LQH2MCN150K02 [Linear]
20mA LED Driver and OLED Driver with Integrated Schottky in 3mm x 2mm DFN; 20毫安LED驱动器和OLED驱动器,集成肖特基二极管采用3mm x 2mm DFN封装型号: | LQH2MCN150K02 |
厂家: | Linear |
描述: | 20mA LED Driver and OLED Driver with Integrated Schottky in 3mm x 2mm DFN |
文件: | 总24页 (文件大小:450K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LT3498
20mA LED Driver and
OLED Driver with Integrated
Schottky in 3mm x 2mm DFN
DESCRIPTION
FEATURES
The LT®3498 is a dual output boost converter featuring a
2.3MHzPWMLEDDriverandPFMOLEDDriver.Itincludes
an internal power switch and Schottky diode for each
driver. Both converters can be independently shut down
and modulated. This highly integrated power solution is
ideal for dual display electronic devices.
■
Dual Output Boost for Dual Display Devices
■
Drives Up to Six White LEDs and OLED/LCD Bias
■
Internal Power Switches and Schottky Diodes
■
Independent Dimming and Shutdown
■
200mV High Side Sense on LED Driver Allows
“One-Wire Current Source”
■
Wide Input Voltage Range: 2.5V to 12V
The2.3MHzstep-upconverterisdesignedtodriveuptosix
white LEDs in series from a Li-Ion cell. The device features
a unique high side LED current sense that enables the part
tofunctionasa“one-wire”currentsource—onesideofthe
LEDstringcanbereturnedtogroundanywhere.Traditional
LED drivers use a grounded resistor to sense LED current,
requiring a 2-wire connection to the LED string.
■
Wide Output Voltage Range: Up to 32V
■
2.3MHz PWM Frequency for LED Driver
■
PFM for OLED Driver is Non-Audible Over Entire
Load Range
■
Open LED Protection (27V Maximum on CAP1 Pin)
■
OLED Output Disconnect
■
Available in 12-Pin DFN Package
■
The PFM OLED driver is a low noise boost converter that
featuresanovelcontroltechnique.*Theconvertercontrols
power delivery by varying both the peak inductor current
and switch off time. This technique results in low output
voltage ripple, as well as, high efficiency over a wide load
range. The off time of the switch is not allowed to exceed a
fixed level, guaranteeing a switching frequency that stays
above the audio band.
1mm Tall Solution Height
APPLICATIONS
■
Cellular Phones
■
PDAs, Handheld Computers
■
Digital Cameras
■
MP3 Players
■
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
GPS Receivers
*Patent Pending
TYPICAL APPLICATION
Li-Ion to Six White LEDs and OLED/LCD Bias
OLED Efficiency
80
75
70
65
60
55
50
45
40
400
350
300
250
200
150
100
50
V
= 3V TO 5V
V
V
= 3.6V
IN
IN
OUT2
4.7µF
0.47µF
= 16V
LOAD FROM V
OUT2
15µH
15µH
16V
24mA
1µF
CAP1 SW1
V
SW2 CAP2 V
OUT2
IN
LT3498
LED1 CTRL1 GND1 GND2 CTRL2 FB2
OFF OFF
10Ω
10µF
2.21MΩ
20mA
ON
ON
POWER LOSS
FROM V
SHUTDOWN
AND
DIMMING
CONTROL
SHUTDOWN
AND
OUT2
CONTROL
0
100
0.1
1
10
3498 TA01
LED CURRENT (mA)
3498 TA01b
3498f
1
LT3498
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Notes 1, 2)
TOP VIEW
Input Voltage (V )....................................................12V
IN
1
2
3
4
5
6
LED1
CTRL1
GND1
GND2
CTRL2
FB2
12 CAP1
11 SW1
CTRL1 and CTRL2 Voltage........................................12V
FB2 Voltage..............................................................2.5V
10
9
V
IN
13
V
OUT2
Voltage ...........................................................32V
SW2
SW1 and SW2 Voltage..............................................32V
CAP1 and CAP2 Voltage............................................32V
LED1 Voltage ............................................................32V
Operating Junction Temperature Range...–40°C to 85°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range...................–65°C to 150°C
8
CAP2
7
V
OUT2
DDB PACKAGE
12-LEAD (3mm × 2mm) PLASTIC DFN
= 125°C, θ = 160°C/W
T
JMAX
JA
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER
LT3498EDDB
DDB PART MARKING
LCQF
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 the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C, V = 3V, V
= V
= 3V.
A
IN
CTRL1
CTRL2
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Minimum Operating Voltage
Maximum Operating Voltage
Supply Current (LED Off, OLED Off)
Supply Current (LED On, OLED Off)
2.5
12
10
2
V
V
= 3V, V
= 3V, V
= 0V, V
= 3V, V
= 0V
8
µA
IN
CTRL1
CTRL2
CTRL2
V
IN
V
= 0V, V
= 24V,
1.6
mA
CTRL1
= 23V
CAP1
LED1
Supply Current (LED Off, OLED On)
Supply Current (LED On, OLED On)
V
= 3V, V
= 0V, V
= 3V, V
= 3V, V = 3V
230
280
µA
IN
CTRL1
CTRL2
CTRL2
FB2
V
V
= 3V, V
= 3V, V
= 24V,
1.65
2.05
mA
IN
LED1
CTRL1
CAP1
= 23V
●
V
V
V
for Full LED Current
1.5
V
CTRL1
CTRL2
CTRL1
for Full OLED Brightness
●
●
or V
to Turn On I
125
mV
mV
nA
CTRL2
C
V
and V
to Shut Down I
75
CTRL1
CTRL2
C
CTRL1, CTRL2 Pin Bias Current
100
LED Driver
●
LED Current Sense Voltage (V
– V
)
LED
V
V
= 24V, I = 200mA
190
200
20
210
30
mV
µA
CAP
CAP1
SW
CAP1, LED1 Pin Bias Current
= 16V, V
= 16V
CAP1
LED1
V
, V
Common Mode Minimum Voltage
2.5
2.8
V
CAP1 LED1
●
●
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
1.8
88
2.3
90
MHz
%
300
425
250
mA
Switch V
I
= 200mA
SW
mV
CESAT
3498f
2
LT3498
ELECTRICAL CHARACTERISTICS The
●
denotes the specifications which apply over the full operating
= V = 3V.
