LT1932
`Constant-Current DC/DC
`LED Driver in ThinSOT
`
`DESCRIPTIOU
`The LT®1932 is a fixed frequency step-up DC/DC converter
`designed to operate as a constant-current source. Be-
`cause 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.
`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 battery-
`powered 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 1m A 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.
`, LTC and LT are registered trademarks of Linear Technology Corporation.
`ThinSOT is a trademark of Linear Technology Corporation.
`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA02
`
`Kinetic Technologies, Inc.
` Ex. 1004
`
`1932f
`
`1
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`FEATURES
`n Up to 80% Efficiency
`n Inherently Matched LED Current
`n Adjustable Control of LED Current
`n Drives Five White LEDs from 2V
`n Drives Six White LEDs from 2.7V
`n Drives Eight White LEDs from 3V
`n Disconnects LEDs In Shutdown
`n 1.2MHz Fixed Frequency Switching
`n Uses Tiny Ceramic Capacitors
`n Uses Tiny 1mm-Tall Inductors
`n Regulates Current Even When VIN > VOUT
`n Operates with VIN as Low as 1V
`n Low Profile (1mm) ThinSOTTM Package
`APPLICATIO SU
`n Cellular Telephones
`n Handheld Computers
`n Digital Cameras
`n Portable MP3 Players
`n Pagers
`
`TYPICAL APPLICATIOU
`Li-Ion Driver for Four White LEDs
`
`VIN
`2.7V TO 4.2V
`
`L1
`6.8µH
`
`D1
`
`C1
`4.7µF
`
`PWM
`DIMMING
`CONTROL
`
`5
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`15mA
`
`SHDN
`RSET
`4
`RSET
`1.50k
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN EMK212BJ105
`D1:ZETEX ZHCS400
`L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8
`
`C2
`1µF
`
`1932 TA01
`
`

`
`LT1932
`
`ABSOLUTE AXI U RATI GS
`W
`W W
`U
`(Note 1)
`VIN Voltage ............................................................. 10V
`SHDN Voltage ......................................................... 10V
`SW Voltage ............................................................. 36V
`LED Voltage ............................................................. 36V
`RSET Voltage ............................................................. 1V
`Junction Temperature.......................................... 125(cid:176) C
`Operating Temperature Range (Note 2) .. –40(cid:176) C to 85(cid:176) C
`Storage Temperature Range ................. –65(cid:176) C to 150(cid:176) C
`Lead Temperature (Soldering, 10 sec).................. 300(cid:176) C
`
`PACKAGE/ORDER I FOR ATIO
`U
`U
`W
`
`TOP VIEW
`
`SW 1
` GND 2
`LED 3
`
`6 VIN
`5 SHDN
`4 RSET
`
`S6 PACKAGE
`6-LEAD PLASTIC SOT-23
`TJMAX = 125(cid:176) C, q JA = 250(cid:176) C/ W
`
`ORDER PART
`NUMBER
`
`LT1932ES6
`
`S6 PART MARKING
`LTST
`
`Consult LTC Marketing for parts specified with wider operating temperature ranges.
`
`ELECTRICAL CHARACTERISTICS
`The l denotes specifications that apply over the full operating temperature
`range, otherwise specifications are at TA = 25(cid:176) C. VIN = 1.2V, VSHDN = 1.2V, unless otherwise noted.
`PARAMETER
`CONDITIONS
`Minimum Input Voltage
`Quiescent Current
`
`RSET Pin Voltage
`LED Pin Voltage
`LED Pin Current
`
`LED Pin Current Temperature Coefficient
`Switching Frequency
`Maximum Switch Duty Cycle
`Switch Current Limit
`Switch VCESAT
`SHDN Pin Current
`
`Start-Up Threshold (SHDN Pin)
`Shutdown Threshold (SHDN Pin)
`Switch Leakage Current
`
`VRSET = 0.2V
`VSHDN = 0V
`RSET = 1.50k
`RSET = 1.50k, VIN < VOUT (Figure 1)
`RSET = 562W
`, VIN = 1.5V
`RSET = 750W
`, VIN = 1.2V
`RSET = 1.50k, VIN = 1.2V
`RSET = 4.53k, VIN = 1.2V
`ILED = 15mA
`VIN = 1V
`
`ISW = 300mA
`VSHDN = 0V
`VSHDN = 2V
`
`MIN
`
`TYP
`
`1.2
`0.1
`100
`120
`38
`30
`15
`5
`–0.02
`1.2
`95
`550
`150
`0
`15
`
`33
`25
`12.5
`
`0.8
`90
`400
`
`0.85
`
`l
`
`MAX
`1
`1.6
`1.0
`
`180
`45
`36
`17.5
`
`1.6
`
`780
`200
`0.1
`30
`
`0.25
`5
`
`UNITS
`V
`mA
`m A
`mV
`mV
`mA
`mA
`mA
`mA
`mA/(cid:176) C
`MHz
`%
`mA
`mV
`m A
`m A
`V
`V
`m A
`
`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(cid:176) C to 70(cid:176) C.
`Specifications over the – 40(cid:176) C to 85(cid:176) C operating temperature range are
`assured by design, characterization and correlation with statistical process
`controls.
`
`2
`
`1932f
`
`

