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LT3494/LT3494A Micropower Low Noise Boost Converters with Output Disconnect FEATURES
DESCRIPTION
The LT(R)3494/LT3494A are low noise boost converters with integrated power switch, Schottky diode and output disconnect circuitry. The parts use a novel* control technique resulting in low output voltage ripple as well as high efficiency over a wide load current range. This technique guarantees that the switching frequency stays above the audio band for the entire load range. The parts feature a high performance NPN power switch with a 350mA and 180mA current limit for the LT3494A and LT3494 respectively. The quiescent current is a low 65A, which is further reduced to less than 1A in shutdown. The internal disconnect circuitry allows the output voltage to be isolated from the input during shutdown. An auxiliary reference input (CTRL pin) overrides the internal 1.225V feedback reference with any lower value allowing full control of the output voltage during operation. The LT3494/LT3494A are available in a tiny 8-lead 3mm x 2mm DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Patent pending.

Low Quiescent Current 65A in Active Mode 1A in Shutdown Mode Switching Frequency is Non-Audible Over Entire Load Range Integrated Power NPN: 350mA Current Limit (LT3494A) 180mA Current Limit (LT3494) Integrated Schottky Diode Integrated Output Disconnect Integrated Output Dimming Wide Input Range: 2.3V to 16V Wide Output Range: Up to 40V Tiny 8-Lead 3mm x 2mm DFN Package
APPLICATIONS

OLED Power Low Noise Power MP3 Players
TYPICAL APPLICATION
OLED Power Supply from One Li-Ion Cell
VIN 3V TO 4.2V 15H 4.7F SW VCC SHDN CTRL CAP VOUT 2.21M FB GND
3494 TA01a
Output Voltage Ripple vs Load Current
15 VOUT PEAK-TO-PEAK RIPPLE (mV) LT3494 FIGURE 5 CIRCUIT 100MHz MEASUREMENT BW EFFICIENCY (%) 90 80 70 60 50 40 30 0 0.1 1 10 LOAD CURRENT (mA) 100
3494 TA01b
Efficiency and Power Loss vs Load Current
VIN = 3.6V 280 LOAD FROM CAPACITOR LOAD FROM VOUT 240 200 160 120 80 40 0 100
3494 TA01c
POWER LOSS (mW)
0.22F VOUT 16V 16mA 2.2F
10
LT3494
5
20 0.1
1 10 LOAD CURRENT (mA)
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LT3494/LT3494A ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW SW 1 GND 2 VCC 3 CTRL 4 9 8 7 6 5 CAP VOUT FB SHDN
VCC Voltage ...............................................................16V SW Voltage ...............................................................40V CAP Voltage ..............................................................40V VOUT Voltage .............................................................40V SHDN Voltage ...........................................................16V CTRL Voltage ............................................................16V FB Voltage ................................................................2.5V Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) ... -40C to 85C Storage Temperature Range................... -65C to 125C
DDB PACKAGE 8-LEAD (3mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 76C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER LT3494EDDB LT3494AEDDB
DDB PART MARKING LCCD LCRW
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage FB Resistor Quiescent Current Quiescent Current in Shutdown Minimum Switch Off Time Maximum Switch Off Time Switch Current Limit Switch VCESAT Switch Leakage Current Schottky Forward Voltage Schottky Reverse Leakage PMOS Disconnect VCAP - VOUT SHDN Input Voltage High SHDN Input Voltage Low SHDN Pin Bias Current VSHDN = 3V VSHDN = 0V CONDITIONS
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 3V, VSHDN = VCC, unless otherwise noted. (Note 2)
MIN TYP 2.3 VCTRL = 3V (Note 3) Not Switching VSHDN = 0V, VCC = 3V After Start-Up Mode, VFB = 1V, VCTRL = 3V (Note 4) During Start-Up Mode, VFB = 0.2V, VCTRL = 3V (Note 4) VFB = 1.5V LT3494A (Note 5) LT3494 (Note 5) LT3494A, ISW = 200mA LT3494, ISW = 100mA VSW = 5V, VSHDN = 0 IDIODE = 100mA IOUT = 10mA, VCAP = 5V 1.5 0.3 5 0 10 0.1

MAX 2.5 16 1.245 184 75 1
UNITS V V V k A A ns ns
1.205 179
1.225 182 65 0 100 450
15 225 115
20 350 180 180 110 0.01 900 0.05 250
30 450 250
s mA mA mV mV
1 1100 1
A mV A mV V V A A
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LT3494/LT3494A ELECTRICAL CHARACTERISTICS
PARAMETER CTRL Pin Bias Current CTRL to FB Offset Maximum Shunt Current CONDITIONS VCTRL = 0.5V, Current Flows Out of Pin VCTRL = 0.5V VFB = 1.3V, VCAP = 5V
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 3V, VSHDN = VCC, unless otherwise noted. (Note 2)
MIN TYP 20 8 230 MAX 100 15 UNITS nA mV A
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3494/LT3494A are guaranteed to meet performance specifications from 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: Internal reference voltage is determined by finding VFB voltage level which causes quiescent current to increase 20A above "Not Switching" level. Note 4: If CTRL is overriding the internal reference, Start-Up mode occurs when VFB is less then half the voltage on CTRL. If CTRL is not overriding the internal reference, Start-Up mode occurs when VFB is less then half the voltage of the internal reference. Note 5: Current limit guaranteed by design and/or correlation to static test.
