LT3048 Series Low Noise Bias Generator in 2mm × 2mm DFN FEATURES DESCRIPTION Generates Low Noise Bias Voltage from Single Cell Li-Ion Battery nn Output Current: Up to 40mA nn Low Output Ripple and Noise: <500µV P-P nn Boost Regulator nn 1MHz Operation (LT3048) nn 2.2MHz Operation (LT3048-XX) nn Integrated Schottky Diode nn Low Dropout Linear Regulator nn 1.235V Feedback Voltage (LT3048) nn Low Noise: <120µV RMS (10Hz to 100kHz) nn 0.1% Load Regulation nn Fixed 3.3V, 5V, 12V, 15V and Adjustable Output Options nn Short-Circuit and Thermal Protection nn Load Disconnect in Shutdown nn Available in 2mm × 2mm DFN Package The LT®3048 series generate low noise, low ripple bias supplies from input voltages of 2.7V to 4.8V. nn The LT3048 includes a boost regulator and a LDO linear regulator. The boost regulator provides power to the linear regulator. The boost regulator output voltage is regulated to 1.1V above the LDO output, optimizing LDO ripple rejection and transient response. Fixed frequency operation and current mode control allow the use of very small inductors and results in low, predictable output ripple. The linear regulator in the LT3048 generates a programmable output and the LT3048-XX generate fixed output voltages. High power supply ripple rejection combined with a low noise internal reference results in less than 500µVP-P output ripple and noise. The LT3048 is available in a 8-lead 2mm × 2mm DFN package. APPLICATIONS L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Sensor Bias nn Op Amp Supply nn TYPICAL APPLICATION Efficiency 10µH SW 1µF VIN 70 4.7µF BSTOUT 60 LDOIN LT3048-15 LDOOUT OFF ON BYP EN GND 3048 TA01a 1nF 1µF OUT 15V VIN (V) IOUT (mA) 2.7 19 3.3 22 3.6 24 EFFICIENCY (%) IN 2.7V TO 4.8V 80 50 40 30 LDOOUT = 15V L = 10µH DCR = 650mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 0 0 5 10 20 15 LOAD CURRENT (mA) 25 3048 TA01b 3048fa For more information www.linear.com/LT3048 1 LT3048 Series ABSOLUTE MAXIMUM RATINGS (Note 1) VIN...............................................................................6V SW.............................................................................25V BSTOUT.....................................................................23V LDOIN........................................................................22V LDOOUT.....................................................................22V FB................................................................................6V BYP.........................................................................±0.3V EN................................................................................6V Operating Junction Temperature Range (Note 2) E-Grade............................................... –40°C to 125°C I-Grade............................................... –40°C to 125°C Maximum Junction Temperature........................... 