LT1932 - Constant-Current DC/DC LED Driver in ThinSOT

LT1932
Constant-Current DC/DC
LED Driver in ThinSOT
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FEATURES
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DESCRIPTIO
The LT®1932 is a fixed frequency step-up DC/DC converter
designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is
ideal for driving light emitting diodes (LEDs) whose light
intensity is proportional to the current passing through
them, not the voltage across their terminals.
Up to 80% Efficiency
Inherently Matched LED Current
Adjustable Control of LED Current
Drives Five White LEDs from 2V
Drives Six White LEDs from 2.7V
Drives Eight White LEDs from 3V
Disconnects LEDs In Shutdown
1.2MHz Fixed Frequency Switching
Uses Tiny Ceramic Capacitors
Uses Tiny 1mm-Tall Inductors
Regulates Current Even When VIN > VOUT
Operates with VIN as Low as 1V
Low Profile (1mm) ThinSOTTM Package
With an input voltage range of 1V to 10V, the device works
from a variety of input sources. The LT1932 accurately
regulates LED current even when the input voltage is
higher than the LED voltage, greatly simplifying batterypowered designs. A single external resistor sets LED
current between 5mA and 40mA, which can then be easily
adjusted using either a DC voltage or a pulse width
modulated (PWM) signal. When the LT1932 is placed in
shutdown, the LEDs are disconnected from the output,
ensuring a quiescent current of under 1µA for the entire
circuit. The device’s 1.2MHz switching frequency permits
the use of tiny, low profile chip inductors and capacitors to
minimize footprint and cost in space-conscious portable
applications.
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APPLICATIO S
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Cellular Telephones
Handheld Computers
Digital Cameras
Portable MP3 Players
Pagers
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
Li-Ion Driver for Four White LEDs
L1
6.8µH
C1
4.7µF
85
D1
6
1
VIN
SW
LT1932
PWM
DIMMING
CONTROL
5
SHDN
RSET
4
RSET
1.50k
LED
GND
3
C2
1µF
15mA
80
VIN = 4.2V
75
VIN = 2.7V
70
65
60
2
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK212BJ105
D1:ZETEX ZHCS400
L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8
EFFICIENCY (%)
VIN
2.7V TO 4.2V
Efficiency
55
0
1932 TA01
5
10
15
LED CURRENT (mA)
20
1932 TA02
1932f
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LT1932
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ABSOLUTE
RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
VIN Voltage ............................................................. 10V
SHDN Voltage ......................................................... 10V
SW Voltage ............................................................. 36V
LED Voltage ............................................................. 36V
RSET Voltage ............................................................. 1V
Junction Temperature .......................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
TOP VIEW
SW 1
6 VIN
GND 2
5 SHDN
LED 3
4 RSET
LT1932ES6
S6 PART MARKING
S6 PACKAGE
6-LEAD PLASTIC SOT-23
LTST
TJMAX = 125°C, θJA = 250°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
Minimum Input Voltage
MAX
1
V
Quiescent Current
VRSET = 0.2V
VSHDN = 0V
1.2
0.1
RSET Pin Voltage
RSET = 1.50k
100
LED Pin Voltage
RSET = 1.50k, VIN < VOUT (Figure 1)
120
180
mV
LED Pin Current
RSET = 562Ω, VIN = 1.5V
RSET = 750Ω, VIN = 1.2V
RSET = 1.50k, VIN = 1.2V
RSET = 4.53k, VIN = 1.2V
38
30
15
5
45
36
17.5
mA
mA
mA
mA
LED Pin Current Temperature Coefficient
ILED = 15mA
Switching Frequency
VIN = 1V
Maximum Switch Duty Cycle
33
25
12.5
0.8
1.2
90
95
400
mA
µA
mV
– 0.02
●
Switch Current Limit
1.6
1.0
UNITS
mA/°C
1.6
MHz
%
550
780
mA
Switch VCESAT
ISW = 300mA
150
200
mV
SHDN Pin Current
VSHDN = 0V
VSHDN = 2V
0
15
0.1
30
µA
µA
0.25
V
V
5
µA
Start-Up Threshold (SHDN Pin)
Shutdown Threshold (SHDN Pin)
Switch Leakage Current
0.85
Switch Off, VSW = 5V
0.01
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: The LT1932E is guaranteed to meet 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.
