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November 2012
Rev. 1.1.0
Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001
GENERAL DESCRIPTION
The XRP7613 is a non-synchronous step down
converter with integrated FET optimized to
drive high power LEDs at up to 1.2A of
continuous current. A wide 7.0V to 36V input
voltage range allows for single supply
operations from industry standard 12V, 18V or
24V power rails.
Based on a hysteretic PFM control scheme, the
XRP7613 can operate at switching frequency
of up to 1MHz and allows for small external
components selection while providing very fast
transient response and achieving excellent
efficiency. The output current is programmable
from 150mA to 1.2A through an external
sense resistor.
Output current dimming is supported through
an analog signal or PWM logic signal at up to
40kHz. A dynamic LED current thermal control
further enhances the reliability of the end
application by linearly reducing the LED
current as temperature raises.
An open LED, LED short circuit, over
temperature and under voltage lock out
protection insures safe operations under
abnormal operating conditions.
The XRP7613 is offered in RoHS compliant,
“green”/halogen free 8-pin Exposed Pad SOIC
package.
APPLICATIONS
General Lighting and Displays
Architectural and Accent Lighting
Medical and Industrial Instrumentation
Video Projectors
FEATURES
1.2A Continuous Output LED Current
150mA to 1.2A Programmable Range
7V to 36V Single Rail Input Voltage
PWM & Analog Dimming Capability
Up to 40kHz Frequency
LED Current Foldback Thermal Control
Selectable Automatic Linear Dimming of
LED Current with temperature
Shutdown Control
Built-in Soft Start
Open LED, LED Short Circuit and Over
Temperature Protections
RoHS Compliant “Green”/Halogen Free
8-pin Exposed Pad SOIC Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: XRP7613 Application Diagrams
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© 2012 Exar Corporation 2/12 Rev. 1.1.0
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.
Input Voltage VIN .................................................... 40V
ISEN Voltage ................................(VIN+0.3V) to (VIN-5V)
EN/DIM Voltage............................................ -0.3V to 5V
Junction Temperature .......................................... 150°C
Storage Temperature .............................. -65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 260°C
ESD Rating (HBM - Human Body Model) ..........................
All pins ................................................................ 2kV
OPERATING RATINGS
Input Voltage Range VIN ...................................... 7V-36V
Operating Temperature Range ................... -40°C to 85°C
Thermal Resistance ......................................................
ϴJA1 ............................................................... 60°C/W
ϴJC1 ............................................................... 15°C/W
Note 1: Package is placed on 2-layer PCB with 2 ounces
copper and 2 square inch, connected with 8 vias.
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Ambient Temperature of TJ = TA = 25°C only; limits applying over the
full Operating Ambient Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test,
design, or statistical correlation. Typical values represent the most likely parametric norm at TA = 25°C, and are provided
for reference purposes only. Unless otherwise indicated, VIN = 12V, L=47µH, 1 x LED and ILED=330mA and TA= 25°C.
Parameter
Min.
Typ.
Max.
Units
Conditions
Quiescent Current
0.5
1
mA
Output switching
EN/DIM floating, f=250kHz
35
45
µA
Output not swithing
EN/DIM<0.2V
Mean Current Sense Threshold
Voltage
95
100
105
mV
Measured on ISEN pin with respect to VIN.
ISEN Threshold Hysteresis
-15
+15
%
ILED Output Current Range
150
1200
mA
VIN=12V
Efficiency
93
%
VIN=12V, VOUT=7.2V, L=47µF, ILED=330mA
Switch On Resistance RDS(ON)
0.5
Ω
N-MOSFET (PVDD2=5V)
Switch Leakage Current
1
5
µA
Operating Frequency fSW
350
kHz
EN/DIM floating, L=47µF, ILED=330mA,1xLED
Minimum Switch On Time
180
ns
Minimum Switch OFF Time
280
ns
VREF Voltage
2.46
2.5
2.54
V
VREF Output Current
250
µA
Recommended Duty Cycle
Range at fSW_MAX
30
70
%
Under Voltage Lock Out
Threshold
6
V
VIN Rising
5.5
VIN Falling
Maximum Dimming Frequency
40
kHz
EN/DIM Input Level Logic High
1.3
V
EN/DIM Input Level Analog
0.4
1.25
V
EN/DIM Input Level Logic Low
0.2
V
EN/DIM Shutdown Delay
16
ms
EN/DIM Pull Up Current
3.7
µA
Thermal Shutdown
Temperature
150
°C
Thermal Shutdown Hysteresis
30
°C
Thermal Regulation Input
Level
0.4
V
R1=10kΩ, RTH=1.91kΩ
0.28
R1=10kΩ, RTH=1.265kΩ
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© 2012 Exar Corporation 3/12 Rev. 1.1.0
BLOCK DIAGRAM
Fig. 2: XRP7613 Block Diagram
PIN ASSIGNMENT
Fig. 3: XRP7613 Pin Assignment
PGND 1LX
8
XRP7613
HSOIC-8
VIN 2
EN/DIM 4
ISEN 3
GND
7
VREF
6
TH
5
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© 2012 Exar Corporation 4/12 Rev. 1.1.0
PIN DESCRIPTION
Name
Pin
Description
PGND
1
Power ground pin.
