LT3467 [Linear]
1A Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control; 1A低噪声高电流LED电荷泵，具有独立手电筒/闪光灯电流控制
| 型号： | LT3467 |
| 厂家： | 
Linear |
| 描述： | 1A Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control |
| 文件： | 总12页 (文件大小：105K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3216
1A Lo w No ise Hig h Curre nt
LED Cha rg e Pum p with
Ind e p e nd e nt To rc h/ Fla sh Curre nt Co ntro l
U
FEATURES
DESCRIPTIO
The LTC®3216 is a low noise, high current charge pump
DC/DC converter designed to power high current LEDs.
The part includes an accurate programmable current
source capable of driving loads up to 1A from a 2.9V to
4.4V input. Low external parts count (two flying capaci-
tors, two programming resistors and two bypass capaci-
■
High Efficiency Operation: 1x, 1.5x or 2x Boost
Modes with Automatic Mode Switching
Ultralow Dropout ILED Current Control
Output Current up to 1A
Low Noise Constant Frequency Operation*
Independent Low Current/High Current
Programming and Enable Pins
■
■
■
■
tors at V and CPO) make the LTC3216 ideally suited for
IN
■
■
■
■
■
■
■
■
Wide V Range: 2.9V to 4.4V
small, battery-powered applications.
IN
Open/Shorted LED Protection
LED Disconnect in Shutdown
Low Shutdown Current: 2.5µA
4% LED Current Programming Accuracy
Automatic Soft-Start Limits Inrush Current
No Inductors
Built-in soft-start circuitry prevents excessive inrush cur-
rentduringstart-up.Highswitchingfrequencyenables the
use of small external capacitors. Independent high and
low current settings are programmed by two external
resistors. Shutdown mode and current output levels are
selected via two logic inputs.
Tiny Application Circuit (All Components <1mm
Profile)
An ultralow dropout current source maintains accurate
LED current at very low ILED voltages. Automatic mode
switching optimizes efficiency by monitoring the voltage
across the LED current source and switching modes only
whenILED dropoutis detected. TheLTC3216is availablein
a small 3mm × 4mm 12-Lead DFN package.
■
3mm × 4mm 12-Lead DFN Package
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APPLICATIO S
■
LED Torch/Camera Light Supply for Cell Phones,
PDAs and Digital Cameras
Generic Lighting and/or Flash/Strobe Applications
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 6411531.
■
U
TYPICAL APPLICATIO
C1
C2
Torch Mode Efficiency vs V
IN
2.2µF
2.2µF
100
90
80
70
60
50
40
30
20
10
0
I
= 200mA
LED
+
–
+
–
C1
V
C1 C2
C2
CPO
2.9V TO 4.4V
C
IN
C
4.7µF
IN
CPO
2.2µF
LTC3216
I
LED1
EN2
LED
EN1
EN2
EN1 (TORCH)
EN2 (FLASH)
I
I
I
LED
SET1
SET2
EN1
P
/PIN
LED
0
1
0
1
0
0
1
1
0 (SHUTDOWN)
200mA (TORCH)
600mA
LUMILEDS LXCL-PWF1
V = 3V TYP AT 200mA
20k
1%
6.65k
1%
F
800mA (FLASH)
2.8
3.6
4.0 4.2
3.0 3.2 3.4
3.8
4.4
3216 TA01a
V
IN
(V)
LED1: LUMILEDS LXCL-PWF1 LUXEON FLASH
3216 TA01b
3216fa
1
LTC3216
W W U W
U
W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
TOP VIEW
ORDER PART
NUMBER
V to GND................................................–0.3V to 5.5V
CPO to GND ..............................................–0.3V to 5.5V
IN
+
+
–
C2
C1
1
2
3
4
5
6
12 C1
