LTC3783
PWM LED Driver and Boost,
Flyback and SEPIC Controller
DESCRIPTIO
The LTC
®
3783 is a current mode LED driver and boost,
flyback and SEPIC controller that drives both an N-channel
power MOSFET and an N-channel load PWM switch.
When using an external load switch, the PWMIN input not
only drives PWMOUT, but also enables controller GATE
switching and error amplifier operation, allowing the con-
troller to store load current information while PWMIN is
low. This feature (patent pending) provides extremely fast,
true PWM load switching with no transient overvoltage or
undervoltage issues; LED dimming ratios of 3000:1 can be
achieved digitally, avoiding the color shift normally asso-
ciated with LED current dimming. The FBP pin allows
analog dimming of load current, further increasing the
effective dimming ratio by 100:1 over PWM alone.
In applications where output load current must be re-
turned to V
IN
, optional constant current/constant voltage
regulation controls either output (or input) current or
output voltage and provides a limit for the other. I
LIM
provides a 10:1 analog dimming ratio.
For low- to medium-power applications, No R
SENSE
mode
can utilize the power MOSFET’s on-resistance to eliminate
the current-sense resistor, thereby maximizing efficiency.
The IC’s operating frequency can be set with an external
resistor over a 20kHz to 1MHz range and can be synchro-
nized to an external clock using the SYNC pin.
The LTC3783 is available in the 16-lead DFN and TSSOP
packages.
FEATURES
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True Color PWM
TM
Delivers Constant Color with
3000:1 Dimming Ratio
Fully Integrated Load FET Driver for PWM Dimming
Control of High Power LEDs
100:1 Dimming from Analog Inputs
Wide FB Voltage Range: 0V to 1.23V
Constant Current or Constant Voltage Regulation
Low Shutdown Current: I
Q
= 20µA
1% 1.23V Internal Voltage Reference
2% RUN Pin Threshold with 100mV Hysteresis
Programmable Operating Frequency (20kHz to
1MHz) with One External Resistor
Synchronizable to an External Clock Up to 1.3f
OSC
Internal 7V Low Dropout Voltage Regulator
Programmable Output Overvoltage Protection
Programmable Soft-Start
Can be Used in a No R
SENSE
TM
Mode for V
DS
< 36V
16-Lead DFN and TSSOP Packages
APPLICATIO S
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High Voltage LED Arrays
Telecom Power Supplies
42V Automotive Systems
24V Industrial Controls
IP Phone Power Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
True Color PWM and No R
SENSE
are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patent pending.
TYPICAL APPLICATIO
V
IN
6V TO 16V
(< TOTAL V
F
OF LEDs)
1M
LTC3783
RUN
V
IN
PWMIN OV/FB
I
TH
PWMOUT
SS
I
LIM
GATE
V
REF
FBP
SENSE
FBN
INTV
CC
GND
FREQ
SYNC
350mA PWM LED Boost Application
10µF
×2
2.2µH
ZETEX ZLL51000
V
OUT
<25V
237k
LED*
STRING
C
OUT
10µF
V
PWMIN
5V/DIV
V
OUT
0.2V/DIV
AC COUPLED
I
L
2.5A/DIV
105k
0.1µF
10µF
10k
6k
M1
M2
4.7µF
0.05Ω
12.4k
0.3Ω
GND
I
LED
0.5A/DIV
M1, M2: SILICONIX Si4470EY
*LUMILEDS LHXL-BW02
3783 TA01a
U
U
U
Typical Waveforms
1µs/DIV
3783 TA01b
3783f
1
LTC3783
ABSOLUTE
AXI U
RATI GS
V
IN
, SENSE, FBP, FBN Voltages ................ – 0.3V to 42V
INTV
CC
Voltage ........................................... – 0.3V to 9V
INTV
CC
Output Current ........................................ 75mA
GATE Output Current ................................ 50mA (RMS)
PWMOUT Output Current ......................... 25mA (RMS)
V
REF
Ouput Current ................................................ 1mA
GATE, PWMOUT Voltages ..... –0.3V to (V
INTVCC
+ 0.3V)
I
TH
, I
LIM
, SS Voltages .............................. – 0.3V to 2.7V
RUN, SYNC, PWMIN Voltages .................... – 0.3V to 7V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
FBN
FBP
I
LIM
V
REF
FREQ
SYNC
PWMIN
PWMOUT
1
2
3
4
5
6
7
8
17
16 RUN
15 I
TH
14 OV/FB
13 SS
12 SENSE
11 V
IN
10 INTV
CC
9
GATE
ORDER PART
NUMBER
LTC3783EDHD
DHD PART MARKING
3783
DHD PACKAGE
16-LEAD (5mm
×
4mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/ W
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 12V, V
RUN
= 1.5V, V
SYNC
= 0V, V
FBP
= V
REF
, R
T
= 20k, unless otherwise specified.
