XRP2997 [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 |
厂家: | EXAR CORPORATION |
描述: | 8-Channel Constant Current Linear LED Driver With Smart TalkTM |
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 TalkTM
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 TalkTM technology, 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
is
configured to operate under the following
conditions and parameters:
Smart TalkTM Power Optimization
Parallel Operations Support
PWM and Analog Dimming
Input voltage range VCC: .............................. 4.2V – 5.5V
Input voltage range VLED:....................................... <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 TalkTM
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 (VLED). Current value is
controlled by RSET. Connect unused channel(s) to GND.
CHx
NC
12
11
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 VCC.
PWM
FBX input pin
13
14
15
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
FB
ISET pin
Connect resistor RSET from this pin to ground to set LED channel current as per
I
CHANNEL=1.194x400/RSET
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.
16
17
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
18
19
Ground pin
AGND
VCC
Input Voltage pin
Must be closely decoupled to GND pin with a 0.1μF ceramic capacitor.
Enable pin
20
5, 6
EN
PGND
EP
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.
© 2011 Exar Corporation
2/7
Rev. 2.2.0
XRP7618
8-Channel Constant Current Linear LED Driver With
Smart TalkTM
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
P
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 ꢇꢋꢐꢊꢑ ꢆ 400
ꢀꢁꢂꢃ
ꢄ
ꢈꢉꢂꢊꢋꢌꢍ
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 ILEDMAX is the required
LED current per channel.
LED CHANNELS
CURRENT SETTING
The maximum LED current per channel
(ILEDMAX) can be set up to 100mA per channel
through the ISET pin for each XRP7618
through an external resistor RSET. The value
can be calculated by the following formula:
ꢅ ꢆ 1.194ꢇ 400 ꢆ 1.194ꢇ
ꢀꢁꢂꢃ
ꢄ
ꢄ
ꢈꢉꢂꢊꢋꢌꢍ
ꢈꢉꢂꢊꢋꢌꢍ
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 (VLED).
Connect unused channel(s) to GND.
P
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 ILEDMAX
.
The supported external PWM signal frequency
is 100Hz to 25kHz.
© 2011 Exar Corporation
3/7
Rev. 2.2.0
XRP7618
8-Channel Constant Current Linear LED Driver With
Smart TalkTM
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at VCC = 5V, RISET = 8kΩ, TA = 25°C, unless otherwise specified - Schematic and BOM from Application
Information section of this datasheet.
1kHz
100Hz
25kHz
20
18
16
14
12
10
8
6
4
2
0
0
20
40
60
Duty cycle (%)
80
100
Fig. 5: PWM Dimming: Current per Channel vs Duty Cycle
Fig. 4: Current per Channel vs Temperature
59
59
58
57
56
58
57
56
0.5
1.0
1.5
2.0
2.5
3.0
4
4.2
4.4
4.6
4.8
5
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
90
80
70
60
50
40
30
20
10
0
10
20
30
40
Rset (kΩ)
Fig. 9: Current per Channel vs RSET resistor
Fig. 8: Maximum Output Current vs Voltage per Channel
© 2011 Exar Corporation
4/7
Rev. 2.2.0
XRP7618
8-Channel Constant Current Linear LED Driver With
Smart TalkTM
EVALUATION BOARD SCHEMATICS
© 2011 Exar Corporation
5/7
Rev. 2.2.0
XRP7618
8-Channel Constant Current Linear LED Driver With
Smart TalkTM
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
1
146-6686-02
XRP7618IGB-F
XRP7618 Evaluation Board
XRP7618
EVAL BD
U1, U2
C1, C2
R1, R6
R2, R7
R3, R8
Exar Corp.
Exar Corp.
2
2
2
2
2
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.
Panasonic Corp.
Panasonic Corp.
GRM21BR71H104KA01L
ERJ-3EKF4701V
0603
0603
ERJ-3EKF8201V
0603
ERJ-3EKF2402V
2
6
0Ω Resistor
Panasonic Corp.
0603
0603
R13, R14
ERJ-3GEY0R00V
R4, R5, R9,
R10, R11, R12
Not populated
3
2
1
1x8 Pin Header
2x3 Pin Header
1x1 Pin Header
Wurth Elektronik
Wurth Elektronik
Wurth Elektronik
CONN.HEAD 0.1”
CONN.HEAD 0.1”
CONN.HEAD 0.1”
SV1, SV2, SV3
SV4, SV5
SV6
61300811121
61300621121
61300111121
© 2011 Exar Corporation
6/7
Rev. 2.2.0
XRP7618
8-Channel Constant Current Linear LED Driver With
Smart TalkTM
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?
E
XAR
CORPORATION
H
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.
© 2011 Exar Corporation
7/7
Rev. 2.2.0
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