11 GND
EN2, EN1 ......................................... –0.3V to V + 0.3V
–
IN
LTC3216EDE
CPO
10 C2
13
ICPO, IILED (Note 2) ........................................... 1500mA
I
9
8
7
VIN
EN2
EN1
SET1
CPO Short-Circuit Duration ............................. Indefinite
Operating Temperature Range (Note 3) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
I
LED
DFN PART
MARKING
I
SET2
DE12 PACKAGE
12-LEAD (4mm × 3mm) PLASTIC DFN
3216
EXPOSED PAD IS GND (PIN 13)
MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 43°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V = 3.6V, C = C1 = C2 = 2.2µF, CCPO = 4.7µF
IN
IN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Power Supply
V
Operating Voltage
Operating Current
●
●
2.9
4.4
V
IN
I
VIN
I
= 0mA, 1x Mode
= 0mA, 1.5x
= 0mA, 2x Mode
300
7
9.2
µA
mA
mA
CPO
I
CPO
I
CPO
I
VIN
Shutdown Current
EN2 = EN1 = LOW
2.5
7
µA
LED Current
LED Current Ratio (I /I
)
I
= 200mA to 800mA
3120
3250
120
3380
mA/mA
mV
LED SET1/2
LED
I
Dropout Voltage
Mode Switch Threshold, I = 200mA
LED
LED
Mode Switching Delay
(LED Warmup Time)
EN1 = HIGH, EN2 = LOW
EN1 = LOW or HIGH, EN2 = HIGH
150
2
ms
ms
LED Current On Time
Charge Pump (CPO)
1x Mode Output Voltage
1.5x Mode Output Voltage
2x Mode Output Voltage
1x Mode Output Impedance
1.5x Mode Output Impedance
2x Mode Output Impedance
CLK Frequency
EN to LED Current On
130
µs
I
= 0mA
= 0mA
= 0mA
V
IN
V
V
CPO
I
4.6
5.1
CPO
I
V
CPO
0.25
1.5
Ω
V = 3.4V, V < 4.6V, C1 = C2 = 2.2µF
Ω
IN
CPO
V = 3.2V, V < 5.1V, C1 = C2 = 2.2µF
1.7
Ω
IN
CPO
●
0.6
1.4
0.9
1.2
MHz
EN1, EN2
High Level Input Voltage (V )
●
●
●
●
V
V
IH
Low Level Input Voltage (V )
0.4
1
IL
Input Current (I )
–1
–1
µA
µA
IH
Input Current (I )
1
IL
3216fa
2
LTC3216
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V = 3.6V, C = C1 = C2 = 2.2µF, CCPO = 4.7µF
IN
IN
PARAMETER
, I
CONDITIONS
MIN
TYP
MAX
UNITS
I
SET1 SET2
V
, V
I
= 50µA
●
●
1.195
1.22
1.245
321
V
ISET1 ISET2
SETX
I
, I
µA
ISET1 ISET2
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 3: The LTC3216E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 2: Based on long-term current density limitations. Assumes an
operating duty cycle of ≤ 10% under absolute maximum conditions for
durations less than 10 seconds. Max current for continuous operation is
500mA.
U W
TA = 25°C unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
ILED Dropout Voltage
vs LED Current
ILED Pin Current
vs ILED Pin Voltage
ILED vs RSET
600
500
400
300
200
100
0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1200
1000
800
600
400
200
0
V
IN
= 3.6V
I
= 500mA
LED
400mA
300mA
200mA
100mA
1000
0
200
400
600
800
0
35
0
0.2
0.4
0.6
0.8
1.0
5
10 15 20 25 30
(kΩ)
40
LED CURRENT (mA)
R
SET
I
PIN VOLTAGE (V)
LED
3216 G01
1573 G06
3216 G02
1.5x Mode Charge Pump
Open-Loop Output Resistance
2x Mode Charge Pump
Open-Loop Output Resistance
(2V – VCPO)/ICPO vs Temperature
1x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(1.5V – VCPO)/ICPO vs Temperature
IN
IN
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.31
0.29
0.27
0.25
0.23
0.21
0.19
0.17
