LT3494/LT3494A Micropower Low Noise Boost Converters with Output Disconnect FEATURES DESCRIPTION ■ The LT®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 65μA, which is further reduced to less than 1μA 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 × 2mm DFN package. ■ ■ ■ ■ ■ ■ ■ ■ Low Quiescent Current 65μA in Active Mode 1μA 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 × 2mm DFN Package APPLICATIONS ■ ■ ■ OLED Power Low Noise Power MP3 Players , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Patent pending. TYPICAL APPLICATION Output Voltage Ripple vs Load Current OLED Power Supply from One Li-Ion Cell 0.22μF SW CAP VCC VOUT 2.21M LT3494 SHDN FB CTRL GND 2.2μF 3494 TA01a 70 10 VOUT 16V 16mA VIN = 3.6V 80 EFFICIENCY (%) 4.7μF VOUT PEAK-TO-PEAK RIPPLE (mV) 15μH 90 LT3494 FIGURE 5 CIRCUIT 100MHz MEASUREMENT BW 5 0 0.1 1 10 LOAD CURRENT (mA) 100 3494 TA01b 280 LOAD FROM CAPACITOR 240 LOAD FROM VOUT 200 60 160 50 120 40 80 30 40 20 0.1 1 10 LOAD CURRENT (mA) POWER LOSS (mW) VIN 3V TO 4.2V 15 Efficiency and Power Loss vs Load Current 0 100 3494 TA01c 3494fb 1 LT3494/LT3494A ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) 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 .......................... 125°C Operating Temperature Range (Note 2) ... –40°C to 85°C Storage Temperature Range................... –65°C to 125°C TOP VIEW CAP SW 1 8 GND 2 7 VOUT 6 FB 5 SHDN VCC 3 9 CTRL 4 DDB PACKAGE 8-LEAD (3mm × 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 76°C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB ORDER PART NUMBER DDB PART MARKING LT3494EDDB LT3494AEDDB 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 The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VSHDN = VCC, unless otherwise noted. (Note 2) PARAMETER CONDITIONS MIN Minimum Operating Voltage TYP MAX 2.3 2.5 V 16 V V Maximum Operating Voltage Feedback Voltage VCTRL = 3V (Note 3) FB Resistor ● 1.205 1.225 1.245 ● 179 182 184 UNITS kΩ Quiescent Current Not Switching 65 75 μA Quiescent Current in Shutdown V⎯S⎯H⎯D⎯N = 0V, VCC = 3V 0 1 μA Minimum Switch Off Time After Start-Up Mode, VFB = 1V, VCTRL = 3V (Note 4) During Start-Up Mode, VFB = 0.2V, VCTRL = 3V (Note 4) Maximum Switch Off Time VFB = 1.5V Switch Current Limit LT3494A (Note 5) LT3494 (Note 5) Switch VCESAT LT3494A, ISW = 200mA LT3494, ISW = 100mA 180 110 Switch Leakage Current VSW = 5V, V⎯S⎯H⎯D⎯N = 0 0.01 1 μA Schottky Forward Voltage IDIODE = 100mA 900 1100 mV 0.05 1 μA 100 450 ● 15 20 30 μs 225 115 350 180 450 250 mA mA Schottky Reverse Leakage PMOS Disconnect VCAP – VOUT IOUT = 10mA, VCAP = 5V SHDN Input Voltage High mV mV 250 mV 1.5 V SHDN Input Voltage Low SHDN Pin Bias Current ns ns VSHDN = 3V VSHDN = 0V 5 0 0.3 V 10 0.1 μA μA 3494fb 2 LT3494/LT3494A ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VSHDN = VCC, unless otherwise noted. (Note 2) PARAMETER CONDITIONS CTRL Pin Bias Current VCTRL = 0.5V, Current Flows Out of Pin MIN CTRL to FB Offset VCTRL = 0.5V Maximum Shunt Current VFB = 1.3V, VCAP = 5V 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 0°C to 85°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. 600 400 200 0 0.1 nA 8 15 mV μA VOUT vs CTRL Voltage 20 LT3494 1.5 FIGURE 5 CIRCUIT VCC = 3.6V 1.0 VOUT = 16V VOUT VOLTAGE (V) VOUT VOLTAGE CHANGE (%) SWITCHING FREQUENCY (kHz) 800 UNITS 100 TA = 25°C unless otherwise noted. 