XRP2997_1108 [EXAR]

8-Channel Constant Current Linear LED Driver With Smart TalkTM; 8通道恒流线性LED驱动器与智能TalkTM


型号：	XRP2997_1108
厂家：	EXAR CORPORATION
描述：	8-Channel Constant Current Linear LED Driver With Smart TalkTM 8通道恒流线性LED驱动器与智能TalkTM 驱动器
文件：	总7页 (文件大小：752K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

August 2011

Rev. 2.2.0

GENERAL DESCRIPTION

EVALUATION BOARD MANUAL

The XRP7618 is an 8-channel, high voltage,

constant-current sink LED driver capable of

sinking up to 100mA current per channel. With

outputs rated at 30V, the XRP7618 can control

strings of multiple LEDs with better than

±1.5% channel to channel current matching.

LED channel current is programmed via an

external resistor within a 10mA to 100mA

range. Dimming is supported up to 25kHz or

through an analog signal. Featuring Exar’s

Smart Talk^TMtechnology, when combined with

a boost converter, XRP7618 maximizes the

overall system efficiency by dynamically

reporting the minimum LED voltage necessary

to maintain current regulation mode.

FEATURES

 8 Constant-Current Channels

 Adjustable up to 100mA per Channel

 Channel Paralleling for higher Current

 ±1.5% Current Matching Accuracy

STANDARD CONFIGURATION

 Up to 30V LED Channel Voltage Range

 5V Biasing Voltage and Control

The

XRP7618EVB

evaluation

board

configured to operate under the following

conditions and parameters:

 Smart Talk^TMPower Optimization

 Parallel Operations Support

 PWM and Analog Dimming

Input voltage range V_CC: .............................. 4.2V – 5.5V

Input voltage range V_LED:....................................... <30V

Number of LED strings:.....................................16 (2x8)

LED current per string:

 UVLO, Open LED & Over Temperature

protection

3 selectable pre-set levels ............. 20mA-60mA-100mA

Adj. Level..........................................10mA to 100mA

 20-pin TSSOP (EP) Package

EVALUATION BOARD SCHEMATICS

Fig. 1: XRP7618 Evaluation Board Schematics

Exar Corporation

www.exar.com

48720 Kato Road, Fremont CA 94538, USA

Tel. +1 510 668-7000 – Fax. +1 510 668-7001

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

PIN ASSIGNMENT

Fig. 2: XRP7618 Pin Assignment

PIN DESCRIPTION

Name

Pin Number

Description

CH1 to CH8 pins

1, 2, 3, 4,

7, 8, 9, 10

Connect an LED between each pin and LED supply rail voltage (V_LED). Current value is

controlled by R_SET. Connect unused channel(s) to GND.

CHx

Not Connected

PWM pin

This must be held HIGH to enable the output drivers. It can be used for PWM dimming up

to 25kHz. If not used, connect to V_CC.

PWM

FBX input pin

Used in parallel configuration as an interface terminal by connecting it to FB pin of the

next XRP7618. If not used, leave it unconnected.

FBX

ISET

ISET pin

Connect resistor R_SETfrom this pin to ground to set LED channel current as per

_CHANNEL=1.194x400/R_SET

FB pin

Samples the LED cathode voltage on each channel and outputs the lowest voltage to the

step-up converter.

SDB output pin

SDB signal is synchronous with the PWM signal during PWM Dimming. SDB pin outputs

low logic to the step-up converter under conditions such as shutdown or when all channels

are inactive.

SDB

SDBX input pin

Used in parallel configuration as an interface terminal by connecting it to SDB pin of the

next XRP7618. If not used, connect it to GND.

SDBX

Ground pin

AGND

VCC

Input Voltage pin

Must be closely decoupled to GND pin with a 0.1μF ceramic capacitor.

Enable pin

5, 6

PGND

This pin must be held HIGH to enable the XRP7618.

Ground pin

Exposed Pad

Connect to ground

Exposed Pad

ORDERING INFORMATION

Refer to XRP7618’s datasheet and/or www.exar.com for exact and up to date ordering information.

2/7

Rev. 2.2.0

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

USING THE EVALUATION BOARD

ANALOG DIMMING CONTROL

Besides PWM dimming control, the LED

current can be controlled continuously (from

highest to lowest LED current) by raising the

voltage at the bottom of RSET from 0V

normally to 1V max, respectively. RSET value

may be determined as

OWERING UP THE XRP7618 CIRCUIT

The XRP7618 Evaluation Board can be

powered from a single +4.2V to +5.5V power

supply. Connect with short leads directly to

the “VCC” and “GND” posts on connector SV1.

Note the XRP7618 will remain in “shutdown”

until the “Enable” and “PWM” pins are held

high or resistors R11 and R12 are fitted with

0R resistors.

ꢎ1.194 ꢏ ꢇ_ꢋꢐꢊꢑ ꢆ 400

ꢀ_ꢁꢂꢃ

ꢄ

ꢈ_{ꢉꢂꢊꢋꢌꢍ}

where, 1.194V is a typical ISET pin voltage,

VMOD is an adjustment voltage applied to the

bottom side of RSET, 400 is the typical current

multiplication ratio, and I_LEDMAXis the required

LED current per channel.

