Analog Devices LINEAR LTM 8005 User manual

LTM8005
1
Rev. B
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TYPICAL APPLICATION
FEATURES DESCRIPTION
38VIN Boost µModule Regulator for
LED Drive with 10A Switch
The LT M
®
8005 is a 38VIN, 38VOUT boost µModule (power
micromodule) LED driver designed to regulate current or
voltage and is ideal for driving LEDs. The fixed frequency
and current mode architecture result in stable operation
over a wide range of supply and output voltages. Spread
spectrum frequency modulation (SSFM) can be activated
for improved electromagnetic compatibility (EMC) perfor-
mance. The ground-referred voltage FB pin serves as the
input for several LED protection features, and also allows the
converter to operate as a constant voltage source. The PWM
input provides LED dimming ratios of up to 3000:1, and the
CTRL inputs provide additional analog dimming capability.
The low profile package enables utilization of unused
space on the bottom of PC boards. The LTM8005 is pack-
aged in thermally enhanced, compact over-molded Ball
Grid Array (BGA) package suitable for automated assem-
bly by standard surface mount equipment. The LTM8005
is RoHS compliant.
350mA at 30.5V to 35.5V LED String from 6V to 27V VIN (Boost) with Spread Spectrum
APPLICATIONS
n Wide Input Voltage Range: 5V to 38V
n Supports Boost or SEPIC Power Topologies
n Adjustable LED Current Up to 1.6A
n 40V 10A Internal Power Switch
n Wide Temperature Range: –40°C to 150°C
n Input and Output Current Reporting
n Internal Switch for PWM and Output Disconnect
n Internal Spread Spectrum Frequency Modulation
n 3000:1 True Color PWM™ Dimming
n Open LED Protection with OPENLED Flag
n Short-Circuit Protection and SHORTLED Flag
n Soft-Start with Programmable Fault Restart Timer
n 9mm × 11.25mm × 2.22mm BGA
n High Power LED, High Voltage LED
n Accurate Current-Limited Voltage Regulators
All registered trademarks and trademarks are the property of their respective owners.
LTM8005
8005 TA01a
EN/UVLO
OVLO
PWM
VREF
CTRL1
CTRL2
VOUT
ISN
LED
AUX
FB
ISMON
RAMPSS VC RT GND OPENLED SHORTLED
IVINPVIN IVINN SW DA
LED
STRING
COUT
2×
4.7µF
50V
L
8.2µH
L: COILCRAFT XAL7030-822ME
CIN, COUT: MURATA GRM31CR71H475KA12
PIN NOT USED IN THIS CIRCUIT: IVINCOMP
100k
93.1k
1M
19.1k
4.7k 23.2k
f = 350kHz
10nF
6.8nF
0.1µF
0.1µF
CIN
2×
4.7µF
50V
12.4k
374k
VIN
6V TO 27V
18.7k

LTM8005
2
Rev. B
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PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
VIN, EN/UVLO, IVINN, IVINP .....................................50V
ISN Above LED..........................................................40V
SW, ISN, LED, VOUT, VOUT-DA..................................40V
CTRL1, CTRL2 ………………...................................15V
PWM, SHORTLED, OPENLED ...................................12V
FB, OVLO ....................................................................8V
Maximum Junction Temperature
(E-Grade, I-Grade) ............................................ 125°C
Maximum Junction Temperature (H-Grade).......... 150°C
Storage Temperature............................................. 150°C
Peak Solder Reflow Body Temperature ................. 260°C
(Note 1)
FG H JK
E
ABCD
2
1
4
3
5
6
7
8
BGA PACKAGE
80-Pad (11.25mm ×9mm ×2.22mm)
θ
JA
= 19.3°C/W, θ
JCBOTTOM
= 3.0°C/W,
θJCTOP = 16.3°C/W, θJB = 7.2°C/W, WEIGHT = 0.4g
θVALUES DETERMINED PER JEDEC 15-9, 51-12
TOP VIEW
GND
CTRL2
CTRL1
RT
SS
VC
FB
GND
BANK 5
ISN
IVINN
VIN
BANK 2
SW
BANK 1
GND
IVINP
EN/UVLO
IVINCOMP
AUX
ISMON
BANK 6
LED
BANK 4 VOUT
BANK 3 DA
OPENLED SHORTLED RAMP
PWM
VREF
OVLO
ORDER INFORMATION
Part Number Terminal Finish Part Marking* Package Type MSL Rating Temperature Range
Device Finish Code
LTM8005EY#PBF SAC305 (RoHS) LTM8005 e1 BGA 3 –40°C to 125°C
LTM8005IY#PBF SAC305 (RoHS) LTM8005 e1 BGA 3 –40°C to 125°C
LTM8005HY#PBF SAC305 (RoHS) LTM8005 e1 BGA 3 –40°C to 150°C
Contact the factory for parts specified with wider operating temperature
ranges. *Device temperature grade is identified by a label on the shipping
container. Pad or ball finish code is per IPC/JEDEC J-STD-609.