temperature range, otherwise specifications are at T = 25°C, V = 3V, V
A
IN
CTRL1
CTRL2
PARAMETER
CONDITIONS
MIN
TYP
0.1
27
MAX
5
UNITS
µA
V
Switch Leakage Current
CAP1 Pin Overvoltage Protection
Schottky Forward Voltage
Schottky Reverse Leakage
OLED Driver
V
SW1
= 16V
26
28
I
= 100mA
= 20V
0.8
V
SCHOTTKY1
V
6
µA
REVERSE1
●
●
Feedback Voltage
V
= 3V (Note 3)
1.18
177
1.215
182
150
1
1.25
186
V
kΩ
ns
CTRL2
Feedback Resistor
Minimum Switch Off Time
Minimum Switch Off Time
Maximum Switch Off Time
Switch Current Limit
After Start-Up
During Start-Up (Note 4)
µs
●
V
FB2
= 1.5V
15
20
30
µs
180
300
260
0.1
400
mA
mV
µA
mV
µA
mV
mV
µA
Switch V
I
= 200mA
= 16V
CESAT
SW2
Switch Leakage Current
Schottky Forward Voltage
Schottky Reverse Leakage
V
SW2
5
2
I
= 100mA
= 20V
800
SCHOTTKY2
V
REVERSE2
OUT2
PMOS Disconnect V
CTRL2 to FB2 Offset
– V
I
= 10mA, V = 5V
CAP2
250
8
CAP2
OUT2
V
V
= 0.5V
15
CTRL2
Maximum Shunt Current
= 1.3V
220
FB2
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: Internal reference voltage is determined by finding V voltage
level which causes quiescent current to increase 20µA above “Not
Switching” level.
FB2
Note 4: If CTRL2 is overriding the internal reference, start-up mode
Note 2: The LT3498 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C junction
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
occurs when V is less then half the voltage on CTRL2. If CTRL2 is not
FB2
overriding the internal reference, start-up mode occurs when V is less
FB2
then half the voltage of the internal reference.
3498f
3
LT3498
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, unless otherwise specified.
A
Shutdown Current
LED Switch Saturation
Voltage (V
LED Schottky Forward
Voltage Drop
(V
= V
= 0V)
)
CESAT1
CTRL1
CTRL2
500
450
400
350
300
250
200
150
100
50
15
12
9
400
T = –50°C
350
T = –50°C
T = 125°C
300
250
T = 25°C
T = 25°C
T = 125°C
200
150
T = 125°C
T = 25°C
6
100
50
0
3
0
T = –50°C
0
0
4
6
8
10
12
2
0
50 100 150 200 250 300 350 400
SWITCH CURRENT (mA)
200
400
800
0
1000
600
V
(V)
IN
SCHOTTKY FORWARD DROP (mV)
3498 G03
1635 G07
3498 G02
Sense Voltage (V
– V
)
Sense Voltage (V
vs Temperature
– V
)
Sense Voltage (V
– V
)
CAP1
LED1
CAP1
LED1
CAP1
LED1
vs V
vs V
CAP1
CTRL1
206
202
198
194
190
186
206
202
198
194
190
186
240
200
T = 25°C
T = –50°C
T = 125°C
160
120
T = 125°C
T = 25°C
T = –50°C
80
40
0
–50 –25
0
25
50
75 100 125
0
5
15
CAP1 VOLTAGE (V)
20
25
10
0
500
V
1000
(mV)
1500
2000
TEMPERATURE (°C)
CTRL1
3498 G06
3498 G04
3498 G05
LED Current Limit
vs Temperature
Open Circuit Output
Clamp Voltage
Input Current in Output
Open Circuit
6
5
500
450
400
350
300
29
28
27
26
25
T = –50°C
T = 150°C
T = 150°C
T = 25°C
4
3
T = 25°C
T = –50°C
2
1
0
2
4
6
8
10
12
–50 –25
0
25
50
75 100 125
0
4
6
8
10
12
2
V
(V)
TEMPERATURE (°C)
V
(V)
IN
IN
3498 G09
3498 G07
3498 G08
3498f
4
LT3498
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, unless otherwise specified.
A
LED Switching Frequency
vs Temperature
OLED Switch Saturation
Voltage (V
OLED Schottky Forward
Voltage Drop
)
CESAT2
300
250
200
150
100
50
2.6
400
350
300
250
T = 125°C
2.5
2.4
T = 125°C
T = –50°C
T = 25°C
2.3
2.2
2.1
2.0
1.9
200
150
T = 25°C
100
50
0
T = –50°C
0
1.8
0
100
150
200
250
300
50
–25
0
50
75 100 125
200
400
800
–50
25
0
1000 1200
600
SWITCH CURRENT (mA)
TEMPERATURE (°C)
SCHOTTKY FORWARD DROP (mV)
3498 G12
3498 G11
3498 G10
V
vs V
OUT2
V
vs Temperature
= 16V)
OUT2
CTRL2
OUT2
OUT2
(V
= 16V)
(V
V
Load Regulation
OUT2
6
3
18
16
14
12
10
8
2.0
1.5
1.0
0.5
0
0
–0.5
6
–3
–1.0
–1.5
–2.0
4
2
–6
0
–50 –25
0
25
50
75 100 125
0
2000
10
20
LOAD CURRENT (mA)
40
500
1000
1500
0
50
30
TEMPERATURE (°C)
CTRL2 VOLTAGE (V)
3498 G13
3498 G14
3498 G15
OLED Minimum
OLED Switching Frequency
vs Load Current
Switching Frequency
Peak Inductor Current
1200
1000
800
600
400
200
0
80
600
70
60
550
500
50
40
30
20
10
450
400
350
300
250
0
200
0.1
1
10
100
–25
0
50
75 100 125
–50
25
–25
0
50
75 100 125
–50
25
LOAD CURRENT (mA)
TEMPERATURE (°C)
TEMPERATURE (°C)
3498 G17
3498 G16
3498 G18
3498f
5
LT3498
TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, unless otherwise specified.
A
OLED Switching Waveforms
with No Load
LED Switching Waveforms
LED Transient Response
V
OUT2
10mV/DIV
V
V
CAP1
5V/DIV
SW
AC COUPLED
10V/DIV
V
CTRL1
SW2 VOLTAGE
V
CAP1
5V/DIV
10V/DIV
50mV/DIV
I
L
I
L
INDUCTOR
CURRENT
50mA/DIV
100mA/
DIV
200mA/
DIV
3498 G19
3498 G20
3498 G21
500ns/DIV
1ms/DIV
5µs/DIV
V
= 3.6V
V = 3.6V
IN
V
V
= 3.6V
IN
IN
OUT2
FRONT PAGE APPLICATION
FRONT PAGE APPLICATION
= 16V
OLED Switching Waveforms
with 35mA Load
OLED Switching Waveforms
During Start-Up
OLED Switching Waveforms
with 4mA Load
V
CAP2
VOLTAGE
5V/DIV
OUT2
V
OUT2
10mV/DIV
AC
10mV/DIV
AC COUPLED
COUPLED
V
SW2
VOLTAGE
10V/DIV
OUT2
SW2
VOLTAGE
10V/DIV
VOLTAGE
5V/DIV
INDUCTOR
CURRENT
200mA/DIV
INDUCTOR
CURRENT
100mA/DIV
INDUCTOR
CURRENT
200mA/DIV
3498 G24
3498 G23
3498 G22
500µs/DIV
500ns/DIV
2µs/DIV
V
V
= 3.6V
V
V
= 3.6V
IN
OUT2
V
V
= 3.6V
IN
OUT2
IN
OUT2
= 16V
= 16V
= 16V
PIN FUNCTIONS
LED1 (Pin 1): Connection Point Between the Anode of the
Highest LED and the Sense Resistor. The LED current can
be programmed by:
CTRL2 (Pin 5): Dimming and Shutdown Pin. Connect it
below 75mV to disable the low noise boost converter.