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Frequency vs Load Currrent
1400 LT3494 FIGURE 5 CIRCUIT 1200 VCC = 3.6V VOUT = 16V 1000 800 600 400 200 0 0.1 2.0
TA = 25C unless otherwise noted.
Load Regulation
LT3494 1.5 FIGURE 5 CIRCUIT VCC = 3.6V 1.0 VOUT = 16V 0.5 0 -0.5 -1.0 -1.5 -2.0 VOUT VOLTAGE (V) 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 40 20
VOUT vs CTRL Voltage
LT3494 FIGURE 5 CIRCUIT VCC = 3.6V 15 VOUT = 16V LOAD CURRENT = 1mA
SWITCHING FREQUENCY (kHz)
VOUT VOLTAGE CHANGE (%)
10
5
0 0.1 0.3 0.5 0.7 0.9 1.1 CTRL VOLTAGE (V) 1.3 1.5
1 10 LOAD CURRENT (mA)
100
3494 G01
3494 G02
3494 G03
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LT3494/LT3494A TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage vs Temperature
2.0 OUTPUT VOLTAGE CHANGE (%) LT3494 1.5 FIGURE 5 CIRCUIT SWITCHING FREQUENCY (kHz) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120
3494 G04
TA = 25C unless otherwise noted. Quiescent Current-Not Switching
100 95 90
Minimum Switching Frequency
51.0 50.5 50.0 IVCC (A) 49.5 49.0 48.5 48.0 47.5 47.0 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120
3494 G05
VCC = 3.6V NO LOAD
85 80 75 70 65 60 55 50 3 4 5 7 6 VCC (V) 8 9 10
3494 G06
SHDN Current vs SHDN Voltage
20 PEAK INDUCTOR CURRENT (mA) 400
Peak Inductor Current (LT3494)
FIGURE 5 CIRCUIT VCC = 3.6V 350 VOUT = 16V 700 PEAK INDUCTOR CURRENT (mA)
Peak Inductor Current (LT3494A)
FIGURE 6 CIRCUIT VCC = 3.6V 650 VOUT = 16V
SHDN PIN CURRENT (A)
15
300 250 200 150 100 -40 -20
600 550 500 450 400 -40 -20
10
5
0 0 2 10 12 4 6 8 SHDN PIN VOLTAGE (V) 14 16
0
20 40 60 80 TEMPERATURE (C)
100 120
3494 G08
0
20 40 60 80 TEMPERATURE (C)
100 120
3494 G09
3494 G07
LT3494 Switching Waveforms at No Load
FIGURE 5 CIRCUIT VOUT 10mV/DIV AC COUPLED VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV
LT3494 Switching Waveforms at 1mA Load
FIGURE 5 CIRCUIT VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV INDUCTOR CURRENT 100mA/DIV
LT3494 Switching Waveforms at 25mA Load
FIGURE 5 CIRCUIT
SW VOLTAGE 10V/DIV
INDUCTOR CURRENT 50mA/DIV VCC = 3.6V VOUT = 16V 5s/DIV
3494 G10
INDUCTOR CURRENT 100mA/DIV VCC = 3.6V VOUT = 16V 2s/DIV
3494 G11
VCC = 3.6V VOUT = 16V
500ns/DIV
3494 G12
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LT3494/LT3494A TYPICAL PERFORMANCE CHARACTERISTICS
LT3494A Switching Waveforms at No Load
FIGURE 6 CIRCUIT VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV
TA = 25C unless otherwise noted. LT3494A Switching Waveforms at 30mA Load
VOUT 10mV/DIV AC COUPLED FIGURE 6 CIRCUIT
LT3494A Switching Waveforms at 5mA Load
FIGURE 6 CIRCUIT
SW VOLTAGE 10V/DIV INDUCTOR CURRENT 200mA/DIV VCC = 3.6V VOUT = 16V 2ms/DIV
3494 G14
INDUCTOR CURRENT 50mA/DIV VCC = 3.6V VOUT = 16V 5ms/DIV
3494 G13
INDUCTOR CURRENT 100mA/DIV
VCC = 3.6V VOUT = 16V
500ns/DIV
3494 G15
LT3494 Start-Up Waveforms
FIGURE 5 CIRCUIT VOUT VOLTAGE 50mV/DIV AC COUPLED
LT3494 Transient Response
FIGURE 5 CIRCUIT 10mA15mA10mA LOAD PULSE VOUT 50mV/DIV AC COUPLED
LT3494A Transient Response
FIGURE 6 CIRCUIT 15mA30mA15mA LOAD PULSE
CAP VOLTAGE 5V/DIV VOUT VOLTAGE 5V/DIV INDUCTOR CURRENT 100mA/DIV
INDUCTOR CURRENT 100mA/DIV
INDUCTOR CURRENT 200mA/DIV
VCC = 3.6V VOUT = 16V
200s/DIV
3494 G16
VCC = 3.6V VOUT = 16V
100s/DIV
3494 G17
VCC = 3.6V VOUT = 16V
100s/DIV
3494 G18
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LT3494/LT3494A PIN FUNCTIONS
