Richtek RT8561AGQW Schematic [ru]

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RT8561A

High Voltage 8-CH LED Driver

General Description

The RT8561Ais a 40V 8-CH LEDdriver capable of delivering 30mA to each channel with 10 LEDs (3.6V per diode), total of 80 LEDs with one driver. The RT8561A is a current mode boost converter operated 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 RT8561A 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 the RT8561A. Analog dimming is linearly controlled by an external voltage. With an on-chip output clamping amplifier and a 300kΩ resistor, PWM dimming signal is easily low-pass filtered to an analog dimming signal with one external capacitor for noise-free PWM dimming. A very high contrast ratio true digital PWM dimming can be achieved by driving ACTL pin with a PWM signal.

Other protecting features include programmable output over voltage protection, LED current limit, PWM switch current limit and thermal shutdown.

The RT8561A is packaged with a tiny footprint package of WQFN-24L 4x4 packages.

Ordering Information

RT8561A

Package Type

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

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.

Features

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

zChannel Current Programmable 10mA to 30mA and Matched to 1.5%

zCurrent Mode PWM 1MHz Boost Converter

zEasy Analog and Digital Dimming Control

zProgrammable Soft Start

zAutomatic Detecting Unconnected and/or Broken Channel

zProgrammable Over Voltage Protection

zDisconnects LED in Shutdown

zProviding High Accuracy Digital Dimming by PWM at ACTL Pin

zVIN Under Voltage Lockout

zOver Temperature Protection

zCurrent Limiting Protection

zSmall 24-Lead WQFN Package

zRoHS Compliant and Halogen Free

Applications

zUMPC and Notebook Computer Backlight

zGPS, Portable DVD Backlight

zDesk Lights and Room Lighting

Pin Configurations

(TOP VIEW)

 

GND

GND

GND

GND

SW

SW

 

 

 

24

23

22

21

20

19

 

 

LED1

1

 

 

 

 

 

18

VCC

LED2

2

 

 

 

 

 

17

CREG

LED3

3

 

GND

 

 

16

LED8

LED4

4

 

 

 

15

LED7

 

 

 

 

 

LED5

5

 

 

 

 

 

14

LED6

OVP

6

 

 

 

 

25

13

EN

 

 

 

 

 

 

7

8

9

10

11

12

 

 

 

VC

NC

SS

RISET

ACTL

DCTL

 

 

 

WQFN-24L 4x4

 

 

Marking Information

CZ= : Product Code

CZ=YM YMDNN : Date Code

DNN

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8561A-02 April 2012

www.richtek.com

 

1

Richtek RT8561AGQW Schematic

RT8561A

 

 

 

 

 

 

 

 

 

Typical Application Circuit

 

 

 

 

 

 

 

 

VIN

 

 

 

 

 

 

VOUT

 

6V to 24V

L

D

 

 

 

 

40V MAX

 

 

10µH

 

 

 

 

 

 

 

 

 

 

 

COUT

 

 

 

 

 

RVIN1

CVIN1

 

 

10µF

:

:

:

:

 

 

 

 

10 LED String

10µF

 

 

 

:

:

... :

:

10

 

 

 

RT8561A

:

:

:

:

 

 

 

 

 

:

:

:

:

 

 

 

19, 20 SW

 

LED1 1

 

 

 

 

 

 

18 VCC

 

 

 

 

 

CVIN1

1k

 

LED2 2

.

 

 

 

13

 

 

 

 

 

 

2.2µF

5V

EN

 

 

.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

R1

6 OVP

 

LED7 15 .

 

 

 

 

 

 

 

 

 

R2

 

 

 

LED8 16

RISET

 

 

 

 

 

 

 

 

 

20 x 4.75

 

 

 

 

 

 

4.75k

 

 

 

17 CREG

RISET 10

ILED (mA) = RISET (kΩ)

4.7µF

 

 

 

 

9 SS

 

 

 

 

 

 

 

 

 

GND 21, 22, 23, 24, 25 (Exposed Pad)

0.1µF

7

VC

 

 

 

 

 

 

1k

 

 

 

 

RVC

12 DCTL

 

ACTL 11

 

 

 

 

 

 

 

 

 

 

1.8k

 

 

 

 

 

PWM Signal

 

CVC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

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

VIN

 

VOUT

6V to 24V

L

40V MAX

 

10µH

D

COUT

RVIN1

CVIN1

 

 

 

10µF

:

:

:

:

 

 

 

 

 

10 LED String

10µF

 

 

 

 

:

: ...

:

:

10

 

 

 

 

RT8561A

:

:

:

:

 

 

 

 

 

 

:

:

:

:

 

 

 

 

19, 20 SW

 

LED1 1

 

 

 

 

 

 

 

18 VCC

 

 

 

 

 

CVIN1

 

1k

 

LED2 2

.

 

 

 

 

13

 

 

 

 

 

 

2.2uF

5V

 

EN

 

 

.

 

 

 

 

 

 

 

 

 

 

 

VOUT

R1

 

6 OVP

 

LED7 15 .

