LTC3210EUD-3 [Linear Systems]
MAIN/CAM LED Controller in 3mm x 3mm QFN;
| 型号： | LTC3210EUD-3 |
| 厂家： | 
Linear Systems |
| 描述： | MAIN/CAM LED Controller in 3mm x 3mm QFN |
| 文件： | 总16页 (文件大小：225K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3210
MAIN/CAM LED Controller
in 3mm × 3mm QFN
Features
Description
n Low Noise Charge Pump Provides High Efficiency
TheLTC®3210isalownoisechargepumpDC/DCconverter
designed to drive four MAIN LEDs and one high current
CAM LED for camera lighting. The LTC3210 requires only
four small ceramic capacitors and two current set resis-
tors to form a complete LED power supply and current
controller.
with Automatic Mode Switching
n Multimode Operation: 1x, 1.5x, 2x
n Individual Full-Scale Current Set Resistors
n Up to 500mA Total Output Current
n Single Wire EN/Brightness Control for MAIN and
CAM LEDs (8 Brightness Steps)
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up and mode changes. High switching
frequency enables the use of small external capacitors.
Independent MAIN and CAM full-scale current settings
are programmed by two external resistors. Shutdown
mode and current output levels are selected via two logic
inputs.
n 64:1 Brightness Control Range for MAIN Display
n Four 25mA Low Dropout MAIN LED Outputs
n One 400mA Low Dropout CAM LED Output
n Low Noise Constant Frequency Operation*
n Low Shutdown Current: 3µA
n Internal Soft-Start Limits Inrush Current During
Startup and Mode Switching
n Open/Short LED Protection
n No Inductors
n 3mm × 3mm 16-Lead Plastic QFN Package
The full-scale current through the LEDs is programmed
via external resistors. ENM and ENC are toggled to adjust
the LED currents via internal counters and DACs. The
part is shut down when both ENM and ENC are low for
150µs (typ).
applications
n Multi-LED Light Supply for Cellphones/DSCs/PDAs
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 6411531.
The charge pump optimizes efficiency based on the volt-
age across the LED current sources. The part powers up
in 1x mode and will automatically switch to boost mode
whenever any enabled LED current source begins to en-
ter dropout. The LTC3210 is available in a 3mm × 3mm
16-lead QFN package.
typical application
4-LED MAIN Display
Efficiency vs VBAT Voltage
C2
C3
2.2µF
2.2µF
100
90
C1P C1M
V
BAT
C2P
C2M
80
70
60
50
40
30
20
10
0
MAIN
CAM
CPO
V
BAT
C1
2.2µF
C4
2.2µF
LTC3210
MLED1
MLED2
MLED3
MLED4
CLED
ENM
ENC
ENM
ENC
4 LEDs AT 9mA/LED
(TYP V AT 9mA = 3V, NICHIA NSCW100)
3210 TA01
F
T
= 25°C
A
RM
RC
GND
3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4
(V)
30.1k
1%
24.3k
1%
V
BAT
3210 TA01b
3210fb
ꢀ
LTC3210
pin conFiguration
absolute maximum ratings
(Note 1)
TOP VIEW
V
, CPO to GND........................................–0.3V to 6V
BAT
ENM, ENC ...................................–0.3V to (V
+ 0.3V)
BAT
16 15 14 13
I
I
I
(Note 2)....................................................... 600mA
CPO
MLED1-4
CLED
C1P
CPO
1
2
3
4
12 GND
11 CLED
.................................................................30mA
(Note 2)...................................................... 450mA
17
ENM
ENC
RC
10
9
CPO Short-Circuit Duration.............................. Indefinite
Operating Temperature Range (Note 3) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
MLED1
5
6
7
8
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
= 125°C, θ = 68°C/W
T
JMAX
JA
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
orDer inFormation
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
16-Lead (3mm × 3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
LTC3210EUD#PBF
LTC3210EUD#TRPBF
LBXH
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
The l denotes the specifications which apply over the full operating
electrical characteristics
temperature range, otherwise specifications are at TA = 25°C.VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, RM = 30.1k, RC = 24.3k,
ENM = high, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
V
Operating Voltage