1932f
2
LT1932
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TYPICAL PERFOR A CE CHARACTERISTICS
Switch Saturation Voltage (VCESAT)
Switch Current Limit
TJ = 25°C
250
200
TJ = –50°C
150
100
SWITCHING FREQUENCY (MHz)
300
1.8
VIN = 1.2V
600
TJ = 125°C
PEAK CURRENT (mA)
SWITCH SATURATION VOLTAGE (mV)
350
VIN = 10V
500
400
300
200
100
50
0
Switching Frequency
2.0
700
400
0
100
200
400
500
300
SWITCH CURRENT (mA)
50
25
75
0
TEMPERATURE (°C)
100
LED Pin Voltage
LED CURRENT (mA)
LED PIN VOLTAGE (mV)
300
TJ = 25°C
150
TJ = –50°C
100
45
35
RSET = 750Ω
30
25
20
RSET = 1.50k
15
35
0
– 50 – 25
40
Quiescent Current
20
RSET = 1.50k
15
RSET = 4.53k
0
75
50
25
TEMPERATURE (°C)
0
100
125
0
2
4
6
INPUT VOLTAGE (V)
8
10
1932 G06
Switching Waveforms
SHDN Pin Current
50
45
1.75
VSW
10V/DIV
TJ = –50°C
40
1.50
VIN = 10V
SHDN PIN CURRENT
QUIESCENT CURRENT (mA)
25
1932 G05
2.00
125
RSET = 750Ω
30
5
1932 G04
1.25
1.00
VIN = 1.2V
0.75
0.50
IL1
200mA/DIV
VOUT
20mV/DIV
AC COUPLED
ILED
10mA/DIV
35
TJ = 25°C
30
25
20
TJ = 125°C
VIN = 3V
0.5µs/DIV
4 WHITE LEDs
ILED = 15mA
CIRCUIT ON FIRST PAGE
OF THIS DATA SHEET
15
10
0.25
0
– 50 – 25
35
10
RSET = 4.53k
5
15 20 25 30
LED CURRENT (mA)
100
RSET = 562Ω
40
10
50
10
50
25
0
75
TEMPERATURE (°C)
LED Current
RSET = 562Ω
40
5
0.4
50
45
350
0
0.6
1932 G03
LED CURRENT (mA)
400
0
0.8
LED Current
TJ = 125°C
VIN = 1.2V
1.0
0
–50 –25
125
50
250
VIN = 10V
1.2
1932 G02
1932 G01
200
1.4
0.2
0
–50 –25
600
1.6
5
75
50
25
TEMPERATURE (°C)
0
100
125
1932 G07
0
0
2
6
8
4
SHDN PIN VOLTAGE (V)
1093 G09
10
1932 G08
1932f
3
LT1932
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PI FU CTIO S
SW (Pin 1): Switch Pin. This is the collector of the internal
NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI.
RSET (Pin 4): A resistor between this pin and ground
programs the LED current (that flows into the LED pin).
This pin is also used to provide LED dimming.
GND (Pin 2): Ground Pin. Tie this pin directly to local
ground plane.
SHDN (Pin 5): Shutdown Pin. Tie this pin higher than
0.85V to turn on the LT1932; tie below 0.25V to turn it off.
LED (Pin 3): LED Pin. This is the collector of the internal
NPN LED switch. Connect the cathode of the bottom LED
to this pin.
VIN (Pin 6): Input Supply Pin. Bypass this pin with a
capacitor to ground as close to the device as possible.
W
BLOCK DIAGRA
D1
L1
VOUT
VIN
C1
5
SHDN
6
VIN
1
DRIVER
SW
C2
Q1
+
×5
0.04Ω
–
1.2MHz
OSCILLATOR
+
S
Σ
+
3
LED
ILED
Q2
DRIVER
+
Q
–
A2
R
–
A1
+
LED CURRENT
REFERENCE
2
4
GND
ISET
1932 F01
RSET
RSET
Figure 1. LT1932 Block Diagram
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OPERATIO
The LT1932 uses a constant frequency, current mode
control scheme to regulate the output current, ILED.
