View LT1932_28473.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Final Electrical Specifications
LT1932 Constant-Current DC/DC LED Driver in ThinSOT
July 2001
FEATURES
s s s s s s s s s s s s s
DESCRIPTIO
Up to 80% Efficiency Inherently Matched LED Current Drives Five White LEDs from 2V Drives Six White LEDs from 2.7V Drives Eight White LEDs from 3V Precise, Adjustable Control of LED Current 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
The LT(R)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. 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 1A 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.
APPLICATIO S
s s s s s
Cellular Telephones Handheld Computers Digital Cameras Portable MP3 Players Pagers
TYPICAL APPLICATIO
L1 6.8H
Li-Ion Driver for Four White LEDs
D1 85 80 75 70 65 60 55 0
1932 TA01
VIN 2.7V TO 4.2V
C1 4.7F
6 VIN LT1932 5
1 SW 3 15mA
PWM DIMMING CONTROL
SHDN RSET 4 RSET 1.50k
LED GND 2
C2 1F
EFFICIENCY (%)
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1:ZETEX ZHCS400 L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8
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.
U
Efficiency
VIN = 4.2V VIN = 2.7V 5 10 15 LED CURRENT (mA) 20
1932 TA02
U
U
1
LT1932
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW SW 1 GND 2 LED 3 6 VIN 5 SHDN 4 RSET
VIN Voltage ............................................................. 10V SHDN Voltage ......................................................... 10V SW Voltage ............................................................. 36V LED Voltage ............................................................. 36V RSET Voltage ............................................................. 1V Junction Temperature .......................................... 125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT1932ES6 S6 PART MARKING LTST
S6 PACKAGE 6-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 250C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.2V, VSHDN = 1.2V, unless otherwise noted.
PARAMETER Minimum Input Voltage Quiescent Current RSET Pin Voltage LED Pin Voltage LED Pin Current VRSET = 0.2V VSHDN = 0V RSET = 1.50k RSET = 1.50k, VIN < VOUT (Figure 1) RSET = 562, VIN = 1.5V RSET = 750, VIN = 1.2V RSET = 1.50k, VIN = 1.2V RSET = 4.53k, VIN = 1.2V ILED = 15mA VIN = 1V
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP 1.2 0.1 100 120
MAX 1 1.6 1.0 180 42 34 17.5
UNITS V mA A mV mV mA mA mA mA mA/C MHz % mA mV A A V V A
34 26 12.5
38 30 15 5 - 0.02 1.2 95 550 150 0 15
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
0.8 90 400
1.6 780 200 0.1 30 0.25
ISW = 300mA VSHDN = 0V VSHDN = 2V 0.85 Switch Off, VSW = 5V
0.01
5
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 0C to 70C. Specifications over the - 40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
2
U
W
U
U
WW
W
LT1932 TYPICAL PERFOR A CE CHARACTERISTICS
Switch Saturation Voltage (VCESAT)
400 700
SWITCHING FREQUENCY (MHz)
SWITCH SATURATION VOLTAGE (mV)
350
PEAK CURRENT (mA)
300 250 200 150 100 50 0 0 100
TJ = 125C TJ = 25C 500 400 300 200 100
TJ = -50C
400 500 300 SWITCH CURRENT (mA)
200
LED Pin Voltage
400 350
LED PIN VOLTAGE (mV)
300
LED CURRENT (mA)
250 TJ = 125C 200 150 TJ = -50C 100 50 0 0 5 10 15 20 25 30 LED CURRENT (mA) 35 40 TJ = 25C
30 25 20 15 10 5 0 - 50 - 25 0
RSET = 750
LED CURRENT (mA)
Quiescent Current