SYMBOL
V
IN
I
Q
PARAMETER
Input Voltage Range
Input Voltage Supply Current
Continuous Mode
Shutdown Mode
Rising RUN Input Threshold Voltage
Falling RUN Input Threshold Voltage
RUN Pin Input Threshold Hysteresis
1.223
(Note 4)
V
OV/FB
= 1.5V, V
ITH
= 0.75V
V
RUN
= 0V
CONDITIONS
MIN
3
1.5
20
1.348
1.248
100
1.273
TYP
MAX
36
UNITS
V
mA
µA
V
V
mV
3783f
Main Control Loop/Whole System
V
RUN+
V
RUN–
V
RUN(HYST)
2
U
U
W
W W
U
W
(Note 1)
FREQ, V
REF
, OV/FB Voltages .....................– 0.3V to 1.5V
Operating Junction Temperature Range
(Note 2) .................................................. – 40°C to 85°C
Junction Temperature (Note 3) ............ – 40°C to 125°C
Storage Temperature Range
DFN Package ................................... – 65°C to 125°C
TSSOP Package ............................... – 65°C to 150°C
Lead Temperature (Soldering, 10sec)
TSSOP Package ............................................... 300°C
TOP VIEW
FBN
FBP
I
LIM
V
REF
FREQ
SYNC
PWMIN
PWMOUT
1
2
3
4
5
6
7
8
17
16 RUN
15 I
TH
14 OV/FB
13 SS
12 SENSE
11 V
IN
10 INTV
CC
9
GATE
ORDER PART
NUMBER
LTC3783EFE
FE PACKAGE
16-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/ W
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
LTC3783
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 12V, V
RUN
= 1.5V, V
SYNC
= 0V, V
FBP
= V
REF
, R
T
= 20k, unless otherwise specified.
SYMBOL
I
RUN
I
SENSE(ON)
I
SENSE(OFF)
I
SS
V
REF
I
REF
PARAMETER
RUN Pin Input Current
125
V
SENSE
= 0V
V
SENSE
= 36V
V
SS
= 0V
1.218
1.212
0.5
3V
≤
V
IN
≤
36V
0mA
≤
I
REF
≤
0.5mA
0.002
0.2
165
25
18
7
1.212
1.230
–0.4
50
–3
100
10
1.7
14
500
R
FREQ
= 20kΩ
250
20
85
V
SYNC
= 0V to 5V
V
SYNC
= 0V to 5V
1.2
0.5
100
With Sense Resistor, 10mV Overdrive
No R
SENSE
Mode
170
300
300
90
1.25
25
0.8/f
OSC
350
1000
97
1.3
ns
ns
V
V
kΩ
ns
ns
3
1.248
2.5V < V
FBP
< 36V
0V
≤
V
FBP
≤
V
REF
2.5V < V
FBP
< 36V
0V
≤
V
FBP
≤
V
REF
2.5V < V
FBP
≤
36V (V
ILIM
= V
REF
)
2.5V < V
FBP
≤
36V (V
ILIM
= 0.123V)
V
FBP
≤
V
REF
2.5V < V
FBP
< 36V
60
0.02
1.0
SENSE Pin Current (GATE High)
SENSE Pin Current (GATE Low)
Soft-Start Pin Output Current
Reference Voltage
●
CONDITIONS
MIN
TYP
5
150
70
0.2
–50
1.230
MAX
180
UNITS
nA
mV
µA
µA
µA
V
SENSE(MAX)
Maximum Current Sense Threshold
Voltage/Temperature Reference
1.242
1.248
V
V
mA
%/V
%/mA
°C
°C
nA
%
V
µA
µA
mV
mV
mV
mmho
mmho
V/V
kHz
kHz
%
Max Reference Pin Output Current