Operation can be best understood by referring to the
block diagram in Figure 1. At the start of each oscillator
cycle, the SR latch is set, turning on power switch Q1. The
signal at the noninverting input of the PWM comparator
A2 is proportional to the switch current, summed together with a portion of the oscillator ramp. When this
signal reaches the level set by the output of error amplifier
A1, comparator A2 resets the latch and turns off the
power switch. In this manner, A1 sets the correct peak
current level to keep the LED current in regulation. If A1’s
output increases, more current is delivered to the output;
if it decreases, less current is delivered. A1 senses the
LED current in switch Q2 and compares it to the current
reference, which is programmed using resistor RSET. The
RSET pin is regulated to 100mV and the output current,
ILED, is regulated to 225 • ISET. Pulling the RSET pin higher
than 100mV will pull down the output of A1, turning off
power switch Q1 and LED switch Q2.
1932f
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LT1932
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APPLICATIO S I FOR ATIO
Inductor Selection
Several inductors that work well with the LT1932 are listed
in Table 1. Many different sizes and shapes are available.
Consult each manufacturer for more detailed information
and for their entire selection of related parts. As core
losses at 1.2MHz are much lower for ferrite cores that for
the cheaper powdered-iron ones, ferrite core inductors
should be used to obtain the best efficiency. Choose an
inductor that can handle at least 0.5A and ensure that the
inductor has a low DCR (copper wire resistance) to minimize I2R power losses. A 4.7µH or 6.8µH inductor will be
a good choice for most LT1932 designs.
Table 1. Recommended Inductors
PART
L
(µH)
MAX
DCR
(mΩ)
MAX
HEIGHT
(mm)
ELJEA4R7
ELJEA6R8
4.7
6.8
180
250
2.2
2.2
Panasonic
(714) 373-7334
www.panasonic.com
LQH3C4R7M24
LQH3C100M24
4.7
10
260
300
2.2
2.2
Murata
(814) 237-1431
www.murata.com
efficiency by up to 12% over the smaller, thinner ones.
Keep this in mind when choosing an inductor.
The value of inductance also plays an important role in the
overall system efficiency. While a 1µH inductor will have
a lower DCR and a higher current rating than the 6.8µH
version of the same part, lower inductance will result in
higher peak currents in the switch, inductor and diode.
Efficiency will suffer if inductance is too small. Figure 3
shows the efficiency of the Typical Application on the front
page of this data sheet, with several different values of the
same type of inductor (Panasonic ELJEA). The smaller
values give an efficiency 3% to 5% lower than the 6.8µH
value.
85
VENDOR
LB2016B4R7
LB2016B100
4.7
6.8
250
350
1.6
1.6
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
CMD4D06-4R7
CMD4D06-6R8
CLQ4D10-4R7
CLQ4D10-6R8
4.7
6.8
4.7
6.8
216
296
162
195
0.8
0.8
1.2
1.2
Sumida
(847) 956-0666
www.sumida.com
PANASONIC
ELJEA6R8
EFFICIENCY (%)
80
SUMIDA
CLQ4D10-6R8
75
SUMIDA
CMD4D06-6R8
70
65 TAIYO YUDEN
LB2016B6R8
60
TAIYO YUDEN
LB2012B6R8
55
0
5
VIN = 3.6V
4 WHITE LEDs
ALL ARE 10µH
INDUCTORS
10
15
LED CURRENT (mA)
20
1932 F02
Figure 2. Efficiency for Several Different Inductor Types
Inductor Efficiency Considerations
80
6.8µH
EFFICIENCY (%)
Many applications have thickness requirements that restrict component heights to 1mm or 2mm. There are 2mm
tall inductors currently available that provide a low DCR
and low core losses that help provide good overall efficiency. Inductors with a height of 1mm (and less) are
becoming more common, and a few companies have
introduced chip inductors that are not only thin, but have
a very small footprint as well. While these smaller inductors will be a necessity in some designs, their smaller size
gives higher DCR and core losses, resulting in lower
efficiencies. Figure 2 shows efficiency for the Typical
Application circuit on the front page of this data sheet, with
several different inductors. The larger devices improve
85
22µH
4.7µH
75
2.2µH
70
65
VIN = 3.6V
4 WHITE LEDs
PANASONIC ELJEA
INDUCTORS
60
55
0
5
10
15
LED CURRENT (mA)
20
1932 F03
Figure 3. Efficiency for Several Different Inductor Values
1932f
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LT1932
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APPLICATIO S I FOR ATIO
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple
voltage. Because they have an extremely low ESR and are
available in very small packages, multilayer ceramic capacitors are an excellent choice. X5R and X7R type
capacitors are preferred because they retain their capacitance over wider voltage and temperature ranges than
other types such as Y5V or Z5U. A 1µF or 2.2µF output
capacitor is sufficient for most applications. Always use a
capacitor with a sufficient voltage rating. Ceramic capacitors do not need to be derated (do not buy a capacitor with
a rating twice what your application needs). A 16V ceramic capacitor is good to more than 16V, unlike a 16V
tantalum, which may be good to only 8V when used in
certain applications. Low profile ceramic capacitors with
a 1mm maximum thickness are available for designs
having strict height requirements.