`
`LT1932
`
`TYPICAL PERFOR A CE CHARACTERISTICS
`UW
`
`Switch Saturation Voltage (VCESAT)
`
`Switch Current Limit
`
`Switching Frequency
`
`VIN = 10V
`
`VIN = 1.2V
`
`2.0
`1.8
`
`1.6
`
`1.4
`1.2
`
`1.0
`
`0.8
`
`0.6
`
`0.4
`0.2
`
`SWITCHING FREQUENCY (MHz)
`
`VIN = 1.2V
`
`VIN = 10V
`
`700
`
`600
`
`500
`
`400
`
`300
`
`200
`
`100
`
`PEAK CURRENT (mA)
`
`TJ = 125°C
`TJ = 25°C
`
`TJ = –50°C
`
`100
`
`200
`400
`300
`SWITCH CURRENT (mA)
`
`500
`
`600
`
`0
`–50
`
`–25
`
`50
`25
`75
`0
`TEMPERATURE (°C)
`
`100
`
`125
`
`0
`–50
`
`–25
`
`1932 G01
`
`1932 G02
`
`50
`25
`0
`75
`TEMPERATURE (°C)
`
`100
`
`125
`
`1932 G03
`
`400
`
`350
`
`300
`
`250
`
`200
`
`150
`
`100
`
`50
`
`SWITCH SATURATION VOLTAGE (mV)
`
`0
`
`0
`
`LED Pin Voltage
`
`LED Current
`
`LED Current
`
`400
`
`350
`
`300
`
`250
`
`200
`
`150
`
`TJ = 125°C
`
`TJ = 25°C
`
`50
`
`45
`
`40
`
`35
`
`30
`
`25
`
`20
`
`RSET = 562Ω
`
`RSET = 750Ω
`
`50
`
`45
`
`40
`
`35
`
`30
`
`25
`
`20
`
`RSET = 562Ω
`
`RSET = 750Ω
`
`RSET = 1.50k
`
`RSET = 4.53k
`
`0
`
`2
`
`4
`6
`INPUT VOLTAGE (V)
`
`8
`
`10
`
`15
`
`10
`
`5 0
`
`LED CURRENT (mA)
`
`RSET = 1.50k
`
`RSET = 4.53k
`
`–25
`
`75
`0
`50
`25
`TEMPERATURE (°C)
`
`100
`
`125
`
`15
`
`10
`
`5 0
`
`–50
`
`LED CURRENT (mA)
`
`TJ = –50°C
`
`5
`
`10
`
`15
`25
`20
`LED CURRENT (mA)
`
`30
`
`35
`
`40
`
`100
`
`50
`
`0
`
`0
`
`LED PIN VOLTAGE (mV)
`
`Quiescent Current
`
`SHDN Pin Current
`
`Switching Waveforms
`
`1932 G04
`
`1932 G05
`
`1932 G06
`
`1093 G09
`
`1932f
`
`3
`
`TJ = –50°C
`
`TJ = 25°C
`
`TJ = 125°C
`
`VSW
`10V/DIV
`
`IL1
`200mA/DIV
`VOUT
`20mV/DIV
`AC COUPLED
`ILED
`10mA/DIV
`
`0.5m s/DIV
`
`VIN = 3V
`4 WHITE LEDs
`ILED = 15mA
`CIRCUIT ON FIRST PAGE
`OF THIS DATA SHEET
`
`0
`
`2
`
`6
`4
`SHDN PIN VOLTAGE (V)
`
`8
`
`10
`
`1932 G08
`
`50
`
`45
`
`40
`
`35
`
`30
`
`25
`
`20
`
`15
`
`10
`
`5 0
`
`SHDN PIN CURRENT
`
`VIN = 10V
`
`VIN = 1.2V
`
`2.00
`
`1.75
`
`1.50
`
`1.25
`
`1.00
`
`0.75
`
`0.50
`
`0.25
`
`QUIESCENT CURRENT (mA)
`
`0
`–50
`
`–25
`
`75
`0
`50
`25
`TEMPERATURE (°C)
`
`100
`
`125
`
`1932 G07
`
`