Operating Current
2.9
4.5
V
BAT
I
I
I
I
= 0, 1x Mode, MLED LSB Setting
= 0, 1.5x Mode
= 0, 2x Mode
0.375
2.5
4.5
mA
mA
mA
VBAT
CPO
CPO
CPO
l
l
V
Shutdown Current
ENM = ENC = LOW
3
6
µA
BAT
MLED1, MLED2, MLED3, MLED4 Current
LED Current Ratio (I /I
)
I
= Full Scale
463
515
100
1
567
A/A
mV
%
MLED RM
MLED
LED Dropout Voltage
LED Current Matching
Mode Switch Threshold, I
= Full Scale
MLED
Any Two Outputs, I
= Full Scale
MLED
MLED Current, 3-Bit Exponential DAC
1 ENM Strobe (FS)
2 ENM Strobes
3 ENM Strobes
4 ENM Strobes
5 ENM Strobes
6 ENM Strobes
20
10
mA
mA
mA
mA
mA
mA
mA
5
2.5
1.25
0.625
0.312
7 ENM Strobes (FS/64)
3210fb
ꢁ
LTC3210
electrical characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, RM = 30.1k, RC = 24.3k,
ENM = high, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Unused MLED Detection
Test Current
l
l
MLED Tied to CPO
4
16
µA
V
Threshold Voltage
CLED Current
V
– V
0.5
1.5
CPO
MLED
l
LED Current Ratio (I
/I
)
I
= Full Scale
6750
7500
500
8250
A/A
mV
CLED RC
CLED
LED Dropout Voltage
Mode Switch Threshold, I
= Full Scale
CLED
CLED Current, 3-Bit Linear DAC
1 ENC Strobe (FS)
7 ENC Strobes (FS/7)
380
54
mA
mA
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
CLOCK Frequency
I
I
I
= 0mA
= 0mA
= 0mA
V
V
V
CPO
CPO
CPO
BAT
4.55
5.05
0.5
V
Ω
V
V
= 3.4V, V
= 3.2V, V
= 4.6V (Note 4)
= 5.1V (Note 4)
3.15
3.95
0.8
Ω
BAT
BAT
CPO
CPO
Ω
MHz
ms
Mode Switching Delay
CPO Short Circuit Detection
Threshold Voltage
0.4
l
l
0.4
10
1.3
30
V
Test Current
CPO = 0V, ENM = ENC = Low
mA
ENC, ENM
l
l
l
l
V
0.4
V
V
IL
V
1.4
10
–1
IH
I
I
ENM = ENC = 3.6V
ENM = ENC = 0V
15
20
1
µA
µA
IH
IL
ENC, ENM Timing
l
l
t
t
t
Minimum Pulse Width
60
50
ns
µs
PW
SD
EN
Low Time to Shutdown (ENC and ENM = Low)
150
150
250
250
Current Source Enable Time
(ENC or ENM = High) (Note 5)
l
50
µs
RM, RC
, V
l
l
V
1.16
1.20
1.24
70
V
RM RC
I
, I
RM RC
µA
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 3: The LTC3210E is guaranteed to meet performance specifications
from 0°C to 85°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. Maximum current for continuous
operation is 300mA.
Note 4: 1.5x mode output impedance is defined as (1.5V – V )/I
.
BAT
CPO OUT
2x mode output impedance is defined as (2V – V )/I
.
BAT
CPO OUT
Note 5: If the part has been shut down then the initial enable time is about
100µs longer due to the bandgap enable time.
3210fb
ꢂ
LTC3210
typical perFormance characteristics
TA = 25°C unless otherwise stated.
1.5x CPO Ripple
Dropout Time from Shutdown
Dropout Time When Enabled
V
CPO
C
= 3.6V
= 200mA
= 2.2µF
BAT
I
2X
2X
CPO
1V/DIV
CPO
1V/DIV
CPO
1.5X
1.5X
1X
1X
V
CPO
EN
2V/DIV
ENC
2V/DIV
50mV/DIV
AC-COUPLED
MODE
RESET
MODE
RESET
ENM = HIGH
250µs/DIV
3210 G01
3210 G02
3210 G03
500µs/DIV
500ns/DIV
1.5x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(1.5VBAT – VCPO)/ICPO
1x Mode Switch Resistance
vs Temperature
2x CPO Ripple
0.70
0.65
3.8
3.6
I
= 200mA
CPO
V
= 3.6V
= 200mA
= 2.2µF
V
V
= 3V
= 4.2V
BAT
BAT
CPO
I
CPO
CPO
C
C2 = C3 = C4 = 2.2µF
3.4
3.2
3.0
2.8
2.6
2.4
V
0.60
0.55
CPO
20mV/DIV
V
= 3.3V
BAT
AC-COUPLED
V
= 3.6V
BAT
0.50
0.45
0.40
V
= 3.9V
10
BAT
3210 G04
500ns/DIV
–40
–15
35
60
85
–15
10
35
85
–40
60
TEMPERATURE (°C)
TEMPERATURE (°C)
3210 G05
3210 G06
2x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(2VBAT – VCPO)/ICPO
2x Mode CPO Voltage
vs Load Current
1.5x Mode CPO Voltage
vs Load Current
4.8
4.6
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.6
4.4
C2 = C3 = C4 = 2.2µF
C2 = C3 = C4 = 2.2µF
V
V
= 3V
BAT
CPO
= 4.8V
V
= 3.3V
V
C2 = C3 = C4 = 2.2µF
BAT
V
BAT
= 3.6V
= 3.4V
BAT
BAT
V
= 3.5V
4.2
4.0
3.8
3.6
3.4
3.2
4.4
4.2
V
= 3.5V
V
= 3.6V
BAT
BAT
V
= 3.4V
BAT
V
= 3.3V
BAT
4.0
3.8
3.6
V
= 3.2V
= 3.1V
BAT
V
= 3.2V
BAT
V
= 3.1V
V
BAT
BAT
V
= 3V
200
V
BAT
= 3V
400
BAT
0
100
300
400
500
–15
10
35
85
0
100
300
LOAD CURRENT (mA)
–40
60
200
500
LOAD CURRENT (mA)
TEMPERATURE (°C)
3210 G07
3210 G09
3210 G08
3210fb
ꢃ
LTC3210
typical perFormance characteristics
TA = 25°C unless otherwise stated.