Ceramic capacitors also make a good choice for the input
decoupling capacitor, which should be placed as close as
possible to the LT1932. A 2.2µF or 4.7µF input capacitor
is sufficient for most applications. Table 2 shows a list of
several ceramic capacitor manufacturers. Consult the
manufacturers for detailed information on their entire
selection of ceramic parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
turned off (typically less than one-third the time), so a 0.4A
or 0.5A diode will be sufficient for most designs.
Table 3. Recommended Schottky Diodes
PART
VENDOR
MBR0520
MBR0530
MBR0540
ON Semiconductor
(800) 282-9855
www.onsemi.com
ZHCS400
ZHCS500
Zetex
(631) 543-7100
www.zetex.com
Programming LED Current
The LED current is programmed with a single resistor
connected to the RSET pin (see Figure 1). The RSET pin is
internally regulated to 100mV, which sets the current
flowing out of this pin, ISET, equal to 100mV/RSET. The
LT1932 regulates the current into the LED pin, ILED, to 225
times the value of ISET. For the best accuracy, a 1% (or
better) resistor value should be used. Table 4 shows
several typical 1% RSET values. For other LED current
values, use the following equation to choose RSET.
 0.1V 
RSET = 225 • 

 ILED 
Table 4. RSET Resistor Values
ILED (mA)
RSET VALUE
VENDOR
PHONE
URL
40
562Ω
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
30
750Ω
1.13k
Murata
(814) 237-1431
www.murata.com
20
Kemet
(408) 986-0424
www.kemet.com
15
1.50k
10
2.26k
5
4.53k
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, are the ideal choice for LT1932
applications. Table 3 shows several different Schottky
diodes that work well with the LT1932. Make sure that the
diode has a voltage rating greater than the output voltage.
The diode conducts current only when the power switch is
Most white LEDs are driven at maximum currents of 15mA
to 20mA. Some higher power designs will use two parallel
strings of LEDs for greater light output, resulting in 30mA
to 40mA (two strings of 15mA to 20mA) flowing into the
LED pin.
1932f
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LT1932
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APPLICATIO S I FOR ATIO
Open-Circuit Protection
For applications where the string of LEDs can be disconnected or could potentially become an open circuit, a zener
diode can be added across the LEDs to protect the LT1932
(see Figure 4). If the device is turned on without the LEDs
present, no current feedback signal is provided to the LED
pin. The LT1932 will then switch at its maximum duty
cycle, generating an output voltage 10 to 15 times greater
than the input voltage. Without the zener, the SW pin could
see more than 36V and exceed its maximum rating. The
zener voltage should be larger than the maximum forward
voltage of the LED string.
L1
6.8µH
D1
VIN
6
1
VIN
SW
24V
If the RSET pin is used, increasing the duty cycle will
decrease the brightness. Using this method, the LEDs are
dimmed using RSET and turned off completely using
SHDN. If the RSET pin is used to provide PWM dimming,
the approximate value of RPWM should be (where VMAX is
the “high” value of the PWM signal):
V

RPWM = RSET •  MAX – 1
 0.15V 
In addition to providing the widest dimming range, PWM
brightness control also ensures the “purest” white LED
color over the entire dimming range. The true color of a
white LED changes with operating current, and is the
“purest” white at a specific forward current, usually 15mA
or 20mA. If the LED current is less than or more than this
value, the emitted light becomes more blue. For color
LCDs, this often results in a noticeable and undesirable
blue tint to the display.
LT1932
C1
4.7µF
5
SHDN
LED
RSET
GND
4
2
3
C2
1µF
15mA
RSET
1.50k
1932 F04
Figure 4. LED Driver with Open-Circuit Protection
Dimming Using a PWM Signal
PWM brightness control provides the widest dimming
range (greater than 20:1) by pulsing the LEDs on and off
using the control signal. The LEDs operate at either zero or
full current, but their average current changes with the
PWM signal duty cycle. Typically, a 5kHz to 40kHz PWM
signal is used. PWM dimming with the LT1932 can be
accomplished two different ways (see Figure 6). The
SHDN pin can be driven directly or a resistor can be added
to drive the RSET pin.
