

 

 

 

 

 

 

 

 

R5

2.2µF

 

CH1

15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5V

1k

 

1 EN

CH2

14

 

 

 

 

 

 

 

 

 

 

...

 

 

 

 

 

 

R6 1k

 

 

 

 

 

 

 

 

 

 

Analog

 

6 PWM

CH7

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dimming

 

 

22 COMP

CH8

7

 

 

 

 

 

 

 

 

 

 

 

 

R2

 

 

 

 

R1

 

 

24 VDC

OVP

16

 

 

 

VOUT

 

 

 

 

 

 

 

 

 

 

1.8k

C3

 

3 SS

ISET

11

 

 

 

 

 

 

 

C2

 

 

 

R3

 

 

 

 

4.7µF

 

 

GND

 

 

RISET

 

 

 

 

 

3.9nF

 

C4

 

 

 

 

 

 

 

 

 

 

5, Exposed Pad (25)

4.75k

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILED (mA) =

20 x 4.75

 

 

 

 

Note :

 

 

 

 

 

 

 

 

RISET (kΩ)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.Due to the limitaion of maximum duty, 5V input can support typically to VOUT = 33V.

2.Due to the limitaion of maximum duty, 4V input can support typically to VOUT = 26V.

Figure 3. Wide Range VIN Application by Connecting VCC Pin to LCD Driver Power AVDD

Function Block Diagram

 

 

 

 

 

 

LX1, LX2

 

 

 

VIN

 

-

OSC

 

 

 

 

 

S

 

CH1

 

 

 

5.6V

+

+

 

 

 

 

R

 

 

 

OVP

 

+

-

 

 

 

 

R

 

 

 

1.2V

 

 

 

 

 

-

 

 

 

 

 

EN

 

-

+ -

+

CH2

 

 

 

1.6V

+

Shutdown

.

 

 

 

5V

 

 

-

 

 

VDC

 

 

 

.

 

 

LDO

 

 

 

 

 

 

 

 

VOUT

 

.

 

 

COMP

 

 

 

 

 

 

 

 

Regulation

+

CH7

 

 

 

 

 

Unit

 

 

 

 

 

 

 

-

 

 

 

 

5uA

 

 

5V

 

 

 

 

 

 

 

 

 

 

SS

 

 

 

 

 

 

 

 

 

 

 

+

CH8

 

 

PWM

 

 

+

 

 

 

 

 

-

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ISET

 

DS8562-01

April

2011

 

 

 

 

www.richtek.com

 

 

 

 

 

 

 

3

RT8562

Functional Pin Description

Pin No.

Pin Name

 

 

Pin Function

 

 

 

 

 

1

EN

Chip enable pin, when pulled low, chip is in shutdown mode.

 

 

 

 

 

2, 4, 21

NC

No Internal Connection.

 

 

 

 

 

3

SS

Soft Start Pin, a capacitor of at least 10nF is required for soft start.

 

 

 

 

 

5,

GND

Ground pin of the chip. The exposed pad must be soldered to a large PCB and

25 (Exposed Pad)

connected to GND for maximum power dissipation.

 

 

Analog/Digital dimming control. When using analog dimming,

6

PWM

 

20 x 4.75

 

 

ILED (mA) =

 

for VPWM ≥ 1.2V.

 

 

RISET(kΩ)

11

ISET

A resistor or a current from DAC on this pin programs the full LED current.

 

 

 

10, 9, 8, 7

CH5 to CH8

Channel 5 to Channel 8 LED current sink. Leave the pin unconnected if not used.

15, 14, 13, 12

CH1 to CH4

Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not used.

16

OVP

Over Voltage Protection. PWM boost converter turns off when VOVP goes

higher than 1.2V.

 

 

17, 18

PGND1,

Power Ground (LX1/LX2 power return).

PGND2

 

 

 

 

19, 20

LX1, LX2

PWM boost converter switch node.

 

 

 

22

COMP

PWM boost converter loop compensation node.

 

 

 

23

VIN

Power supply of the chip. For good bypass, a low ESR capacitor is required.

 

 

 

24

VDC

Put 1μF capacitor on this pin to stabilize the 5V output of the internal regulator.

This regulator is for chip internal use only.

 

 

Absolute Maximum Ratings (Note 1)

z Supply Voltage, VIN ------------------------------------------------------------------------------------------------------

28V

z LX1, LX2 Pin Voltage at Switching Off --------------------------------------------------------------------------------

45V

z CH1 to CH8 Pin ------------------------------------------------------------------------------------------------------------

35V

z PWM, EN, OVP Pin Voltage -------------------------------------------------------------------------------------------

−0.3V to 5.5V

z Power Dissipation, PD @ TA = 25°C

 

WQFN-24L 4x4 ------------------------------------------------------------------------------------------------------------

1.923W

z Package Thermal Resistance (Note 2)

 

WQFN-24L 4x4, θJA -------------------------------------------------------------------------------------------------------

52°C/W

WQFN-24L 4x4, θJC ------------------------------------------------------------------------------------------------------

7°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) ----------------------------------------------------------------------------------------------

2kV

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

200V

Recommended Operating Conditions

(Note 4)

z Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------

6V to 24V

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

−40°C to 125°C

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

−40°C to 85°C

 

 

www.richtek.com

DS8562-01 April 2011

4

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