As the pin voltage is ramped from 0V to 1.5V, the output
ramps up to the programmed output voltage.
200mV
RSENSE1
ILED1
=
FB2 (Pin 6): Feedback Pin. Reference voltage is 1.215V.
There is an internal 182kΩ resistor from FB2 to GND. To
CTRL1 (Pin 2): Dimming and Shutdown Pin. Connect this
pin below 75mV to disable the white LED driver. As the
pin voltage is ramped from 0V to 1.5V, the LED current
achieve desired output voltage, choose R according to
FB2
the following formula:
V
⎛
⎞
OUT2
ramps from 0 to (I
= 200mV / R
).
RFB2 =182•
−1 kΩ
LED1
SENSE1
⎜
⎝
⎟
⎠
1.215
GND1, 2 (Pins 3, 4): Ground. Tie directly to local ground
plane. GND1 and GND2 are connected internally.
3498f
6
LT3498
PIN FUNCTIONS
V
(Pin 7): Drain of Output Disconnect PMOS.
SW1 (Pin 11): Switch Pin. Connect the inductor of the
white LED driver at this pin. Minimize metal trace area at
this pin to minimize EMI.
OUT2
Place a bypass capacitor from this pin to GND. See the
Applications Information section.
CAP2 (Pin 8): Output of the OLED Driver. This pin is
connected to the cathode of the internal Schottky diode.
Place a bypass capacitor from this pin to GND.
CAP1 (Pin 12): Output of the White LED Driver. This pin is
connectedtothecathodeoftheinternalSchottky. Connect
theoutputcapacitortothispinandthesenseresistorfrom
this pin to the LED1 pin.
SW2 (Pin 9): Switch Pin. This is the collector of the in-
ternal NPN power switch. Minimize the metal trace area
connected to this pin to minimize EMI.
Exposed Pad (Pin 13): Ground. The Exposed Pad must
be soldered to the PCB.
V
(Pin 10): Input Supply Pin. Must be locally by-
IN
passed.
BLOCK DIAGRAM
L2
10µF
L1
15µF
C
IN
4.7µF
9
10
V
11
SW1
CAP1
SW2
COMPARATOR
IN
12
CAP2
–
+
8
R
Q
Q1
A2
S
C2
0.47µF
OVERVOLTAGE
PROTECTION
START-UP
CONTROL
DRIVER
A3
+
–
R
R
SENSE1
10Ω
Σ
RAMP
GENERATOR
C1
1µF
V
OUT2
7
DRIVER
2.3MHz
OSCILLATOR
+
SWITCH
CONTROL
C3
10µF
Q2
–
+
+
A4
LED1
DISCONNECT
CONTROL
1
–
A1
R
C
SHUNT
CONTROL
C
C
R
FB2
2.21MΩ
+
VREF
+
A5
–
182kΩ
GND2
FB2
CTRL2
CTRL1 GND1
2 3
4
6
5
3498 BD
3498f
7
LT3498
OPERATION—LED DRIVER
The LED portion of the LT3498 uses a constant-frequency,
current mode control scheme to provide excellent line
and load regulation. Operation can be best understood
by referring to the Block Diagram.
reduced, the device will begin skipping pulses. This will
result in some low frequency ripple, although the average
LED current remains regulated down to zero. The photo in
Figure 1 details circuit operation driving four white LEDs
at 2mA load. Peak inductor current is less than 60mA and
the regulator operates in discontinuous mode, meaning
the inductor current reaches zero during the discharge
phase. After the inductor current reaches zero, the SW1
pin exhibits ringing due to the LC tank circuit formed
by the inductor in combination with the switch and the
diode capacitance. This ringing is not harmful; far less
spectral energy is contained in the ringing than in the
switch transitions.
At power-up, the capacitor at the CAP1 pin is charged up
to V (input supply voltage) through the inductor and the
IN
internal Schottky diode. If CTRL1 is pulled higher than
125mV, the bandgap reference, the start-up bias and the
oscillatorareturnedon.Atthestartofeachoscillatorcycle,
the power switch Q1 is turned on. A voltage proportional
to the switch current is added to a stabilizing ramp and the
resulting sum is fed into the positive terminal of the PWM
comparator, A2. When this voltage exceeds the level at the
negative input of A2, the PWM logic turns off the power
switch. The level at the negative input of A2 is set by the
error amplifier A1, and is simply an amplified version of
I
L
50mA/DIV
the difference between the V
and V
voltage and
CAP1
LED1
the bandgap reference. In this manner the error amplifier,
A1, sets the correct peak current level in inductor L1 to
keep the output in regulation. The CTRL1 pin is used to
adjust the LED current. The LED Driver is shutdown when
CTRL1 is pulled lower than 75mV.
V
SW
10V/DIV
3498 F01
200ns/DIV
V
= 4.2V
IN
I
= 2mA
LED
4 LEDs
Minimum Output Current
Figure 1. Switching Waveforms with
Four White LEDs at 2mA Load
The LED Driver of the LT3498 can drive a 4-LED string at
2mA LED current, without pulse-skipping, using the same
external components shown in the application circuit on
the front page of this data sheet. As current is further
3498f
8
LT3498
OPERATION—OLED DRIVER
The low noise boost of the LT3498 uses a novel control
scheme to provide high efficiency over a wide range
of output current. In addition, this technique keeps the
switching frequency above the audio band over all load
conditions.
parameters to achieve regulation. During the start-up of
the circuit, special precautions are taken to ensure that
the inductor current remains under control.
Because the switching frequency is never allowed to fall
below approximately 50kHz, a minimum load must be
present to prevent the output voltage from drifting too
high.Thisminimumloadisautomaticallygeneratedwithin
thepartviatheShuntControlblock.Thelevelofthiscurrent
is adaptable, removing itself when not needed to improve
efficiency at higher load levels.