If the SHDN pin is used, increasing the duty cycle will
increase the LED brightness. Using this method, the LEDs
can be dimmed and turned off completely using the same
control signal. A 0% duty cycle signal will turn off the
LT1932, reducing the total quiescent current to zero.
When a PWM control signal is used to drive the SHDN pin
of the LT1932 (see Figure 6), the LEDs are turned off and
on at the PWM frequency. The current through them
alternates between full current and zero current, so the
average current changes with duty cycle. This ensures
that when the LEDs are on, they can be driven at the
appropriate current to give the purest white light. Figure
5 shows the LED current when a 5kHz PWM dimming
control signal is used with the LT1932. The LED current
waveform cleanly tracks the PWM control signal with no
delays, so the LED brightness varies linearly with the
PWM duty cycle.
VPWM
2V/DIV
ILED
10mA/DIV
50µs/DIV
1932 F05
Figure 5. PWM Dimming Using the SHDN Pin
1932f
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LT1932
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APPLICATIO S I FOR ATIO
Dimming Using a Filtered PWM Signal
While the direct PWM method provides the widest dimming range and the purest white light output, it causes the
LT1932 to enter into Burst Mode® operation. This operation may be undesirable for some systems, as it may
reflect some noise to the input source at the PWM frequency. The solution is to filter the control signal by adding
a 10k resistor and a 0.1µF capacitor as shown in Figure 6,
converting the PWM to a DC level before it reaches the
RSET pin. The 10k resistor minimizes the capacitance seen
by the RSET pin.
Dimming Using a Logic Signal
For applications that need to adjust the LED brightness in
discrete steps, a logic signal can be used as shown in
Figure 6. RMIN sets the minimum LED current value (when
the NMOS is off):
 0.1V 
RMIN = 225 • 

 ILED(MIN) 


0.1V
RINCR = 225 • 

 ILED(INCREASE) 
Dimming Using a DC Voltage
For some applications, the preferred method of brightness
control uses a variable DC voltage to adjust the LED
current. As the DC voltage is increased, current flows
through RADJ into RSET, reducing the current flowing out
LT1932
RSET
SHDN
5
4


VMAX – 0.1V
RADJ = 225 • 

 ILED(MAX) – ILED(MIN) 
Regulating LED Current when VIN > VOUT
The LT1932 contains special circuitry that enables it to
regulate the LED current even when the input voltage is
higher than the output voltage. When VIN is less than VOUT,
the internal NPN LED switch (transistor Q2 in Figure 1) is
saturated to provide a lower power loss. When VIN is
greater than VOUT, the NPN LED switch comes out of
saturation to keep the LED current in regulation.
Soft-Start/Controlling Inrush Current
RINCR sets how much the LED current is increased when
the NMOS is turned on:
LT1932
of the RSET pin, thus reducing the LED current. Choose the
RADJ value as shown below where VMAX is the maximum
DC control voltage, ILED(MAX) is the current programmed
by RSET, and ILED(MIN) is the minimum value of ILED (when
the DC control voltage is at VMAX).
For many applications, it is necessary to minimize the
inrush current at start-up. When first turned on and the
LED current is zero, the LT1932 will initially command the
maximum switch current of 500mA to 600mA, which may
give an inrush current too high for some applications. A
soft-start circuit (Figure 7) can be added to significantly
reduce the start-up current spike. Figure 8 shows that
without soft-start the input current reaches almost 600mA.
Figure 9 shows that when the soft-start circuit is added,
the input current has only a brief 300mA spike, and on
average does not exceed 100mA.
Burst Mode is a registered trademark of Linear Technology Corporation.