`
`LT1932
`
`UUPI FU CTIO S
`U
`SW (Pin 1): Switch Pin. This is the collector of the internal
`NPN power switch. Minimize the metal trace area con-
`nected to this pin to minimize EMI.
`GND (Pin 2): Ground Pin. Tie this pin directly to local
`ground plane.
`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.
`
`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.
`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.
`VIN (Pin 6): Input Supply Pin. Bypass this pin with a
`capacitor to ground as close to the device as possible.
`
`VOUT
`
`C2
`
`LED
`
`3
`
`ILED
`
`DRIVER
`
`Q2
`
`– +
`
`A1
`
`LED CURRENT
`REFERENCE
`
`ISET
`
`4
`
`RSET
`
`RSET
`
`1932 F01
`
`L1
`
`D1
`
`S· 5
`
`+
`
`+
`
`–+
`
`A2
`
`SW
`
`1
`
`Q1
`
`–+
`
`0.04Ω
`
`1.2MHz
`OSCILLATOR
`
`2
`
`GND
`
`Figure 1. LT1932 Block Diagram
`
`BLOCK DIAGRA W
`
`VIN
`
`C1
`
`SHDN
`
`5
`
`VIN
`
`6
`
`DRIVER
`
`Q
`
`S
`
`R
`
`OPERATIOU
`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 to-
`gether 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
`
`4
`
`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
`
`

`
`LT1932
`
`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 1m H inductor will have
`a lower DCR and a higher current rating than the 6.8m H
`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 6.8m H
`value.
`
`SUMIDA
`CLQ4D10-6R8
`
`PANASONIC
`ELJEA6R8
`
`SUMIDA
`CMD4D06-6R8
`
`TAIYO YUDEN
`LB2016B6R8
`
`TAIYO YUDEN
`LB2012B6R8
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`VIN = 3.6V
`4 WHITE LEDs
`ALL ARE 10µH
`INDUCTORS
`15
`
`20
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`Figure 2. Efficiency for Several Different Inductor Types
`
`1932 F02
`
`6.8µH
`
`2.2µH
`
`22µH
`4.7µH
`
`VIN = 3.6V
`4 WHITE LEDs
`PANASONIC ELJEA
`INDUCTORS
`15
`
`20
`
`10
`LED CURRENT (mA)
`
`0
`
`5
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`Figure 3. Efficiency for Several Different Inductor Values
`
`1932 F03
`
`1932f
`
`5
`
`APPLICATIO S I FOR ATIOWU U U
`
`
`
`
`
`
`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 mini-
`mize I2R power losses. A 4.7m H or 6.8m H inductor will be
`a good choice for most LT1932 designs.
`Table 1. Recommended Inductors
`MAX
`DCR
`(mW
`)
`180
`250
`
`PART
`ELJEA4R7
`ELJEA6R8
`
`L
`(m H)
`4.7
`6.8
`
`MAX
`HEIGHT
`(mm)
`2.2
`2.2
`
`VENDOR
`Panasonic
`(714) 373-7334
`www.panasonic.com
`Murata
`(814) 237-1431
`www.murata.com
`Taiyo Yuden
`(408) 573-4150
`www.t-yuden.com
`Sumida
`(847) 956-0666
`www.sumida.com
`
`LQH3C4R7M24
`LQH3C100M24
`
`LB2016B4R7
`LB2016B100
`
`CMD4D06-4R7
`CMD4D06-6R8
`CLQ4D10-4R7
`CLQ4D10-6R8
`
`4.7
`10
`
`4.7
`6.8
`
`4.7
`6.8
`4.7
`6.8
`
`260
`300
`
`250
`350
`
`216
`296
`162
`195
`
`2.2
`2.2
`
`1.6
`1.6
`
`0.8
`0.8
`1.2
`1.2
`
`Inductor Efficiency Considerations
`Many applications have thickness requirements that re-
`strict 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 effi-
`ciency. 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 induc-
`tors 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
`
`