The operation of the part can be better understood by
referring to the Block Diagram. The part senses the
output voltage by monitoring the voltage on the FB2 pin.
The user sets the desired output voltage by choosing the
value of the external topside feedback resistor. The part
incorporates a precision 182kΩ bottom-side feedback
resistor. Assuming that output voltage adjustment is not
used (CTRL2 pin is tied to 1.5V, or greater), the internal
The low-noise boost of the LT3498 also has an integrated
Schottky diode and PMOS output disconnect switch. The
PMOS switch is turned on when the part is enabled. When
thepartisinshutdown,thePMOSswitchturnsoff,allowing
reference (V
= 1.215V) sets the voltage to which FB2
REF
will servo during regulation.
the V
node to go to ground. This type of disconnect
OUT2
The Switch Control block senses the output of the ampli-
fier and adjusts the switching frequency, as well as other
function is often required in power supplies.
APPLICATIONS INFORMATION—LED DRIVER
80
Inductor Selection
75
A 15µH inductor is recommended for most applications
70
for the LED driver of the LT3498. Although small size and
high efficiency are major concerns, the inductor should
65
have low core losses at 2.3MHz and low DCR (copper
60
wire resistance). Some small inductors in this category
15uH Murata LQH32CN150K53
15uH Murata LQH2MCN150K02
15uH Cooper SD3110-150
15uH Toko D312C
55
are listed in Table 1. The efficiency comparison of different
inductors is shown in Figure 2.
50
15uH Coilcraft DO3314-153ML
Table 1: Recommended Inductors
45
5
10
20
0
15
MAX
DCR
(Ω)
CURRENT
RATING
(mA)
LED CURRENT (mA)
L
(µH)
3498 F02
PART
VENDOR
Figure 2. Efficiency Comparison of Different Inductors
LQH32CN150K53
LQH2MCN150K02
LQH32CN100K53
LQH2MCN100K02
15
15
10
10
0.58
1.6
0.3
1.2
300
200
450
225
Murata
www.murata.com
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
LT3498 LED driver applications. Use only X5R and X7R
types, because they retain their capacitance over wider
temperature ranges than other types, such as Y5V or
Z5U. A 4.7µF input capacitor and a 1µF output capacitor
are sufficient for most applications.
SD3110-150
15
0.764
380
Cooper
www.cooperet.com
1001AS-150M
(TYPE D312C)
15
15
0.80
0.86
360
680
Toko
www.toko.com
D03314-153ML
Coilcraft
www.coilcraft.com
3498f
9
LT3498
APPLICATIONS INFORMATION—LED DRIVER
Inrush Current
Table 2: Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden
(800) 368-2496
The LT3498 LED Driver has a built-in Schottky diode.
www.t-yuden.com
When supply voltage is applied to the V pin, an inrush
IN
AVX
(803) 448-9411
www.avxcorp.com
current flows through the inductor and Schottky diode
and charges up the CAP1 voltage. The Schottky diode
for the LED Driver of the LT3498 can sustain a maximum
current of 1A.
Murata
(714) 852-2001
www.murata.com
Overvoltage Protection
For low DCR inductors, which are usually the case for this
application, the peak inrush current can be simplified as
follows:
The LED driver of the LT3498 has an internal open-circuit
protectioncircuit.Inthecasesofoutputopencircuit,when
the LEDs are disconnected from the circuit or the LEDs
fail open-circuit, V
driver will then switch at a very low frequency to minimize
input current. The V and input current during output
open-circuit are shown in the Typical Performance Char-
acteristics. Figure 3 shows the transient response when
the LEDs are disconnected.
r
α =
is clamped at 27V (typ). The LED
CAP1
2•L
r2
4•L2
CAP1
1
L •C
ω =
–
V – 0.6
L •ω
α π
• exp – •
⎛
⎝
⎞
IN
IPK
=
⎜
⎟
⎠
ω 2
where L is the inductance, r is the DCR of the inductor
and C is the output capacitance.
I
L
200mA/DIV
Table 3 gives inrush peak currents for some component
selections.
Table 3: Inrush Peak Currents
V
CAP1
LEDs DISCONNECTED
AT THIS POINT
10V/DIV
3498 F03
V
(V)
r (Ω)
L (µH)
C
(µF)
I (A)
P
IN
OUT
500µs/DIV
V
= 3.6V
IN
4.2
0.58
1.6
15
15
15
15
1
0.828
0.682
0.794
0.803
FRONT PAGE APPLICATION CIRCUIT
4.2
4.2
4.2
1
1
1
Figure 3. Transient Response with
LEDs Disconnected From Output
0.8
0.739
3498f
10
LT3498
APPLICATIONS INFORMATION—LED DRIVER
Programming LED Current
The LED current can be set by:
The feedback resistor (R
) and the sense voltage
200mV
SENSE1
ILED
≈
≈
, when VCTRL1 >1.5V
(V
– V
) control the LED current. The CTRL1 pin
CAP1
LED1
RSENSE1
VCTRL1
6.25•RSENSE1
controls the sense reference voltage as shown in the
Typical Performance Characteristics. For CTRL1 higher
than 1.5V, the sense reference is 200mV, which results in
full LED current. To have accurate LED current, precision
resistorsarepreferred(1%isrecommended).Theformula
ILED
, when VCTRL1 <1.25V
Feedback voltage variation versus control voltage is
given in the Typical Performance Characteristics.
and table for R
selection are shown below.
SENSE
200mV
ILED
Using a Filtered PWM Signal
RSENSE1
=
A filtered PWM signal can be used to control the bright-
ness of the LED string. The PWM signal is filtered (Figure 4)
by a RC network and fed to the CTRL1 pin.
Table 4: R
Value Selection for 200mV Sense
SENSE1
(mA)
I
R
(Ω)
LED
SENSE1
5
40
The corner frequency of R1, C1 should be much lower
than the frequency of the PWM signal. R1 needs to be
much smaller than the internal impedance of the CTRL1
pin which is 10MΩ (typ).
10
15
20
20
13.3
10
Dimming Control
Therearethreedifferenttypesofdimmingcontrolcircuits.
The LED current can be set by modulating the CTRL1 pin
with a DC voltage, a filtered PWM signal or directly with
a PWM signal.
LT3498
R1
100kΩ
PWM
10kHz TYP
CTRL1
3498 F04
C1
0.1µF
Using a DC Voltage
Forsomeapplications,thepreferredmethodofbrightness
control is a variable DC voltage to adjust the LED current.