125°C Storage Temperature Range................... –65°C to 150°C PIN CONFIGURATION LT3048-XX LT3048 TOP VIEW TOP VIEW SW 1 8 BSTOUT SW 1 VIN 2 7 EN VIN 2 GND 3 BYP 4 9 GND 6 LDOIN GND 3 5 LDOOUT BYP 4 DC PACKAGE 8-LEAD (2mm × 2mm) PLASTIC DFN 8 BSTOUT 9 GND 7 EN 6 LDOOUT 5 FB DC PACKAGE 8-LEAD (2mm × 2mm) PLASTIC DFN θJA = 102°C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB θJA = 102°C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3048EDC#PBF LT3048EDC#TRPBF LGRR 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048IDC#PBF LT3048IDC#TRPBF LGRR 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048EDC-15#PBF LT3048EDC-15#TRPBF LGKK 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048IDC-15#PBF LT3048IDC-15#TRPBF LGKK 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048EDC-12#PBF LT3048EDC-12#TRPBF LGQQ 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048IDC-12#PBF LT3048IDC-12#TRPBF LGQQ 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048EDC-5#PBF LT3048EDC-5#TRPBF LGQR 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048IDC-5#PBF LT3048IDC-5#TRPBF LGQR 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048EDC-3.3#PBF LT3048EDC-3.3#TRPBF LGQS 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LT3048IDC-3.3t#PBF LT3048IDC-3.3#TRPBF LGQS 8-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 2 3048fa For more information www.linear.com/LT3048 LT3048 Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, EN/UVLO = 3V, unless otherwise noted. Parameter applies to all options unless specified. PARAMETER CONDITIONS MIN VIN Operating Range TYP 2.7 MAX 4.8 UNITS V Boost Regulator BSTOUT-LDOOUT Regulation Voltage l 1 1.1 1.2 V BSTOUT-VIN Regulation Voltage LDOOUT < VIN 1.1 V VIN Quiescent Current Not Switching EN ≤ 0.4V 475 0.1 600 1 µA µA Switching Frequency LT3048 l 0.75 0.7 1.00 1.00 1.25 1.30 MHz MHz l 1.7 1.6 2.2 2.2 2.7 2.8 MHz MHz LT3048-XX Maximum Duty Cycle LT3048 LT3048-XX 93 86 95 90 Switch Current Limit (Note 3) 300 400 Switch VCESAT ISW = 200mA Diode Forward Drop IDIODE = 100mA EN Voltage High % % 500 mA 220 mV 0.84 V 1.25 V EN Voltage Low 0.4 V µA LDO Linear Regulator LDO Quiescent Current LT3048: Supplied by LDOIN 14 20 LT3048-XX: Supplied by BSTOUT 14 20 FB Pin Current FB Regulation Voltage 60 LT3048: ILOAD = 100µA, FB = LDOOUT LT3048: 100µA ≤ ILOAD ≤ 40mA l 1.216 1.210 µA nA 1.235 1.235 1.254 1.260 2 6 V V FB Load Regulation LT3048: ∆ILOAD = 100µA to 40mA LDOOUT Regulation Voltage LT3048-15: ILOAD = 100µA LT3048-15: 100µA ≤ ILOAD ≤ 40mA l 14.775 14.625 15.00 15.00 15.225 15.375 V V LT3048-12: ILOAD = 100µA LT3048-12: 100µA ≤ ILOAD ≤ 40mA l 11.82 11.70 12.00 12.00 12.18 12.30 V V LT3048-5: ILOAD = 100µA LT3048-5: 100µA ≤ ILOAD ≤ 40mA l 4.925 4.875 5.00 5.00 5.075 5.125 V V LT3048-3.3: ILOAD = 100µA LT3048-3.3: 100µA ≤ ILOAD ≤ 40mA l 3.250 3.217 3.300 3.300 3.350 3.383 V V LT3048-15: ∆ILOAD = 100µA to 40mA 20 45 mV LT3048-12: ∆ILOAD = 100µA to 40mA 20 45 mV LT3048-5: ∆ILOAD = 100µA to 40mA 12 25 mV LT3048-3.3: ∆ILOAD = 100µA to 40mA 9 18 mV LDOOUT Load Regulation mV 3048fa For more information www.linear.com/LT3048 3 LT3048 Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, EN/UVLO = 3V, unless otherwise noted. Parameter applies to all options unless specified. PARAMETER CONDITIONS LDOOUT Voltage Noise BW = 10Hz to 100kHz COUT = 1µF LT3048: CBYP = 0nF, ILOAD = 40mA, LDOOUT = 1.235V LT3048: CBYP = 1nF, ILOAD = 40mA, LDOOUT = 1.235V 38 25 µVRMS µVRMS LT3048-15: CBYP = 0nF, ILOAD = 24mA LT3048-15: CBYP = 1nF, ILOAD = 24mA 250 