CLED Pin Dropout Voltage
vs CLED Pin Current
MLED Pin Dropout Voltage
vs MLED Pin Current
Oscillator Frequency
vs VBAT Voltage
500
400
300
200
100
0
850
840
830
820
810
800
790
780
770
100
90
80
70
60
50
40
30
20
10
0
V
= 3.6V
BAT
V
= 3.6V
BAT
T
= 25°C
A
T
= 85°C
A
T
= –40°C
A
760
50 100 150 200 250 300 350 400
0
2
4
6
8
10 12 14 16 18 20
2.7
3.0
3.3
V
3.6
VOLTAGE (V)
4.5
3.9
4.2
CLED PIN CURRENT (mA)
MLED PIN CURRENT (mA)
BAT
3210 G10
3210 G11
3210 G12
V
BAT Shutdown Current
1x Mode No Load VBAT Current
vs VBAT Voltage
1.5x Mode Supply Current vs ICPO
(IVBAT – 1.5ICPO
vs VBAT Voltage
)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
20
15
10
5
800
780
760
740
720
700
680
660
640
620
600
V
= 3.6V
BAT
RM = 33.2k
RC = 24.3k
T
= 25°C
A
T
A
= –40°C
A
T
= 85°C
0
3.9
3.6
VOLTAGE (V)
4.5
2.7
3.0
3.3
V
4.2
0
100
200
300
400
500
2.7
3.0
3.6
3.9
4.2
4.5
3.3
V
VOLTAGE (V)
LOAD CURRENT (mA)
BAT
BAT
3210 G13
3210 G14
3210 G15
2x Mode Supply Current vs ICPO
CLED Pin Current
vs CLED Pin Voltage
(IVBAT – 2ICPO
)
20
400
V
= 3.6V
V
= 3.6V
BAT
BAT
360
320
280
240
200
160
120
80
15
10
5
40
0
0
0
100
200
300
400
500
0
0.2
0.4
0.6
0.8
1
LOAD CURRENT (mA)
CLED PIN VOLTAGE (V)
3210 G16
3210 G17
3210fb
ꢄ
LTC3210
typical perFormance characteristics
TA = 25°C unless otherwise stated.
MLED Pin Current
vs MLED Pin Voltage
CLED Current
vs ENC Strobe Pulses
400
22
20
18
16
14
12
10
8
V
= 3.6V
BAT
V
= 3.6V
BAT
RC = 24.3k
350
300
250
200
150
100
50
6
4
2
0
0
0.00
7
6
4
3
2
1
0
5
0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
0.02
NUMBER OF ENC STROBE PULSES
MLED PIN VOLTAGE (V)
3210 G18
3210 G19
MLED Current
vs ENM Strobe Pulses
Efficiency vs VBAT Voltage
90
80
70
60
50
40
30
20
10
0
20
18
16
14
12
10
8
V
= 3.6V
BAT
RM = 33.2k
6
4
300mA LED CURRENT
(TYP V AT 300mA = 3.1V, AOT-2015HPW
F
2
T
= 25°C
A
0
2.9 3.05 3.2 3.35 3.5 3.65
4.4
3.8 3.95 4.1 4.25
0
6
5
4
3
2
1
7
V
(V)
NUMBER OF ENM STROBE PULSES
BAT
3210 G21
3210 G20
3210fb
ꢅ
LTC3210
pin Functions
C1P, C2P, C1M, C2M (Pins 1, 16, 14, 13): Charge Pump
Flying Capacitor Pins. A 2.2µF X7R or X5R ceramic ca-
pacitor should be connected from C1P to C1M and C2P
to C2M.
is set via the ENM input, and the programming resistor
connected between RM and GND. Each of the four LED
outputs can be disabled by connecting the output directly
to CPO. A 10µA current will flow through each directly
connected LED output.