`
`LT1932
`
`
`
`
`
`APPLICATIO S I FOR ATIOWU U U
`
`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 ca-
`pacitors are an excellent choice. X5R and X7R type
`capacitors are preferred because they retain their capaci-
`tance over wider voltage and temperature ranges than
`other types such as Y5V or Z5U. A 1m F or 2.2m F output
`capacitor is sufficient for most applications. Always use a
`capacitor with a sufficient voltage rating. Ceramic capaci-
`tors do not need to be derated (do not buy a capacitor with
`a rating twice what your application needs). A 16V ce-
`ramic 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 2.2m F or 4.7m F 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
`VENDOR
`PHONE
`URL
`Taiyo Yuden
`(408) 573-4150
`www.t-yuden.com
`Murata
`(814) 237-1431
`www.murata.com
`Kemet
`(408) 986-0424
`www.kemet.com
`
`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
`
`6
`
`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
`ON Semiconductor
`MBR0530
`(800) 282-9855
`MBR0540
`www.onsemi.com
`ZHCS400
`Zetex
`ZHCS500
`(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.
`(cid:230)Ł(cid:231) (cid:246)ł(cid:247)
`
`225
`
`•
`
`R
`SET
`
`=
`
`0 1.
`
`V
`I
`LED
`Table 4. RSET Resistor Values
`ILED (mA)
`40
`30
`20
`15
`10
`5
`
`RSET VALUE
`562W
`750W
`1.13k
`1.50k
`2.26k
`4.53k
`
`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
`
`

`
`
`
`
`
`
`APPLICATIO S I FOR ATIOWU U U
`Open-Circuit Protection
`For applications where the string of LEDs can be discon-
`nected 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.
`
`VIN
`
`L1
`6.8µH
`
`D1
`
`C1
`4.7µF
`
`5
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`15mA
`
`SHDN
`RSET
`4
`RSET
`1.50k
`
`24V
`
`C2
`1µF
`
`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.
`
`LT1932
`
`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):
`
`R
`PWM
`
`=
`
`R
`SET
`
`•
`
`V
`MAX
`
`.0 15
`V
`
`(cid:230)Ł(cid:231) (cid:246)ł(cid:247)
`
`–
`
`1
`
`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.
`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
`
`50m s/DIV
`
`1932 F05
`
`Figure 5. PWM Dimming Using the SHDN Pin
`
`1932f
`
`7
`
`

`
`LT1932
`
`
`
`
`APPLICATIO S I FOR ATIOWU U U
`
`Dimming Using a Filtered PWM Signal
`While the direct PWM method provides the widest dim-
`ming range and the purest white light output, it causes the
`LT1932 to enter into Burst Mode® operation. This opera-
`tion may be undesirable for some systems, as it may
`reflect some noise to the input source at the PWM fre-
`quency. The solution is to filter the control signal by adding
`a 10k resistor and a 0.1m F 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):
`
`R
`MIN
`
`=
`
`225
`
`•
`
`(cid:230)Ł(cid:231) (cid:246)ł(cid:247)
`
`V
`0 1.
`
`(
`)
`LED MIN
`
`I
`
`RINCR sets how much the LED current is increased when
`the NMOS is turned on:
`
`R
`INCR
`
`=
`
`225
`
`•
`
`(cid:230)Ł(cid:231) (cid:246)ł(cid:247)
`
`V
`0 1.
`
`(
`)
`LED INCREASE
`
`I
`
`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
`
`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).
`
`R
`
`ADJ
`
`=
`
`225
`
`•
`
`(cid:230)Ł(cid:231) (cid:246)ł(cid:247)
`
`V
`
`0 1– .
`I
`–
`(
`)
`LED MIN
`
`V
`MAX
`I
`(
`)
`LED MAX
`
`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
`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
`
`PWM
`
`LT1932
`RSET
`4
`
`PWM
`
`10k
`
`RPWM
`
`PWM
`
`LT1932
`RSET
`4
`
`RADJ
`
`VDC
`
`RSET
`
`0.1µF
`
`RSET
`
`RSET
`
`PWM
`
`FILTERED PWM
`
`DC VOLTAGE
`
`LOGIC
`
`Figure 6. Five Methods of LED Dimming
`
`LT1932
`RSET
`4
`
`RINCR
`
`RMIN
`
`LOGIC
`SIGNAL
`
`1932 F06
`
`1932f
`
`LT1932
`SHDN
`5
`
`PWM
`
`8
`
`