VIN
2
Power supply input pin.
Place an input decoupling capacitor as close as possible to this pin.
ISEN
3
LED current setting pin.
Connect resistor RSET from this pin to VIN (pin 2) to define nominal average LED current.
EN/DIM
4
Dimming and Enable pin.
For automatic startup, leave pin floating.
TH
5
LED temperature protection sense input.
Connect temperature thermal sense resistors to turn off output current above a preset
temperature threshold.
VREF
6
Reference Voltage for thermal protection.
GND
7
Ground pin.
LX
8
Connect to the output inductor.
GND
Exposed
Pad
Power ground pin.
ORDERING INFORMATION
Part Number
Ambient
Temperature
Range
Marking
Package
Packing
Quantity
Note 1
Note 2
XRP7613IDBTR-F
-40°C≤TA≤+125°C
XRP7613I
YYWWF
X
HSOICN-8
Exp. Pad
2.5K/Tape & Reel
Halogen Free
XRP7613EVB
XRP7613 Evaluation Board
“YY” = Year – “WW” = Work Week – “X” = Lot Number when applicable.
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© 2012 Exar Corporation 5/12 Rev. 1.1.0
TYPICAL PERFORMANCE CHARACTERISTICS
Fig. 4: Efficiency versus Input Voltage
Fig. 5: Efficiency versus Input Voltage
Fig. 6: VSET versus Input Voltage at ILED=330mA
Fig. 7: VSET versus Input Voltage at ILED=770mA
Fig. 8: VSET versus Input Voltage at ILED=1.1A
Fig. 9: LED Current versus EN/DIM Voltage
95
100
105
110
115
120
010 20 30 40
VSET (mV)
VIN (V)
ILED = 330mA
L = 47µH
2xLED
1xLED
3xLED
95
100
105
110
115
120
010 20 30 40
VSET (mV)
VIN (V)
ILED = 770mA
L = 47µH
2xLED
3xLED
1xLED
95
100
105
110
115
120
010 20 30 40
VSET (mV)
VIN (V)
ILED = 1.1A
L = 47µH
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© 2012 Exar Corporation 6/12 Rev. 1.1.0
Fig. 10: Thermal Regulation
Fig. 11: Thermal Regulation Threshold versus Temperature
Fig. 12: Switch Waveform
VIN=12V, ILED=350mA, 3 LEDs
Fig. 13: Switch Waveform
VIN=12V, ILED=700mA, 1 LED
Fig. 14: PWM Dimming
VIN=24V, Duty Cycle = 50%, fPWM=40kHz
Fig. 15: Short Circuit
VIN=12V
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© 2012 Exar Corporation 7/12 Rev. 1.1.0
Fig. 16: frequency versus input voltage, ILED=330mA
Fig. 17: frequency versus input voltage, ILED=770mA
Fig. 18: frequency versus input voltage, ILED=1.1A
0
100
200
300
400
500
600
700
010 20 30 40
f (kHz)
VIN (V)
ILED = 330mA
L = 47µH
1xLED
2xLED
3xLED
0
100
200
300
400
500
010 20 30 40
f (kHz)
VIN (V)
ILED = 770mA
L = 47µH
1xLED
2xLED
3xLED
0
50
100
150
200
250
300
350
010 20 30 40
f (kHz)
VIN (V)
ILED = 1.1A
L = 47µH
2xLED
3xLED
1xLED
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© 2012 Exar Corporation 8/12 Rev. 1.1.0
APPLICATION INFORMATION
HYSTERETIC OPERATION
The XRP7613 is a hysteretic step-down LED
driver. It uses ±15% double-ended hysteresis
to regulate the average LED current to the
value programmed by RSET (refer to figure 1).