CPO (Pin 2): Output of the Charge Pump Used to Power
All LEDs. This pin is enabled or disabled using the ENM
and ENC inputs. A 2.2µF X5R or X7R ceramic capacitor
should be connected to ground.
RM, RC (Pins 8, 9): LED Current Programming Resistor
Pins. The RM and RC pins will servo to 1.2V. Resistors
connected between each of these pins and GND are used
to set the CLED and MLED current levels. Connecting
a resistor 12k or less will cause the LTC3210 to enter
overcurrent shutdown.
ENM, ENC (Pins 3, 10): Inputs. The ENM and ENC pins
are used to program the LED output currents. Each input
is strobed up to 7 times to decrement the internal 3-bit
DACs from full-scale to 1LSB. The counter will stop at
1 LSB if the strobing continues. The pin must be held
high after the final desired positive strobe edge. The data
is transferred after a 150µs (typ) delay. Holding the ENM
or ENC pin low will set the LED current to 0 and will reset
the counter after 150µs (typ). If both inputs are held low
for longer than 150µs (typ) the part will go into shutdown.
The charge pump mode is reset to 1x whenever ENC goes
low or when the part is in shutdown mode.
CLED (Pin 11): Output. CLED is the CAM current source
output. The LED is connected between CPO (anode) and
CLED (cathode). The current to the LED output is set via
the ENC input, and the programming resistor connected
between RC and GND.
GND (Pin 12): Ground. This pin should be connected to
a low impedance ground plane.
V
(Pin15):Supplyvoltage.Thispinshouldbebypassed
BAT
with a 2.2µF, or greater low ESR ceramic capacitor.
MLED1, MLED2, MLED3, MLED4 (Pins 4, 5, 6, 7):
Outputs. MLED1 to MLED4 are the MAIN current source
outputs. The LEDs are connected between CPO (anodes)
and MLED1-4 (cathodes). The current to each LED output
Exposed Pad (Pin 17): This pad should be connected
directly to a low impedance ground plane for optimal
thermal and electrical performance.
3210fb
ꢆ
LTC3210
block Diagram
C1P
1
C1M
14
C2P
16
C2M
13
800kHz
OSCILLATOR
12 GND
15
V
2
CPO
BAT
CHARGE PUMP
–
+
ENABLE CP
+
–
1.215V
4
5
6
7
MLED1
MLED2
MLED3
MLED4
TIMER
ENABLE MAIN
500Ω
8
3
RM
3-BIT
DOWN
COUNTER
3-BIT
EXPONENTIAL
DAC
MLED
CURRENT
SOURCES
4
ENM
250k
+
–
1.215V
TIMER
TIMER
SHUTDOWN
ENABLE CAM
3-BIT
500Ω
RC
9
3-BIT
DOWN
COUNTER
CLED
CURRENT
SOURCE
10
11 CLED
LINEAR
DAC
ENC
250k
3210 BD
3210fb
ꢇ
LTC3210
operation
Power Management
current is achieved ENM is stopped high. The output cur-
rent then changes to the programmed value after 150µs
(typ). The counter will stop when the LSB is reached. The
output current is set to 0 when ENM is toggled low after
the output has been enabled. If strobing is started within
150µs (typ), after ENM has been set low, the counter will
continue to count down. After 150µs (typ) the counter
is reset.
The LTC3210 uses a switched capacitor charge pump to
boost CPO to as much as 2 times the input voltage up to
5.1V. The part starts up in 1x mode. In this mode, V is
BAT
connected directly to CPO. This mode provides maximum
efficiencyandminimumnoise. TheLTC3210willremainin
1x mode until an LED current source drops out. Dropout
occurs when a current source voltage becomes too low
fortheprogrammedcurrenttobesupplied. Whendropout
is detected, the LTC3210 will switch into 1.5x mode. The
CPO voltage will then start to increase and will attempt
The CLED current is delivered by a programmable current
source. Eight linear current settings (0mA to 380mA, RC
= 24.3k) are available by strobing the ENC pin. Each posi-
tive strobe edge decrements a 3-bit down counter which
controls a 3-bit linear DAC. When the desired current is
reached, ENC is stopped high. The output current then
changes to the programmed value after 150µs (typ). The
counter will stop when the LSB is reached. The output
currentissetto0whenENCistoggledlowaftertheoutput
has been enabled. If strobing is started within 150µs(typ)
after ENC has been set low, the counter will continue to
count down. After 150µs (typ) the counter is reset.