2.00 1.75
QUIESCENT CURRENT (mA)
1.50 1.25 1.00 0.75 0.50 0.25 0 - 50 - 25 0
SHDN PIN CURRENT
VIN = 10V
VIN = 1.2V
75 50 25 TEMPERATURE (C)
UW
1932 G01
Switch Current Limit
2.0
VIN = 1.2V VIN = 10V
Switching Frequency
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 VIN = 10V VIN = 1.2V
600
600
0 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
1932 G02
1932 G03
LED Current
50 45 40 35 RSET = 562 50 45 40 35 30 25 20 15 10 RSET = 4.53k 5 0 75 50 25 TEMPERATURE (C) 100 125
LED Current
RSET = 562
RSET = 750
RSET = 1.50k
RSET = 1.50k
RSET = 4.53k
0
2
4 6 INPUT VOLTAGE (V)
8
10
1932 G06
1932 G04
1932 G05
SHDN Pin Current
50 45 40 35 30 25 20 15 10 5 100 125 0 0 2 6 8 4 SHDN PIN VOLTAGE (V) 10
1932 G08
Switching Waveforms
TJ = -50C
VSW 10V/DIV IL1 200mA/DIV VOUT 20mV/DIV AC COUPLED ILED 10mA/DIV VIN = 3V 0.5s/DIV 4 WHITE LEDs ILED = 15mA CIRCUIT ON FIRST PAGE OF THIS DATA SHEET
1093 G09
TJ = 25C
TJ = 125C
1932 G07
3
LT1932
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. 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.
BLOCK DIAGRA
VIN C1
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
4
W
U
U
U
U
L1 SHDN VIN SW
D1 VOUT 1 Q1 C2
5
6 DRIVER
+
0.04 x5
-
1.2MHz OSCILLATOR S Q R A2
+ +
+
DRIVER Q2
3
LED ILED
- -
A1
+
LED CURRENT REFERENCE
2
GND
4 ISET
1932 F01
RSET RSET
Figure 1. LT1932 Block Diagram
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.
LT1932
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 4.7H or 6.8H inductor will be a good choice for most LT1932 designs.
Table 1. Recommended Inductors
L (H) 4.7 6.8 4.7 10 4.7 6.8 4.7 6.8 4.7 6.8 MAX DCR (m) 180 250 260 300 250 350 216 296 162 195 MAX HEIGHT (mm) 2.2 2.2 2.2 2.2 2.0 2.0 0.8 0.8 1.2 1.2
PART ELJEA4R7 ELJEA6R8 LQH3C4R7M24 LQH3C100M24 LB2016B4R7 LB2016B100 CMD4D06-4R7 CMD4D06-6R8 CLQ4D10-4R7 CLQ4D10-6R8
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
EFFICIENCY (%)
Inductor Efficiency Considerations 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
EFFICIENCY (%)
U
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 1H inductor will have a lower DCR and a higher current rating than the 6.8H 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 6.8H value.
85 80 75 70 65 TAIYO YUDEN LB2016B6R8 60 TAIYO YUDEN LB2012B6R8 55 0 5 SUMIDA CLQ4D10-6R8 SUMIDA CMD4D06-6R8 PANASONIC ELJEA6R8 VIN = 3.6V 4 WHITE LEDs ALL ARE 10H INDUCTORS 20
1932 F02
W
UU
10 15 LED CURRENT (mA)
Figure 2. Efficiency for Several Different Inductor Types
85 80 6.8H 75 70 65 60 55 0 5 VIN = 3.6V 4 WHITE LEDs PANASONIC ELJEA INDUCTORS 10 15 LED CURRENT (mA) 20
1932 F03
22H 4.7H
2.2H
Figure 3. Efficiency for Several Different Inductor Values
5
LT1932
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 1F or 2.2F 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 2.2F or 4.7F 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 Taiyo Yuden Murata Kemet PHONE (408) 573-4150 (814) 237-1431 (408) 986-0424 URL www.t-yuden.com www.murata.com 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
U
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 MBR0520 MBR0530 MBR0540 ZHCS400 ZHCS500 VENDOR ON Semiconductor (800) 282-9855 www.onsemi.com Zetex (631) 543-7100 www.zetex.com
W
UU
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) 40 30 20 15 10 5 RSET VALUE 562 750 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.