 

 

 

 

 

 

 

 

 

 

R2

 

 

 

 

LED8 16

RISET

 

 

 

 

 

 

 

 

 

 

 

 

20 x 4.75

 

 

 

 

 

 

 

4.75k

 

 

 

 

 

17 CREG

RISET 10

 

ILED (mA) = RISET (kΩ)

4.7µF

 

 

 

 

 

 

9 SS

 

 

 

 

 

 

 

 

 

 

GND 21, 22, 23, 24, 25 (Exposed Pad)

0.1µF

 

7 VC

 

 

 

 

 

 

1k

 

 

Analog

 

RVC

 

12 DCTL

 

ACTL 11

 

 

 

 

 

 

 

 

 

1.8k

 

 

 

 

 

 

 

 

Dimming

CVC

3.9nF DCTL can be floating or connected to ACTL

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

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8561A-02 April 2012

2

RT8561A

VIN

 

 

 

6V to 24V

L

 

D

 

10µH

 

RVIN1

CVIN1

 

 

10µF

 

 

10

 

 

 

 

 

19, 20

 

 

 

18

CVIN1

 

1k

13

2.2µF

5V

 

 

 

 

VOUT

R1

 

6

 

 

 

 

R2

 

 

 

 

 

17

4.7µF

 

 

9

 

 

 

0.1µF

 

 

7

RVC

 

1k

12

1.8k

 

 

 

CVC

 

 

 

3.9nF

 

 

 

PWM Signal

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

40V MAX

 

 

 

COUT

 

 

 

 

 

 

 

 

 

 

10µF

 

 

:

:

...

:

:

 

 

 

 

 

 

10 LED String

 

 

 

 

:

:

:

:

 

RT8561A

 

 

:

:

 

:

:

 

 

 

 

 

:

:

 

:

:

 

 

SW

 

 

1

 

 

 

 

 

 

 

VCC

 

LED1

 

 

 

 

 

 

 

 

LED2

2

.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN

 

 

 

.

 

 

 

 

 

 

OVP

 

LED7

15 .

 

 

 

 

 

 

 

 

LED8

16

 

RISET

 

 

 

 

 

 

 

 

 

 

ILED (mA) =

20 x 4.75

CREG

RISET

10

 

4.75k

 

 

 

 

 

 

 

 

 

RISET (kΩ)

SS

 

 

 

 

 

 

 

 

 

 

VC

 

GND 21, 22, 23, 24, 25 (Exposed Pad)

DCTL

 

ACTL

11

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

 

Figure 3. 1MHz, 20mA Full Scale Current PWM to Analog Dimming Control

 

VIN

 

 

 

 

 

 

VOUT

4V to 36V

 

 

 

 

 

 

 

L

D

 

 

 

 

 

40V MAX

 

10µH

 

 

 

 

 

 

 

 

CVIN1

 

 

COUT

 

 

 

 

 

VAVDD

 

 

10µF

 

:

:

:

:

10µF

 

 

 

 

6V to 24V

 

 

 

 

 

:

:

... :

:10 LED String

 

 

 

 

RT8561A

 

:

:

:

:

 

 

19, 20 SW

 

:

:

:

:

RVIN1

 

 

 

 

 

 

 

10

 

18 VCC

LED1 1

 

 

 

 

 

 

 

 

 

 

CVIN1

 

LED2

2

.

 

 

 

1k

 

 

 

 

 

2.2µF

13 EN

 

 

 

 

 

 

5V

 

 

.

 

 

 

V

R1

6 OVP

LED7

15 .

 

 

 

 

OUT

 

 

 

 

 

 

 

 

R2

 

 

LED8 16

 

RISET

 

 

 

 

 

 

 

 

20 x 4.75

 

 

 

 

 

 

 

4.75k

 

 

17

CREG

RISET 10

 

ILED (mA) = RISET (kΩ)

 

 

 

 

 

4.7µF

9 SS

 

 

 

 

 

 

 

0.1µF

7 VC

GND 21, 22, 23, 24, 25 (Exposed Pad)

 

RVC

12

DCTL

ACTL

11

 

 

 

 

 

1.8k

 

 

 

 

PWM Signal

 

CVC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

Note :

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

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

Figure 4. Wide Range VINApplication by Connecting VCC Pin to LCDDriver Power AVDD

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8561A-02 April 2012

www.richtek.com

3

RT8561A

Function Block Diagram

 

 

 

 

 

 

SW

VCC

 

-

 

OSC

 

 

 

 

S

LED1

 

5.6V

+

 

 

+

 

 

 

R

OVP

 

+

 

 

-

 

 

 

R

1.2V

 

 

 

 

-

 

 

 

 

EN

 

-

 

 

+ -

LED2

 

 

 

 

 

 

 

 

+

 

1.6V

+

Shutdown

 

 

 

-

 

 

 

 

 

 

CREG

5V

 

 

 

 

 

LDO

 

 

 

 

 

 

 

 

 

 

 

VC

 

 

 

 

VOUT

LED7

 

 

 

 

Regulation

 

 

 

 

 

Unit

+

 

 

 

 

 

 

-

 

 

 

 

 

 

5V

 

5uA

 

 

 

 

SS

 

 

 

 

 

 

 

 

 

 

 

 

LED8

 

 

 

 

 

+

+

 

 

1.2V

 

-

 

 

 

-

DCTL

 

+

 

300k

 

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

 

ACTL

RISET

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8561A-02 April 2012

4

 

 

 

 

RT8561A

Functional Pin Description

Pin No.