to reach 1.5x V
up to 4.6V. Any subsequent dropout
BAT
will cause the part to enter the 2x mode. The CPO voltage
will attempt to reach 2x V up to 5.1V. The part will be
BAT
reset to 1x mode whenever the part is shut down or when
ENC goes low.
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 to minimize
inputcurrentrippleandCPOvoltageripple.In1.5xmodethe
flyingcapacitorsarechargedinseriesduringthefirstclock
phase and stacked in parallel on V
BAT
The full-scale output current is calculated as follows:
during the second
BAT
MLED full-scale output current
= (1.215V/(RM + 500)) • 515
phase.Thissequenceofcharginganddischargingtheflying
capacitors continues at a constant frequency of 800kHz.
CLED full-scale output current
= (1.215V/(RC + 500)) • 7500
When both ENM and ENC are held low for 150µs (typ)
the part will go into shutdown. See Figure 1 for timing
information.
LED Current Control
TheMLEDcurrentsaredeliveredbythefourprogrammable
current sources. Eight current settings (0mA to 20mA,
RM = 30.1k) are available by strobing the ENM pin. Each
positive strobe edge decrements a 3-bit down counter
which controls an exponential DAC. When the desired
ENC resets the mode to 1x on a falling edge.
t
≥
t
t
SD 150µs (TYP)
PW 60ns
EN 150µs (TYP)
ENM
OR ENC
PROGRAMMED
CURRENT
LED
CURRENT
ENM = ENC = LOW
SHUTDOWN
3210 F01
Figure 1. Current Programming and Shutdown Timing Diagram
3210fb
ꢈ
LTC3210
operation
Soft-Start
the example of driving white LEDs from a 3.1V supply. If
the LED forward voltage is 3.8V and the current sources
require 100mV, the advantage voltage for 1.5x mode is
3.1V • 1.5 – 3.8V – 0.1V or 750mV. Notice that if the input
voltage is raised to 3.2V, the advantage voltage jumps to
900mV— a 20% improvement in available strength.
Initially, when the part is in shutdown, a weak switch
connects V to CPO. This allows V to slowly charge
BAT
BAT
the CPO output capacitor to prevent large charging
currents.
The LTC3210 also employs a soft-start feature on its
charge pump to prevent excessive inrush current and
supplydroopwhenswitchingintothestep-upmodes. The
current available to the CPO pin is increased linearly over
a typical period of 150µs. Soft-start occurs at the start of
both 1.5x and 2x mode changes.
FromFigure2,for1.5xmodetheavailablecurrentisgivenby:
(1.5VBAT – VCPO
ROL
)
IOUT
=
For 2x mode, the available current is given by:
(2VBAT – VCPO
ROL
)
IOUT
=
Charge Pump Strength and Regulation
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
internally, and are dependent on the charge pump modes
as shown in Table 1.
Notice that the advantage voltage in this case is 3.1V • 2
– 3.8V – 0.1V = 2.3V. R is higher in 2x mode but a sig-
OL
nificant overall increase in available current is achieved.
Typical values of R as a function of temperature are
OL
shown in Figure 3 and Figure 4.
Table 1. Charge Pump Output Regulation Voltages
CHARGE PUMP MODE
REGULATED V
4.55V
CPO
Shutdown Current
1.5x
2x
In shutdown mode all the circuitry is turned off and the
5.05V
LTC3210 draws a very low current from the V supply.
BAT
Furthermore, CPO is weakly connected to V . The
BAT
WhentheLTC3210operatesineither1.5xmodeor2xmode,
thechargepumpcanbemodeledasaThevenin-equivalent
circuit to determine the amount of current available from
the effective input voltage and effective open-loop output
LTC3210 enters shutdown mode when both the ENM
and ENC pins are brought low for 150µs (typ). ENM and
ENC have 250k internal pull down resistors to define
the shutdown state when the drivers are in a high imped-
ance state.
resistance, R (Figure 2).