LT1932
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 6.8H VIN D1
6 VIN LT1932 C1 4.7F 5 SHDN RSET 4 RSET 1.50k
1 SW 3 15mA
24V
LED GND 2
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.
U
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. 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.
C2 1F
1932 F04
W
UU
VPWM 2V/DIV
ILED 10mA/DIV
50s/DIV
1932 F05
Figure 5. PWM Dimming Using the SHDN Pin
7
LT1932
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 ModeTM 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 0.1F 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)
RINCR sets how much the LED current is increased when the NMOS is turned on:
0.1V RINCR = 225 * ILED(INCREASE)
LT1932 SHDN 5 PWM
LT1932 RSET 4 RPWM PWM RSET
PWM
PWM
FILTERED PWM
Figure 6. Five Methods of LED Dimming
8
U
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).
VMAX - 0.1V RADJ = 225 * ILED(MAX) - ILED(MIN)
W
UU
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.
Burst Mode is a trademark of Linear Technology Corporation.
LT1932 RSET 4 10k RPWM PWM RSET 0.1F
LT1932 RSET 4 RADJ VDC RSET
LT1932 RSET 4 RINCR LOGIC SIGNAL
1932 F06
RMIN
DC VOLTAGE
LOGIC
LT1932
APPLICATIO S I FOR ATIO
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 7.
TYPICAL APPLICATIO S
5V Driver for 16 White LEDs
D1
VIN 5V 6 VIN
EFFICIENCY (%)
L1 10H
1 SW LT1932 3
C1 4.7F 5V DC DIMMING CONTROL
5
SHDN RSET 4 RSET 750
LED GND 2
51.1k
100 30mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
100
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN GMK325BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C100M24
U
L1 D1 C1 C2 1 2 GND 3 6 5 4 VIN SHDN RSET DIMMING CONTROL
1932 F07
W
U
UU
Figure 7. Recommended Component Placement
Efficiency
80 75 70 65 60 55 50 0 5 10 15 20 LED CURRENT (mA) 25 30
C2 2.2F
1932 TA14b
1932 TA14a
9
LT1932
TYPICAL APPLICATIO S
Single Cell Driver for One White LED
L1 4.7H D1
80 75
VIN 1V TO 1.5V 6 VIN
SW LT1932 3 15mA
EFFICIENCY (%)
C1 4.7F 2.5V PWM DIMMING CONTROL
5
SHDN RSET 4 RSET 1.50k
LED GND 2
24.9k
C1, C2: TAIYO YUDEN JMK212BJ475 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
Single Cell Driver for Two White LEDs
L1 4.7H D1
80 75
VIN 1V TO 1.5V 6 VIN
LT1932 C1 4.7F 2.5V PWM DIMMING CONTROL 5 SHDN RSET 24.9k 4 RSET 1.50k (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
1932 TA04a
LED GND 2
3 15mA
EFFICIENCY (%)
SW
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
10
U
1
1
Efficiency
VIN = 1.5V 70 VIN = 1.1V 65 60 55 50 0 2.5
C2 4.7F
(408) 573-4150 (631) 543-7100 (814) 237-1431
1932 TA03a
5 7.5 10 LED CURRENT (mA)
12.5
15
1932 TA03b
Efficiency
VIN = 1.5V VIN = 1.1V
70 65 60 55 50 0 2.5 5 7.5 10 LED CURRENT (mA)
C2 2.2F
12.5
15
1932 TA04b
LT1932
TYPICAL APPLICATIO S
2-Cell Driver for Two White LEDs
L1 4.7H D1
85 80
VIN 1.8V TO 3V 6 VIN
SW LT1932 3 15mA
EFFICIENCY (%)
C1 4.7F 2.5V DC DIMMING CONTROL
5
SHDN RSET 4 RSET 1.50k
LED GND 2
60.4k
