LT3964
Dual 36V Synchronous 1.6A
Buck LED Driver with I
2
C
FEATURES
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DESCRIPTION
The
LT
®
3964
is a dual synchronous step-down DC/DC
converter with I
2
C interface designed to operate as a
constant-current and constant-voltage source and is ideal
for driving LEDs. The fixed frequency and peak current
mode topology result in stable operation over a wide range
of supply and output voltages. The ground referred volt-
age FB pin serves as the input for several LED protection
features, and also allows the converter to operate as a
constant-voltage source. The maximum output current is
set by an external resistor, and the output current ampli-
fier has a rail-to-rail common mode range. LT3964 uses
an I
2
C interface to communicate with a microcontroller
to read LED faults, write PWM and analog dimming reg-
isters and set fault masking. The I
2
C PWM input provides
LED dimming ratios up to 8192:1. The I
2
C programmable
CTRL register sets the gain of the external CTRL pin, and
maximum current sense threshold, providing additional
analog dimming capability.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents, including 7199560, 7321203, 7746300.
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Wide Input Voltage Range: 4V to 36V
Two Independent 1.6A/40V Synchronous Bucks
I
2
C Interface for Internal True Color PWM™ Dimming
(8192:1), Analog Dimming and Fault Reporting
1000:1 External True Color PWM Dimming and
10:1 External Analog Dimming
PMOS Switch Driver for PWM and Output Disconnect
±3% Constant Current Regulation
Adjustable Frequency: 200kHz to 2MHz
Frequency Synchronization with Clock Output
Programmable OPENLED Protection with Reporting
Short-Circuit Protection with Reporting
Programmable Undervoltage Lockout with Hysteresis
Internal Compensation
9 Unique Device Addresses for I
2
C
Available in 5mm × 6mm 36-Lead QFN Package
APPLICATIONS
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General Purpose, Industrial, Medical and
Automotive Lighting
Constant-Current, Constant-Voltage Source
TYPICAL APPLICATION
50W Dual Buck 1A LED Driver
31V TO 36V
(ENABLED AT 33V,
SHUTDOWN
AT 31V)
10µF
×2
2.2µF
100k
V
IN1
GND
EN/UVLO
3.92k PWM1
PWM2
INTV
CC
2.2µF
100k
ALERT
V
IN2
INTV
CC
499k
2.2µF
GND
T
SET
RT
SYNC/CLKOUT
SCL
SDA
ISP2
ISN2
PWMTG2
ADDR1 ADDR2
INTV
CC
3964 TA01a
BST1
SW1
100
0.22µF
10µH
1M
2.2µF
100mΩ
Efficiency, V
IN
= 34V
BOTH CHANNELS ARE ON
95
EFFICIENCY (%)
1A,
8 LEDs
UP TO
26V
PWM1
PWM2
CTRL1
CTRL2
INTV
CC
FB1
43.2k
ISP1
ISN1
PWMTG1
BST2
0.22µF
SW2
10µH
1M
FB2
43.2k
2.2µF
100mΩ
90
85
80
75
70
100 200 300 400 500 600 700 800 900 1000
I
LED
(mA)
3964 TA01b
LT3964
165k
27.4k
2MHz
1A,
8 LEDs
UP TO
26V
2-WIRE
I
2
C INTERFACE
3964fb
For more information
www.linear.com/LT3964
1
LT3964
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
SYNC/CLKOUT
TOP VIEW
BST1
28 ISP1
27 ISN1
26 PWMTG1
25 SGND
37
PGND
24 FB1
23 FB2
22 SGND
21 PWMTG2
20 ISN2
19 ISP2
11 12 13 14 15 16 17 18
V
IN2
V
IN2
SW2
SW2
NC
ADDR2
ADDR1
BST2
SW1
SW1
T
SET
V
IN1
V
IN1
V
IN1
, V
IN2
, EN/UVLO .................................................40V
ISP1, ISN1, ISP2, ISN2 ..............................................40V
PWMTG1, PWMTG2, RT .......................................Note 2
SW1, SW2.................................................................40V