OL
R
is dependent on a number of factors including the
OL
3.8
V
V
= 3V
BAT
CPO
switchingterm,1/(2f •C ),internalswitchresistances
OSC FLY
= 4.2V
3.6
andthenonoverlapperiodoftheswitchingcircuit.However,
C2 = C3 = C4 = 2.2µF
for a given R , the amount of current available will be
3.4
3.2
3.0
2.8
2.6
2.4
OL
directly proportional to the advantage voltage of 1.5V
BAT
–CPOfor1.5xmodeand2V –CPOfor2xmode.Consider
BAT
R
OL
+
+
CPO
1.5V
OR 2V
BAT
BAT
–
–15
10
35
85
–40
60
–
TEMPERATURE (˚C)
3210 F03
Figure 2. Charge Pump Thevenin-Equivalent Circuit
Figure 3. Typical 1.5x ROL vs Temperature
3210fb
ꢀ0
LTC3210
operation
4.6
sources and charge pump until the die has cooled by
about 15°C. This thermal cycling will continue until the
fault has been corrected.
V
V
= 3V
BAT
CPO
= 4.8V
4.4
C2 = C3 = C4 = 2.2µF
4.2
4.0
3.8
3.6
3.4
3.2
Mode Switching
The LTC3210 will automatically switch from 1x mode
to 1.5x mode and subsequently to 2x mode whenever
a dropout condition is detected at an LED pin. Dropout
occurs when a current source voltage becomes too low
for the programmed current to be supplied. The time
from drop-out detection to mode switching is typically
0.4ms.
–15
10
35
85
–40
60
TEMPERATURE (˚C)
3210 F04
Figure 4. Typical 2x ROL vs Temperature
The part is reset back to 1x mode when the part is shut
down (ENM = ENC = Low) or on the falling edge of ENC.
An internal comparator will not allow the main switches to
Thermal Protection
The LTC3210 has built-in overtemperature protection.
At internal die temperatures of around 150°C thermal
shutdown will occur. This will disable all of the current
connect V and CPO in 1x mode until the voltage at the
CPO pin has decayed to less than or equal to the voltage
BAT
at the V pin.
BAT
applications inFormation
V , CPO Capacitor Selection
BAT
The output ripple in 2x mode is very small due to the fact
that load current is supplied on both cycles of the clock.
ThestyleandvalueofthecapacitorsusedwiththeLTC3210
determineseveralimportantparameterssuchasregulator
controlloopstability,outputripple,chargepumpstrength
and minimum start-up time.
Bothstyleandvalueoftheoutputcapacitorcansignificantly
affect the stability of the LTC3210. As shown in the Block
Diagram, the LTC3210 uses a control loop to adjust the
strength of the charge pump to match the required output
current.Theerrorsignaloftheloopisstoreddirectlyonthe
output capacitor. The output capacitor also serves as the
dominant pole for the control loop. To prevent ringing or
instability,itisimportantfortheoutputcapacitortomaintain
at least 1.3µF of capacitance over all conditions.
To reduce noise and ripple, it is recommended that low
equivalentseriesresistance(ESR)ceramiccapacitorsare
used for both CV
and C . Tantalum and aluminum
BAT
CPO
capacitors are not recommended due to high ESR.
The value of C directly controls the amount of output
CPO
ripple for a given load current. Increasing the size of C
CPO
In addition, excessive output capacitor ESR >100mΩ will
tend to degrade the loop stability. Multilayer ceramic chip
capacitorstypicallyhaveexceptionalESRperformanceand
when combined with a tight board layout will result in very
will reduce output ripple at the expense of higher start-up
current. The peak-to-peak output ripple of the 1.5x mode
is approximately given by the expression:
IOUT
(3f0SC •CCPO
good stability. As the value of C
controls the amount of
controls the amount of
CPO
VRIPPLE(P−P)
=
(3)
)
output ripple, the value of CV
BAT
ripple present at the input pin(V ). The LTC3210’s input
currentwillberelativelyconstantwhilethechargepumpis
either in the input charging phase or the output charging
BAT
Wheref istheLTC3210oscillatorfrequencyortypically
OSC
800kHz and C
is the output storage capacitor.
CPO
3210fb
ꢀꢀ
LTC3210
applications inFormation
phase but will drop to zero during the clock nonoverlap
times. Since the nonoverlap time is small (~35ns), these
missing “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 higher ESR. Therefore, ceramic capacitors are
recommended for low ESR. Input noise can be further
reduced by powering the LTC3210 through a very small
series inductor as shown in Figure 5. 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.
example, over rated voltage 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.
