LTC3454
1
3454f
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
GND (EXPOSED PAD)
LED
EN2 (FLASH)
V
C
EN1 (TORCH)
EN2 EN1
I
LED
0
0
0 (SHUTDOWN)
0
1
150mA
1
0
850mA
1
1
1A
0.1
mF
LED: LUMILEDS LXL-PWF1
L1: SUMIDA CDRH6D28-5RONC
I
SET1
R
ISET1
20.5k
1%
I
SET2
SW1
A
B
D
C
SW2
V
OUT
V
IN
V
IN
1- CELL
Li-Ion
2.7V-4.2V
LTC3454
1MHz
BUCK-BOOST
10
mF
10
mF
L1
5
mH
I
LED
3453 TA01a
R
ISET2
3.65k
1%
LED
V
IN
(V)
2.7
EFFICIENCY (%)
75
80
85
4.3
5.5
5.1
3454 TA01b
70
65
60
3.1
3.9
3.5
4.7
90
95
100
I
LED
= 150mA
I
LED
= 1A
T
A
= 25
°C
EFFICIENCY = (V
OUT
V
LED
)I
LED
/V
IN
I
IN
LED Power Effi ciency vs V
IN
1A Synchronous Buck-Boost
High Current LED Driver
The LTC
®
3454 is a synchronous buck-boost DC/DC
converter optimized for driving a single high power LED
at currents up to 1A from a single cell Li-Ion battery in-
put. The regulator operates in either synchronous buck,
synchronous boost, or buck-boost mode depending on
input voltage and LED forward voltage. P
LED
/P
IN
effi ciency
greater than 90% can be achieved over the entire usable
range of a Li-Ion battery (2.7V to 4.2V).
LED current is programmable to one of four levels, includ-
ing shutdown, with dual external resistors and dual enable
inputs. In shutdown no supply current is drawn.
A high constant operating frequency of 1MHz allows the
use of small external components. The LTC3454 is offered
in a low profi le (0.75mm) thermally enhanced 10-lead
(3mm × 3mm) DFN package.
Cell Phone Camera Flash
Cell Phone Torch Lighting
Digital Cameras
PDAs
Misc Li-Ion LED Drivers
High Effi ciency: >90% Typical in Torch Mode,
>80% in Flash Mode
Wide V
IN
Range: 2.7V to 5.5V
Up to 1A Continuous Output Current
3.5% LED Current Programming Accuracy
Internal Soft-Start
Open/Shorted LED Protection
Constant Frequency 1MHz Operation
Zero Shutdown Current
Overtemperature Protection
Small Thermally Enhanced 10-Lead (3mm × 3mm)
DFN Package
High Effi ciency Torch/Flash LED Driver
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
LTC3454
2
3454f
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
ELECTRICAL CHARACTERISTICS
LTC3454EDD
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply Voltage (V
IN
)
2.7
5.5
V
Input DC Supply Current
(Typicals at V
IN
= 3.6V, R
ISET1
= R
ISET2
= 20.5k)
Normal
Operation
2.7V
V
IN
5.5V (Note 4)
825 1200
µA
Shutdown
2.7V
V
IN
5.5V; V
EN1
= V
EN2
= 0V
0
1
µA
UVLO
V
IN
< UVLO Threshold; V
EN1
= V
EN2
= V
IN
5
10 µA
Undervoltage Lockout Threshold
V
IN
Rising
2.05
2.3
V
V
IN
Falling
1.75
1.90
V
V
EN1
, V
EN2
DC Threshold for Normal Operation (V
IH
)
0.68 1.2
V
V
EN1
, V
EN2
DC Threshold for Shutdown (V
IL
)
0.2 0.66
V
V
EN1
, V
EN2
Input Current
1
1
µA
I
SET1
and I
SET2
Servo Voltage
3.08k R
ISET1
||R
ISET2
20.5k
780 800 812
mV
788 800 812
mV
LED Output Current to Programming Current Ratio
I
LED
/(I
ISET1
+ I
ISET2
), I
LED
= 500mA (Note 5)
3725 3850 3975 mA/mA
3775 3850 3925 mA/mA
LED Pin Voltage
I
LED
=
1A
105
mV
Regulated Maximum V
OUT
LED Pin Open, Programmed I
LED
= 1A
4.95 5.15 5.35
V
PMOS Switch R
ON
Switches A and D (V
OUT
=
3.6V)
170 m
NMOS Switch R
ON
Switches
B
and
C
130 m
Forward Current Limit
Switch A
2.5
3.4
A
Reverse Current Limit
Switch D (V
OUT
=
3.6V)
275
mA
PMOS Switch Leakage
Switches A, D
1
1
µA
NMOS Switch Leakage
Switches B, C
1
1
µA
Oscillator Frequency
0.9
1.0
1.15
MHz
Soft-Start
Time
200
µs
TOP VIEW
DD PACKAGE
10-LEAD (3mm
× 3mm) PLASTIC DFN
10
9
6
7
8
11
4
5
3
2
1
SW1
V
IN
V
C
V
OUT
SW2
EN1
EN2
I
SET1
I
SET2
LED
V
IN
, SW1, SW2, V
OUT
Voltage ...................... 0.3V to 6V
V
C
, EN1, EN2, I
SET1
, I
SET2
Voltage ............................. 0.3V to (V
IN
+ 0.3V) or 6V
LED Peak Current ...................................................1.25A
Storage Temperature Range ................... 65°C to 125°C
Operating Temperature Range (Note 2) ... 40°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
ORDER PART NUMBER
DD PART MARKING
T
JMAX
= 125°C,
JA
= 40°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
LBQX
(Note 1)
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C, V
IN
= 3.6V, R
ISET
= 20.5k unless otherwise noted. (Note 2)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3454 is guaranteed to meet specifi cations from 0°C to
70°C. Specifi cations 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 PD according to the following formula:
T
J
= T
A
+ (PD ·
JA
°C/W).