BST1, BST2 ............................................................44.5V
BST1 to SW1, BST2 to SW2 ....................................4.5V
FB1, FB2, CTRL1, CTRL2, ADDR1, ADDR2 ..................5V
SYNC/CLKOUT, PWM1, PWM2, T
SET
..........................6V
SDA, SCL,
ALERT
........................................................6V
INTV
CC
..................................................................Note 3
Operating Junction Temperature (Notes 4, 5)
LT3964E/LT3964I .............................. –40°C to 125°C
LT3964H ............................................ –40°C to 150°C
Storage Temperature Range .................. –60°C to 150°C
36 35 34 33 32 31 30 29
RT 1
CTRL1 2
CTRL2 3
EN/UVLO 4
INTV
CC
5
ALERT
6
PWM1 7
PWM2 8
SDA 9
SCL 10
UHE PACKAGE
36-LEAD (5mm
×
6mm) PLASTIC QFN
θ
JA
= 43°C/W,
θ
JC
= 5°C/W
EXPOSED PAD (PIN 37) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3964EUHE#PBF
LT3964IUHE#PBF
LT3964HUHE#PBF
TAPE AND REEL
LT3964EUHE#TRPBF
LT3964IUHE#TRPBF
LT3964HUHE#TRPBF
http://www.linear.com/product/LT3964#orderinfo
PART MARKING
3964
3964
3964
PACKAGE DESCRIPTION
36-Lead (5mm × 6mm) Plastic QFN
36-Lead (5mm × 6mm) Plastic QFN
36-Lead (5mm × 6mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
Consult ADI Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
NC
2
3964fb
For more information
www.linear.com/LT3964
LT3964
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V, V
EN/UVLO
= 5V, CTRL1 = CTRL2 = 2V, PWM1 = PWM2 = 2V
unless otherwise noted.
PARAMETER
V
IN1
, V
IN2
Operating Supply Range
V
IN1
Pin Quiescent Current
V
IN1
Pin Shutdown Current
V
IN2
Pin Quiescent Current
V
IN2
Pin Shutdown Current
EN/UVLO Threshold Voltage Falling
EN/UVLO Rising Hysteresis
EN/UVLO Input Low Voltage
EN/UVLO Pin Bias Current Low
EN/UVLO Pin Bias Current High
Linear Regulator
INTV
CC
Regulation Voltage
INTV
CC
Line Regulation
INTV
CC
Load Regulation
INTV
CC
Undervoltage Lockout
INTV
CC
Undervoltage Lockout Hysteresis
INTV
CC
Current Limit
Dropout (V
IN1
– V
INTVCC
)
Error Amplifier
Full Scale LED Current Sense Threshold
(V
(ISP1-ISN1)
, V
(ISP2-ISN2)
)
1/2 Scale LED Current Sense Threshold
(V
(ISP1-ISN1)
, V
(ISP2-ISN2)
)
ISP1,2 = 24V, CTRL1,2 = 1.5V, ADIM1,2[7:0] = 0xFF
ISP1,2 = 0V, CTRL1,2 = 1.5V, ADIM1,2[7:0] = 0xFF
ISP1,2 = 24V, CTRL1,2 = 0.7V, ADIM1,2[7:0] = 0xFF
ISP1,2 = 0V, CTRL1,2 = 0.7V, ADIM1,2[7:0] = 0xFF
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
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TYP
2.5
MAX
36
200
1
UNITS
V
mA
µA
µA
µA
µA
µA
V
mV
V
µA
nA
V
%/V
%/mA
4
Not Switching
EN/UVLO = 1.15V, PWM1,2 = 0V
EN/UVLO = 0V
Not Switching
EN/UVLO = 1.15V, PWM1,2 = 0V
EN/UVLO = 0V
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1
10
1
1
1.158
1.18
60
1.202
0.4
EN/UVLO = 1.15V
EN/UVLO = 1.3V
I
INTVCC
=
–30mA,
Non Switching
6V ≤ V
IN1
≤ 40V
–30mA
≤ I
INTVCC
≤ 0mA
3.1
V
IN1
= 12V, V
INTVCC
= 3V
V
IN1
= 4V, I
INTVCC
=
–20mA,
Not Switching
97
96
47
46
22
21
7
6
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4
2
3.9
4
0.03
0.03
3.2
50
110
300
100
100
50
50
25
25
10
10
930
6
6
10
11
350
5
30
10
20
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100
4.1
3.3
V
mV
mA
mV
103
104
53
54
28
29
13
14
mV
mV
mV
mV
mV
mV
mV
mV
mV
1/4th Scale LED Current Sense Threshold ISP1,2 = 24V, CTRL1,2 = 0.7V, ADIM1,2[7:0] = 0x7F
(V
(ISP1-ISN1)