• Recommended LGA and BGA PCB Assembly and Manufacturing
Procedures
• LGA and BGA Package and Tray Drawings

LTM8005
3
Rev. B
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ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage l5 V
LED DC Current CTRL1=1.5V
CTRL1=0.6V
CTRL1=0.2V
1.65
0.8
0.16
A
A
A
SW Current Limit 10 12 14 A
SW RDS(ON) 19 mΩ
ISMON Voltage ILED=1.5A 0.88 0.96 V
Quiescent Current into VIN EN/UVLO=0V (Disabled), PWM=0V
EN/UVLO=1.15V, PWM=0V
RT=82.5K to GND, FB=1.5V (Not Switching)
35
40
3.5
µA
µA
mA
VREF Voltage IREF=–100µA l1.95 2.00 2.08 V
VREF Line Regulation 5V < VIN < 48V 0.1 %
VREF Load Regulation –100µA < IREF < 0µA 1 %
SS Current Sourcing, SS=0V
Sinking, ILED Overcurrent
28
2.8
µA
µA
ILED Overcurrent Threshold 2.4 A
ISN-LED RDS(ON) 53 mΩ
VC Output Impedance 2000 kΩ
VC Standby Input Bias Current PWM=0V –20 20 nA
VC Pin Current VC=1.2V, Sourcing
VC=1.2V, Sinking
10
30
µA
µA
Voltage at FB pin l1.23 1.25 1.27 V
FB Amplifier gm500 µS
FB Pin Input Bias Current Current Out of Pin, FB=VFB 200 nA
FB OPENLED Threshold OPENLED Falling 1.176 1.222 V
FB Overvoltage Threshold 1.26 1.34 V
FB SHORTLED Threshold SHORTLED Falling 300 350 mV
LED Current C/10 Threshold 0.16 A
Input Current Limit Threshold IVINP–IVINN 53 67 mV
IVINCOMP Voltage IVINP–IVINN=60mV 1.2 V
Switching Frequency RT=82.5k
RT=26.1k
RT=6.65k
85
240
800
105
300
1000
125
360
1200
kHz
kHz
kHz
Switching Frequency Modulation RAMP=2V 70 %
RAMP Input Low Threshold 1 V
RAMP Input High Threshold 2 V
RAMP Pin Source Current RAMP=0.4V 12 µA
RAMP Pin Sink Current RAMP=1.6V 12 µA
CTRL1, CTRL2 Pin Current CTRL1, CTRL2=1V 200 nA
PWM Input Threshold Rising 1 V
PWM Pin Bias Current 10 µA
The ldenotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at TA= 25°C. CTRL1=CTRL2=PWM=5V, unless otherwise noted (Note 2).