Pin Name

 

 

Pin Function

 

 

 

 

 

 

LED1, LED2,

Channel 1 to Channel 5 LED current sink. Leave the pin unconnected if not

1, 2, 3, 4, 5

LED3, LED4,

 

LED5

used.

 

 

 

 

6

OVP

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

 

 

higher than 1.2V.

7

VC

PWM boost converter loop compensation node.

 

 

 

 

 

8

NC

No Internal Connection.

 

 

 

 

 

9

SS

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

 

 

 

 

 

10

RISET

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

 

 

 

11

ACTL

Analog/Digital dimming control. When using analog dimming,

ILED (mA) =

20 x 4.75

for VACTL ≥ 1.2V.

 

 

 

 

 

 

 

 

RISET (kΩ)

 

 

By adding a 0.1μF filtering capacitor on the ACTL pin, the PWM dimming

12

DCTL

signal on the DCTL pin will be averaged out and converted into analog

 

 

dimming signal on the ACTL pin.

 

 

 

13

EN

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

 

 

 

14, 15, 16

LED6, LED7,

Channel 6 to Channel 8 LED current sink. Leave the pin unconnected if not

LED8

used.

 

 

 

 

17

CREG

1μF capacitor should be placed on this pin to stabilize the 5V output of the

internal regulator. This regulator is for chip internal use only.

 

 

18

VCC

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

 

 

 

19, 20

SW

PWM boost converter switch node.

 

 

 

21, 22, 23, 24,

GND

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

25 (Exposed Pad)

and connected to GND for maximum power dissipation.

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8561A-02 April 2012

www.richtek.com

5

RT8561A

Absolute Maximum Ratings

(Note 1)

 

 

 

 

 

 

z Supply Voltage, VCC -----------------------------------------------------------------------------------------------------

 

 

 

 

 

 

−0.3V to 28V

z SW Pin Voltage at Switching Off --------------------------------------------------------------------------------------

 

 

 

 

−0.3V to 45V

z LED1 to LED8 Pin---------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

−0.3V to 35V

z DCTL, ACTL, 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, VCC ----------------------------------------------------------------------------------------------

 

 

 

 

 

 

6V to 24V

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

 

 

 

 

 

 

−40°C to 125°C

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

 

 

 

 

 

 

−40°C to 85°C

Electrical Characteristics

 

 

 

 

 

 

 

(VCC = 17V, TA = 25°C, unless otherwise specified)

 

 

 

 

 

 

Parameter

 

Symbol

Test Conditions

Min

Typ

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

 

Supply Current

 

 

IVCC

VC ≤ 0.2V (Switching off)

--

3

5

 

mA

VIN Under Voltage Lockout

 

VUVLO

VIN Rising

 

--

5.6

5.95

 

V

Threshold

 

 

VIN Falling

 

--

4.9

--

 

 

 

 

 

 

 

Shutdown Current

 

 

ISHDN

VEN ≤ 0.7V

 

--

--

10

 

μA

EN Threshold

 

Logic-High

 

VEN_H

 

 

1.6

--

5

 

V

Voltage

 

Logic-Low

 

VEN_L

 

 

--

--

1

 

 

 

 

 

 

 

PWM Threshold

 

Logic-High

 

VPWM_H

 

 

1.3

--

5

 

V

Voltage

 

Logic-Low

 

VPWM_L

 

 

--

--

0.15

 

 

 

 

 

 

 

EN Pin Input Current

 

IEN

VEN ≤ 5V

 

--

--

0.1

 

μA

LED Current Programming

 

 

 

 

 

 

 

 

 

LED Current

 

 

ILED

2V > VLED > 0.6V, RISET = 4.75kΩ,

19

20

21

 

mA

 

 

VACTL > 1.2V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2V > VLED > 0.6V, RISET = 4.75kΩ,

 

 

 

 

 

LEDs Current Matching

 

 

VACTL > 1.2V, Calculating

--

--

1.5

 

%

 

 

 

 

 

(I(MAX) I(MIN)) / IAverage x 100%

 

 

 

 

 

RISET Pin Voltage

 

VRISET

3.6kΩ ≤ RISET ≤ 9.6kΩ, VACTL > 1.2V

1.17

1.2

1.23

 

V

Input Current of ACTL

 

IACTL

0.3V ≤ VACTL ≤ 1.2V

--

1

2

 

μA

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

 

 

 

 

 

 

DS8561A-02

April 2012

6

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