∆V
REF
/∆V
IN
Reference Voltage Line Regulation
∆V
REF
/∆I
REF
Reference Voltage Load Regulation
T
MAX
T
HYST
I
OV/FB
V
OV/FB(FB)
I
FBP
, I
FBN
Overtemperature SD Threshold
Rising
Overtemperature Hysteresis
OV/FB Pin Input Current
OV/FB Pin Regulation Voltage
Error Amplifier Input Current
Error Amplifier
∆V
OV/FB(OV)
OV/FB Overvoltage Lockout Threshold V
OV/FB(OV)
– V
OV/FB(NOM)
in %, V
FBP
≤
V
REF
V
FBP
– V
FBN
Error Amplifier Offset Voltage
(Note 5)
g
m
A
VOL
Oscillator
f
OSC
D
MAX
f
SYNC
/f
OSC
t
SYNC(MIN)
t
SYNC(MAX)
V
IH(SYNC)
R
SYNC
t
ON(MIN)
Oscillator Frequency
Oscillator Frequency Range
Maximum Duty Cycle
Error Amplifier Transconductance
Error Amplifier Open-Loop Gain
Recommended Max SYNC Freq Ratio f
OSC
= 300kHz (Note 6)
SYNC Minimum Input Pulse Width
SYNC Maximum Input Pulse Width
SYNC Input Voltage High Level
SYNC Input Pull-Down Resistance
Minimum On-time
V
HYST(SYNC)
SYNC Input Voltage Hysteresis
3783f
3
LTC3783
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
J
= 25°C.
V
IN
= 12V, V
RUN
= 1.5V, V
SYNC
= 0V, V
FBP
= V
REF
, R
T
= 20k, unless otherwise specified.
SYMBOL
V
INTVCC
UVLO
PARAMETER
INTV
CC
Regulator Output Voltage
INTV
CC
Undervoltage Lockout
Thresholds
INTV
CC
Line Regulation
INTV
CC
Load Regulation
INTV
CC
Dropout Voltage
Bootstrap Mode INTV
CC
Supply
Current in Shutdown
GATE Driver Output Rise Time
GATE Driver Output Fall Time
GATE Driver Peak Current Sourcing
GATE Driver Peak Current Sinking
PWMIN Pin Input Threshold Voltages
CONDITIONS
V
OV/FB
= 1.5V
Rising INTV
CC
Falling INTV
CC
Hysteresis
12V
≤
V
IN
≤
36V
0
≤
I
INTVCC
≤
10mA
V
IN
= 7V, I
INTVCC
= 10mA
V
SENSE
= 0V
V
SENSE
= 7V
C
L
= 3300pF (Note 7)
C
L
= 3300pF (Note 7)
V
GATE
= 0V
V
GATE
= 7V
Rising PWMIN
Falling PWMIN
Hysteresis
C
L
= 3300pF (Note 7)
C
L
= 3300pF (Note 7)
V
PWMOUT
= 0V
V
PWMOUT
= 7V
–1
●
MIN
6.5
1.8
TYP
7
2.3
2.1
0.2
2
–0.1
300
25
15
15
8
0.5
1
1.6
0.8
0.8
100
30
16
0.25
0.50
MAX
7.5
2.5
UNITS
V
V
V
V
mV/V
%
Low Dropout Regulator
∆V
INTVCC
∆V
IN
∆V
LDO(LOAD)
V
DROPOUT
I
INTVCC(SD)
6
500
mV
µA
µA
ns
ns
A
A
V
V
V
kΩ
ns
ns
A
A
GATE/PWMOUT Drivers
t
r(GATE)
t
f(GATE)
I
PK(GATE,RISE)
I
PK(GATE,FALL)
V
PWMIN
R
PWMIN
t
r(PWMOUT)
t
f(PWMOUT)
PWMIN Input Pull-Up Resistance
PWMOUT Driver Output Rise Time
PWMOUT Driver Output Fall Time
I
PK(PWMOUT,RISE)
PWMOUT Driver Peak Current Sourcing
I
PK(PWMOUT,FALL)
