Richtek RT8560AGQW Schematic [ru]

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RT8560A

High Voltage 4 Channel LED Driver

General Description

The RT8560A is a 60V 4-channel LED driver capable of delivering 30mA to each channel with 15 LEDs (3.6V per diode) total 60 LEDs with one driver. The RT8560A is a current mode boost converter opearated at 1MHz switching frequency, wide VIN range covers from 6V to 40V and the on-chip current switch is rated at 1.5A.

The PWM output voltage loop selects and regulates the LED pin with the highest voltage string to 0.9V allowing voltage mismatches between LED strings. The RT8560A automatically detects and disconnects any unconnected and/or broken strings during operation from PWM loop to prevent VOUT from over voltage.

The 3% matched LED currents on all channels are simply programmed with a resistor or a current sink. Both analog dimming and digitally controlled PWM dimming are supported by RT8560A. Analog dimming is linearly controlled by an external voltage. With an on-chip output clampping amplifier and a 200kΩ 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 EN pin to PWM shutdown the chip or by driving ACTL pin.

Other protecting features include programmable PWM output over voltage protection, LED curren limit, PWM switch current limit and thermal shutdown. The RT8560A is packaged with a tiny footprint package of WQFN-20L 4x4 packages.

Pin Configurations

(TOP VIEW)

 

GND

GND

LED1

LED2

LED3

 

 

20

19

18

17

16

 

GND

1

 

 

 

15

LED4

GND

2

 

 

 

14

VC

GND

3

 

GND

13

SS

SW

4

 

 

21

12

OVP

SW

5

 

 

 

11

EN

 

6

7

8

9

10

 

 

VCC2

VCC1

RISET

ACTL

DCTL

 

 

WQFN-20L 4x4

 

Features

zHigh Voltage : VIN up to 40V, VOUT up to 60V, Driving up to 60 x 3.6V LEDs (15 each channel)

zChannel Current Programmabe 4mA to 30mA and Matched to 3% Accuracy

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 Digital Dimming : Providing High Accuracy Digital Dimming by PWM at ACTL Pin or EN Pin

zVIN Under Voltage Lockout

zOver Temperature Protection

zCurrent Limiting Protection

zSmall 20-Lead WQFN Package

zRoHS Compliant and Halogen Free

Applications

zUMPC and Notebook Computer Backlight

zGPS, Portable DVD Backlight

zDesk Lights and Room Lighting

Ordering Information

RT8560A

Package Type

QW : WQFN-20L 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.

Marking Information

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

DS8560A-01 April 2011

www.richtek.com

1

RT8560A

Typical Application Circuit

VIN

 

COUT3

 

 

 

 

 

 

 

 

6V to 40V

 

1µF

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L

D

 

 

 

60V MAX

 

 

 

10µH

 

 

 

 

 

 

 

 

 

CVIN

 

15 LED String

:

:

:

:

 

 

 

10µF

 

 

 

 

 

RVCC1

 

 

RT8560A

 

:

:

:

:

COUT1 COUT2

R4

 

 

:

:

:

:

10

C2

4, 5 SW

 

 

:

:

:

:

 

 

 

 

 

 

18

 

 

 

 

 

 

 

 

 

7 VCC1

LED1

 

 

 

 

 

 

CVCC1

R3

 

LED2

17

 

 

 

 

 

 

1µF

5V

1k

11 EN

LED3

16

 

 

 

 

 

 

VOUT

R1

 

12 OVP

LED4

15

 

RISET

 

 

5.36k

 

 

 

 

 

 

ILED = 20mA ×

 

 

R2

 

RISET

8

 

5.36k

 

RVCC2

 

 

 

 

 

 

RISET

 

 

 

 

 

R5

 

 

 

 

VIN

10

 

6 VCC2

 

 

 

 

 

 

 

 

 

ACTL

9

 

1k

 

 

 

 

 

 

CVCC2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PWM Signal

 

 

 

1µF

 

DCTL

10

 

 

 

 

 

 

14 VC

 

 

 

 

 

 

 

 

 