2.0 LT3494 FIGURE 5 CIRCUIT 1200 VCC = 3.6V VOUT = 16V 1000 MAX 20 Note 3: Internal reference voltage is determined by finding VFB voltage level which causes quiescent current to increase 20μA 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. Load Regulation 1400 TYP 230 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency vs Load Currrent ● 0.5 0 –0.5 LT3494 FIGURE 5 CIRCUIT VCC = 3.6V 15 VOUT = 16V LOAD CURRENT = 1mA 10 5 –1.0 –1.5 –2.0 1 10 LOAD CURRENT (mA) 100 3494 G01 0 5 10 15 20 25 30 LOAD CURRENT (mA) 0 35 40 3494 G02 0.1 0.3 0.5 0.7 0.9 1.1 CTRL VOLTAGE (V) 1.3 1.5 3494 G03 3494fb 3 LT3494/LT3494A TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Temperature 100 51.0 LT3494 1.5 FIGURE 5 CIRCUIT VCC = 3.6V NO LOAD 50.5 1.0 0.5 0 –0.5 –1.0 –1.5 95 90 50.0 85 49.5 IVCC (μA) SWITCHING FREQUENCY (kHz) OUTPUT VOLTAGE CHANGE (%) Quiescent Current–Not Switching Minimum Switching Frequency 2.0 49.0 48.5 0 20 40 60 80 TEMPERATURE (°C) 50 0 20 40 60 80 TEMPERATURE (°C) 3 100 120 SHDN Current vs SHDN Voltage Peak Inductor Current (LT3494) 5 0 10 12 4 6 8 SHDN PIN VOLTAGE (V) 14 16 300 250 200 150 100 –40 –20 0 20 40 60 80 TEMPERATURE (°C) 100 120 550 500 450 400 –40 –20 3494 G10 100 120 LT3494 Switching Waveforms at 25mA Load FIGURE 5 CIRCUIT SW VOLTAGE 10V/DIV INDUCTOR CURRENT 100mA/DIV INDUCTOR CURRENT 100mA/DIV INDUCTOR CURRENT 50mA/DIV 20 40 60 80 TEMPERATURE (°C) VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV SW VOLTAGE 10V/DIV 0 3494 G09 FIGURE 5 CIRCUIT VOUT 10mV/DIV AC COUPLED 5μs/DIV 600 LT3494 Switching Waveforms at 1mA Load FIGURE 5 CIRCUIT VCC = 3.6V VOUT = 16V FIGURE 6 CIRCUIT VCC = 3.6V 650 VOUT = 16V 3494 G08 LT3494 Switching Waveforms at No Load 10 9 Peak Inductor Current (LT3494A) FIGURE 5 CIRCUIT VCC = 3.6V 350 VOUT = 16V 3494 G07 VOUT 10mV/DIV AC COUPLED 8 700 PEAK INDUCTOR CURRENT (mA) PEAK INDUCTOR CURRENT (mA) 10 7 6 VCC (V) 3494 G06 400 15 5 4 3494 G05 20 2 70 55 3494 G04 0 75 60 47.0 –40 –20 100 120 80 65 48.0 47.5 –2.0 –40 –20 SHDN PIN CURRENT (μA) TA = 25°C unless otherwise noted. VCC = 3.6V VOUT = 16V 2μs/DIV 3494 G11 VCC = 3.6V VOUT = 16V 500ns/DIV 3494 G12 3494fb 4 LT3494/LT3494A TYPICAL PERFORMANCE CHARACTERISTICS LT3494A Switching Waveforms at No Load LT3494A Switching Waveforms at 5mA Load FIGURE 6 CIRCUIT FIGURE 6 CIRCUIT VOUT 10mV/DIV AC COUPLED VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV SW VOLTAGE 10V/DIV INDUCTOR CURRENT 50mA/DIV INDUCTOR CURRENT 100mA/DIV VCC = 3.6V VOUT = 16V 5ms/DIV TA = 25°C unless otherwise noted. 3494 G13 VOUT VOLTAGE 50mV/DIV AC COUPLED 2ms/DIV 3494 G14 VCC = 3.6V VOUT = 16V 200μs/DIV 3494 G16 VCC = 3.6V VOUT = 16V 500ns/DIV 3494 G15 LT3494A Transient Response FIGURE 5 CIRCUIT 10mA→15mA→10mA LOAD PULSE VOUT 50mV/DIV AC COUPLED INDUCTOR CURRENT 100mA/DIV INDUCTOR CURRENT 100mA/DIV FIGURE 6 CIRCUIT INDUCTOR CURRENT 200mA/DIV LT3494 Transient Response FIGURE 5 CIRCUIT CAP VOLTAGE 5V/DIV VOUT VOLTAGE 5V/DIV VOUT 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV VCC = 3.6V VOUT = 16V LT3494 Start-Up Waveforms LT3494A Switching Waveforms at 30mA Load FIGURE 6 CIRCUIT 15mA→30mA→15mA LOAD PULSE INDUCTOR CURRENT 200mA/DIV VCC = 3.6V VOUT = 16V 100μs/DIV 3494 G17 VCC = 3.6V VOUT = 16V 100μs/DIV 3494 G18 3494fb 5 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. 