The CTRL1 pin voltage can be modulated to set the dim-
ming of the LED string. As the voltage on the CTRL1 pin
increases from 0V to 1.5V, the LED current increases from
Figure 4. Dimming Control Using a Filtered PWM Signal
0toI . AstheCTRL1pinvoltageincreasesbeyond1.5V,
LED
it has no effect on the LED current.
3498f
11
LT3498
APPLICATIONS INFORMATION—LED DRIVER
Direct PWM Dimming
The PWM signal should traverse between 0V to 5V, to
ensure proper turn-on and -off of the driver and the NMOS
transistor Q1. When the PWM signal goes high, the LEDs
Changing the forward current flowing in the LEDs not only
changestheintensityoftheLEDs,italsochangesthecolor.
The chromaticity of the LEDs changes with the change in
forward current. Many applications cannot tolerate any
shift in the color of the LEDs. Controlling the intensity of
the LEDs with a direct PWM signal allows dimming of the
LEDs without changing the color. In addition, direct PWM
dimming offers a wider dimming range to the user.
are connected to ground and a current of I
SENSE1
= 200mV /
LED
R
flows through the LEDs. When the PWM signal
goes low, the LEDs are disconnected and turn off. The
MOSFET ensures that the LEDs quickly turn off without
discharging the output capacitor which in turn allows the
LEDs to turn on faster. Figure 6 shows the PWM dimming
waveforms for the circuit in Figure 5.
Dimming the LEDs via a PWM signal essentially involves
turning the LEDs on and off at the PWM frequency. The
typical human eye has a limit of ~60 frames per second.
By increasing the PWM frequency to ~80Hz or higher,
the eye will interpret that the pulsed light source is con-
tinuously on. Additionally, by modulating the duty cycle
(amount of “on-time”), the intensity of the LEDs can be
controlled. The color of the LEDs remains unchanged in
this scheme since the LED current value is either zero or
a constant value.
I
LED
20mA/DIV
I
L
200mA/DIV
PWM
5V/DIV
3498 F06
2ms/DIV
V
= 3V
IN
4 LEDs
Figure 5 shows a Li-Ion powered driver for four white
LEDs. Direct PWM dimming method requires an external
NMOS tied between the cathode of the lowest LED in the
string and ground as shown in Figure 5. A simple logic
level Si2304 MOSFET can be used since its source is
connected to ground. The PWM signal is applied to the
CTRL1 pin of the LT3498 and the gate of the MOSFET.
Figure 6. Direct PWM Dimming Waveforms
80
V
= 3.4V
IN
4 LEDs
75
100Hz = PWM
V
IN
3V TO 5V
C
IN
R
70
65
SENSE1
10Ω
1µH
L1
15µH
CAP1 SW1
V
SW2 CAP2 V
IN OUT2
60
55
50
LT3498
C
OUT1
1µF
LED1
CTRL1
CTRL2
FB2
GND1
GND2
Q1
Si2304BDS
0
2
4
6
8
10 12 14 16 18 20
LED CURRENT (mA)
5V
0V
100k
3498 F07
3498 F05
Figure 7. PWM Dimming Efficiency
PWM
FREQ
Figure 5. Li-Ion to Four White LEDs
with Direct PWM Dimming
3498f
12
LT3498
APPLICATIONS INFORMATION—LED DRIVER
The time it takes for the LED current to reach its pro-
grammed value sets the achievable dimming range for a
given PWM frequency. For example, the settling time of
the LED current in Figure 6 is approximately 40µs for a
3V input voltage. The achievable dimming range for this
application and 100Hz PWM frequency can be determined
using the following method.
The dimming range can be further extended by changing
the amplitude of the PWM signal. The height of the PWM
signalsetsthecommandedsensevoltageacrossthesense
resistorthroughtheCTRL1pin.Inthismannerbothanalog
dimming and direct PWM dimming extend the dimming
range for a given application. The color of the LEDs no
longer remains constant because the forward current of
the LED changes with the height of the CTRL1 signal. For
the four LED application described above, the LEDs can
be dimmed first, modulating the duty cycle of the PWM
signal.Oncetheminimumdutycycleisreached,theheight
of the PWM signal can be decreased below 1.5V down to
125mV. The use of both techniques together allows the
average LED current for the four LED application to be
variedfrom20mAdowntolessthan20µA. Figure9shows
the application for dimming using both analog dimming
and PWM dimming. A potentiometer must be added to
ensure that the gate of the NMOS receives a logic-level
signal, while the CTRL1 signal can be adjusted to lower
amplitudes.
Example:
f = 100Hz, tSETTLE = 40µs
1
f
1
100
tPERIOD = =
= 0.01s
0.01s
tSETTLE 40µs
tPERIOD
DimRange =
=
= 250 :1
MinDuty Cycle =
40µs
0.01s
tSETTLE
tPERIOD
• 100 =
• 100 = 0.4%
Duty Cycle Range = 100% → 0.4% at 100Hz
V
IN
3V TO 5V
C
IN
1µH
R
Thecalculationsshowthatfora100Hzsignalthedimming
range is 250:1. In addition, the minimum PWM duty cycle
of 0.4% ensures that the LED current has enough time to
settle to its final value. Figure 8 shows the dimming range
achievable for three different frequencies with a settling
time of 40µs.
SENSE1
10Ω
L1
15µH
CAP1 SW1
V
SW2 CAP2 V
IN OUT2
LT3498
C
OUT1
1µF
LED1
CTRL1
CTRL2
FB2
GND1
GND2
5V
0V
10000
PWM
FREQ
3498 F09
PULSING MAY BE VISIBLE
1000
100
10
Q1
Si2304BDS
100k
Figure 9. Li-Ion to Four White LEDs with
Both PWM Dimming and Analog Dimming
1
10
100
1000
10000
PWM FREQUENCY (Hz)
3498 F08
Figure 8. Dimming Ratio vs Freqeuncy
3498f
13
LT3498
APPLICATIONS INFORMATION—OLED DRIVER
Inductor Selection
Capacitor Selection
Several recommended inductors that work well with the
OLED driver of the LT3498 are listed in Table 5, although
there are many other manufacturers and devices that can
be used. Consult each manufacturer for more detailed
information and for their entire selection of related parts.
Many different sizes and shapes are available. Use the
equations and recommendations in the next few sections
to find the correct inductance value for your design.