0.15
I
= 200mA
CPO
V
IN
= 3.3V
V
IN
= 3.6V
V
= 3.9V
IN
V
= 3V
= 4.2V
= C1 = C2 = 2.2µF
= 4.7µF
V = 3V
IN
IN
V
V
CPO
= 4.8V
CPO
C
C = C1 = C2 = 2.2µF
IN
IN
C
CPO
C
CPO
= 4.7µF
–15
10
TEMPERATURE (°C)
60
–40
85
35
–40
60
85
–40
60
85
–15
10
35
–15
10
35
TEMPERATURE (°C)
TEMPERATURE (°C)
3216 G07
3216 G06
3216 G05
3216fa
3
LTC3216
U W
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
Input Shutdown Current
vs Input Voltage
Oscillator Frequency
vs Supply Voltage
Efficiency vs V
IN
100
90
80
70
60
50
40
30
20
10
0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
930
920
910
900
890
880
870
860
850
840
200mA
T
= 25°C
A
T
= 25°C
A
400mA
T
A
= 85°C
600mA
T = –40°C
A
T
A
= –40°C
T
A
= 85°C
I
= 800mA
LED
LED = LXCL-PWF1 LUMILEDS
2.9 3.1
3.5 3.7 3.9 4.1
4.5
4.0 4.2
4.4
3.3
4.3
2.8
3.0 3.2 3.4
3.6
3.8
2.9 3.1
3.5 3.7 3.9 4.1
INPUT VOLTAGE (V)
4.5
3.3
4.3
V
IN
(V)
SUPPLY VOLTAGE (V)
3216 G04
3216 G11
3216 G03
ISET/ILED Current Ratio vs ILED
Current
3400
3350
3300
3250
3200
3150
3100
1.5x Mode CPO Output Ripple
T
= –40°C
A
T
A
= 25°C
V
CPO
50mV/DIV
A/C COUPLED
T
A
= 85°C
3216 G12
V
IN
= 3.6V
500ns/DIV
I
= 200mA
0
100 200 300 400 500 600 700 800 900
CURRENT(mA)
CPO
I
LED
3216 G15
Charge Pump Mode Switching
and Input Current
2x Mode CPO Output Ripple
V
CPO
1V/DIV
V
CPO
I
VIN
20mV/DIV
A/C COUPLED
500mA/DIV
EN2
5V/DIV
3216 G14
3216 G13
V
IN
= 3V
1ms/DIV
V
IN
= 3.6V
500ns/DIV
I
= 400mA
CPO
3216fa
4
LTC3216
U
U
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PI FU CTIO S
C2+, C1+, C2–, C1– (Pins 1, 2, 10, 12): Charge Pump
Flying Capacitor Pins. A 2.2µF X5R or X7R ceramic
capacitor should be connected from C1+ to C1– and from
C2+ to C2–.
EN1/EN2 (Pins 7, 8): Inputs. The EN1 and EN2 pins are
used to select which current level is being supplied to the
LED, as well as to put the part into shutdown mode. The
truth table for these pins is as follows:
Truth Table
CPO (Pin 3): Output. CPO is the output of the Charge
Pump. This pin may be enabled or disabled using the EN1
and EN2 inputs. A 4.7µF X5R or X7R ceramic capacitor is
required from CPO to GND.
EN1
0
EN2
0
MODE
Shutdown
1
0
Low Current
0
1
High Current
Low + High Current
I
SET1/ISET2 (Pins 4, 6): LED Current Programming Resis-
1
1
tor Pins. The ISET1 and ISET2 pins will servo to 1.22V.
Resistors connected between each of these pins and GND
are used to set the high and low LED current levels.
Connecting a resistor of 2kΩ or less will cause the
LTC3216 to enter overcurrent shutdown mode.
V (Pin 9): Power. Supply voltage for the LTC3216. V
shouldbebypassedwitha2.2µForgreaterlowimpedance
ceramic capacitor to GND.
IN
IN
GND (Pin 11): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
ILED (Pin5):Output.ILED is theLEDcurrentsourceoutput.
The LED is connected between CPO (anode) and ILED
(cathode). The current into the ILED pin is set via the EN1
and EN2 inputs, and the programming resistors con-
nected from ISET2 and ISET1 to GND.
EXPOSED PAD (Pin 13): Control Signal Ground. This pad
must be soldered to a low impedance ground plane for
optimum thermal and electrical performance.