PWMOUT Driver Peak Current Sinking
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
The LTC3783E is guaranteed to meet performance specifications
from 0°C to 85°C junction temperature. Specifications over the – 40°C to
85°C operating temperature range are assured by design, characterization
and correlation with statistical process controls.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 43°C/W) for the DFN
T
J
= T
A
+ (P
D
• 38°C/W) for the TSSOP
Note 4:
The dynamic input supply current is higher due to power MOSFET
gate charging (Q
G
• f
OSC
). See Operation section.
Note 5:
The LTC3783 is tested in a feedback loop which servos V
FBN
to
V
FBP
= V
VREF
with the I
TH
pin forced to the midpoint of its voltage range
(0.3V
≤
V
ITH
≤
1.2V; midpoint = 0.75V).
Note 6:
In a synchronized application, the internal slope compensation is
increased by 25%. Synchronizing to a significantly higher ratio will reduce
the effective amount of slope compensation, which could result in sub-
harmonic oscillation for duty cycles greater than 50%
Note 7:
Rise and fall times are measured at 10% and 90% levels.
3783f
4
LTC3783
TYPICAL PERFOR A CE CHARACTERISTICS
V
REF
vs Temperature
1.25
1.235
1.20
V
REF
(V)
V
REF
(V)
V
REF
(V)
1.15
1.10
1.05
1.00
–50
0
50
100
TEMPERATURE (°C)
I
Q
vs Temperature (PWMIN Low)
1.6
1.4
1.2
1.0
I
Q
(mA)
0.8
0.6
0.4
0.2
0
–75
–25
125
75
TEMPERATURE (°C)
25
175
3783 G04
DYNAMIC I
Q
(mA)
I
Q
(mA)
RUN Thresholds vs V
IN
1.6
1.5
1.4
RUN HIGH
RUN THRESHOLDS (V)
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0
10
20
V
IN
(V)
30
40
3783 G07
RUN THRESHOLDS (V)
RUN LOW
1.32
1.30
1.28
1.26
1.24
1.22
–50
RUN LOW
R
T
(kΩ)
U W
3783 G01
T
A
= 25°C unless otherwise specified
V
REF
Load Regulation
1.235
V
REF
Line Regulation
1.233
1.233
1.231
1.231
V
IN
= 12V
1.229
1.229
V
IN
= 2.5V
1.227
1.227
150
1.225
1.225
0
10
20
V
IN
(V)
3783 G02
30
40
0
1
3
2
I
REF
(mA)
4
5
3783 G03
I
Q
vs V
IN
(PWMIN Low)
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
0
0
10
30
20
V
IN
(V)
40
50
3783 G05
Dynamic I
Q
vs Frequency
30
25
20
15
10
5
0
C
L
= 3300pF
I
Q(TOT)
= 1.3mA + Q
G
• f
0
0.5
1
FREQUENCY (MHz)
1.5
3783 G06
RUN Thresholds vs Temperature
1.40
1.38
1.36
1.34
RUN HIGH
R
T
vs Frequency
1000
100
10
1
0
100
TEMPERATURE (°C)
50
150
3783 G08
1
10
100
1000
FREQUENCY (kHz)
10000
3783 G09
3783f
5
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