LT1932
RSET
4
RPWM
LT1932
RSET
10k
RSET
4
RPWM
PWM
PWM
LT1932
RSET
RSET
4
RADJ
PWM
RINCR
VDC
0.1µF
RSET
LOGIC
SIGNAL
RMIN
1932 F06
PWM
PWM
FILTERED PWM
DC VOLTAGE
LOGIC
Figure 6. Five Methods of LED Dimming
1932f
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LT1932
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APPLICATIO S I FOR ATIO
L1
6.8µH
IIN
D1
VOUT
VIN
C3
0.047µF
C1
4.7µF
6
1
VIN
SW
Q1
2N3904
LT1932
5
SHDN
RSET
LED
C2
1µF
3
R1
1.5k
GND
4
RSET
1.50k
2
1932 F07
SOFT-START
CIRCUIT
Figure 7. Soft-Start Circuit for the LT1932
VOUT
5V/DIV
VOUT
5V/DIV
IIN
200mA/DIV
IIN
200mA/DIV
100µs/DIV
100µs/DIV
1932 F08
Figure 8. Input Current at Start-Up Without Soft-Start
1932 F09
Figure 9. Input Current at Start-Up with Soft-Start
Board Layout Considerations
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To maximize efficiency, switch rise and fall times are made
as short as possible. To prevent radiation and high frequency resonance problems, proper layout of the high
frequency switching path is essential. Minimize the length
and area of all traces connected to the SW pin and always
use a ground plane under the switching regulator to
minimize interplane coupling. The signal path including
the switch, output diode D1 and output capacitor C2,
contains nanosecond rise and fall times and should be
kept as short as possible. In addition, the ground connection for the RSET resistor should be tied directly to the GND
pin and not be shared with any other component, ensuring
a clean, noise-free connection. Recommended component placement is shown in Figure 10.
L1
D1
C2
GND
C1
1
6
VIN
2
5
SHDN
3
4
RSET
DIMMING
CONTROL
1932 F10
Figure 10. Recommended Component Placement
1932f
9
LT1932
U
TYPICAL APPLICATIO S
Efficiency
Single Cell Driver for One White LED
L1
4.7µH
VIN
1V TO 1.5V
80
D1
75
1
VIN
SW
VIN = 1.5V
LT1932
C1
4.7µF
2.5V PWM
DIMMING
CONTROL
5
LED
SHDN
24.9k
RSET
GND
4
2
3
C2
4.7µF
EFFICIENCY (%)
6
15mA
70
VIN = 1.1V
65
60
55
RSET
1.50k
50
0
C1, C2: TAIYO YUDEN JMK212BJ475
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
(408) 573-4150
(631) 543-7100
(814) 237-1431
2.5
1932 TA03a
L1
4.7µH
80
2.5V PWM
DIMMING
CONTROL
SHDN
24.9k
LED
RSET
GND
4
2
3
C2
2.2µF
15mA
EFFICIENCY (%)
SW
LT1932
5
75
VIN = 1.5V
70
VIN = 1.1V
1
VIN
C1
4.7µF
15
Efficiency
D1
6
12.5
1932 TA03b
Single Cell Driver for Two White LEDs
VIN
1V TO 1.5V
5
7.5
10
LED CURRENT (mA)
65
60
55
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN LMK212BJ225
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
50
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA04a
2.5
5
7.5
10
LED CURRENT (mA)
12.5
15
1932 TA04b
1932f
10
LT1932
U
TYPICAL APPLICATIO S
Efficiency
2-Cell Driver for Two White LEDs
L1
4.7µH
VIN
1.8V TO 3V
85
D1
80
1
VIN
SW
VIN = 3V
LT1932
C1
4.7µF
2.5V DC
DIMMING
CONTROL
5
LED
SHDN
60.4k
RSET
GND
4
2
3
C2
2.2µF
EFFICIENCY (%)
6
15mA
75
VIN = 1.8V
70
65
60
RSET
1.50k
55
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN LMK212BJ225
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
5
1932 TA15a
L1
4.7µH
20
1932 TA15b
2-Cell Driver for Three White LEDs
VIN
1.8V TO 3V
10
15
LED CURRENT (mA)
Efficiency
85
D1
80
1
VIN
SW
VIN = 3V
LT1932
C1
4.7µF
2.5V DC
DIMMING
CONTROL
5
SHDN
60.4k
LED