LTM8005
4
Rev. B
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ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
EN/UVLO Threshold Voltage Falling 1.22 V
EN/UVLO Threshold Voltage Rising 1.24 V
EN/UVLO Pin Bias Current EN/UVLO=1.15V, VIN = 12V 19 µA
OPENLED Output Low IOPENLED=0.5mA 0.3 V
SHORTLED Output Low ISHORTLED=0.5mA 0.3 V
OVLO Threshold Voltage Rising
Falling
1.21
1.17
1.30
1.26
V
V
The ldenotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at TA= 25°C. CTRL1=CTRL2=PWM=5V, unless otherwise noted (Note 2).
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTM8005E is guaranteed to meet performance specifications
from 0°C to 125°C internal. Specifications over the full –40°C to
125°C internal operating temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTM8005I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8005MP is
guaranteed to meet specifications over the full –55°C to 125°C internal
operating temperature range. The LTM8005H is guaranteed to meet
specifications over the full –40°C to 150°C internal operating temperature
range. Note that the maximum internal temperature is determined by
specific operating conditions in conjunction with board layout, the rated
package thermal resistance and other environmental factors.
Note 3: The LTM8005 contains over-temperature protection that is
intended to protect the device during momentary overload conditions. The
internal temperature exceeds the maximum operating junction temperature
when the over-temperature protection is active. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.

LTM8005
5
Rev. B
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TYPICAL PERFORMANCE CHARACTERISTICS
VREF vs Load
Switching Frequency
vs SS Voltage
Demonstration Circuit DC2257A
Output Current Ripple 34V at 1.2A
LED, 12VIN
DC2257A Conducted EMI with and
without Spread Spectrum Enabled
LED Current vs CTRL1 LED Current vs CTRL2
LED Current vs FB
(CTRL1=CTRL2=VREF)
TA= 25°C, unless otherwise noted.
CTRL1 VOLTAGE (V)
0
0.25
0.50
0.75
1
1.25
1.50
0
0.4
0.8
1.2
1.6
2.0
LED CURRENT (A)
8005 G01
CTRL2 VOLTAGE (V)
0
0.25
0.50
0.75
1
1.25
1.50
0
0.4
0.8
1.2
1.6
2.0
LED CURRENT (A)
8005 G02
V
FB
(V)
0
0.3
0.6
0.9
1.2
1.5
0
0.5
1.0
1.5
2.0
LED CURRENT (A)
8005 G03
VREF vs Load Current
LOAD CURRENT (µA)
0
45
90
135
180
0
0.5
1.0
1.5
2.0
2.5
VREF (V)
8005 G04
V
SS
(V)
0
0.3
0.6
0.9
1.2
1.5
RT= 23.2k
0
70
140
210
280
350
FREQUENCY (kHz)
8005 G05
1µs/DIV
CURRENT RIPPLE
50mA/DIV
8005 G06
C
RAMP
= 22nF
SPREAD SPECTRUM DISABLED
SPREAD SPECTRUM ENABLED
FREQUENCY (MHz)
0.1
1.1
2.1
3.0
4.0
5.0
1
21
41
60
80
100
EMISSIONS (dBµV)
8005 G07

LTM8005
6
Rev. B
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TYPICAL PERFORMANCE CHARACTERISTICS
Output Disconnect Response
(Short Circuit)
Output Disconnect Response
(Input > Output)
DC2257A CISPR 22 Radiated
Results Without Spread Spectrum
DC2257A CISPR 22 Radiated
Results With Spread Spectrum
TA= 25°C, unless otherwise noted.
500ns/DIV
VOUT
10V/DIV
VLED
10V/DIV
ILED
10A/DIV
8005 G10
1ms/DIV
VIN
10V/DIV
VOUT
10V/DIV
VLED
10V/DIV
8005 G11
SPREAD SPECTRUM DISABLED
FREQUENCY (MHz)
0
250
500
750
1000
0
10
20
30
40
EMISSIONS (dBµV/m)
8005 G08
SPREAD SPECTRUM ENABLED
FREQUENCY (MHz)
0
250
500
750
1000
0
10
20
30
40
EMISSIONS (dBµV/m)
8005 G09

LTM8005
7
Rev. B
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PIN FUNCTIONS
GND (Bank 1, Pin K1, Pin K8): Tie these GND pins to a
local ground plane below the LTM8005 and the circuit
components. In most applications, the bulk of the heat
flow out of the LTM8005 is through these pads, so the
printed circuit design has a large impact on the thermal
performance of the part. See the PCB Layout and Thermal
Considerations sections for more details. Return the feed-
back divider to this net.