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
2-Cell Driver for Three White LEDs
L1 4.7H D1
VIN 1.8V TO 3V 6 VIN
EFFICIENCY (%)
SW LT1932 3 15mA
C1 4.7F 2.5V DC DIMMING CONTROL
5
SHDN RSET 4 RSET 1.50k
LED GND 2
60.4k
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
U
1
1
Efficiency
VIN = 3V 75 VIN = 1.8V 70 65 60 55 0 5
C2 2.2F
(408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
1932 TA15a
10 15 LED CURRENT (mA)
20
1932 TA15b
Efficiency
85 80 VIN = 3V 75 VIN = 1.8V 70 65 60 55
C2 2.2F
(408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
0
1932 TA06a
5
10 15 LED CURRENT (mA)
20
1932 TA06b
11
LT1932
TYPICAL APPLICATIO S
2-Cell Driver for Four White LEDs
VIN 1.8V TO 3V L1 4.7H D1
85 80 VIN = 3V 75 VIN = 1.8V 70 65 60 55 0 5
C1 4.7F PWM DIMMING CONTROL
6 VIN LT1932 5 SHDN RSET 4 RSET 1.50k
1 SW 3 15mA
LED GND 2
C2 1F
EFFICIENCY (%)
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
2-Cell Driver for Five White LEDs
VIN 2V TO 3V C1 4.7F PWM DIMMING CONTROL 5 6 VIN LT1932 SHDN RSET 4 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 LED GND 2 3 C2 1F L1 4.7H D1
EFFICIENCY (%)
1 SW
12
U
Efficiency
(408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
1932 TA07a
10 15 LED CURRENT (mA)
20
1932 TA07b
Efficiency
85 80 75 70 VIN = 2V 65 60 55 0
1932 TA05a
VIN = 3V
15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
5
10 15 LED CURRENT (mA)
20
1932 TA05b
LT1932
TYPICAL APPLICATIO S
Li-Ion Driver for Two White LEDs
VIN 2.7V TO 4.2V 6 VIN LT1932 C1 4.7F 3.3V PWM DIMMING CONTROL 5 SHDN RSET 31.6k 4 RSET 1.50k (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334
1932 TA08a
L1 6.8H
EFFICIENCY (%)
SW 3 15mA
GND 2
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8
Li-Ion Driver for Three White LEDs
VIN 2.7V TO 4.2V 6 VIN LT1932 C1 4.7F 3.3V PWM DIMMING CONTROL 5 SHDN RSET 31.6k 4 RSET 1.50k (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334
1932 TA09a
L1 6.8H
SW 3 15mA
EFFICIENCY (%)
GND 2
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ225 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8
U
1
Efficiency
85 80 75 70 65 60 55 0 5 10 15 LED CURRENT (mA) 20
1932 TA08b
D1
VIN = 4.2V VIN = 2.7V
LED
C2 2.2F
Efficiency
85 80 VIN = 4.2V VIN = 2.7V
D1
1
75 70 65 60 55 0 5
LED
C2 2.2F
10 15 LED CURRENT (mA)
20
1932 TA09b
13
LT1932
TYPICAL APPLICATIO S
Li-Ion Driver for Four White LEDs
VIN 2.7V TO 4.2V L1 6.8H D1 85 80 75 70 65 60 55 0 (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334
1932 TA10a
C1 4.7F
6 VIN LT1932 5
1 SW 3 15mA
PWM DIMMING CONTROL
SHDN RSET 4 RSET 1.50k
LED GND 2
C2 1F
EFFICIENCY (%)
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8
Li-Ion Driver for Five White LEDs
L1 4.7H D1
VIN 2.7V TO 4.2V C1 4.7F PWM DIMMING CONTROL 5 6 VIN
SW LT1932 3
EFFICIENCY (%)
SHDN RSET 4 RSET 1.50k
GND 2
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
14
U
1
Efficiency
VIN = 4.2V VIN = 2.7V
5
10 15 LED CURRENT (mA)
20
1932 TA10b
Efficiency
85 80 75 70 65 60 55 0