The small size and low ESR of ceramic capacitors makes
them suitable for most OLED Driver applications. X5R and
X7R types are recommended because they retain their ca-
pacitance over wider voltage and temperature ranges than
other types such as Y5V or Z5U. A 4.7µF input capacitor
and a 10µF output capacitor are sufficient for most appli-
cations for the OLED Driver. Always use a capacitor with
a sufficient voltage rating. Many capacitors rated at 10µF,
particularly 0805 or 0603 case sizes, have greatly reduced
capacitancewhenbiasvoltagesareapplied.Besuretocheck
actualcapacitanceatthedesiredoutputvoltage. Generally
a 1206 size capacitor will be adequate. A 0.47µF capaci-
tor placed on the CAP node is recommended to filter the
Table 5: Recommended Inductors
MAX
DCR
(Ω)
CURRENT
RATING
(mA)
L
(µH)
PART
VENDOR
LQH32CN100K53
LQH2MCN100K02
LQH32CN150K53
LQH2MCN150K02
10
10
15
15
0.3
1.2
0.58
1.6
450
225
300
200
Murata
www.murata.com
inductor current while the larger 10µF placed on the V
OUT
node will give excellent transient response and stability.
Table 6 shows a list of several capacitor manufacturers.
Consult the manufacturers for more detailed information
and for their entire selection of related parts.
SD3110-100
SD3110-150
10
15
0.505
0.764
470
380
Cooper
www.cooperet.com
Inductor Selection—Boost Regulator
Table 6. Recommended Ceramic Capacitor Manufacturers
The formula below calculates the appropriate inductor
value to be used for the low noise boost regulator of
the LT3498 (or at least provides a good starting point).
This value provides a good tradeoff in inductor size and
system performance. Pick a standard inductor close to
this value. A larger value can be used to slightly increase
the available output current, but limit it to around twice
the value calculated below, as too large of an inductance
will decrease the output voltage ripple without providing
much additional output current. A smaller value can be
used (especially for systems with output voltages greater
than 12V) to give a smaller physical size. Inductance can
be calculated as:
MANUFACTURER
Taiyo Yuden
AVX
PHONE
URL
408-573-4150
843-448-9411
814-237-1431
408-986-0424
www.t-yuden.com
www.avxcorp.com
www.murata.com
www.kemet.com
Murata
Kemet
Setting Output Voltage and the Auxiliary
Reference Input
The OLED driver of the LT3498 is equipped with both an
internal 1.215V reference and an auxiliary reference input.
This allows the user to select between using the built-in
reference, and supplying an external reference voltage.
The voltage at the CTRL2 pin can be adjusted while the
chip is operating to alter the output voltage of the LT3498
for purposes such as display dimming or contrast adjust-
ment. To use the internal 1.215V reference, the CTRL2 pin
must be held higher than 1.5V. When the CTRL2 pin is
held between 0V and 1.5V the OLED driver will regulate
the output such that the FB2 pin voltage is nearly equal to
theCTRL2pinvoltage. AtCTRL2voltagescloseto1.215V,
L = (VOUT2 − VIN(MIN) + 0.5V) • 0.66(µH)
where V
is the desired output voltage and V
is
OUT2
IN(MIN)
the minimum input voltage. Generally, a 10µH or 15µH
inductor is a good choice.
3498f
14
LT3498
APPLICATIONS INFORMATION—OLED DRIVER
a soft transition occurs between the CTRL2 pin and the
Choosing a Feedback Node
internal reference. Figure 10 shows this behavior.
ThesinglefeedbackresistormaybeconnectedtotheV
pin or to the CAP2 pin (see Figure 11). Regulating the
OUT2
1.500
1.250
1.000
0.750
0.500
0.250
0
V
pin eliminates the output offset resulting from the
OUT2
voltage drop across the output disconnect PMOS. Regu-
lating the CAP2 pin does not compensate for the voltage
drop across the output disconnect, resulting in an output
voltage V
that is slightly lower than the voltage set by
OUT2
the resistor divider. Under most conditions, it is advised
that the feedback resistor be tied to the V
pin.
OUT2
Connecting the Load to the CAP2 Node
0
0.5
0.8
1.0
1.3
1.5
0.3
The efficiency of the converter can be improved by con-
necting the load to the CAP2 pin instead of the V pin.
CTRL2 VOLTAGE (V)
OUT2
3498 F10
The power loss in the PMOS disconnect circuit is then
Figure 10. CTRL2 to FB2 Transfer Curve
made negligible. By connecting the feedback resistor to
the V
pin, no quiescent current will be consumed
OUT2
To set the maximum output voltage, select the values of
in the feedback resistor string during shutdown since
the PMOS transistor will be open (see Figure 12). The
disadvantage of this method is that the CAP2 node can-
not go to ground during shutdown, but will be limited to
R
FB2
according to the following equation:
V
⎛
⎞
OUT2
RFB2 =182•
–1 , kΩ
⎜
⎝
⎟
⎠
1.215
around a diode drop below V . Loads connected to the
IN
When CTRL2 is used to override the internal reference,
the output voltage can be lowered from the maximum
value down to nearly the input voltage level. If the voltage
source driving the CTRL2 pin is located at a distance to
the LT3498, a small 0.1µF capacitor may be needed to
bypass the pin locally.
part should only sink current. Never force external power
supplies onto the CAP2 or V
pins. The larger value
OUT2
output capacitor should be placed on the node to which
the load is connected.
I
CAP1
SW1
V
SW2
LT3498
LED1 CTRL1 GND1 GND2 CTRL2
CAP2
V
OUT2
CAP1
SW1
V
SW2
LT3498
LED1 CTRL1 GND1 GND2 CTRL2
CAP2
V
LOAD
C3
C2
IN
OUT2
IN
R
FB2
R
FB2
FB2
FB2
3498 F12
C2
Figure 12. Improved Efficiency
CAP1
SW1
V
SW2
LT3498
LED1 CTRL1 GND1 GND2 CTRL2
CAP2
V
C3
IN
OUT2
FB2
R
FB2
3498 F11
Figure 11. Feedback Connection Using
the CAP2 Pin or the V Pin
OUT2
3498f
15
LT3498
APPLICATIONS INFORMATION—OLED DRIVER
Maximum Output Load Current
Step 4: Calculate the nominal output current:
The maximum output current of a particular LT3498
circuit is a function of several circuit variables. The fol-
lowing method can be helpful in predicting the maximum
load current for a given circuit:
IIN(AVG) • VIN • 0.75
VOUT2
IOUT(NOM)
=
amps
Step 5: Derate output current:
= I • 0.7 amps
I
Step 1: Calculate the peak inductor current:
OUT
OUT(NOM)
V • 400 •10–9
For low output voltages the output current capability will
beincreased. Whenusingoutputdisconnect(loadcurrent
IN
IPK = ILIMIT
where I
+
amps
L
taken from V
), these higher currents will cause the
OUT2
is 0.3A for the OLED driver. L is the induc-
drop in the PMOS switch to be higher resulting in reduced
output current capability than those predicted by the
preceding equations.
LIMIT
tance value in Henrys and V is the input voltage to the
IN
boost circuit.