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5: This parameter is tested using a feedback loop which servos V
C
to 1.8V.
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/
LTC3454
3
3454f
Undervoltage Lockout Threshold
vs Temperature
Enable Thresholds
vs Temperature
Enable Thresholds vs V
IN
I
SET1,2
Servo Voltage
vs Temperature
LED Current Programming Ratio
vs Temperature
V
LED
vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
TEMPERATURE (
°C)
55
1.4
UVLO THRESHOLD (V)
1.5
1.7
1.8
1.9
2.4
2.1
15
25
45
125
3454 G01
1.6
2.2
2.3
2.0
35
5
65
85 105
V
IN
RISING
V
IN
FALLING
TEMPERATURE (
°C)
55
200
ENABLE THRESHOLDS (mV)
300
500
600
700
1200
900
15
25
45
125
3454 G02
400
1000
1100
800
35
5
65
85 105
V
IH
V
IL
V
IN
= 3.6V
V
IN
(V)
2.7
200
ENABLE THRESHOLDS (mV)
300
500
600
700
1200
900
3.5
5.5
3454 G03
400
1000
1100
800
3.1
3.9
4.3
4.7
5.1
V
IH
T
A
= 25
°C
V
IL
TEMPERATURE (
°C)
55
788
V
ISET1,2
(mV)
792
800
804
808
15
25
45
125
3454 G04
796
35
5
65
85 105
812
V
IN
= 3.6V
R
ISET1,2
= 15k
I
SET1,2
Servo Voltage vs V
IN
V
IN
(V)
2.7
V
ISET1,2
(mV)
804
808
812
3.9
4.7
3454 G05
800
796
3.1
3.5
4.3
5.1
5.5
792
788
T
A
= 25
°C
R
ISET1
= R
ISET2
= 15k
I
SET1,2
Servo Voltage vs R
ISET
R
ISET
(k
)
3
V
ISET1,2
(mV)
804
808
812
15
23
3454 G06
800
796
7
11
19
27
31
792
788
V
IN
= 3.6V
T
A
= 25
°C
TEMPERATURE (
°C)
55
RATIO
3850
3900
3950
105
3454 G07
3800
3750
3650
15
25
65
35
125
5
45
85
3700
4050
4000
V
IN
= 3.6V
PROGRAMMED I
LED
= 1A
PROGRAMMED I
LED
= 500mA
PROGRAMMED I
LED
= 150mA
LED Current Programming Ratio
vs V
IN
V
IN
(V)
2.7
RATIO
3850
3900
3950
5.1
3454 G08
3800
3750
3650
3.5
4.3
3.1
5.5
3.9
4.7
3700
4050
4000
PROGRAMMED I
LED
= 500mA
T
A
= 25
°C
TEMPERATURE (
°C)
55
V
LED
(mV)
90
120
150
5
45
125
3454 G09
60
30
0
35 15
25
65
85 105
V
IN
= 3.6V
PROGRAMMED
I
LED
= 100mA
PROGRAMMED
I
LED
= 500mA
PROGRAMMED
I
LED
= 1A
LTC3454
4
3454f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
LED
vs V
IN
Maximum Regulated V
OUT
vs Temperature
LED Power Effi ciency
vs LED Current
Maximum Regulated V
OUT
vs V
IN
V
IN
(V)
2.7
40
V
LED
(mV)
42
46
48
50
60
54
3.5
4.3
4.7
3454 G10
44
56
58
52
3.1
3.9
5.1
5.5
PROGRAMMED I
LED
= 500mA
T
A
= 25
°C
TEMPERATURE (
°C)
55
V
OUT
(V)
5.10
5.15
5.20
105
3454 G11
5.05
5.00
4.90
15
25
65
35
125
5
45
85
4.95
5.40
5.30
5.35
5.25
PROGRAMMED I
LED
= 1A
V
IN
= 3.6V
V
IN
(V)
2.7
V
OUT
(V)
5.10
5.15
5.20
5.1
3454 G12
5.05
5.00
4.90
3.5
4.3
5.5
3.1
3.9
4.7
4.95
5.40
5.30
5.35
5.25
PROGRAMMED I
LED
= 1A
T
A
= 25
°C
Oscillator Frequency
vs Temperature
PROGRAMMED I
LED
(mA)
100
V
OUT
(V)
5.10
5.15
5.20
900
3454 G13