, V
(ISP2-ISN2)
) Modulated by
ISP1,2 = 0V, CTRL1,2 = 0.7V, ADIM1,2[7:0] = 0x7F
I
2
C Input ADIM1,2[7:0]
1/10th Scale LED Current Sense
Threshold (V
(ISP1-ISN1)
, V
(ISP2-ISN2)
)
ISP1,2/ISN1,2 Overcurrent Protection
Threshold (V
(ISP1-ISN1)
, V
(ISP2-ISN2)
)
C/10 Current Sense Threshold
(V
(ISP1-ISN1)
, V
(ISP2-ISN2)
)
ISP1, ISP2 Input Current Bias Current
ISN1, ISN2 Input Current Bias Current
CTRL1, CTRL2 Input Bias Current
CTRL1, CTRL2 PWM Shutdown Threshold
CTRL1, CTRL2 PWM Threshold Hysteresis
FB1, FB2 Regulation Voltage (V
FB
)
FB1, FB2 Overvoltage Threshold
ISP1,2 = 24V
ISP1,2 = 24V, CTRL1,2 = 0.3V, ADIM1,2[7:0] = 0xFF
ISP1,2 = 0V, CTRL1,2 = 0.3V, ADIM1,2[7:0] = 0xFF
ISP1,2 = 24V
ISP1,2 = 24V
ISP1,2 = 0V
PWM1,2 = 2V (ACTIVE)
PWM1,2 = 0V (STANDBY)
PWM1,2 = 2V (ACTIVE)
PWM1,2 = 0V (STANDBY)
V
CTRL1
, V
CTRL2
= 1V
15
16
8
mV
mV
µA
µA
µA
nA
200
150
1.197
1.19
nA
mV
mV
V
V
V
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100
30
1.163
1.17
1.18
1.18
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V
FB
+ 43mV V
FB
+ 53mV V
FB
+ 63mV
For more information
www.linear.com/LT3964
3
LT3964
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V, V
EN/UVLO
= 5V, CTRL1 = CTRL2 = 2V, PWM1 = PWM2 = 2V
unless otherwise noted.
PARAMETER
FB1, FB2 OPENLED Threshold
FB1, FB2 SHORTLED Threshold
FB1, FB2 Pin Input Bias Current
Feedback Line Regulation
T
SET
Pin Voltage
T
SET
Pin Bias Current
Oscillator
RT Pin Voltage
Switching Frequency
R
T
= 357k
R
T
= 60.4k
R
T
= 27.4k
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
250
20
0.001
630
40
0.96
MAX
270
200
UNITS
V
mV
nA
%/V
mV
V
FB
–
43mV V
FB
–
53mV V
FB
–
63mV
Current Out of Pin, FB = 1V
4V ≤ V
IN1
≤ 36V
Current Out of Pin, T
SET
= 400mV
200
nA
V
186
0.93
1.86
1.5
200
1.0
2.0
100
214
1.07
2.14
kHz
MHz
MHz
kΩ
V
SYNC/CLKOUT Pin Resistance to GND
SYNC/CLKOUT Input High Threshold
SYNC/CLKOUT Input Low Threshold
SYNC/CLKOUT Output Duty Cycle
SYNC/CLKOUT Output Voltage High
SYNC/CLKOUT Output Voltage Low
SYNC/CLKOUT Output Rise Time
SYNC/CLKOUT Output Fall Time
Logic
ALERT
Output Low
PWM1, PWM2 Input High Voltage
PWM1, PWM2 Input Low Voltage
PWM1, PWM2 Resistance to GND
Power Switch
Top Switch On Resistance
Top Switch Current Limit
Bottom Switch On Resistance
Bottom Switch Current Limit
SW Leakage Current
Minimum Off Time
Minimum ON Time
PWMTG Gate Driver
PWMTG ON Voltage (V
ISP1-PWMTG1
,
V
ISP2-PWMTG2
)
PWMTG OFF Voltage (V
ISP1-PWMTG1
,
V
ISP2-PWMTG2
)
PWMTG Turn-On Time
PWMTG Turn-Off Time
ISP1,2 = 36V
ISP1,2 = 36V
C
LOAD
= 500pF, ISP1,2 = 36V
C
LOAD
= 500pF, ISP1,2 = 36V
V
IN
= 36V, V
SW
= 0V, 36V
I
SW
= 1A
1.6
–1.5
20
20
I
SW
= 1A
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0.4
CONFIG[6] = 1 (Clock Output Enabled)
CONFIG[6] = 1 (Clock Output Enabled)
CONFIG[6] = 1 (Clock Output Enabled)
C
SYNC/CLKOUT
= 50pF, CONFIG[6] = 1 (Clock
Output Enabled)
C
SYNC/CLKOUT
= 50pF, CONFIG[6] = 1 (Clock
Output Enabled)
I
ALERT
= 1mA
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V
%
V
V
ns
ns
30
50
4
0.1
40
20
70
0.3
300
1.18
1.1
1.15
280
200
1.6
1.8
180
2
50
40
7.5
0
70
40
2.4
1.5
70
65
9.5
0.3
2
1.3
mV
V
V
kΩ
mΩ
A
mΩ
A
µA
ns
ns
V
V
ns
ns
4
3964fb
For more information
www.linear.com/LT3964
LT3964
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V, V
EN/UVLO
= 5V, CTRL1 = CTRL2 = 2V, PWM1 = PWM2 = 2V
unless otherwise noted.