Step 2: Calculate the inductor ripple current:
Inrush Current
V
+ 1– V • 150 • 10–9
(
)
When V is stepped from ground to the operating voltage
OUT2
IN
IN
IRIPPLE
=
amps
while the output capacitor is discharged, a higher level of
inrushcurrentwillflowthroughtheinductorandintegrated
Schottky diode into the output capacitor. Conditions that
increaseinrushcurrentincludealargermoreabruptvoltage
L
where V
is the desired output voltage.
OUT2
If the inductor ripple current is less then the peak current,
then the circuit will only operate in discontinuous conduc-
tion mode. The inductor value should be increased so
step at V , a larger output capacitor tied to the CAP2 pin,
IN
and an inductor with a low saturation current. While the
internaldiodeisdesignedtohandlesuchevents,theinrush
current should not be allowed to exceed 1A. For circuits
that use output capacitor values within the recommended
range and have input voltages of less than 5V, inrush cur-
rent remains low, posing no hazard to the device. In cases
that I
< I . An application circuit can be designed
RIPPLE
PK
to operate only in discontinuous mode, but the output
current capability will be reduced.
Step 3: Calculate the average input current:
where there are large steps at V (more than 5V) and/or
IN
IRIPPLE
IIN(AVG) = IPK
–
amps
a large capacitor is used at the CAP2 pin, inrush current
2
should be measured to ensure safe operation.
3498f
16
LT3498
APPLICATIONS INFORMATION—LED AND OLED DRIVER
Board Layout Considerations
node. The FB2 connection for the feedback resistor R
FB2
should be tied directly from the V
pin to the FB2
OUT2
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
properlayoutofhighfrequencyswitchingpathsisessential.
Minimize the length and area of all traces connected to
the switching node pins (SW1 and SW2). Keep the sense
voltage pins (CAP1 and LED1) away from the switching
pin and be kept as short as possible, ensuring a clean,
noise-free connection. Place C and C next to the
OUT1
OUT2
CAP1 and CAP2 pins respectively. Always use a ground
planeendertheswitchingregulatortominimizeinterplane
coupling. Recommendedcomponentplacementisshown
in Figure 13.
R
SENSE1
LED1
CAP1
C1
SW1
1
2
3
4
5
6
12
11
10
9
CTRL1
GND
L1
L2
GND
V
IN
C
IN
CTRL2
SW2
8
7
R
FB2
C3
C2
V
OUT2
FB2
V
OUT2
CAP2
3498 F13
GND
VIAS TO GROUND PLANE REQUIRED TO
IMPROVE THERMAL PERFORMANCE
VIAS TO V
OUT2
Figure 13. Recommended Board Layout
3498f
17
LT3498
TYPICAL APPLICATIONS
Li-Ion to Two White LEDs and OLED/LCD Bias
V
= 3V TO 5V
C
C2
0.47µF
IN
IN
4.7µF
C1
1µF
L1
10µH
L2
10µH
16V
24mA
CAP1 SW1
V
SW2
CAP2 V
OUT2
C3
10µF
IN
LT3498
20mA
R
FB2
LED1 CTRL1 GND1 GND2 CTRL2
FB2
2.21MΩ
R
SENSE1
OFF
OFF
ON
10Ω
ON
SHUTDOWN
SHUTDOWN
AND
AND
3498 TA02
DIMMING
CONTROL
CONTROL
C
, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
IN
C1: TAIYO YUDEN GMK212BJ105KG
C3: TAIYO YUDEN TMK316BJ106ML
L1, L2: MURATA LQH32CN100K53
LED Efficiency
IN
V
= 3.6V, 2 LEDs
75
70
65
60
55
50
45
40
0
5
10
20
15
LED CURRENT (mA)
3498 TA02b
3498f
18
LT3498
TYPICAL APPLICATIONS
Li-Ion to Two White LEDs and OLED/LCD Bias
V
= 3V TO 5V
C
C2
0.47µF
IN
IN
4.7µF
L1
10µH
L2
10µH
16V
24mA
CAP1 SW1
V
SW2
CAP2 V
OUT2
C3
10µF
IN
C1
1µF
LT3498
R
R
SENSE1
FB2
LED1 CTRL1 GND1 GND2 CTRL2
OFF OFF
FB2
10Ω
2.21MΩ
ON
ON
SHUTDOWN
SHUTDOWN
AND
AND
20mA
DIMMING
CONTROL
CONTROL
3498 TA03
C
, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
IN
C1: TAIYO YUDEN GMK212BJ105KG
C3: TAIYO YUDEN TMK316BJ106ML
L1, L2: MURATA LQH32CN100K53
LED Efficiency
= 3.6V, 2 LEDs
V
IN
80
75
70
65
60
55
50
45
40
0
5
10
20
15
LED CURRENT (mA)
3498 TA03b
3498f
19
LT3498
TYPICAL APPLICATIONS
Li-Ion to Three White LEDs and OLED/LCD Bias
V
= 3V TO 5V
C
C2
0.47µF
IN
IN
4.7µF
L1
15µH
L2
10µH
16V
24mA
CAP1 SW1
V
SW2
CAP2 V
OUT2
C3
10µF
IN
C1
1µF
LT3498
R
R
SENSE1
FB2
LED1 CTRL1 GND1 GND2 CTRL2
OFF OFF
FB2
10Ω
2.21MΩ
ON
ON
SHUTDOWN
SHUTDOWN
AND
AND
20mA
DIMMING
CONTROL
CONTROL
3498 TA04
C
, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
IN
C1: TAIYO YUDEN GMK212BJ105KG
C3: TAIYO YUDEN TMK316BJ106ML
L1: MURATA LQH32CN150K53
L2: MURATA LQH32CN100K53
LED Efficiency
= 3.6V, 3 LEDs
V
IN
80
75
70
65
60
55
50
45
0
5
10
LED CURRENT (mA)
20
15
3498 TA04b
3498f
20
LT3498
TYPICAL APPLICATIONS
Li-Ion to Four White LEDs and OLED/LCD Bias
V
= 3V TO 5V
C
C2
0.47µF
IN
IN
4.7µF
L1
15µH
L2
10µH
16V
24mA
CAP1 SW1
V
SW2
CAP2 V
OUT2
C3
10µF
IN
C1
1µF
LT3498
R
R
SENSE1
FB2
LED1 CTRL1 GND1 GND2 CTRL2
OFF OFF
FB2
10Ω
2.21MΩ
ON
ON
SHUTDOWN
SHUTDOWN
AND
AND
DIMMING
CONTROL
CONTROL
20mA