60 µVRMS µVRMS LT3048-12: CBYP = 0nF, ILOAD = 31mA LT3048-12: CBYP = 1nF, ILOAD = 31mA 225 60 µVRMS µVRMS LT3048-5: CBYP = 0nF, ILOAD = 40mA LT3048:-5: CBYP = 1nF, ILOAD = 40mA 145 50 µVRMS µVRMS LT3048-3.3: CBYP = 0nF, ILOAD = 40mA LT3048-3.3: CBYP = 1nF, ILOAD = 40mA 120 42 µVRMS µVRMS LT3048: fRIPPLE = 1.0MHz, ILOAD = 40mA LT3048: fRIPPLE = 2.2MHz, ILOAD = 40mA 60 53 dB dB 80 mA Ripple Rejection MIN Current Limit l 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 LT3048E is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The 4 45 TYP MAX UNITS LT3048I is guaranteed over the full –40°C to 125°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125°C. Note 3: Current limit guaranteed by design and/or correlation to static test. Slope compensation reduces current limit at higher duty cycle. 3048fa For more information www.linear.com/LT3048 LT3048 Series TYPICAL PERFORMANCE CHARACTERISTICS LT3048 FB Load Regulation 1.255 1.255 1.250 1.250 1.245 1.245 LT3048 Switching Frequency 1.3 FB VOLTAGE (V) FB VOLTAGE (V) 1.260 SWITCHING FREQUENCY (MHz) LT3048 FB Voltage 1.260 1.240 1.240 1.235 1.235 1.230 1.230 1.225 1.225 1.220 1.220 1.215 1.215 1.210 –50 –25 0 50 25 75 TEMPERATURE (°C) 100 1.210 125 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 LT3048 LDOOUT Noise VIN = 3.6V VOUT = 1.235V L = 5.6μH CBSTOUT = 4.7μF CLDOOUT = 1μF CBYP = 1nF ILOAD = 40mA 50 40 30 LDOOUT = 15V L = 10µH DCR = 650mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 10 0 1M 3048 G04 LT3048-15 LDOOUT Voltage 0 5 10 20 15 LOAD CURRENT (mA) 15.0 14.9 14.8 14.7 25 0 5 10 15 20 25 30 LOAD CURRENT (mA) 14.9 14.8 14.7 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3048 G07 60 –50 50 –100 40 30 –150 –200 ILOAD 20 10 –250 –300 VIN = 3.6V 10µs/DIV VOUT = 15V L = 10µH CLDOOUT = 1µF CBYP = 1nF ILOAD = 4mA TO 20mA 10000 3048 G08 For more information www.linear.com/LT3048 0 NOISE SPECTRAL DENSITY (nV/√Hz) OUTPUT VOLTAGE DEVIATION (mV) LDOOUT VOLTAGE (V) 15.0 VOUT 40 LT3048-15 LDOOUT Noise 70 LOAD CURRENT (mA) 15.1 0 35 3048 G06 LT3048-15 Transient Response 50 15.2 125 15.1 3048 G05 15.3 100 15.2 20 100k 0 50 25 75 TEMPERATURE (°C) 15.3 LDOOUT VOLTAGE (V) EFFICIENCY (%) NOISE SPECTRAL DENSITY (nV/√Hz) 10 1k 10k FREQUENCY (Hz) –25 LT3048-15 LDOOUT Load Regulation 60 100 0.8 3048 G03 70 10 0.9 0.7 –50 40 80 100 0.01 1.0 LT3048-15 Efficiency 1000 0.1 1.1 3048 G02 3048 G01 1 1.2 1000 100 VIN = 3.6V VOUT = 15V L = 10μH CBSTOUT = 4.7μF CLDOOUT = 1μF CBYP = 1nF ILOAD = 24mA 10 1 0.1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 3048 G09 3048fa 5 LT3048 Series TYPICAL PERFORMANCE CHARACTERISTICS Operating Waveforms: DCM LT3048-12 Efficiency Operating Waveforms: CCM 80 70 VSW 5V/DIV VSW 5V/DIV EFFICIENCY (%) IL 100mA/DIV 60 IL 100mA/DIV 50 40 30 VOUT = 12V L = 10µH DCR = 650mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 3048 G10 500ns/DIV VIN = 3.6V VOUT = 15V L = 10µH ILOAD = 20mA 12.3 12.2 12.2 12.1 12.0 12.9 12.7 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 12.0 11.9 –25 0 50 25 75 TEMPERATURE (°C) 3048 G13 LDOOUT VOLTAGE (V) EFFICIENCY (%) 40 VOUT = 5V L = 4.7µH DCR = 350mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 0 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 