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. Tie directly to local ground plane. V CC (Pin 3): Input Supply Pin. Must be locally bypassed. CTRL (Pin 4): Dimming Pin. If not used, tie CTRL to 1.5V or higher. If in use, drive CTRL below 1.225V to override the internal reference. See Applications Information for more information. SHDN (Pin 5): Shutdown Pin. Tie to 1.5V or more to enable device. Ground to shut down. FB (Pin 6): Feedback Pin. Reference voltage is 1.225V. There is an internal 182k resistor from the FB pin to GND. To achieve the desired output voltage, choose R1 according to the following formula: VOUT(MAX ) R1 = 182 * - 1 k 1.225 VOUT (Pin 7): Drain of Output Disconnect PMOS. Place a bypass capacitor from this pin to GND. See Applications Information. CAP (Pin 8): This is the cathode of the internal Schottky diode. Place a bypass capacitor from this pin to GND. Exposed Pad (Pin 9): Ground. This pin must be soldered to PCB.
BLOCK DIAGRAM
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LT3494/LT3494A OPERATION
The LT3494/LT3494A use a novel control scheme to provide high efficiency over a wide range of output current. In addition, this technique keeps the switching frequency above the audio band over all load conditions. The operation of the part can be better understood by refering to the Block Diagram. The part senses the output voltage by monitoring the voltage on the FB pin. The user sets the desired output voltage by choosing the value of the external top feedback resistor. The parts incorporate a precision 182k bottom feedback resistor. Assuming that output voltage adjustment is not used (CTRL pin is tied to 1.5V or greater), the internal reference (VREF = 1.225V) sets the voltage at which FB will servo to during regulation. The Switch Control block senses the output of the amplifier and adjusts the switching frequency as well as other parameters to achieve regulation. During the start-up of the circuit, special precautions are taken to insure that the inductor current remains under control. Because the switching frequency is never allowed to fall below approximately 50kHz, a minimum load must be present to prevent the output voltage from drifting too high. This minimum load is automatically generated within the part via the Shunt Control block. The level of this current is adaptable, removing itself when not needed to improve efficiency at higher load levels. The LT3494/LT3494A also have an integrated Schottky diode and PMOS output disconnect switch. The PMOS switch is turned on when the part is enabled via the SHDN pin. When the parts are in shutdown, the PMOS switch turns off, allowing the VOUT node to go to ground. This type of disconnect function is often required in power supplies. The only difference between the LT3494A and LT3494 is the level of the current limit. The LT3494A has a typical peak current limit of 350mA while the LT3494 has a 180mA limit.
APPLICATIONS INFORMATION
Choosing an Inductor Several recommended inductors that work well with the LT3494/LT3494A are listed in Table 1, although there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts. Many different sizes and shapes are available. Use the equations and recommendations in the next few sections to find the correct inductance value for your design. Inductor Selection--Boost Regulator The formula below calculates the appropriate inductor value to be used for a boost regulator using the LT3494/ LT3494A (or at least provides a good starting point).