`
`LT1932
`
`
`
`APPLICATIO S I FOR ATIOWU U U
`
`
`
`
`
`IIN
`
`VIN
`
`L1
`6.8µH
`
`D1
`
`C1
`4.7µF
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`5
`
`SHDN
`RSET
`4
`RSET
`1.50k
`
`Q1
`2N3904
`
`VOUT
`
`C3
`0.047µF
`
`R1
`1.5k
`
`SOFT-START
`CIRCUIT
`Figure 7. Soft-Start Circuit for the LT1932
`
`C2
`1µF
`
`1932 F07
`
`1932f
`
`9
`
`VOUT
`5V/DIV
`
`IIN
`200mA/DIV
`
`VOUT
`5V/DIV
`
`IIN
`200mA/DIV
`
`100m s/DIV
`
`1932 F08
`
`100m s/DIV
`
`1932 F09
`
`Figure 8. Input Current at Start-Up Without Soft-Start
`
`Figure 9. Input Current at Start-Up with Soft-Start
`
`VIN
`
`SHDN
`
`DIMMING
`CONTROL
`
`1932 F10
`
`L1
`
`C1
`
`6 5 4
`
`RSET
`
`1 2 3
`
`D1
`
`C2
`
`GND
`
`Figure 10. Recommended Component Placement
`
`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 fre-
`quency 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 connec-
`tion 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 compo-
`nent placement is shown in Figure 10.
`
`

`
`LT1932
`
`TYPICAL APPLICATIO SU
`
`Single Cell Driver for One White LED
`
`Efficiency
`
`VIN = 1.5V
`
`VIN = 1.1V
`
`0
`
`2.5
`
`5
`7.5
`10
`LED CURRENT (mA)
`
`12.5
`
`15
`
`1932 TA03b
`
`Efficiency
`
`VIN = 1.5V
`
`VIN = 1.1V
`
`
`
`0
`
`2.5
`
`5
`7.5
`10
`LED CURRENT (mA)
`
`12.5
`
`15
`
`1932 TA04b
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`50
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`50
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`C1, C2: TAIYO YUDEN JMK212BJ475
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`1932 TA03a
`
`Single Cell Driver for Two White LEDs
`
`VIN
`1V TO 1.5V
`
`C1
`4.7µF
`
`5
`
`L1
`4.7µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`24.9k
`
`2.5V PWM
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`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
`
`C2
`2.2µF
`
`1932 TA04a
`
`10
`
`1932f
`
`VIN
`1V TO 1.5V
`
`C1
`4.7µF
`
`5
`
`L1
`4.7µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`C2
`4.7µF
`
`24.9k
`
`2.5V PWM
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`

`
`TYPICAL APPLICATIO SU
`
`2-Cell Driver for Two White LEDs
`
`Efficiency
`
`LT1932
`
`1932f
`
`11
`
`VIN = 3V
`
`VIN = 1.8V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA15b
`
`Efficiency
`
`VIN = 3V
`
`VIN = 1.8V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA06b
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`VIN
`1.8V TO 3V
`
`C1
`4.7µF
`
`5
`
`L1
`4.7µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`C2
`2.2µF
`
`60.4k
`
`2.5V DC
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`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
`
`1932 TA15a
`
`2-Cell Driver for Three White LEDs
`
`VIN
`1.8V TO 3V
`
`C1
`4.7µF
`
`5
`
`L1
`4.7µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`60.4k
`
`2.5V DC
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN EMK316BJ225
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`(408) 573-4150
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`C2
`2.2µF
`
`1932 TA06a
`
`