SW (Bank 2):Power Switch Node. This is the drain of the
internal power switching MOSFET. For boost, buck-boost
mode and buck mode topologies, connect this bank to
the inductor and the DA bank. For a SEPIC, connect this
bank to an inductor winding and the positive coupling
capacitor terminal.
DA (Bank 3):Power Diode Anode. For boost, buck-boost
mode and buck mode topologies, connect this bank to
the inductor and the SW bank. For a SEPIC, connect this
bank to an inductor winding and the negative coupling
capacitor terminal.
VOUT (Bank 4):Power Output Pins. Apply the output filter
capacitor between these pins and the GND pins.
ISN (Bank 5):Output Current Sense Resistor. The
LTM8005 incorporates a sense resistor between VOUT
and ISN to set the output current regulation point and
for output current monitoring. If a larger output current
is required, apply an external resistor between VOUT and
ISN. Keep this pin voltage within 0.3V of VOUT.
LED (Bank 6):LED Current Output. Connect the anode of
the LED string to this bank.
VIN (Pin F1): Input Power. The VIN pin supplies current to
the LTM8005’s internal regulators and circuitry, and must
be bypassed with a 0.22µF (or larger) capacitor placed
close to the LTM8005.
IVINN (Pin F2): Input Sense Resistor Signal. Apply an
external sense resistor between IVINP and IVINN to set
the maximum input current and for input current moni-
toring. If this function is not required, tie both IVINP and
IVINN to VIN. Keep this pin voltage within 0.3V of VIN.
EN/UVLO (Pin G1): Enable and Precision UVLO. An accu-
rate 1.22V falling threshold with externally programmable
hysteresis detects when power is OK to enable switching.
Rising hysteresis is generated by the external resistor
divider, an internal 499kΩ resistor between EN/UVLO and
VIN and an accurate internal 3µA pull-down current. Above
the threshold, EN/UVLO input bias current is sub-µA.
Below the falling threshold, a 3µA pull-down current is
enabled so the user can optimize the hysteresis with the
external resistor selection. An undervoltage condition
resets soft-start. The EN/UVLO pin may be connected
directly to VIN, but do not drive this pin directly from
another low impedance voltage source. If EN/UVLO must
be driven from a voltage source, do so with at least a 50Ω
series resistor.
IVINP (Pin G2): Input Sense Resistor Signal. Apply an
external sense resistor between IVINP and IVINN to set
the maximum input current and for input current moni-
toring. If this function is not required, tie both IVINP and
IVINN to VIN. Keep this pin voltage within 0.3V of VIN.
OVLO (Pin H1): Input Overvoltage Lockout Pin. An
accurate 1.25V rising threshold detects when power is
OK to enable switching. If not used, tie this pin to GND.
IVINCOMP (Pin H2): Input Current Sense Amplifier Output
Pin. The voltage at IVINCOMP pin is proportional to IIN as
VIVINCOMP = IIN • RINSNS • 20. A 10nF capacitor to GND
is provided internally at this pin to compensate the input
current loop. Do not load this pin with a current and do not
drive this pin with an external source, although additional
capacitance may be added externally.
SHORTLED (Pin H7): An open-collector pull-down on
SHORTLED asserts when any of the following conditions
happen:
1. FB < 0.3V after SS pin reaches 1.7V at start-up.
2. LED overcurrent (ILED > 2.4A).
To function, the pin requires an external pull-up resistor.
SHORTLED status is only updated during PWM high state
and latched during PWM low state. SHORTLED remains
asserted until the SS pin is discharged below 0.2V. If not
used, leave floating or tie to GND.