W
BLOCK DIAGRA
+
–
+
–
C1
C1
C2
1
C2
10
2
12
3
CPO
1X MODE: CPO = V
IN
1.5X MODE: CPO = 4.6V
2X MODE: CPO = 5.1V
OSCILLATOR
–
+
V
REF
MODE
CONTROL
DROPOUT
DETECTOR
5
I
LED
V
IN
9
EN2
EN1
8
7
CURRENT
SOURCE
CONTROL
CONTROL
LOGIC
3216 BD
11
6
4
13
GND
I
I
GND
SET2
SET1
3216fa
5
LTC3216
U
OPERATIO
The LTC3216 uses a fractional switched capacitor charge internally,andaredependentonthechargepumpmodeas
pump to power a high current LED with a programmed shown in Table 1.
regulated current. The part starts up into the 1x mode. In
Table 1. Charge Pump Output Regulation Voltages
this mode, V is directly connected to CPO. This mode
IN
Charge Pump Mode
V
CPO
provides maximum efficiency and minimum noise. The
LTC3216 will remain in this mode until the LED current
source begins to dropout. When dropout is detected, the
LTC3216 will switch to 1.5x mode after a soft-start period.
Any subsequent dropout detected will cause the part to
enter 2x mode. The part may be reset to 1x mode by
bringingthepartintoshutdownmodeandthenreenabling
the part.
1.5x
2x
4.6V
5.1V
In shutdown mode all circuitry is turned off and the
LTC3216 draws a very low current from the V supply.
Furthermore,CPOis weaklyconnectedtoV .TheLTC3216
enters shutdown mode when both the EN1 and EN2 pins
are brought low. Since EN1 and EN2 are high impedance
CMOS inputs they should never be allowed to float. To
ensure that their states are defined they must always be
driven with valid logic levels.
IN
IN
A two phase nonoverlapping clock activates the charge
pump switches. In the 2x mode, the flying capacitors are
charged on alternate clock phases from V . While one
IN
capacitor is being charged from V , the other is stacked
IN
Thermal Protection
on top of V and connected to the output. Alternatively, in
IN
the 1.5x mode the flying capacitors are charged in series
during the first clock phase, and stacked in parallel on top
The LTC3216 has built-in overtemperature protection.
Thermal shutdown circuitry will shutdown the ILED output
when the junction temperature exceeds approximately
150°C. It will re-enable the ILED output once the junction
temperature drops back to approximately 135°C. The
LTC3216 will cycle in and out of thermal shutdown indefi-
nitely without latch up or damage until the heat source is
removed.
of V on the second clock phase. This sequence of
IN
charging and discharging the flying capacitors continues
at a free running frequency of 900kHz (typ).
The current delivered to the LED load is controlled by the
internal programmable current source. Three discrete
current settings (Low, High and Low + High) are available
and may be selected via the EN2 and EN1 pins. The values
of these currents may be selected by choosing the appro-
priate programming resistors. Each resistor is connected
between the ISET2 or ISET1 pin and GND. The resistor
values needed to attain the desired current levels can be
determined by equation 1.
Soft-Start
To prevent excessive inrush current during start-up and
mode switching, the LTC3216 employs built-in soft-start
circuitry. Soft-start is achieved by increasing the amount
of current available to the output charge storage capacitor
linearly over a period of approximately 250µs.
RSET1/2 = 3965/ILED
(1)
A resistor value of 2kΩ or less (i.e. a short-circuit) will
cause the LTC3216 to enter overcurrent shutdown mode.
This mode will prevent damage to the part by shutting
down the high power sections of the chip.
Charge Pump Strength
When the LTC3216 operates in either the 1.5x mode or 2x
mode, the charge pump can be modeled as a Thevenin-
equivalent circuit to determine the amount of current
available from the effective input voltage and effective
open-loop output resistance, ROL(Figure 1).
Regulation is achieved by sensing the voltage at the CPO
pin and modulating the charge pump strength based on
the error signal. The CPO regulation voltages are set
3216fa
6
LTC3216
U
OPERATIO
R
OL
to500mAcontinuously, andupto1A forpulsedoperation
with a 10% duty cycle. Pulsed operation may be achieved
by toggling the EN1 and EN2 bits. In either continuous or
pulsed operation, proper board layout is required for
effective heat sinking.
+
1.5V
IN
+
OR
2V
CPO
–
IN
–
Mode Switching
Figure 1. Charge Pump Open-Loop Thevenin-Equivalent Circuit
The LTC3216 will automatically switch from 1x mode to
1.5x mode, and subsequently from 1.5x mode to 2x mode
whenever a dropout condition is detected at the ILED pin.