LED CHANNELS

CURRENT SETTING

The maximum LED current per channel

(I_LEDMAX) can be set up to 100mA per channel

through the ISET pin for each XRP7618

through an external resistor R_SET. The value

can be calculated by the following formula:

ꢅ ꢆ 1.194ꢇ 400 ꢆ 1.194ꢇ

ꢀ_ꢁꢂꢃ

ꢄ

ꢈ_{ꢉꢂꢊꢋꢌꢍ}

The XRP7618 Evaluation Board implements

three switchable preset levels of current per

channel (20mA, 60mA and 100mA). These

levels are selected via jumpers SV4 and SV5.

Additionally, resistors R4 and R19 (not

populated by default) provide support for a

fixed current level (jumpers SV4 and SV5

must be taken off). XRP7618EVB comes with

the SV4 and SV5 jumpers set to 20mA current

setting by default.

Fig. 3: XRP7618 Analog Dimming Control

If adjustment voltage VMOD isn’t used, RSET

resistor should be connected to ground.

Resistors R5 and R10 (not populated by

default) support the analog dimming scheme

(jumpers SV4 and SV5 must be taken off).

Connect the LEDs between each channel pin

and an external LED supply rail voltage (V_LED).

Connect unused channel(s) to GND.

ARALLEL MODE OF OPERATION

Multiple XRP7618s can be placed in parallel to

drive over 8 strings of LEDs; unused channels

should be tied to ground. XRP7618 Evaluation

Board comes with two XRP7618s connected to

each other through their respective FBX and

SDBX pins with 0Ω resistors R13 and R14.

PWM DIMMING

The LED current can be adjusted by applying a

PWM signal to the PWM pin. In this mode, all

enabled channels are adjusted at the same

time and brightness is adjusted from 1% to

100% of I_LEDMAX

The supported external PWM signal frequency

is 100Hz to 25kHz.

3/7

Rev. 2.2.0

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

TYPICAL PERFORMANCE CHARACTERISTICS

All data taken at V_CC= 5V, R_ISET= 8kΩ, T_A= 25°C, unless otherwise specified - Schematic and BOM from Application

Information section of this datasheet.

1kHz

100Hz

25kHz

Duty cycle (%)

100

Fig. 5: PWM Dimming: Current per Channel vs Duty Cycle

Fig. 4: Current per Channel vs Temperature

0.5

1.0

1.5

2.0

2.5

3.0

4.2

4.4

4.6

4.8

5.2

5.4

5.6

Voltage per channel (V)

Input Voltage (V)

Fig. 7: Current per Channel vs Voltage per Channel

Fig. 6: Current per Channel vs Input Voltage

100

Rset (kΩ)

Fig. 9: Current per Channel vs RSET resistor

Fig. 8: Maximum Output Current vs Voltage per Channel

4/7

Rev. 2.2.0

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

EVALUATION BOARD SCHEMATICS

5/7

Rev. 2.2.0

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

EVALUATION BOARD LAYOUT

Fig. 11: Top Side Layout

Fig. 10: Components Placement & Dimensions

Fig. 12: Bottom Side Layout

BILL OF MATERIAL

Qty

Ref.

Manufacturer

Part Number

Size

Component

146-6686-02

XRP7618IGB-F

XRP7618 Evaluation Board

XRP7618

EVAL BD

U1, U2

C1, C2

R1, R6

R2, R7

R3, R8

Exar Corp.

TSSOP20 (EP)

0805

Ceramic 0.1uF, 50V, X7R

4.7KΩ Resistor, 0.1W, 1%

8.2KΩ Resistor, 0.1W, 1%

24KΩ Resistor, 0.1W, 1%

Murata Corp.

Panasonic Corp.

GRM21BR71H104KA01L

ERJ-3EKF4701V

0603

ERJ-3EKF8201V

0603

ERJ-3EKF2402V

0Ω Resistor

Panasonic Corp.

0603

R13, R14

ERJ-3GEY0R00V

R4, R5, R9,

R10, R11, R12

Not populated

1x8 Pin Header

2x3 Pin Header

1x1 Pin Header

Wurth Elektronik

CONN.HEAD 0.1”

SV1, SV2, SV3

SV4, SV5

SV6

61300811121

61300621121

61300111121

6/7

Rev. 2.2.0

XRP7618

8-Channel Constant Current Linear LED Driver With

Smart Talk^TM

REVISION HISTORY

Revision

Date

Description

08/05/2010

09/22/2010

03/28/2011

07/29/2011

Initial release of document

1.0.0

1.1.0

2.0.0

2.1.0

Added evaluation board picture

Added R13 and R14 to isolate FBx and SBDx

Modified schematics C1 and C2 to 100nF

Added default settings information

Corrected schematics for inclusion of R13 and R14

08/18/2011

2.2.0

BOARD REVISION HISTORY

Board Revision

Date

Description

10/29/2010

03/28/2011

146-6686-01

146-6686-02

Initial release of evaluation board

Added R13 and R14 to isolate FBx and SBDx

FOR FURTHER ASSISTANCE

Email:

customersupport@exar.com

Exar Technical Documentation:

http://www.exar.com/TechDoc/default.aspx?

XAR

CORPORATION

EADQUARTERS AND

SALES OFFICES

48720 Kato Road

Fremont, CA 94538 – USA

Tel.: +1 (510) 668-7000

Fax: +1 (510) 668-7030

www.exar.com

NOTICE

EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve

design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein,

conveys no license under any patent or other right, and makes no representation that the circuits are free of patent

infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a

user’s specific application. While the information in this publication has been carefully checked; no responsibility, however,

is assumed for inaccuracies.

EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or

malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its

safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in

writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all

such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.

Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.

7/7

Rev. 2.2.0

XRP2997_1108 [EXAR]

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