Internal current through R1, R2, R3 is a
scaled-down mirror of the LED and inductor
current (refer to figure 2). Internal current is
given by IINT=(VIN-VISEN)/R1. During the off
time FETs N1 and N2 are off. Inductor current
IL ramps down through the external Schottky
diode. As IL decreases 15% below the average
value, the decrease in mirror internal current
triggers the comparator on. N1 and N2 turn on
and on time commences. N2 shorts R3 and
thereby increases the current required to
trigger off the comparator. N1 grounds the
inductor and IL ramps up. As IL increases 15%
over its average value, the increase in mirror
internal current triggers the comparator off
and the cycle repeats.
TURN ON AND TURN OFF DELAY
As explained above when IL decreases 15%
below the average current the comparator
triggers on. However, it takes 280ns (nominal)
before N1 turns on and LX transitions from
high to low voltage (refer to figure 19). The
turn on delay time results in inductor current
ripple ΔIL to exceed -15%. Because this delay
imposes a lower bound on the N1 off time, it
has been specified in the tabulated data as
“Minimum Switch OFF Time”.
When IL increases 15% above the average
current the comparator triggers off. There is a
delay of 180ns before N1 turns off and LX
transitions from low to high voltage. The turn
off delay time pushes the ΔIL above the +15%
set by the hysteretic control. Because this
delay imposes a lower bound on the N1 on
time, it has been specified in the tabulated
data as “Minimum Switch On Time”.
Thus the switching frequency will be lower
than expected because the turn on and turn
off delay time increase ΔIL to more than 30%.
Graphs of typical switching frequency versus
VIN for different operating conditions are
shown in figures 16-18.
Fig. 19: Effect of Delay Time on Inductor Current Ripple
SHUTDOWN CONTROL
A shutdown control function is provided
through the EN/DIM input pin. Connecting the
EN/DIM input pin to ground or to a DC voltage
lower than 200mV for longer than 20ms will
completely shut down the XRP7613. In this
state, the quiescent current is less than 35μA
and the internal reference, error amplifier,
comparators, and biasing circuitry completely
turned off.
SETTING THE LED CURRENT
The output current ILED of XRP7613 can be set
by the external sense resistor RSET. The
relationship between ILED and RSET is
VSET can be determined from graphs in figures
6-8. As an example for the operating
conditions ILED=350mA, VIN=24V, 3xLED;
VSET=105mV from figure 6.
OPERATING FREQUENCY
The operating frequency of the XRP7613 can
be calculated by the following equation
where fS is the operating frequency, TON is the
switch on time and TOFF is the switch off time.
IL(avg)
+15%
-15%
LX
Turn on delay
= 280ns Turn off delay
= 180ns
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The switch on time can be calculated by the
following equation
The switch off time can be calculated by the
following equation
where VIN is the input voltage
VLED is the total LED forward voltage
ILED is the LED average current
RSET is current sense resistance
RL is inductor resistance
RDS(ON) is switch on resistance (0.5Ω typ.)
L is the inductor value
ΔIL is the inductor peak to peak current
VD is diode forward voltage at the LED average
current.
The recommended operating frequency should
not exceed 1MHz.
DIMMING CONTROL
The XRP7613 offers two ways of achieving LED
dimming: standard PWM dimming and analog
dimming. The EN/DIM input pin is used not
only to control the XRP7613 shutdown but also
the PWM and analog dimming functions.
If dimming and/or shutdown controls are not
required, the EN/DIM pin can be left floating
for automatic turn on upon application of
proper VIN.
PWM Dimming
A logic-level PWM signal applied to the EN/DIM
pin can be used for PWM dimming control of
the LEDs. This external signal turns the
MOSFET gate drive on and off, thereby
modulating the average current delivered to
the LED proportional to the duty cycle of the
PWM signal. The EN/DIM signal will shutdown
the XRP7613 when EN/DIM = L and turn-on
the XRP7613 when DIM = H. The DIM signal
needs to be greater than 1.3V minimum to
turn-on and less than 200mV to fully turn-off
the device.
The maximum allowed PWM dimming
frequency that can be applied is 40 KHz.
Analog Dimming
The average current delivered to the LED, ie
the LED brightness, can also be controlled by
applying a variable DC voltage signal to the
EN/DIM pin.
A DC voltage greater than 1.25V will drive
output LED current to 100% of the LED
current as set by the external sense resistor
RSET while a voltage lower than 200mV will
shutdown the XRP7613. When analog dimming
is required, the DC voltage range of EN/DIM
should be between 0.4V to 1.25V in order
modulating the average current delivered to
the LED accordingly.