In the LOW current mode, the part will wait approximately
150ms after dropout is detected before switching to the
next mode. In the HIGH and LOW + HIGH current modes,
the part will wait approximately 2ms before switching to
thenextmode. Thesedelays allowtheLEDtowarmupand
reduce its forward voltage which may remove the dropout
condition.
ROL is dependent on a number of factors including
the oscillator frequency, flying capacitor values and
switch resistances.
From Figure 1, we can see that the output current is
proportional to:
(1.5V – CPO)/ROL or (2V – CPO)/ROL
(2)
IN
IN
in the 1.5x mode or 2x mode respectively.
Current Levels
In order to reset the part back into 1x mode, the LTC3216
must be brought into shutdown (EN1 = EN2 = LOW).
Immediately after the part has been brought to shutdown,
it may be set to the desired output current level via the EN1
and EN2 pins. An internal comparator will not allow the
The LTC3216 may be programmed to have three discrete
current levels. These are the LOW, HIGH and LOW + HIGH
current levels. The LOW and HIGH currents are set by the
resistors connected between ISET1 and ISET2 pins, respec-
tively, to GND. The LOW + HIGH current mode supplies a
currentthatis equaltosumoftheLOWandHIGHcurrents.
mainswitches toconnectV andCPOin1xmodeuntilthe
IN
voltage at the CPO pin has decayed to less than or equal to
the voltage at the V pin.
Due to the low output impedance of this part, care should
betakeninselectingcurrentlevels.This partcansupplyup
IN
3216fa
7
LTC3216
W U U
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APPLICATIO S I FOR ATIO
V , CPO Capacitor Selection
of CCPO controls the amount of output ripple, the value of
CVIN controls the amount of ripple present at the input pin
IN
The style and value of capacitors used with the LTC3216
determineseveralimportantparameters suchas regulator
control loop stability, output ripple, charge pump strength
and minimum start-up time.
(V ). The input current to the LTC3216 will be relatively
IN
constant while the charge pump is on either the input
charging phase or the output charging phase but will drop
to zero during the clock nonoverlap times. Since the
nonoverlaptimeis small(~15ns),thesemissing“notches”
will result in only a small perturbation on the input power
supply line. Note that a higher ESR capacitor such as
tantalum will have higher input noise due to the input
current change times the ESR. Therefore, ceramic capaci-
tors are again recommended for their exceptional ESR
performance. Input noise can be further reduced by pow-
ering the LTC3216 through a very small series inductor as
shown in Figure 2. A 10nH inductor will reject the fast
current notches, thereby presenting a nearly constant
current load to the input power supply. For economy, the
10nH inductor can be fabricated on the PC board with
about 1cm (0.4”) of PC board trace.
To reduce noise and ripple, it is recommended that low
equivalent series resistance (ESR) ceramic capacitors be
used for both CVIN and CCPO. Tantalum and aluminum
capacitors are not recommended because of their high
ESR.
The value of CCPO directly controls the amount of output
ripple for a given load current. Increasing the size of
CCPO will reduce the output ripple at the expense of higher
start-up current. The peak-to-peak output ripple for 1.5x
mode is approximately given by the expression:
VRIPPLE(P-P) = IOUT/(3fOSC • CCPO
)
(3)
Where fOSC is the LTC3216’s oscillator frequency (typi-
cally 900kHz) and CCPO is the output storage capacitor.
10nH
V
IN
Both the style and value of the output capacitor can
significantly affect the stability of the LTC3216. As shown
in the block diagram, the LTC3216 uses a control loop to
adjust the strength of the charge pump to match the
current required at the output. The error signal of this loop
is stored directly on the output charge storage capacitor.
The charge storage capacitor also serves as the dominant
pole for the control loop. To prevent ringing or instability,
it is important for the output capacitor to maintain at least
2.2µF of actual capacitance over all conditions.
0.1µF
2.2µF
LTC3216
GND
3216 F02
Figure 2. 10nH Inductor Used for Input Noise Reduction
(Approximately 1cm of Wire)
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or alumi-
num should never be used for the flying capacitors since
their voltage can reverse upon start-up of the LTC3216.