PARAMETER
I
2
C Port (Note 6)
I
2
C Address
V
IHA
V
ILA
R
INH
R
INL
R
INF
SDA and SCL Input High Voltage
SDA and SCL Input Low Voltage
SDA and SCL Input High Current
SDA and SCL Input Low Current
SDA Output Low Voltage
Clock Operating Frequency
Bus Free Time Between Stop and Start
Condition (t
BUF
)
Hold Time After Repeated Start
Condition (t
HD,SDA
)
Repeated Start Condition Set-Up
Time (t
SU,STA
)
Stop Condition Set-Up Time (t
SU,STO
)
Data Hold Time Output (t
HD,DAT(O)
)
Data Hold Time Input (t
HD,DAT(I)
)
Data Set-Up Time (t
SU,DAT
)
SCL Clock Low Period (t
LOW
)
SCL Clock High Period (t
HIGH
)
Data Fall Time
Data Rise Time
Input Spike Suppress Pulse Width (t
SP
)
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:
Do not apply a positive or negative voltage source to the PWMTG
pin or RT pin, otherwise permanent damage may occur.
Note 3:
Do not apply a positive or negative voltage source to INTV
CC
pin,
otherwise permanent damage may occur. I
INTVCC
= 5mA is the maximum
external load that can be applied. The internal load will be higher due to the
power consumption of the IC.
Note 4:
The LT3964E is guaranteed to meet specified performance
from 0°C to 125°C. Specifications over the
–40°C
to 125°C operating
temperature range are assured by design, characterization and
C
B
= Capacitance of One Bus Line (pF)
C
B
= Capacitance of One Bus Line (pF)
1.3
0.6
0.6
0.6
0
0
250
1.3
0.6
20 + 0.1C
B
20 + 0.1C
B
300
300
50
900
SDA, SCL = 3.3V
Current Out of Pin, SDA, SCL = 0V
I
SDA
= 3mA
XXXX Bits Are Programmed by ADDR[1:2]
High Level Input Voltage for Address Pins ADDR1, ADDR2
Low Level Input Voltage for Address Pins ADDR1, ADDR2
Resistance from ADDR1, ADDR2 to INTV
CC
to Set Chip
Address Bit to 1
Resistance from ADDR1, ADDR2 to GND to Set Chip
Address Bit to 0
Resistance from ADDR1, ADDR2 to GND or INTV
CC
to
Set Chip Address Bit to Float
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
110XXXX[R/W]
MAX
UNITS
INTV
CC
– 0.8
0.6
10
10
1
1.5
0.4
50
50
0.4
400
V
V
kΩ
kΩ
MΩ
V
V
nA
nA
V
kHz
µs
µs
µs
µs
ns
ns
ns
µs
µs
ns
ns
ns
correlation with statistical process controls. The LT3964I is guaranteed
to meet performance specifications over the
–40°C
to 125°C operating
temperature range. The LT3964H is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.
Note 5:
The LT3964 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature is active. Continuous operating above the specified
maximum operating junction temperature may impair device reliability.
Note 6:
All I
2
C serial port timing information is shown in Figure 15.
3964fb
For more information
www.linear.com/LT3964
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