OPENLED (Pin H8): Fault Indicator. An open-collector
pull-down on OPENLED asserts if the FB input is above
1.20V (typical), and the LED current is less than 0.16A
(typical). To function, the pin requires an external pull-up

LTM8005
8
Rev. B
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resistor. OPENLED status is updated only during PWM
high state and latched during PWM low state. If not used,
leave floating or tie to GND.
ISMON (Pin J1): LED Current Report Pin. The LED cur-
rent is reported as VISMON = (LED current)/1.6. Leave the
ISMON pin unconnected if not used. When PWM is low,
ISMON is driven to ground. Bypass with a 47nF capacitor
or higher if needed. Do not drive this pin with an external
source.
AUX (Pin J2): Auxiliary Pin. This pin is internally con-
nected to VOUT to ease layout. Conveniently located next
to FB, it is provided to simplify layout of the output voltage
feedback network.
VREF (Pin J6): Voltage Reference Output Pin. Typically 2V.
This pin drives a resistor divider for the CTRL pins, either
for analog dimming or for temperature limit/compensa-
tion of the LED load. It can supply up to 100µA. Do not
drive this pin with an external source.
PWM (Pin J7): PWM Input Signal Pin. A low signal turns
off switching, idles the oscillator, disconnects the VC pin
from all internal loads, and disconnects the output load
from VOUT. PWM has an internal 500kΩ pull-down resis-
tor. If not used, connect to VREF.
RAMP (Pin J8): The RAMP pin is used for spread spec-
trum frequency modulation. The internal switching fre-
quency is spread out to 70% of the original value, where
the modulation frequency is set by 12µA/(2 • 1V • CRAMP).
If not used, tie this pin to GND.
FB (Pin K2): Voltage Loop Feedback Pin. FB is intended
for constant-voltage regulation or for LED protection/open
LED detection. The internal transconductance amplifier
with output VC regulates FB to 1.25V (nominal) through
the DC/DC converter. If the FB input is regulating the loop,
and LED current is less than 0.15A (typical), the OPENLED
pull-down is asserted. This action may signal an open LED
fault. If FB is driven above 1.3V (by an external power sup-
ply spike, for example), the internal N-Channel MOSFET
is turned off and the load is disconnected from VOUT to
protect the LEDs from an overcurrent event. Do not tie
this pin to GND as the SHORTLED will be asserted and
the part will be shut down.
VC (Pin K3): Transconductance Error Amplifier Output Pin.
Used to stabilize the control loop with an RC network. This
pin is high impedance when PWM is low, a feature that
stores the demanded current state variable for the next
PWM high transition. Connect a capacitor between this pin
and GND;a resistor in series with the capacitor is recom-
mended for fast transient response. Do not leave this pin
open, and do not drive this pin with an external source.
SS (Pin K4): Soft-Start Pin. This pin modulates oscillator
frequency and compensation pin voltage (VC). The soft-
start interval is set with an external capacitor. The pin
has a 28µA (typical) pull-up current source to an internal
2.5V rail. This pin can be used as fault timer. Provided the
SS pin has exceeded 1.7V to complete a blanking period
at start-up, the pull-up current source is disabled and a
2.8µA pull-down current is enabled when any one of the
following fault conditions happen:
1. LED overcurrent (ILED > 2.4A)
2. Output short (FB < 0.3V after start-up)
3. Thermal limit
The SS pin must be discharged below 0.2V to re-initiate
a soft-start cycle. Switching is disabled until SS begins to
recharge. It is important to select a capacitor large enough
that FB can exceed 0.3V under normal load conditions
before SS exceeds 1.7V. Do not leave this pin open and
do not drive this pin with an external source.
RT (Pin K5): Switching Frequency Adjustment Pin. Set
the frequency using a resistor to GND. Do not leave the
RT pin open. Do not drive this pin with an external source.
CTRL1, CTRL2 (Pin K6, K7): Current Sense Threshold
Adjustment. CTRL1 and CTRL2 have identical functions.