GND 1, 2, 3, 19, 20, Exposed Pad (21)

 

 

RVC

 

13 SS

 

 

1.8k

C1

 

 

 

 

 

 

 

 

 

 

CVC

 

 

 

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

 

 

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

VIN

 

COUT3

 

 

 

 

 

 

 

 

6V to 40V

 

1µF

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L

D

 

 

 

 

60V MAX

 

 

 

10µH

 

 

 

 

 

 

 

 

 

CVIN

 

15 LED String

:

:

:

:

 

 

 

10µF

 

 

 

 

 

RVCC1

 

 

RT8560A

 

:

:

:

:

COUT1 COUT2

R4

 

 

:

:

:

:

10

C2

4, 5 SW

 

 

:

:

:

:

 

 

 

 

 

 

18

 

 

 

 

 

 

 

 

 

7 VCC1

LED1

 

 

 

 

 

 

CVCC1

R3

 

LED2

17

 

 

 

 

 

 

1µF

5V

1k

11 EN

LED3

16

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

R1

 

12 OVP

LED4

15

 

RISET

 

 

 

 

 

 

 

 

 

ILED = 20mA ×

5.36k

 

 

R2

 

RISET

8

 

5.36k

 

RVCC2

 

 

 

 

 

 

RISET

 

 

 

 

 

 

 

 

 

 

VIN

10

 

6 VCC2

 

 

 

 

R5

 

Analog

 

 

 

CVCC2

 

ACTL

9

 

 

1k

 

 

 

 

 

 

 

 

 

Dimming

 

 

 

1µF

 

DCTL

10

 

 

 

 

 

 

 

14 VC

 

 

 

 

 

 

 

 

 

GND 1, 2, 3, 19, 20, Exposed Pad (21)

 

 

RVC

 

13 SS

 

 

1.8k

C1

 

 

 

 

 

 

 

 

 

 

CVC

 

 

 

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

 

 

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

www.richtek.com

DS8560A-01 April 2011

2

Richtek RT8560AGQW Schematic

 

 

 

 

 

 

 

 

 

 

 

RT8560A

VIN

 

COUT3

 

 

 

 

 

 

 

 

6V to 40V

 

1µF

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L

D

 

 

 

60V MAX

 

 

 

10µH

 

 

 

 

 

 

 

 

 

CVIN

 

15 LED String

:

:

:

:

 

 

 

10µF

 

 

 

 

 

RVCC1

 

 

RT8560A

 

:

:

:

:

COUT1 COUT2

R4

 

 

:

:

:

:

10

C3

4, 5 SW

 

 

:

:

:

:

 

 

 

 

 

 

18

 

 

 

 

 

 

 

 

 

7 VCC1

LED1

 

 

 

 

 

 

CVCC1

R3

 

LED2

17

 

 

 

 

 

 

1µF

5V

1k

11 EN

LED3

16

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

R1

 

12 OVP

LED4

15

 

RISET

 

 

5.36k

 

 

 

 

 

 

ILED = 20mA ×

 

 

R2

 

RISET

8

 

5.36k

 

RVCC2

 

 

 

 

 

 

RISET

 

 

 

 

 

 

 

 

 

 

VIN

10

 

6 VCC2

ACTL

9

 

 

 

 

 

 

 

 

 

R5

 

 

 

C2

 

 

CVCC2

 

 

 

 

 

 

 

 

 

 

DCTL

10

 

1k

 

 

 

0.1µF

 

 

1µF

 

 

 

 

PWM Signal

 

 

 

 

14 VC

 

 

 

 

 

 

 

 

 

GND 1, 2, 3, 19, 20, Exposed Pad (21)

 

 

RVC

 

13 SS

 

 

1.8k

C1

 

 

 

 

 

 

 

 

 

 

CVC

 

 

 

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

 

 

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

VIN

 

 

 

 

 

 

 

 

 

 

 

4V to 40V

 

 

 

 

 

 

 

 

 

 

 

 

COUT3

 

 

 

 

 

 

 

 

 

 

 

1µF

 