5.05
5.00
4.90
300
500
700
200
1000
400
600
800
4.95
5.40
5.30
5.35
5.25
V
IN
= 3.6V
T
A
= 25
°C
NMOS R
DS(ON)
vs Temperature
TEMPERATURE (
°C)
55
900
FREQUENCY (kHz)
920
960
980
1000
1100
1040
15
25
45
125
3454 G16
940
1060
1080
1020
35
5
65
85 105
V
OUT
= 3V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 5.5V
V
IN
= 4.2V
I
LED
(mA)
100
EFFICIENCY (%)
80
85
90
900
3454 G17
75
70
60
300
500
700
200
1000
400
600
800
65
100
95
V
IN
= 3.6V
T
A
= 25
°C
EFFICIENCY = (V
OUT
V
LED
)I
LED
/V
IN
I
IN
FRONT PAGE APPLICATION
Maximum Regulated V
OUT
vs Programmed LED Current
PMOS R
DS(ON)
vs Temperature
TEMPERATURE (
°C)
55
90
R
DS
(m
)
120
150
180
65
85 105
300
3454 G14
35 15
5
25
45
125
210
240
270
MEASURED AT 500mA
V
IN
= 2.7V
V
IN
= 5.5V
V
IN
= 3.6V
V
IN
= 4.2V
TEMPERATURE (
°C)
55
40
R
DS
(m
)
80
60
100
120
65
85 105
200
3454 G15
35 15
5
25
45
125
140
160
180
MEASURED AT 500mA
V
IN
= 2.7V
V
IN
= 5.5V
V
IN
= 3.6V
V
IN
= 4.2V
LTC3454
5
3454f
PI FU CTIO S
U
U
U
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
EN1 (Pin 1): Enable Input Pin for I
SET1
Current.
EN2 (Pin 2): Enable Input Pin for I
SET2
Current.
I
SET1
(Pin 3): LED Current Programming Pin. A resistor
to ground programs the current through the LED to I
LED
= 3850(0.8V/R
ISET1
). This amount of current adds to any
amount set by EN2/I
SET2
if used.
I
SET2
(Pin 4): LED Current Programming Pin. A resistor
to ground programs the current through the LED to I
LED
= 3850(0.8V/R
ISET2
). This amount of current adds to any
amount set by EN1/I
SET1
if used.
LED (Pin 5): Low Dropout Output for LED Current Biasing.
Connect the LED between V
OUT
and the LED pin.
SW2 (Pin 6): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7µH/5µH.
V
OUT
(Pin 7): Buck-Boost Output Rail. Bypass to GND with
a ceramic capacitor. Recommended value is 10µF.
V
C
(Pin 8): Compensation Point for the Internal Error
Amplifi er Output. Connect a ceramic capacitor from V
C
to GND. Recommended value is 0.1µF.
V
IN
(Pin 9): Voltage Input Supply Pin (2.7V V
IN
5.5V).
Bypass to GND with a ceramic capacitor. Recommended
value is 10µF.
SW1 (Pin 10): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7µH/5µH.
Exposed Pad (Pin 11): Ground Pin. Solder to PCB ground
for electrical contact and optimal thermal performance.
Output Voltage Ripple
Back Page Application
20mV/DIV
500ns/DIV
V
IN
= 3.6V
I
LED
= 500mA
3454 G19
Start-Up Transient
Back Page Application
0V, 0A
CH1, V
OUT
1V/DIV
CH2, I
LED
500mA
FINAL VALUE
CH3, V
EN1
1V/DIV
0V
5ms/DIV
V
IN
= 3.6V
I
LED
= 500mA
3454 G19
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