RSET
GND
4
2
3
C2
2.2µF
15mA
EFFICIENCY (%)
6
75
VIN = 1.8V
70
65
60
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK316BJ225
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
55
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA06a
5
10
15
LED CURRENT (mA)
20
1932 TA06b
1932f
11
LT1932
U
TYPICAL APPLICATIO S
2-Cell Driver for Four White LEDs
L1
4.7µH
VIN
1.8V TO 3V
Efficiency
85
D1
80
C1
4.7µF
6
1
VIN
SW
LT1932
PWM
DIMMING
CONTROL
5
SHDN
LED
RSET
GND
4
2
3
C2
1µF
EFFICIENCY (%)
VIN = 3V
75
VIN = 1.8V
70
65
15mA
60
RSET
1.50k
55
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK212BJ105
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
5
1932 TA07a
L1
4.7µH
20
1932 TA07b
2-Cell Driver for Five White LEDs
VIN
2V TO 3V
10
15
LED CURRENT (mA)
Efficiency
85
D1
C1
4.7µF
6
1
VIN
SW
LT1932
PWM
DIMMING
CONTROL
5
SHDN
LED
RSET
GND
4
2
3
C2
1µF
EFFICIENCY (%)
80
75
VIN = 3V
70
VIN = 2V
65
60
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK316BJ105
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
55
15mA
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA05a
5
10
15
LED CURRENT (mA)
20
1932 TA05b
1932f
12
LT1932
U
TYPICAL APPLICATIO S
Li-Ion Driver for Two White LEDs
L1
6.8µH
85
D1
6
1
VIN
SW
LT1932
C1
4.7µF
3.3V PWM
DIMMING
CONTROL
5
RSET
GND
4
2
31.6k
3
LED
SHDN
C2
2.2µF
15mA
EFFICIENCY (%)
VIN
2.7V TO 4.2V
Efficiency
80
VIN = 4.2V
75
VIN = 2.7V
70
65
60
RSET
1.50k
55
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN LMK212BJ225
D1: ZETEX ZHCS400
L1: PANASONIC ELJEA6R8
(408) 573-4150
(408) 573-4150
(631) 543-7100
(714) 373-7334
5
1932 TA08a
L1
6.8µH
Efficiency
85
D1
VIN = 4.2V
6
1
SW
LT1932
C1
4.7µF
3.3V PWM
DIMMING
CONTROL
5
SHDN
31.6k
LED
RSET
GND
4
2
3
C2
2.2µF
15mA
EFFICIENCY (%)
80
VIN
20
1932 TA08b
Li-Ion Driver for Three White LEDs
VIN
2.7V TO 4.2V
10
15
LED CURRENT (mA)
VIN = 2.7V
75
70
65
60
RSET
1.50k
55
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK316BJ225
D1: ZETEX ZHCS400
L1: PANASONIC ELJEA6R8
(408) 573-4150
(408) 573-4150
(631) 543-7100
(714) 373-7334
1932 TA09a
5
10
15
LED CURRENT (mA)
20
1932 TA09b
1932f
13
LT1932
U
TYPICAL APPLICATIO S
Li-Ion Driver for Four White LEDs
L1
6.8µH
C1
4.7µF
85
D1
6
1
VIN
SW
LT1932
PWM
DIMMING
CONTROL
5
LED
SHDN
RSET
GND
4
2
3
C2
1µF
EFFICIENCY (%)
VIN
2.7V TO 4.2V
Efficiency
15mA
80
VIN = 4.2V
75
VIN = 2.7V
70
65
60
RSET
1.50k
55
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK212BJ105
D1: ZETEX ZHCS400
L1: PANASONIC ELJEA6R8
(408) 573-4150
(408) 573-4150
(631) 543-7100
(714) 373-7334
5
1932 TA10a
C1
4.7µF
Efficiency
85
D1
6
1
VIN
SW
LT1932
PWM
DIMMING
CONTROL
5
SHDN
LED
RSET
GND
4
2
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK316BJ105
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
3
C2
1µF
EFFICIENCY (%)
VIN
2.7V TO 4.2V
20
1932 TA10b
Li-Ion Driver for Five White LEDs
L1
4.7µH
10
15
LED CURRENT (mA)
80
VIN = 4.2V
75
VIN = 2.7V
70
65
60
55
15mA
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA11a
5
10
15
LED CURRENT (mA)
20
1932 TA11b
1932f
14
LT1932
U
TYPICAL APPLICATIO S
Li-Ion Driver for Eight White LEDs
L1
4.7µH
VIN
3V TO 4.2V
Efficiency
85
D1
80
1
VIN
SW
VIN = 4.2V
EFFICIENCY (%)
6
LT1932
C1
4.7µF
3.3V DC
DIMMING
CONTROL
5
LED
SHDN
RSET
GND
4
2
80.6k