Table 2 shows a list of ceramic capacitor manufacturers
and how to contact them:
Table 2. Recommended Capacitor Vendors
AVX
www.avxcorp.com
www.kemet.com
www.murata.com
www.t-yuden.com
www.vishay.com
Kemet
Murata
Taiyo Yuden
Vishay
V
BAT
LTC3210
GND
3210 F05
Layout Considerations and Noise
Figure 5. 10nH Inductor Used for Input Noise
Reduction (Approximately 1cm of Board Trace)
Due to the high switching frequency and the transient
currents produced by the LTC3210, careful board layout
is necessary. A true ground plane and short connections
to all capacitors will improve performance and ensure
proper regulation under all conditions.
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or
aluminum should never be used for the flying capaci-
tors since their voltage can reverse upon start-up of the
LTC3210. Ceramic capacitors should always be used for
the flying capacitors.
The flying capacitor pins C1P, C2P, C1M and C2M will have
high edge rate waveforms. The large dv/dt on these pins
cancoupleenergycapacitivelytoadjacentPCBruns.Mag-
netic fields can also be generated if the flying capacitors
are not close to the LTC3210 (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 the
sensitive node and the LTC3210 pins. For a high quality
AC ground, it should be returned to a solid ground plane
that extends all the way to the LTC3210.
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 1.6µF of capacitance for each
of the flying capacitors. Capacitors of different materials
losetheircapacitancewithhighertemperatureandvoltage
at different rates. For example, a ceramic capacitor made
of X7R material will retain most of its capacitance from
–40°C to 85°C whereas a Z5U or Y5V style capacitor will
lose considerable capacitance over that range. Capacitors
mayalsohaveaverypoorvoltagecoefficientcausingthem
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 capacitance for a given case size
ratherthancomparingthespecifiedcapacitancevalue.For
The following guidelines should be followed when design-
ing a PCB layout for the LTC3210:
• The exposed pad should be soldered to a large cop-
per plane that is connected to a solid, low impedance
ground plane using plated through-hole vias for proper
heat sinking and noise protection.
• Input and output capacitors must be placed close to
the part.
3210fb
ꢀꢁ
LTC3210
applications inFormation
• The flying capacitors must be placed close to the part.
The traces from the pins to the capacitor pad should
be as wide as possible.
At moderate to high output power, the quiescent current
of the LTC3210 is negligible and the expression above is
valid.
• V , CPO traces must be wide to minimize inductance
Once dropout is detected at any LED pin, the LTC3210
enables the charge pump in 1.5x mode.
BAT
and handle high currents.
• LED pads must be large and connected to other layers
of metal to ensure proper heat sinking.
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
for a 1.5x charge pump is approximately 1.5 times the
load current. In an ideal 1.5x charge pump, the power
efficiency would be given by:
• RM and RC pins are sensitive to noise and capacitance.
The resistors should be placed near the part with mini-
mum line width.
Power Efficiency
PLED
PIN
(VLED •ILED
(VBAT •(1.5)•ILED
)
VLED
(1.5•VBAT )
η
IDEAL
=
=
=
)
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
represents lost power whether it is in the charge pump
or the current sources. Stated mathematically, the power
efficiency is given by:
ꢀ
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:
PLED
(VLED •ILED
)
VLED
(2•VBAT )
PLED
PIN
η
IDEAL
=
=
=
η =
PIN (VBAT •(2)•ILED
)
ꢀ
Thermal Management
The efficiency of the LTC3210 depends upon the mode in
which it is operating. Recall that the LTC3210 operates
For higher input voltages and maximum output current,
therecanbesubstantialpowerdissipationintheLTC3210.
Ifthejunctiontemperatureincreasesaboveapproximately
150°C the thermal shut down circuitry will automatically
deactivate the output current sources and charge pump.
Toreducemaximumjunctiontemperature,agoodthermal
connection to the PC board is recommended. Connecting
the Exposed Pad to a ground plane and maintaining a solid
ground plane under the device will reduce the thermal
resistance of the package and PC board considerably.
as a pass switch, connecting V
to CPO, until dropout
BAT
is detected at the LED pin. This feature provides the op-
timum efficiency available for a given input voltage and
LED forward voltage. When it is operating as a switch, the
efficiency is approximated by:
PLED
PIN
(VLED •ILED
(VBAT •IBAT
)
)
VLED
VBAT
η =
=
=
since the input current will be very close to the sum of
the LED currents.