Ceramic capacitors should always be used for the flying
capacitors.
Likewise, excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3216. The closed
loop output resistance of the LTC3216 is designed to be
76mΩ. For a 100mA load current change, the error signal
will change by about 7.6mV. If the output capacitor has
76mΩ or more of ESR, the closed-loop frequency re-
sponse will cease to roll off in a simple one-pole fashion
and poor load transient response of instability could
result. Multilayer ceramic chip capacitors typically have
exceptional ESR performance. MLCCs combined with a
tightboardlayoutwillyieldverygoodstability.As thevalue
The flying capacitors control the strength of the charge
pump. In order to achieve the rated output current it is
necessary to have at least 2.2µF of actual capacitance for
each of the flying capacitors. Capacitors of different mate-
rials lose their capacitance with higher temperature and
voltageatdifferentrates. Forexample, aceramiccapacitor
made of X7R material will retain most of its capacitance
3216fa
8
LTC3216
W U U
APPLICATIO S I FOR ATIO
U
from –40oC to 85oC whereas a Z5U or Y5V style capacitor
will lose considerable capacitance over that range. Z5U
and Y5V capacitors may also have a very poor voltage
coefficient causing them to lose 60% or more of their
capacitance when the rated voltage is applied. Therefore,
when comparing different capacitors, it is often more
appropriate to compare the amount of achievable capaci-
tance for a given case size rather than comparing the
specified capacitance value. For example, over rated volt-
age and temperature conditions, a 1µF, 10V, Y5V ceramic
capacitor in a 0603 case may not provide any more
capacitance than a 0.22µF, 10V, X7R available in the same
case. The capacitor manufacturer’s data sheet should be
consulted to determine what value of capacitor is needed
to ensure minimum capacitances at all temperatures and
voltages.
Power Efficiency
To calculate the power efficiency (η) of a white LED driver
chip, the LED power should be compared to the input
power. The difference between these two numbers repre-
sents lost power whether it is in the charge pump or the
current sources. Stated mathematically, the power effi-
ciency is given by:
PLED
η ≡
(4)
P
IN
The efficiency of the LTC3216 depends upon the mode in
which it is operating. Recall that the LTC3216 operates as
a pass switch, connecting V to CPO, until dropout is
detectedattheILED pin. This featureprovides theoptimum
efficiency available for a given input voltage and LED
forward voltage. When it is operating as a switch, the
efficiency is approximated by:
IN
Table 2 shows a list of ceramic capacitor manufacturers
and how to contact them.
Table 2. Recommended Capacitor Vendors
P
V
LED •I
V
LED
LED
LED
η ≡
=
≈
(5)
AVX
www.avxcorp.com
www.kemet.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
P
V •I
V
IN
IN
IN IN
Kemet
Murata
Taiyo Yuden
Vishay
TDK
since the input current will be very close to the LED
current.
At moderate to high output power, the quiescent current
of the LTC3216 is negligible and the expression above is
valid.
Layout Considerations and Noise
Once dropout is detected at the ILED pin, the LTC3216
enables the charge pump in 1.5x mode.
Due to its high switching frequency and the transient
currents producedbytheLTC3216, carefulboardlayoutis
necessary. A true ground plane and short connections to
allcapacitors willimproveperformanceandensureproper
regulation under all conditions.
The flying capacitor pins C1+, C2+, C1– and C2– will have
very high edge rate waveforms. The large dv/dt on these
pins can couple energy capacitively to adjacent PCB runs.
Magnetic fields can also be generated if the flying capaci-
tors are not close to the LTC3216 (i.e., the loop area is
large). To decouple capacitive energy transfer, a Faraday
shield may be used. This is a grounded PCB trace between
thesensitivenodeandtheLTC3216pins.Forahighquality
AC ground, it should be returned to a solid ground plane
that extends all the way to the LTC3216.