`
`LT1932
`
`TYPICAL APPLICATIO SU
`
`2-Cell Driver for Four White LEDs
`
`Efficiency
`
`VIN = 3V
`
`VIN = 1.8V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA07b
`
`Efficiency
`
`VIN = 3V
`
`VIN = 2V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA05b
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`VIN
`1.8V TO 3V
`
`L1
`4.7µH
`
`D1
`
`C1
`4.7µF
`
`PWM
`DIMMING
`CONTROL
`
`5
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`15mA
`
`SHDN
`RSET
`4
`RSET
`1.50k
`
`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
`
`C2
`1µF
`
`1932 TA07a
`
`2-Cell Driver for Five White LEDs
`
`L1
`4.7µH
`
`D1
`
`VIN
`2V TO 3V
`
`C1
`4.7µF
`
`PWM
`DIMMING
`CONTROL
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`5
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`RSET
`1.50k
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN TMK316BJ105
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`15mA
`
`(408) 573-4150
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`C2
`1µF
`
`1932 TA05a
`
`12
`
`1932f
`
`

`
`TYPICAL APPLICATIO SU
`
`Li-Ion Driver for Two White LEDs
`
`Efficiency
`
`LT1932
`
`1932f
`
`13
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA08b
`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA09b
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`C2
`2.2µF
`
`1932 TA08a
`
`C2
`2.2µF
`
`1932 TA09a
`
`VIN
`2.7V TO 4.2V
`
`C1
`4.7µF
`
`5
`
`L1
`6.8µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`31.6k
`
`3.3V PWM
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`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
`
`VIN
`2.7V TO 4.2V
`
`Li-Ion Driver for Three White LEDs
`
`L1
`6.8µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`15mA
`
`C1
`4.7µF
`
`5
`
`31.6k
`
`3.3V PWM
`DIMMING
`CONTROL
`
`RSET
`1.50k
`
`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
`
`

`
`1932f
`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA10b
`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA11b
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`LT1932
`
`TYPICAL APPLICATIO SU
`
`Li-Ion Driver for Four White LEDs
`L1
`6.8µH
`
`D1
`
`VIN
`2.7V TO 4.2V
`
`C1
`4.7µF
`
`PWM
`DIMMING
`CONTROL
`
`5
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`15mA
`
`SHDN
`RSET
`4
`RSET
`1.50k
`
`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
`
`Li-Ion Driver for Five White LEDs
`
`L1
`4.7µH
`
`D1
`
`C1
`4.7µF
`
`PWM
`DIMMING
`CONTROL
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`5
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`RSET
`1.50k
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN TMK316BJ105
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`15mA
`
`(408) 573-4150
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`C2
`1µF
`
`1932 TA10a
`
`C2
`1µF
`
`1932 TA11a
`
`VIN
`2.7V TO 4.2V
`
`14
`
`

`
`TYPICAL APPLICATIO SU
`
`Li-Ion Driver for Eight White LEDs
`
`Efficiency
`
`LT1932
`
`VIN = 4.2V
`
`VIN = 3V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA13b
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`C2
`1µF
`
`1932 TA13a
`
`VIN
`3V TO 4.2V
`
`C1
`4.7µF
`
`5
`
`80.6k
`
`3.3V DC
`DIMMING
`CONTROL
`
`L1
`4.7µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`RSET
`1.50k
`
`15mA
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN GMK316BJ105
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`(408) 573-4150
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`PACKAGE DESCRIPTIO
`U
`
`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)
`
`2.60 – 3.00
`(.102 – .118)
`
`1.50 – 1.75
`(.059 – .069)
`(NOTE 3)
`
`PIN ONE ID
`
`.95
`(.037)
`REF
`
`.25 – .50
`(.010 – .020)
`(6PLCS, NOTE 2)
`
`S6 SOT-23 0401
`
`1.90
`(.074)
`REF
`
`A1
`
`SOT-23
`(ThinSOT)
`1.00 MAX
`(.039 MAX)
`.01 – .10
`(.0004 – .004)
`.80 – .90
`(.031 – .035)
`.30 – .50 REF
`(.012 – .019 REF)
`
`SOT-23
`(Original)
`.90 – 1.45
`(.035 – .057)
`.00 – 0.15
`(.00 – .006)
`.90 – 1.30
`(.035 – .051)
`.35 – .55
`(.014 – .021)
`
`A A
`
`1
`
`A2
`
`L
`
`A A2
`
`.20
`(.008)
`
`DATUM ‘A’
`
`L
`
`.09 – .20
`(.004 – .008)
`(NOTE 2)
`
`2. DIMENSIONS ARE IN
`
`NOTE:
`1. CONTROLLING DIMENSION: MILLIMETERS
`MILLIMETERS
`(INCHES)
`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
`
`Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
`However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
`tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
`
`1932f
`
`15
`
`