3210fb
ꢀꢂ
LTC3210
package Description
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 p0.05
3.50 p 0.05
2.10 p 0.05
1.45 p 0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 p0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 s 45o CHAMFER
R = 0.115
TYP
0.75 p 0.05
3.00 p 0.10
(4 SIDES)
15 16
PIN 1
TOP MARK
(NOTE 6)
0.40 p 0.10
1
2
1.45 p 0.10
(4-SIDES)
(UD16) QFN 0904
0.200 REF
0.25 p 0.05
0.00 – 0.05
0.50 BSC
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
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
3210fb
ꢀꢃ
LTC3210
revision history (Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
6/10
Update to Note 3
3
3210fb
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
ꢀꢄ
LTC3210
typical application
3-LED MAIN, One LED Camera
C2
2.2µF
C3
2.2µF
C1P C1M
V
BAT
C2P
C2M
CPO
MAIN
CAM
V
BAT
C4
2.2µF
C1
2.2µF
LTC3210
MLED1
MLED2
MLED3
MLED4
CLED
MLED4 DISABLED
ENM
ENC
ENM
ENC
3210 TA02
RM
RC
GND
30.1k
1%
24.3k
1%
relateD parts
PART NUMBER
DESCRIPTION
COMMENTS
LT1618
Constant Current, 1.4MHz, 1.5A Boost Converter
250mA, 1MHz, Multi-Display LED Controller
400mA, 800kHz, Multi-Display LED Controller
VIN: 1.6V to 18V, VOUT(MAX) = 36V, IQ = 1.8mA, ISD <1µA, MS Package
VIN: 2.8V to 4.5V, VOUT(MAX) = 5.5V, IQ = 50µA, ISD <1µA, QFN Package
VIN: 2.8V to 4.5V, VOUT(MAX) = 5.5V, IQ = 50µA, ISD <1µA, QFN Package
LTC3205
LTC3206
LTC3208
High Current Software Configurable Multi-Display
LED Controller
VIN: 2.9V to 4.5V, VOUT = 5.1V, IQ = 250µA, ISD <1µA, 17 Current Sources
(MAIN, SUB, RGB, CAM, AUX), 5 × 5 QFN Package
LTC3209-1/
LTC3209-2
600mA Main/Camera/AUX LED Controller
V : 2.9V to 4.5V, I = 400µA, Up to 94% Efficiency, 4mm × 4mm QFN-20
IN
Q
Package
LTC3210-1
MAIN/CAM LED Controller with 64-Step Brightness V : 2.9V to 4.5V, I = 400µA, 3-Bit DAC Brightness Control for MAIN and
IN Q
Control
CAM LEDs, 3mm × 3mm QFN Package
LTC3214
LTC3215
LTC3216
500mA Camera LED Charge Pump
VIN: 2.9V to 4.5V, Single Output, 3 × 3 DFN Package
700mA Low Noise High Current LED Charge Pump VIN: 2.9V to 4.4V, VOUT(MAX) = 5.5V, IQ = 300µA, ISD <2.5µA, DFN Package
1A Low Noise High Current LED Charge Pump with VIN: 2.9V to 4.4V, VOUT(MAX) = 5.5V, IQ = 300µA, ISD <2.5µA, DFN Package
Independent Flash/Torch Current Control
LTC3217
600mA Low Noise Multi-LED Camera Light
VIN: 2.9V to 4.4V, I = 400µA, Four 100mA Outputs, QFN Package
Q
LTC3440/LTC3441 600mA/1.2A IOUT, 2MHz/1MHz, Synchronous
Buck-Boost DC/DC Converter
VIN: 2.4V to 5.5V, VOUT(MAX) = 5.25V, IQ = 25µA/50µA, ISD <1µA,
MS/DFN Packages
LTC3443
600mA/1.2A IOUT, 600kHz, Synchronous
Buck-Boost DC/DC Converter
VIN: 2.4V to 5.5V, VOUT(MAX) = 5.25V, IQ = 28µA, ISD <1µA, DFN Package
LTC3453
1MHz, 800mA Synchronous Buck-Boost High
Power LED Driver
VIN(MIN): 2.7V to 5.5V, VIN(MAX): 2.7V to 4.5V, IQ = 2.5mA, ISD <6µA,
QFN Package
LT3467/LT3467A
LT3479
1.1A (ISW), 1.3/2.1MHz, High Efficiency Step-Up
DC/DC Converters with Integrated Soft-Start
VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 1.2mA, ISD <1µA, ThinSOT Package
3A, 42V, 3.5MHz Boost Converter
VIN: 2.5V to 24V, VOUT(MAX) = 40V, IQ = 2µA, ISD <1µA DFN, TSSOP Packages
3210fb
LT 0610 REV B • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
ꢀꢅ
●
●
ꢀLINEAR TECHNOLOGY CORPORATION 2006
(408)432-1900 FAX: (408) 434-0507 www.linear.com
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