 

 

 

VOUT

 

 

 

 

VAVDD

 

 

 

 

 

 

 

 

 

 

 

 

L

 

 

 

 

 

60V MAX

 

 

 

6V to 40V

 

 

D

 

 

 

 

 

 

 

10µH

 

 

 

 

 

 

 

 

 

 

CVIN

 

 

15 LED String

:

:

:

:

 

 

 

 

10µF

 

 

 

 

 

 

RVCC1

 

 

 

 

 

:

:

:

:

COUT1

COUT2

 

 

 

 

RT8560A

:

:

:

:

10

C2

R4

 

 

 

 

 

4, 5 SW

 

:

:

:

:

 

 

 

 

 

 

LED1 18

 

 

 

 

 

 

 

 

 

 

7 VCC1

 

 

 

 

 

 

 

CVCC1

 

R3

 

 

LED2 17

 

 

 

 

 

 

 

2.2µF

5V

1k

11 EN

LED3 16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

V

R1

 

12

OVP

LED4 15

 

RISET

 

 

 

5.36k

 

 

 

 

 

ILED = 20mA ×

OUT

 

R2

 

RISET 8

 

5.36k

 

 

 

 

 

 

 

 

 

 

 

RISET

RVCC2

 

 

 

 

 

R5

 

 

 

 

10

 

 

6 VCC2

 

 

 

 

 

 

 

 

ACTL 9

 

1k

 

 

 

 

VIN

 

 

 

 

 

 

 

 

 

CVCC2

 

 

DCTL 10

 

 

 

PWM Signal

 

 

 

 

1µF

 

 

 

 

 

 

 

 

 

 

 

 

14 VC

GND 1, 2, 3, 19, 20, Exposed Pad (21)

 

RVC

 

 

13 SS

 

1.8k

 

C1

 

 

 

 

 

 

 

 

 

 

CVC

 

 

 

 

 

 

 

 

 

 

0.1µF

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

 

 

 

Figure 4. Wide Range VINApplication by Connecting VCC1 to LCDDriver Power AVDD

DS8560A-01 April 2011

www.richtek.com

3

RT8560A

Function Block Diagram

 

 

 

SW

VCC1

-

OSC

 

S

LED1

6.2V

+

+

R

OVP

+

-

R

 

2.5V

-

 

 

 

 

+ -

LED2

 

-

 

EN

 

+

2V

+

Shutdown

-

VCC2

 

 

 

VC

 

VOUT

 

 

Regulation

LED3

 

 

Unit

 

 

+

 

 

 

 

 

 

-

6uA

 

 

5V

SS

 

 

 

 

 

 

 

 

LED4

 

1.2V

1.2V

+

DCTL

+

-

200k

 

 

-

+

 

 

-

 

 

 

 

 

 

ACTL

RISET

www.richtek.com

DS8560A-01 April 2011

4

 

 

RT8560A

Functional Pin Description

Pin Number

Pin Name

Pin Function

 

 

 

1, 2, 3, 19, 20,

GND

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

21 (Exposed Pad)

and connected to GND for maximum power dissipation.

 

4, 5

SW

PWM boost converter switch node.

 

 

Bipolar power switch base current supply. Typical beta of the power NPN

6

VCC2

switch is approximately 70. VCC2 can be connected either to VCC1 or to a

separate lower voltage, as low as 3V, for better system efficiency and/or

 

 

 

 

heat concern. A good bypass is necessary.

7

VCC1

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

8

RISET

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

9

ACTL

Analog/Digital dimming control. When using analog dimming,

ILED = 20mA × 5.36k for VACTL ≥ 1.2V.

 

 

 

 

RISET

 

 

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

10

DCTL

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

 

 

on ACTL pin.

11

EN

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

12

OVP

Over voltage protection. PWM boost converter turns off when VOVP goes

higher than 2.5V.

 

 

13

SS

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

14

VC

PWM boost converter loop compensation node.

18, 17, 16, 15

LED1, LED2,

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

LED3, LED4

used.

 

DS8560A-01 April 2011

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