3
C2
1µF
75
70
VIN = 3V
65
60
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN GMK316BJ105
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
55
15mA
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA13a
5
10
15
LED CURRENT (mA)
20
1932 TA13b
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic SOT-23
(LTC DWG # 05-08-1634)
(LTC DWG # 05-08-1636)
2.80 – 3.10
(.110 – .118)
(NOTE 3)
.20
(.008)
A A2
DATUM ‘A’
L
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
2.60 – 3.00 1.50 – 1.75
(.102 – .118) (.059 – .069)
(NOTE 3)
3. DRAWING NOT TO SCALE
4. DIMENSIONS ARE INCLUSIVE OF PLATING
5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
6. MOLD FLASH SHALL NOT EXCEED .254mm
7. PACKAGE EIAJ REFERENCE IS:
SC-74A (EIAJ) FOR ORIGINAL
JEDEL MO-193 FOR THIN
PIN ONE ID
1.90
(.074)
REF
.09 – .20
(.004 – .008)
(NOTE 2)
A1
SOT-23
(Original)
SOT-23
(ThinSOT)
A
.90 – 1.45
(.035 – .057)
1.00 MAX
(.039 MAX)
A1
.00 – 0.15
(.00 – .006)
.01 – .10
(.0004 – .004)
A2
.90 – 1.30
(.035 – .051)
.80 – .90
(.031 – .035)
L
.35 – .55
(.014 – .021)
.30 – .50 REF
(.012 – .019 REF)
.95
(.037)
REF
.25 – .50
(.010 – .020)
(6PLCS, NOTE 2)
S6 SOT-23 0401
1932f
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LT1932
U
TYPICAL APPLICATIO
Li-Ion Driver for Ten White LEDs
L1
10µH
VIN
2.7V TO 4.2V
Efficiency
80
D1
VIN = 4.2V
75
VIN = 2.7V
1
VIN
SW
LT1932
C1
4.7µF
5
LED
SHDN
RSET
GND
4
2
C2
4.7µF
3
100Ω
RSET
750Ω
EFFICIENCY (%)
6
100Ω
70
65
60
55
30mA
50
0
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK325BJ475
D1: ZETEX ZHCS400
L1: MURATA LQH3C100M24
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
1932 TA16a
5
10
15
20
25
TOTAL LED CURRENT (mA)
1932 TA16b
Li-Ion Driver for Six White LEDs
L1
4.7µH
VIN
2.7V TO 4.2V
Efficiency
85
D1
1
VIN
SW
LT1932
C1
4.7µF
3.3V DC
DIMMING
CONTROL
5
SHDN
RSET
GND
4
2
80.6k
3
LED
C2
1µF
EFFICIENCY (%)
80
6
30
VIN = 4.2V
75
VIN = 2.7V
70
65
60
RSET
1.50k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK316BJ105
D1: ZETEX ZHCS400
L1: MURATA LQH3C4R7M24
55
15mA
(408) 573-4150
(408) 573-4150
(631) 543-7100
(814) 237-1431
0
1932 TA12a
5
10
15
LED CURRENT (mA)
20
1932 TA12b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1615
Micropower DC/DC Converter in 5-Lead ThinSOT
20V at 12mA from 2.5V Input, ThinSOT Package
LT1617
Micropower Inverting DC/DC Converter in 5-Lead ThinSOT
–15V at 12mA from 2.5V Input, ThinSOT Package
LT1618
Constant-Current/Constant-Voltage DC/DC Converter
Drives 20 White LEDs from Li-Ion, MS10 Package
LTC1682
Doubler Charge Pump with Low Noise Linear Regulator
3.3V and 5V Outputs with 60µVRMS Noise, Up to 80mA Output
LT1930
1.4MHz Switching Regulator in 5-Lead ThinSOT
5V at 480mA from 3.3V Input, ThinSOT Package
LT1931
Inverting 1.2MHz Switching Regulator in 5-Lead ThinSOT
– 5V at 350mA from 5V Input, ThinSOT Package
LTC3200
Low Noise Regulated Charge Pump
5V Output with Up to 100mA Output
LTC3201
Ultralow Noise, Charge Pump
100mA, Integrated LP Filter, MSOP8
LTC3202
High Efficiency, Fractional Charge Pump
125mA, Integrated 2-Bit DAC
1932f
16
Linear Technology Corporation
LT/TP 1201 2K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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 LINEAR TECHNOLOGY CORPORATION 2001