Table 1. Recommended Inductors
PART LQH32CN100K53 LQH32CN150K53 CDRH3D11-100 CDHED13/S-150 FOR USE WITH LT3494/LT3494A LT3494 LT3494 LT3494/LT3494A VALUE (H) 10 15 10 15 MAX DCR () 0.3 0.58 0.24 0.55 MAX DC I (mA) 450 300 280 550 SIZE (mm x mm x mm) 3.5 x 2.7 x 1.7 3.5 x 2.7 x 1.7 4.0 x 4.0 x 1.2 4.0 x 4.2 x 1.4 VENDOR Murata www.murata.com Sumida www.sumida.com
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This value provides a good trade off in inductor size and system performance. Pick a standard inductor close to this value. A larger value can be used to slightly increase the available output current, but limit it to around twice the value calculated below, as too large of an inductance will decrease the output voltage ripple without providing much additional output current. A smaller value can be used (especially for systems with output voltages greater than 12V) to give a smaller physical size. Inductance can be calculated as: L = (VOUT - VIN(MIN) + 0.5V) * 0.66 (H) where VOUT is the desired output voltage and VIN(MIN) is the minimum input voltage. Generally, a 10H or 15H inductor is a good choice.
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LT3494/LT3494A APPLICATIONS INFORMATION
Capacitor Selection The small size and low ESR of ceramic capacitors makes them suitable for most LT3494/LT3494A applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A 4.7F input capacitor and a 2.2F to 10F output capacitor are sufficient for most LT3494/LT3494A applications. Always use a capacitor with a sufficient voltage rating. Many capacitors rated at 2.2F to 10F, particularly 0805 or 0603 case sizes, have greatly reduced capacitance when bias voltages are applied. Be sure to check actual capacitance at the desired output voltage. Generally a 1206 size capacitor will be adequate. A 0.22F or 0.47F capacitor placed on the CAP node is recommended to filter the inductor current while the larger 2.2F to 10F placed on the VOUT node will give excellent transient response and stability. Table 2 shows a list of several capacitor manufacturers. Consult the manufacturers for more detailed information and for their entire selection of related parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER Taiyo Yuden AVX Murata Kemet PHONE 408-573-4150 843-448-9411 814-237-1431 408-986-0424 URL www.t-yuden.com www.avxcorp.com www.murata.com www.kemet.com
1.500 1.250 FB VOLTAGE (V) 1.000 0.750 0.500 0.250 0
0
.25
0.5 .75 1.0 CTRL VOLTAGE (V)
1.25
1.5
3494 F01
Figure 1. CTRL to FB Transfer Curve
To set the maximum output voltage, select the values of R1 according to the following equation: VOUT(MAX ) R1 = 182 * - 1 k 1.225 When CTRL is used to override the internal reference, the output voltage can be lowered from the maximum value down to nearly the input voltage level. If the voltage source driving the CTRL pin is located at a distance to the LT3494/LT3494A, a small 0.1F capacitor may be needed to bypass the pin locally. Choosing a Feedback Node The single feedback resistor may be connected to the VOUT pin or to the CAP pin (see Figure 2). Regulating the VOUT pin eliminates the output offset resulting from the voltage drop across the output disconnect PMOS. Regulating the CAP pin does not compensate for the voltage drop across the output disconnect, resulting in an output voltage VOUT that is slightly lower than the voltage set by the resistor divider. Under most conditions, it is advised that the feedback resistor be tied to the VOUT pin.
1 SW 3 5 4 VCC SHDN CTRL 8 CAP VOUT FB GND 7 R1 6 2 VOUT C3 5 4 3 C1 1 SW VCC SHDN CTRL 8 CAP VOUT FB GND 7 R1 6 2
3494 F02
Setting Output Voltage and the Auxiliary Reference Input The LT3494/LT3494A are equipped with both an internal 1.225V reference and an auxiliary reference input. This allows the user to select between using the built-in reference and supplying an external reference voltage. The voltage at the CTRL pin can be adjusted while the chip is operating to alter the output voltage of the LT3494/LT3494A for purposes such as display dimming or contrast adjustment. To use the internal 1.225V reference, the CTRL pin must be held higher than 1.5V. When the CTRL pin is held between 0V and 1.5V, the LT3494 will regulate the output such that the FB pin voltage is nearly equal to the CTRL pin voltage. At CTRL voltages close to 1.225V, a soft transition occurs between the CTRL pin and the internal reference. Figure 1 shows this behavior.