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⎟ kΩ ⎝ 1.225 ⎠ 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. 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 /54054 ).054 6/54 #!0 37 6## 2 34!24 50 #/.42/, &" K n #42, $)3#/..%#4 #/.42/, 37)4#( #/.42/, 3($. 62%& 3(5.4 #/.42/, '.$ "$ 3494fb 6 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. 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: Inductor Selection—Boost Regulator L = (VOUT – VIN(MIN) + 0.5V) • 0.66 (μH) 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). where VOUT is the desired output voltage and VIN(MIN) is the minimum input voltage. Generally, a 10μH or 15μH inductor is a good choice. Table 1. Recommended Inductors PART FOR USE WITH VALUE (μH) MAX DCR (Ω) MAX DC I (mA) SIZE (mm × mm × mm) LQH32CN100K53 LQH32CN150K53 LT3494/LT3494A LT3494 10 15 0.3 0.58 450 300 3.5 × 2.7 × 1.7 3.5 × 2.7 × 1.7 Murata www.murata.com CDRH3D11-100 CDHED13/S-150 LT3494 LT3494/LT3494A 10 15 0.24 0.55 280 550 4.0 × 4.0 × 1.2 4.0 × 4.2 × 1.4 Sumida www.sumida.com VENDOR 3494fb 7 LT3494/LT3494A APPLICATIONS INFORMATION 1.500 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 4.7μF input capacitor and a 2.2μF to 10μF output capacitor are sufficient for most LT3494/LT3494A applications. Always use a capacitor with a sufficient voltage rating. Many capacitors rated at 2.2μF to 10μF, 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 0.22μF or 0.47μF capacitor placed on the CAP node is recommended to filter the inductor current while the larger 2.2μF to 10μF 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. 1.250 Table 2. Recommended Ceramic Capacitor Manufacturers MANUFACTURER PHONE URL Taiyo Yuden 408-573-4150 www.t-yuden.com AVX 843-448-9411 www.avxcorp.com Murata 814-237-1431 www.murata.com Kemet 408-986-0424 www.kemet.com 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. FB VOLTAGE (V) Capacitor Selection 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⎟ kΩ ⎝ 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 0.1μF 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. 3 1 8 SW CAP VCC VOUT C1 7 R1 LT3494 5 4 VOUT SHDN FB CTRL GND 3 C3 1 8 SW CAP VCC VOUT C1 7 R1 LT3494 6 5 2 4 SHDN FB CTRL GND 6 2 3494 F02 Figure 2. Feedback Connection Using the CAP Pin or the VOUT Pin 3494fb 8 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 (2.2μF to 10μF) should be placed on the node to which the load is connected. 3 1 8 SW CAP VCC VOUT C1 ILOAD 7 4 SHDN FB CTRL GND 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. LT3494 5 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. 6 2 3494 F03 Figure 3. Improved Efficiency Maximum Output Load Current Inrush 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: 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 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 where VOUT is the desired output voltage. amps 3494fb 9 LT3494/LT3494A APPLICATIONS INFORMATION the CAP pin will improve efficiency and lower the stress placed on the internal Schottky diode. GND Board Layout Considerations SW 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. GND