In 1.5x boost mode, the efficiency is similar to that of a
linear regulator with an effective input voltage of 1.5 times
the actual input voltage. This is because the input current
fora1.5xchargepumpis approximately1.5times theload
current.Inanideal1.5xchargepump,thepowerefficiency
would be given by:
PLED
V
LED •ILED
V
LED
ηIDEAL
≡
=
≈
(6)
P
IN
V •1.5ILED 1.5V
IN IN
3216fa
9
LTC3216
U
TYPICAL APPLICATIO S
Thermal Management
Similarly, in 2x boost mode, the efficiency is similar to that
of a linear regulator with an effective input voltage of 2
times the actual input voltage. In an ideal 2x charge pump,
the power efficiency would be given by:
For higher input voltages and maximum output current,
therecanbesubstantialpowerdissipationintheLTC3216.
Ifthejunctiontemperatureincreases aboveapproximately
150°C, the thermal shutdown circuitry will automatically
deactivate the output. To reduce maximum junction tem-
perature, a good thermal connection to the PC board is
recommended. Connecting the Exposed Pad to a ground
plane and maintaining a solid ground plane under the
device can reduce the thermal resistance of the package
and PC board considerably.
PLED
VLED •ILED
V
LED
ηIDEAL
≡
=
≈
(7)
P
IN
V •2•ILED 2•V
IN IN
3216fa
10
LTC3216
U
PACKAGE DESCRIPTIO
DE Package
12-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1695)
0.65 ±0.05
3.50 ±0.05
2.20 ±0.05 (2 SIDES)
1.70 ±0.05
PACKAGE OUTLINE
0.25 ± 0.05
0.50
BSC
3.30 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.38 ± 0.10
4.00 ±0.10
(2 SIDES)
R = 0.115
TYP
7
12
R = 0.20
TYP
3.00 ±0.10 1.70 ± 0.10
(2 SIDES)
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
PIN 1
NOTCH
(UE12/DE12) DFN 0603
6
0.25 ± 0.05
1
0.75 ±0.05
0.200 REF
0.50
BSC
3.30 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE A VARIATION OF VERSION
(WGED) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3216fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofits circuits as describedhereinwillnotinfringeonexistingpatentrights.
11
LTC3216
U
TYPICAL APPLICATIO
High Power Camera Light and Flash
C1
C2
2.2µF
2.2µF
+
–
+
–
C1
V
C1 C2
C2
I
(TOTAL) =
LED
2.9V TO 4.4V
CPO
IN
200mA/400mA
C
IN
C
CPO
2.2µF
LTC3216
4.7µF
I
LED
EN1 (TORCH)
EN2 (FLASH)
EN1
EN2
I
I
SET2
SET1
R
SET1
= 20k
1%
R
1%
= 10k
3216 TA02
SET2
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1618
Constant Current, 1.4MHz, 1.5A Boost Converter
V : 1.6V to 18V, V
= 36V, I = 1.8mA, I <1µA
OUT(MAX) Q SD
IN
MS Package
LT1961
1.5A (I ), 1.25MHz, High Efficiency Step-Up
V : 3V to 25V, V
= 35V, I = 0.9mA, I 6µA
OUT(MAX) Q SD
SW
IN
DC/DC Converter
MS8E Package
LTC3205
250mA, 1MHz, Multi-Display LED Controller
V : 2.8V to 4.5V, V
= 5.5V, I = 50uA, I <1µA
Q SD
IN
OUT(MAX)
DFN Package
LTC3206
400mA, 800kHz, Multi-Display LED Controller
V : 2.8V to 4.5V, V
= 5.5V, I = 50uA, I <1µA
Q SD
IN
OUT(MAX)
DFN Package
LTC3453
1MHz, 800mA Synchronous Buck-Boost
High Power LED Driver
V
: 2.7V to 5.5V, V
: 2.7V to 4.5V, I = 2.5mA, I <6µA
IN(MAX) Q SD
IN(MIN)
QFN Package
LT3467/LT3467A
LT3479
1.1A (I ), 1.3/2.1MHz, High Efficiency Step-Up
DC/DC Converter with Integrated Soft-Start
V : 2.4V to 16V, V
ThinSOT Package
= 40V, I = 1.2mA, I <1µA
Q SD
SW
IN
OUT(MAX)
3A, Full Featured DC/DC Converter with Soft-Start and
Inrush Current Protection
V : 2.5V to 24V, V
= 40V, I = 5mA, I <1µA
Q SD
IN
OUT(MAX)
DFN, TSSOP Packages
3216fa
LT/LT 0305 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004
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