C1
LT3494
LT3494
Figure 2. Feedback Connection Using the CAP Pin or the VOUT Pin
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LT3494/LT3494A APPLICATIONS INFORMATION
Connecting the Load to the CAP Node The efficiency of the converter can be improved by connecting the load to the CAP pin instead of the VOUT pin. The power loss in the PMOS disconnect circuit is then made negligible. By connecting the feedback resistor to the VOUT pin, no quiescent current will be consumed in the feedback resistor string during shutdown since the PMOS transistor will be open (see Figure 3). The disadvantage of this method is that the CAP node cannot go to ground during shutdown, but will be limited to around a diode drop below VCC. Loads connected to the part should only sink current. Never force external power supplies onto the CAP or VOUT pins. The larger value output capacitor (2.2F to 10F) should be placed on the node to which the load is connected.
1 SW 3 5 4 VCC SHDN CTRL 8 CAP VOUT FB GND 7 6 2
3494 F03
If the inductor ripple current is greater than the peak current, then the circuit will only operate in discontinuous conduction mode. The inductor value should be increased so that IRIPPLE < IPK. An application circuit can be designed to operate only in discontinuous mode, but the output current capability will be reduced. Step 3: Calculate the average input current: IIN( AVG) = IPK - IRIPPLE amps 2
Step 4: Calculate the nominal output current: IOUT(NOM) = IIN( AVG) * VIN * 0.75 VOUT amps
Step 5: Derate output current: IOUT = IOUT(NOM) * 0.7 amps For low output voltages the output current capability will be increased. When using output disconnect (load current taken from VOUT), these higher currents will cause the drop in the PMOS switch to be higher resulting in reduced output current capability than those predicted by the preceding equations. Inrush Current When VCC is stepped from ground to the operating voltage while the output capacitor is discharged, a higher level of inrush current may flow through the inductor and integrated Schottky diode into the output capacitor. Conditions that increase inrush current include a larger more abrupt voltage step at VIN, a larger output capacitor tied to the CAP pin and an inductor with a low saturation current. While the internal diode is designed to handle such events, the inrush current should not be allowed to exceed 1A. For circuits that use output capacitor values within the recommended range and have input voltages of less than 5V, inrush current remains low, posing no hazard to the device. In cases where there are large steps at VCC (more than 5V) and/or a large capacitor is used at the CAP pin, inrush current should be measured to ensure safe operation. The LT3494A circuits experience higher levels of current during start-up and steady-state operation. An external diode placed from the SW pin to
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C1
ILOAD
LT3494
Figure 3. Improved Efficiency
Maximum Output Load Current The maximum output current of a particular LT3494/ LT3494A circuit is a function of several circuit variables. The following method can be helpful in predicting the maximum load current for a given circuit: Step 1: Calculate the peak inductor current: IPK VIN * 400 * 10 -9 = ILIMIT + amps L
where ILIMIT is 0.180A and 0.350A for the LT3494 and LT3494A respectively. L is the inductance value in Henrys and VIN is the input voltage to the boost circuit. Step 2: Calculate the inductor ripple current: IRIPPLE =
(VOUT + 1- VIN) * 150 * 10 -9
L
amps
where VOUT is the desired output voltage.
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LT3494/LT3494A APPLICATIONS INFORMATION
the CAP pin will improve efficiency and lower the stress placed on the internal Schottky diode. 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 electromagnetic interference (EMI) problems, proper layout of the high frequency switching path is essential. The voltage signal of the SW pin has sharp rising and falling edges. 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. In addition, the FB connection for the feedback resistor R1 should be tied directly from the Vout pin to the FB pin and be kept as short as possible, ensuring a clean, noise-free connection. Recommended component placement is shown in Figure 4.