CAP VOUT GND VCC FB CTRL SHDN 3494 F04 CTRL SHDN VIAS TO GROUND PLANE REQUIRED TO IMPROVE THERMAL PERFORMANCE Figure 4. Recommended Layout TYPICAL APPLICATIONS 3.6V to 16V Efficiency 90 C2 4.7μF 3 1 8 SW CAP TURN ON/OFF VOUT DIMMING 5 4 SHDN R1 CTRL FB GND 80 7 LT3494 6 C3 2.2μF VOUT 2 3494 F05 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 (MΩ) 3.57 3.40 3.24 3.09 2.94 2.80 2.67 2.49 2.37 2.21 2.05 VIN = 3.6V 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 70 280 LOAD FROM CAPACITOR 240 LOAD FROM VOUT 200 60 160 50 120 40 80 30 40 20 0.1 1 10 LOAD CURRENT (mA) POWER LOSS (mW) VOUT VCC C1 0.22μF EFFICIENCY (%) VIN 3V TO 4.2V L1 15μH 0 100 3494 TA01c 3494fb 10 LT3494/LT3494A PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 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 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.56 ± 0.05 (2 SIDES) 0.200 REF 0.75 ±0.05 0 – 0.05 4 0.25 ± 0.05 1 PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) 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 3494fb 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. 11 LT3494/LT3494A TYPICAL APPLICATION L1 10μH VIN 3V TO 4.2V Efficiency and Power Loss vs Load Current D1 80 3 8 SW CAP VCC VOUT 7 LT3494A 5 4 SHDN FB CTRL GND 6 75 70 VOUT R1 300 LOAD FROM CAPACITOR C1 0.47μF C3 10μF 2 3494 F06 C1, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING C3: TAIYO YUDEN TMK316BJ106ML D1: CENTRAL SEMICONDUCTOR CMDSH-3 L1: MURATA LQH32CN100K53 200 65 150 60 55 100 50 50 45 40 0.1 Figure 6. One Li-Ion Cell Input Boost Converter with the LT3494A VIN = 3.6V VOUT = 16V 1 10 LOAD CURRENT (mA) Output Voltage Ripple vs Load Current VOUT PEAK-TO-PEAK RIPPLE (mV) 15 5 0 0.1 1 10 LOAD CURRENT (mA) 100 0 100 3494 F06b 100MHz MEASUREMENT BW 10 250 LOAD FROM VOUT POWER LOSS (mW) 1 EFFICIENCY (%) C2 4.7μF VOUT 25 24 23 22 21 20 19 18 17 16 15 R1 VALUE REQUIRED (MΩ) 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 3494 F06c RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1613 550mA (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1μA, ThinSOT Package LT1615/LT1615-1 300mA/80mA (ISW), High Efficiency Step-Up DC/DC Converters VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20μA, ISD < 1μA, ThinSOT Package LT1930/LT1930A 1A (ISW), 1.2MHz/2.2MHz, High Efficiency Step-Up DC/DC Converters VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2A/5.5mA, ISD < 1μA, ThinSOT Package LT1945 (Dual) Dual Output, Boost/Inverter, 350mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter VIN: 1.2V to 15V, VOUT(MAX) = ±34V, IQ = 40μA, ISD < 1μA, 10-Lead MS Package LT1946/LT1946A 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converters VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA, ISD < 1μA, 8-Lead MS Package LT3467/LT3467A 1.1A (ISW), 1.3MHz/2.1MHz, High Efficiency Step-Up DC/DC Converters with Soft-Start VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 1.2mA, ISD < 1μA, ThinSOT Package LT3463/LT3463A Dual Output, Boost/Inverter, 250mA (ISW), Constant Off-Time, High VIN: 2.3V to 15V, VOUT(MAX) = ±40V, IQ = 40μA, ISD < 1μA, 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 < 1μA, DFN Package 3494fb 12 Linear Technology Corporation LT 0507 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2006