`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`15
`20
`TOTAL LED CURRENT (mA)
`
`25
`
`30
`
`1932 TA16b
`
`Efficiency
`
`VIN = 4.2V
`
`VIN = 2.7V
`
`0
`
`5
`
`10
`LED CURRENT (mA)
`
`15
`
`20
`
`1932 TA12b
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`50
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`EFFICIENCY (%)
`
`EFFICIENCY (%)
`
`COMMENTS
`20V at 12mA from 2.5V Input, ThinSOT Package
`–15V at 12mA from 2.5V Input, ThinSOT Package
`Drives 20 White LEDs from Li-Ion, MS10 Package
`3.3V and 5V Outputs with 60m VRMS Noise, Up to 80mA Output
`5V at 480mA from 3.3V Input, ThinSOT Package
`–5V at 350mA from 5V Input, ThinSOT Package
`5V Output with Up to 100mA Output
`100mA, Integrated LP Filter, MSOP8
`125mA, Integrated 2-Bit DAC
`
` LT/TP 1201 2K • PRINTED IN USA
`
`1932f
`
`ª LINEAR TECHNOLOGY CORPORATION 2001
`
`LT1932
`
`TYPICAL APPLICATIO
`U
`Li-Ion Driver for Ten White LEDs
`
`VIN
`2.7V TO 4.2V
`
`L1
`10µH
`
`D1
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`3
`
`LED
`GND
`2
`
`SHDN
`RSET
`4
`RSET
`750Ω
`
`C1
`4.7µF
`
`5
`
`100Ω
`
`100Ω
`
`30mA
`
`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
`
`Li-Ion Driver for Six White LEDs
`
`L1
`4.7µH
`
`D1
`
`VIN
`2.7V TO 4.2V
`
`6
`VIN
`
`1
`SW
`
`LT1932
`
`C2
`4.7µF
`
`1932 TA16a
`
`C1
`4.7µF
`
`5
`
`80.6k
`
`3.3V DC
`DIMMING
`CONTROL
`
`SHDN
`RSET
`4
`
`3
`
`LED
`GND
`2
`
`C2
`1µF
`
`RSET
`1.50k
`
`15mA
`
`C1: TAIYO YUDEN JMK212BJ475
`C2: TAIYO YUDEN TMK316BJ105
`D1: ZETEX ZHCS400
`L1: MURATA LQH3C4R7M24
`
`(408) 573-4150
`(408) 573-4150
`(631) 543-7100
`(814) 237-1431
`
`1932 TA12a
`
`RELATED PARTS
`PART NUMBER
`DESCRIPTION
`LT1615
`Micropower DC/DC Converter in 5-Lead ThinSOT
`LT1617
`Micropower Inverting DC/DC Converter in 5-Lead ThinSOT
`LT1618
`Constant-Current/Constant-Voltage DC/DC Converter
`LTC1682
`Doubler Charge Pump with Low Noise Linear Regulator
`LT1930
`1.4MHz Switching Regulator in 5-Lead ThinSOT
`LT1931
`Inverting 1.2MHz Switching Regulator in 5-Lead ThinSOT
`LTC3200
`Low Noise Regulated Charge Pump
`LTC3201
`Ultralow Noise, Charge Pump
`LTC3202
`High Efficiency, Fractional Charge Pump
`
`16
`
`Linear Technology Corporation
`1630 McCarthy Blvd., Milpitas, CA 95035-7417
`(408) 432-1900 l FAX: (408) 434-0507 l www.linear.com