3498 TA05
C
, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
IN
C1: TAIYO YUDEN GMK212BJ105KG
C3: TAIYO YUDEN TMK316BJ106ML
L1: MURATA LQH32CN150K53
L2: MURATA LQH32CN100K53
LED Efficiency
= 3.6V, 4 LEDs
V
IN
80
75
70
65
60
55
50
0
5
10
20
15
LED CURRENT (mA)
3498 TA05b
3498f
21
LT3498
TYPICAL APPLICATIONS
Li-Ion to Six White LEDs and OLED/LCD Bias
V
= 3V TO 5V
C
C2
0.47µF
IN
IN
4.7µF
R
SENSE1
L1
15µH
L2
10µH
10Ω
D1
24V
24mA
CAP1 SW1
V
IN
SW2
CAP2 V
OUT2
C3
10µF
LT3498
C1
1µF
R
FB2
LED1 CTRL1 GND1 GND2 CTRL2
FB2
2.21MΩ
20mA
OFF
OFF
ON
ON
SHUTDOWN AND
DIMMING CONTROL
SHUTDOWN AND
CONTROL
3498 TA06
C
IN
, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
C1: TAIYO YUDEN GMK212BJ105KG
C3: TAIYO YUDEN TMK316BJ106ML
D1: CENTRAL SEMICONDUCTOR CMDSH-3
L1: MURATA LQH32CN150K53
L2: MURATA LQH32CN100K53
LED Efficiency,
IN
OLED Efficiency and Power Loss
V
= 3.6V, 6 LEDs
V
= 3.6V, V
= 16V
IN
OUT2
80
75
70
65
60
55
50
80
75
70
65
60
55
50
45
40
400
350
300
250
200
150
100
50
0
1
100
5
10
LED CURRENT (mA)
20
0.1
10
0
15
LOAD CURRENT (mA)
3498 TA06b
LOAD FROM V
OUT2
LOAD FROM CAP2
POWER LOSS FROM V
POWER LOSS FROM CAP2
OUT2
3498 TA06c
3498f
22
LT3498
PACKAGE DESCRIPTION
DDB Package
12-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1723 Rev Ø)
0.64 0.05
(2 SIDES)
0.70 0.05
2.55 0.05
1.15 0.05
PACKAGE
OUTLINE
0.25 0.05
0.45 BSC
2.39 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
R = 0.115
TYP
7
0.40 0.10
12
3.00 0.10
(2 SIDES)
R = 0.05
TYP
2.00 0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
PIN 1
R = 0.20 OR
(SEE NOTE 6)
0.25 × 45°
0.64 0.10
(2 SIDES)
CHAMFER
6
1
(DDB12) DFN 0106 REV Ø
0.23 0.05
0.75 0.05
0.200 REF
0.45 BSC
2.39 0.10
(2 SIDES)
0 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
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
3498f
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.
23
LT3498
TYPICAL APPLICATION
Output Voltage Ripple
vs Load Current
MAXIMUM OUTPUT
CURRENT AT 3V INPUT
(mA)
R
FB2
VALUE REQUIRED
V
(MΩ)
7
6
5
4
3
2
1
0
OUT
25
24
23
22
21
20
19
18
17
16
15
3.57
3.40
3.24
3.09
2.94
2.80
2.67
2.49
2.37
2.21
2.05
12.5
13.4
14.4
15.6
16.8
18.1
19.6
21.2
22.5
24.2
26
1
100
0.1
10
LOAD CURRENT (mA)
3498 TA06d
RELATED PARTS
PART
NUMBER
DESCRIPTION
COMMENTS
LT1932
Constant-Current, 1.2MHz, High Efficiency White LED
Boost Regulator
V
: 1V to 10V; V
= 34V; I = 1.2mA; I = <1µA; ThinSOTTM Package
OUT(MAX) Q SD
IN
LT1937
Constant-Current, 1.2MHz, High Efficiency White LED
Boost Regulator
V
: 2.5V to 10V; V
= 34V; I = 1.9µA; I = <1µA; ThinSOT and
Q SD
IN
OUT(MAX)
OUT(MAX)
SC70 Packages
LT3463/
LT3463A
Dual Output, Boost/Inverter, 250mA I , Constant
V
: 2.3V to 15V; V
= 40V; I = 40µA; I = <1µA; 3mm × 3mm
Q SD
SW
IN
Off-Time, High Efficiency Step-Up DC/DC Converter with DFN-10 Package
Integrated Schottky Diodes
LT3465/
LT3465A
Constant-Current, 1.2/2.7MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
V
: 2.3V to 16V; V
= 40V; I = 40µA; I = <1µA; 3mm × 3mm
Q SD
IN
OUT(MAX)
OUT(MAX)
OUT(MAX)
OUT(MAX)
OUT(MAX)
DFN-10 Package
LT3466/
LT3466-1
Dual Constant-Current, 2MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
V
: 2.3V to 16V; V
= 40V; I = 65µA; I = <1µA; 3mm × 2mm
Q SD
IN
DFN-8 Package
LT3471
Dual Output, Boost/Inverter, 1.3A ISW, 1.2MHZ, High
Efficiency Boost-Inverting DC/DC Converter
V
: 2.4V to 16V; V
= 40V; I = 2.5µA; I = <1µA; 3mm × 3mm
Q SD
IN
DFN-10 Package
LT3473/
LT3473A
40V, 1A , 1.2MHz Micropower Low Noise Boost Converter V : 2.2V to 16V; V
with Output Disconnect
= 36V; I = 150µA; I = <1µA; 3mm × 3mm
Q SD
IN
DFN-12 Package
LT3491
Constant-Current, 2.3MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
V
: 2.5V to 12V; V
= 27V; I = 12.6µA; I = <8µA; 2mm × 2mm
Q SD
IN
DFN-6 and SC70 Packages
LT3494/
LT3494A
40V, 180mA/350mA Micropower Low Noise Boost
Converter with Output Disconnect
V
: 2.3V to 16V; V
= 40V; I = 65µA; I = <1µA; 3mm × 2mm
Q SD
IN
OUT(MAX)
OUT(MAX)
OUT(MAX)
DFN-8 Package
LT3497
Dual 2.3MHz, Full Function LED Driver with Integrated
Schottky Diode and 250:1 True Color PWMTM Dimming
V
: 2.5V to 10V; V
= 32V; I = 6mA; I = <12µA; 3mm × 2mm
Q SD
IN
DFN-10 Package
LT3591
Constant-Current, 1MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode and 80:1 DFN-8 Package
True Color PWM Dimming
V
: 2.5V to 12V; V
= 40V; I = 4mA; I = <9µA; 3mm × 2mm
Q SD
IN
ThinSot and True Color PWM are trademarks of Linear Technology Corporation
3498f
LT 0507 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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