The output current is regulated by CTRL1 or CTRL2.
The pin with the lowest voltage takes precedence. For
0.1V<VCTRLx<1V the LED current is VCTRLx• 1.5A
less an offset. For VCTRLx > 1.2V the current sense
threshold is constant at the full-scale value of 1.6A. For
1V<VCTRLx<1.2V, the dependence of the current sense
threshold upon VCTRLx transitions from a linear function
to a constant value, reaching 98% of full-scale value by
VCTRLx = 1.1V. Do not leave this pin open. If not used, tie
to VREF. Connect either CTRL pin to GND for zero LED
current.
PIN FUNCTIONS

LTM8005
9
Rev. B
For more information www.analog.com
BLOCK DIAGRAM
LTM8005
0.068Ω
499k
10nF
BOOST LED
CONTROLLER
8005 BD
VIN
EN/UVLO
CIN
VIN
VOUT
AUX
FB
ISN
LED
IVINCOMP
COUT
SHORTLED
OPENLED
ISMON
GND
IVINP IVINN SW DA
OVLO
PWM
VREF
CTRL1
CTRL2
SS
RAMP
RT
VC

LTM8005
10
Rev. B
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OPERATION
The LTM8005 is a stand-alone non-isolated switching DC/
DC regulator intended for LED driver applications. This
µModule power converter provides a regulated current
from an input voltage range of 5V to 38V, and up to 38V
output. A simplified block diagram is provided in the pre-
vious section.
The LTM8005 is equipped with a ground referred power
switch and a power rectifier. Connect external power
devices, such as an inductor, to these pins to implement
boost, buck-boost mode, buck mode or SEPIC topologies
to drive a string of LEDs.
The LTM8005 features an integrated sense resistor to
control the LED current. The maximum regulated current
is 1.6A, and this can be reduced by applying a voltage less
than 1.2V to the CTRL1 or CTRL2 pins. The output current
is reported by the voltage on the ISMON pin.
The LTM8005 also features an integrated PMOS discon-
nect switch to implement PWM dimming that is controlled
by a signal on the PWM pin. The PMOS also disconnects
the LEDs during fault conditions.
If input current limiting is desired, apply an external sense
resistor to the IVINP and IVINN pins. The full input current
will flow through this external sense resistor, so choose a
resistor with an appropriate power rating. The LTM8005
will start to decrease the power if the voltage between the
IVINP and INVINN pins exceeds 60mV. A 10nF capacitor
is provided internally to compensate the input current
regulation loop, but additional capacitance may be added
externally to further filter the voltage at the IVINCOMP pin.
The LTM8005 features spread spectrum frequency
modulation, which causes the switching frequency to
modulate to a frequency that is approximately 70% of
the programmed value set by the RT resistor. This modu-
lation decreases the energy emitted at a single frequency,
reducing the EMI amplitude. The modulation behavior is
set by a capacitor on the RAMP pin to GND.
Input voltage turn-on and turn-off thresholds are set
by resistor networks at the EN/UVLO and OVLO pins.
Applying a voltage of greater than 1.24V to the EN/UVLO
pin enables the part.
OPENLED and SHORTLED are active low open drain sta-
tus bits that indicate an open LED or shorted LED condi-
tion. OPENLED transitions to a logic low when the FB pin
rises above 1.2V and the LED current decreases below
160mA. SHORTLED transitions to a logic low when the FB
pin falls below 300mV or the LED current exceeds 2.4A.
Further details on these and other functions are given in
the Applications Information section.
An external soft start capacitor at the SS pin minimizes
the current spike that occurs at start up and the SS pin
also programs hiccup or latchoff mode fault protection.
The LTM8005 is equipped with a thermal shutdown that
inhibits power switching at high junction temperatures.
The activation threshold of this function is above the abso-
lute maximum temperature rating to avoid interfering with
normal operation, so prolonged or repetitive operation
under a condition in which the thermal shutdown activates
may damage or impair the reliability of the device.