Richtek RT8562GQW Schematic [ru]

Marking Information

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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

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
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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

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