PROTECTIONS
LED Open Circuit Protection
Upon detection of an open-circuit on any LED
connected to the XRP7613, the device will shut
down.
LED Short Circuit Protection
Upon detecting a short-circuit on any LED
connected to the XRP7613, the device will
maintain the LED current as set by the
external sense resistor RSET.
UVLO Protection
The XRP7613 has an Under Voltage Lock-Out
comparator to monitor the Input Voltage VIN.
The VIN UVLO threshold is set internally: when
VIN pin is greater than 6.0V the XRP7613 is
permitted to start up pending the removal of
all other faults.
LED Thermal Protection
The XRP7613 includes a LED thermal
regulation circuit to prevent an over
temperature situation on the LED. When the
LED temperature rises above a predefined
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© 2012 Exar Corporation 10/12 Rev. 1.1.0
threshold, the XRP7613 will reduce linearly the
LED current from its nominal set value.
Fig. 20: VTH Voltage
The XRP7613 continuously monitors the LED
temperature by measuring the voltage on its
TH pin. The VTH voltage is created through a
resistive network of a negative temperature
coefficient (NTC) thermistor RTH and a fixed
resistor RT between VREF pin and ground.
By setting RT=10KΩ and using a 103KT1608
thermistor, the voltage on the TH pin will
reduce to 0.4V when the LED temperature
reaches 70°C. The LED average current will be
decreased linearly when VTH is between 0.4V
and 0.28V. If the LED temperature is over
90°C, the voltage on the TH pin will reduce to
0.28V and the LED will be turned off in order
to decrease the LED temperature. When the
voltage on the TH pin rises to 0.3V, the LED
will be turned on again.
If the LED thermal regulation function isn’t
required, the TH pin should be connected
directly to VREF pin to disable this function.
DIODE SELECTION
Schottky diodes, with their low forward
voltage drop and fast reverse recovery, are
the ideal choices for any XRP7613
applications. The forward voltage drop of a
Schottky diode represents the conduction
losses in the diode, while the diode
capacitance (CT or CD) represents the
switching losses. For diode selection, both
forward voltage drop and diode capacitance
need to be considered. Schottky diodes with
higher current ratings usually have lower
forward voltage drop and larger diode
capacitance, which can cause significant
switching losses. A Schottky diode with a 2A
current rating is adequate for most XRP7613
applications.
INPUT CAPACITOR SELECTION
Ceramic capacitors with their low ESR values
and small size are ideal for the XRP7613
applications. When selecting an input
capacitor, a low ESR capacitor is required to
minimize the noise at the device input. It may
be necessary to add an extra small value
ceramic type capacitor in parallel with the
input capacitor to prevent any possible
ringing.
INDUCTOR SELECTION
Recommended inductor values for the
XRP7613 are in the range of 22µH to 68 µH.
The inductor selected should have low core
losses and low DCR.
LAYOUT CONSIDERATION
For proper operations of XRP7613, the
following guidelines should be followed.
1.The input capacitor should be placed as
close as possible to the VIN pin in order to
reduce the input voltage ripple and noise.
2.The inductor, internal power switch,
Schottky diode, output capacitor and the LEDs
should be kept as close as possible.
3.PCB traces with large current should be kept
short and wide.
5.Effect from noise can be reduced by placing
the XRP7613 GND pin as close as possible to
the ground pin of the input bypass capacitor.
6.The ISEN pin and VIN pin should be
connected to the sense resistor directly.
Traces should be routed away from any
potential sources.
7.The VREF pin and TH pin should be
connected to the LED thermal sense resistors
directly. Traces should be routed away from
any potential sources.
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© 2012 Exar Corporation 11/12 Rev. 1.1.0
TYPICAL APPLICATION CIRCUITS
Fig. 21: Typical Application Diagram
PACKAGE SPECIFICATION
8-PIN EXPOSED PAD SOIC
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© 2012 Exar Corporation 12/12 Rev. 1.1.0
REVISION HISTORY
Revision
Date
Description
1.0.0
11/09/2012
Initial Release of Datasheet
1.1.0
11/26/2012
Corrected typographical error L=47µH in Electrical Specification conditions.
FOR FURTHER ASSISTANCE
Email: customersupport@exar.com
powertechsupport@exar.com
Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx?
EXAR CORPORATION
HEADQUARTERS 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 herein 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.