SW GND GND VCC CTRL FB SHDN GND
CAP VOUT
3494 F04
CTRL
SHDN
VIAS TO GROUND PLANE REQUIRED TO IMPROVE THERMAL PERFORMANCE
Figure 4. Recommended Layout
TYPICAL APPLICATIONS
VIN 3V TO 4.2V L1 15H 90 C2 4.7F 3 5 4 1 SW VCC SHDN CTRL 8 CAP VOUT FB GND 7 R1 6 2
3494 F05
3.6V to 16V Efficiency
C1 0.22F VOUT EFFICIENCY (%) VIN = 3.6V 280 LOAD FROM CAPACITOR LOAD FROM VOUT 240 200 160 120 80 40 0 100
3494 TA01c
80 C3 2.2F 70 60 50 40 30 20 0.1
POWER LOSS (mW)
LT3494 TURN ON/OFF VOUT DIMMING
C1, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING C3: MURATA GRM31MR71E225K L1: MURATA LQH32CN150K53
Figure 5. One Li-Ion Cell Input Boost Converter with the LT3494
VOUT 25 24 23 22 21 20 19 18 17 16 15 R1 VALUE REQUIRED (M) 3.57 3.40 3.24 3.09 2.94 2.80 2.67 2.49 2.37 2.21 2.05 MAXIMUM OUTPUT CURRENT AT 3V INPUT (mA) 8.6 9.3 10.0 10.6 11.3 12.1 12.9 13.6 14.8 16.0 17.2
1 10 LOAD CURRENT (mA)
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LT3494/LT3494A PACKAGE DESCRIPTION
DDB Package 8-Lead Plastic DFN (3mm x 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 0.05 (2 SIDES) 0.70 0.05 2.55 0.05 1.15 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.20 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 0.40 0.10 8
3.00 0.10 (2 SIDES)
R = 0.05 TYP
PIN 1 BAR TOP MARK (SEE NOTE 6)
2.00 0.10 (2 SIDES) 0.56 0.05 (2 SIDES) 0.75 0.05
0.200 REF
4 0.25 0.05 2.15 0.05 (2 SIDES)
1 0.50 BSC
PIN 1 R = 0.20 OR 0.25 x 45 CHAMFER
(DDB8) DFN 0905 REV B
0 - 0.05
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
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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.
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LT3494/LT3494A TYPICAL APPLICATION
VIN 3V TO 4.2V L1 10H C2 4.7F 3 5 4 1 SW VCC SHDN CTRL D1 8 CAP VOUT FB GND 7 6 2
3494 F06
Efficiency and Power Loss vs Load Current
80 C1 0.47F VOUT R1 EFFICIENCY (%) C3 10F LOAD FROM CAPACITOR 75 70 65 60 55 50 45 40 0.1 50 VIN = 3.6V VOUT = 16V 1 10 LOAD CURRENT (mA) 0 100 LOAD FROM VOUT 250 POWER LOSS (mW) 200 150 100 300
LT3494A
C1, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING C3: TAIYO YUDEN TMK316BJ106ML D1: CENTRAL SEMICONDUCTOR CMDSH-3 L1: MURATA LQH32CN100K53
Figure 6. One Li-Ion Cell Input Boost Converter with the LT3494A Output Voltage Ripple vs Load Current
15 VOUT PEAK-TO-PEAK RIPPLE (mV) 100MHz MEASUREMENT BW
3494 F06b
10
5
0 0.1 1 10 LOAD CURRENT (mA) 100
3494 F06c
VOUT 25 24 23 22 21 20 19 18 17 16 15
R1 VALUE REQUIRED (M) 3.57 3.40 3.24 3.09 2.94 2.80 2.67 2.49 2.37 2.21 2.05
MAXIMUM OUTPUT CURRENT AT 3V INPUT (mA) 13.0 14.0 15.0 16.5 17.5 19.0 20.0 21.5 23.0 25.0 27.0
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PART NUMBER LT1613 DESCRIPTION 550mA (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter COMMENTS VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1A, ThinSOT Package VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20A, ISD < 1A, ThinSOT Package VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2A/5.5mA, ISD < 1A, ThinSOT Package VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 40A, ISD < 1A, 10-Lead MS Package VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA, ISD < 1A, 8-Lead MS Package VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 1.2mA, ISD < 1A, ThinSOT Package
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LT1946/LT1946A 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converters LT3467/LT3467A 1.1A (ISW), 1.3MHz/2.1MHz, High Efficiency Step-Up DC/DC Converters with Soft-Start
LT3463/LT3463A Dual Output, Boost/Inverter, 250mA (ISW), Constant Off-Time, High VIN: 2.3V to 15V, VOUT(MAX) = 40V, IQ = 40A, ISD < 1A, Efficiency Step-Up DC/DC Converters with Integrated Schottkys DFN Package LT3471 Dual Output, Boost/Inverter, 1.3A (ISW), High Efficiency Boost-Inverting DC/DC Converter VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 2.5mA, ISD < 1A, DFN Package
3494fb LT 0507 REV B * PRINTED IN USA
12 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2006

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