1932 TA11a
VIN = 4.2V VIN = 2.7V
LED
C2 1F
15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
5
10 15 LED CURRENT (mA)
20
1932 TA11b
LT1932
TYPICAL APPLICATIO S
Li-Ion Driver for Eight White LEDs
VIN 3V TO 4.2V 6 VIN LT1932 C1 4.7F 3.3V DC DIMMING CONTROL 5 SHDN RSET 80.6k 4 RSET 1.50k LED GND 2 60 55 0
1932 TA13a
L1 4.7H
SW 3
EFFICIENCY (%)
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN GMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
PACKAGE DESCRIPTIO
.20 (.008) DATUM `A' A A2 2.60 - 3.00 1.50 - 1.75 (.102 - .118) (.059 - .069) (NOTE 3) 1.90 (.074) REF SOT-23 (Original) A A1 A2 L .90 - 1.45 (.035 - .057) .00 - 0.15 (.00 - .006) .90 - 1.30 (.035 - .051) .35 - .55 (.014 - .021) SOT-23 (ThinSOT) 1.00 MAX (.039 MAX) .01 - .10 (.0004 - .004) .80 - .90 (.031 - .035) .30 - .50 REF (.012 - .019 REF) .95 (.037) REF PIN ONE ID A1
L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES)
.09 - .20 (.004 - .008) (NOTE 2)
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
U
U
1
Efficiency
85 80 VIN = 4.2V 75 70 VIN = 3V 65
D1
C2 1F
15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
5
10 15 LED CURRENT (mA)
20
1932 TA13b
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)
.25 - .50 (.010 - .020) (6PLCS, NOTE 2)
S6 SOT-23 0401
15
LT1932
TYPICAL APPLICATIO
L1 10H
Li-Ion Driver for Ten White LEDs
D1 80
VIN 2.7V TO 4.2V 6 VIN
SW LT1932 3 C2 4.7F
EFFICIENCY (%)
C1 4.7F
5
SHDN RSET 4 RSET 750
GND 2 100 30mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
1932 TA16a
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK325BJ475 D1: ZETEX ZHCS400 L1: MURATA LQH3C100M24
Li-Ion Driver for Six White LEDs
VIN 2.7V TO 4.2V 6 VIN LT1932 C1 4.7F 3.3V DC DIMMING CONTROL 5 SHDN RSET 80.6k 4 RSET 1.50k LED GND 2
60 55 0
1932 TA12a
L1 4.7H
EFFICIENCY (%)
SW 3
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24
RELATED PARTS
PART NUMBER LT1615 LT1617 LT1618 LTC1682 LT1930 LT1931 LTC3200 DESCRIPTION Micropower DC/DC Converter in 5-Lead ThinSOT Micropower Inverting DC/DC Converter in 5-Lead ThinSOT Constant-Current/Constant-Voltage DC/DC Converter Doubler Charge Pump with Low Noise Linear Regulator 1.4MHz Switching Regulator in 5-Lead ThinSOT Inverting 1.2MHz Switching Regulator in 5-Lead ThinSOT Low Noise Regulated Charge Pump 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 60VRMS 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
1932i LT/TP 0701 1.5K * PRINTED IN USA
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
Efficiency
VIN = 4.2V 75 1 VIN = 2.7V 70 65 60 55 50 0 5 10 15 20 25 TOTAL LED CURRENT (mA) 30 LED 100
1932 TA16b
Efficiency
85 80
D1
VIN = 4.2V VIN = 2.7V
1
75 70 65
C2 1F
15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431
5
10 15 LED CURRENT (mA)
20
1932 TA12b
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2001

▲Up To Search▲

Price & Availability of LT1932

	To Download LT1932 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .