X RP 7 6 1 8
8-Channel Constant Current Linear LED Driver With
Smart Talk
TM
July 2011
Rev. 1.0.0
GENERAL DESCRIPTION
The XRP7618 is an 8-channel, high voltage,
constant-current sink LED driver capable of
driving 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 control is supported through a
standard PWM scheme up to 25kHz or through
an analog signal.
technology,
Featuring Exar’s Smart Talk
when combined with a boost converter, the
XRP7618 maximizes the overall system
efficiency by dynamically reporting the
minimum LED voltage necessary to maintain
current regulation mode. Multiple channels can
be combined to increase current driving
capability per channel and multiple XRP7618s
can be placed in parallel to drive over 8 strings
of LEDs.
An under voltage lock out, open LED and over
temperature protections insure safe operations
under abnormal operating conditions.
The XRP7618 is available in RoHS compliant,
“green”/halogen free space saving 20-pin
TSSOP (EP) package.
TM
APPLICATIONS
LCD Backlighting
Desktop, Notebook and TV Displays
Industrial and Medical Displays
Signage Backlighting
FEATURES
8 Constant-Current Channels
Adjustable up to 100mA per Channel
Channel Paralleling for higher Current
±1.5% Current Matching Accuracy
Up to 30V LED Channel Voltage Range
5V Biasing Voltage and Control
Smart Talk
TM
Power Optimization
Parallel Operations Support
PWM and Analog Dimming
UVLO, Open LED & Over Temperature
protection
RoHS Compliant Halogen Free,
20-pin TSSOP (EP) Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP7618 Typical Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
X RP 7 6 1 8
8-Channel Constant Current Linear LED Driver With
Smart Talk
TM
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
V
CC
, ISET, EN, FB, SDB, PWM ...................... -0.3V to 6.0V
CHx .......................................................... -0.3V to 30V
Junction Temperature .......................................... 150°C
Storage Temperature .............................. -65°C to 150°C
Power Dissipation ................................ Internally Limited
Lead Temperature (Soldering, 10 sec) ................... 260°C
ESD Rating (HBM - Human Body Model) .................... 6kV
ESD Rating (MM - Machine Model) ...........................200V
OPERATING RATINGS
Input Voltage Range V
CC
.............................. 4.2V to 5.5V
PWM Dimming Frequency.......................0.1KHz to 25KHz
Current per Channel .....................................................
V
CHx
≥0.5V
........................................... 10mA to 25mA
V
CHx
≥1V
.............................................. 10mA to 65mA
V
CHx
≥1.5V
......................................... 10mA to 110mA
Operating Temperature Range ................... -40°C to 85°C
Thermal Resistance
θ
JA
(TSSOP-20) ..................... 35°C/W
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Junction Temperature of T
J
= 25°C only. Minimum and Maximum
limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric
norm at T
J
= 25°C, and are provided for reference purposes only. Unless otherwise indicated, V
CC
= 5V, R
ISET
= 8.2kΩ, T
A
=
25°C.
Parameter
Operating Input Voltage Range V
CC
Shutdown Supply Current
Quiescent Supply Current
Under Voltage Lockout threshold
Under Voltage Lockout Hysteresis
ISET Reference Voltage
Current Multiplication Ratio
Maximum Output Current per Channel
LED Current Matching
Current Sink Saturation Voltage
Output Current Line Regulation
Output Current Load Regulation
Enable Logic LOW
Enable Logic HIGH
PWM Pin Logic LOW
PWM Pin Logic HIGH
SDB Pin Logic LOW
SDB Pin Logic HIGH
Feedback Output Current
Thermal Shutdown Die Temperature
Thermal Shutdown Hysteresis
2.4
5
15
160
20
1.8
0.4
1.8
0.8
1.170
370
23
65
110
-1.5
3.6
Min.
4.2
Typ.
5.0
0.1
0.5
3.8
200
1.194
400
45
70
120
1.5
0.45
0.8
1.2
2
4
0.8
%/V
%
V
V
V
V
V
V
µA
°C
°C
V
%
mA
1.218
430
Max.
5.5
1
1
4.0
Units
V
µA
mA
V
mV
V
I
CHX
/I
SET
V
CHX
=0.5V
V
CHX
=1.0V
V
CHX
=1.5V
Any 2 channels
V
CHX
=1.0V, I
CHX
=60mA
I
CHX
=20mA
I
CHX
=60mA
I
CHX
=100mA
V
CC
=4.2V to 5.5V
V
CHX
=0.5V to 2.8V
XRP7618 is disabled
XRP7618 is active
XRP7618 is disabled
XRP7618 is active
V
EN
=0V
No load
Falling edge
Conditions
© 2011 Exar Corporation
2/10
Rev. 1.0.0
X RP 7 6 1 8
8-Channel Constant Current Linear LED Driver With
Smart Talk
TM
BLOCK DIAGRAM
Fig. 2: XRP7618 Block Diagram
PIN ASSIGNMENT
Fig. 3: XRP7618 Pin Assignment
© 2011 Exar Corporation
3/10
Rev. 1.0.0
X RP 7 6 1 8
8-Channel Constant Current Linear LED Driver With
Smart Talk
TM
PIN DESCRIPTION
Name
CHx
NC
PWM
Pin Number
1, 2, 3, 4,
7, 8, 9, 10
12
11
Description
CH1 to CH8 pins
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.
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
.
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.
ISET pin
Connect resistor R
SET
from this pin to ground to set LED channel current as per
I
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. It outputs low
logic to the step-up converter under conditions such as shutdown or when all channels
are inactive.
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.
Ground pin
Input Voltage pin
Must be closely decoupled to GND pin with a 0.1μF ceramic capacitor.
Enable pin
This pin must be held HIGH to enable the XRP7618.
Ground pin
Exposed Pad
Connect to ground
FBX
13
ISET
14
FB
15
SDB
16
SDBX
AGND
VCC
EN
PGND
EP
17
18
19
20
5, 6
Exposed Pad
ORDERING INFORMATION
Part Number
XRP7618IGB-F
-40°C≤T
A
≤+85°C
XRP7618IGBTR-F
XRP7618EVB
Temperature
Range
Marking
EXAR
XRP7618IGB
YYWWF
XXXX
Package
Packing Quantity
Bulk
TSSOP-20
1.5K/Tape & Reel
Note 1
Note 2
Halogen Free
RoHS Compliant
Exposed Pad
XRP7618 Evaluation Board
“YY” = Year – “WW” = Work Week – “X” = Lot Number, when applicable.
© 2011 Exar Corporation
4/10
Rev. 1.0.0
X RP 7 6 1 8
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.
20
18
1kHz
100Hz
25kHz
Current per Channel (mA)
16
14
12
10
8
6
4
2
0
0
20
40
60
80
100
Duty cycle (%)
Fig. 4: Current per Channel vs Temperature
Fig. 5: PWM Dimming: Current per Channel vs Duty Cycle
59
59
Current per Channel (mA)
58
Current per Channel (mA)
58
57
57
56
4
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
56
0.5
1.0
1.5
2.0
2.5
3.0
Input Voltage (V)
Voltage per channel (V)
Fig. 6: Current per Channel vs Input Voltage
Fig. 7: Current per Channel vs Voltage per Channel
100
90
Current per Channel (mA)
80
70
60
50
40
30
20
10
0
10
20
30
40
Rset (kΩ)
Fig. 8: Maximum Output Current vs Voltage per Channel
Fig. 9: Current per Channel vs RSET resistor
© 2011 Exar Corporation
5/10
Rev. 1.0.0
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