1 10 100 1k 10k FREQUENCY (Hz) 100k LT3048-5 LDOOUT Voltage 5.125 5.100 5.100 5.075 5.075 5.050 5.025 5.000 4.975 4.950 5.050 5.025 5.0 4.975 4.950 4.925 4.925 4.900 4.900 0 5 10 15 20 25 30 LOAD CURRENT (mA) 1M 3048 G15 5.125 4.875 40 VIN = 3.6V VOUT = 12V L = 10μH CBSTOUT = 4.7μF CLDOOUT = 1μF CBYP = 1nF ILOAD = 31mA 10 0.1 125 LDOOUT VOLTAGE (V) 60 30 100 100 LT3048-5 LDOOUT Load Regulation 70 30 1000 3048 G14 LT3048-5 Efficiency 50 25 LT3048-12 LDOOUT Noise 12.1 11.7 –50 40 10 20 15 LOAD CURRENT (mA) 10000 11.0 12.8 5 0 3048 G12 LT3048-12 LDOOUT Voltage 12.3 LDOOUT VOLTAGE (V) LDOOUT VOLTAGE (V) LT3048-12 LDOOUT Load Regulation 0 3048 G11 500ns/DIV NOISE SPECTRAL DENSITY (nV/√Hz) VIN = 3.6V VOUT = 15V L = 2.2µH ILOAD = 15mA 35 40 3048 G17 4.875 –50 –25 0 50 25 75 TEMPERATURE (°C) 100 125 3048 G18 3048 G16 6 3048fa For more information www.linear.com/LT3048 LT3048 Series TYPICAL PERFORMANCE CHARACTERISTICS LT3048-5 LDOOUT Noise 3.38 60 3.36 100 VIN = 3.6V VOUT = 5V L = 4.7μH CBSTOUT = 2.2μF CLDOOUT = 1μF CBYP = 1nF ILOAD = 40mA 10 1 10 100 1k 10k FREQUENCY (Hz) 40 30 VOUT = 3.3V L = 3.3µH DCR = 285mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 100k 0 1M LDOOUT VOLTAGE (V) 50 1000 EFFICIENCY (%) NOISE SPECTRAL DENSITY (nV/√Hz) 10000 0.1 LT3048-3.3 LDOOUT Load Regulation LT3048-3.3 Efficiency 0 5 10 15 20 25 30 LOAD CURRENT (mA) 3048 G19 35 3.34 3.32 3.30 3.28 3.26 3.24 3.22 40 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 40 3048 G21 3048 G20 LT3048-3.3 LDOOUT Voltage LT3048-3.3 LDOOUT Noise NOISE SPECTRAL DENSITY (nV/√Hz) 3.36 LDOOUT VOLTAGE (V) LDOOUT Current Limit 90 10000 3.34 3.32 3.30 3.28 3.26 3.24 3.22 –50 –25 25 75 0 50 TEMPERATURE (°C) 100 80 1000 100 VIN = 3.6V VOUT = 3.3V L = 3.3μH CBSTOUT = 2.2μF CLDOOUT = 1μF CBYP = 1nF ILOAD = 40mA 10 1 0.1 125 70 CURRENT LIMIT (mA) 3.38 10 100 1k 10k FREQUENCY (Hz) 60 50 40 30 20 10 100k 3048 G22 0 –50 1M 0 25 50 75 TEMPERATURE (°C) –25 3048 G23 125 100 3048 G24 Boost Switch Current Limit 500 450 450 400 400 350 300 250 200 150 100 2.0 350 300 250 200 150 100 1.5 1.0 0.5 50 50 0 LT3048-XX Switching Frequency 2.5 FREQUENCY (MHz) SWITCH CURRENT LIMIT (mA) SWITCH CURRENT LIMIT (mA) Boost Switch Current Limit 500 0 20 60 40 DUTY CYCLE (%) 80 100 3048 G25 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3048 G26 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3048 G27 3048fa For more information www.linear.com/LT3048 7 LT3048 Series PIN FUNCTIONS LT3048 LT3048-XX SW (Pin 1): Boost Regulator Switch Node. This is the collector of the internal power transistor and the anode of the internal Schottky diode. SW (Pin 1): Boost Regulator Switch Node. This is the collector of the internal power transistor and the anode of the internal Schottky diode. VIN (Pin 2): Input Supply. Provides operating current to the boost regulator. Bypass to ground. VIN (Pin 2): Input Supply. Provides operating current to the boost regulator. Bypass to ground. GND (Pin 3): Ground. This pin must be soldered to PCB ground. The exposed pad must also be soldered to PCB ground. GND (Pin 3): Ground. This pin must be soldered to PCB ground. The exposed pad must also be soldered to PCB ground. BYP (Pin 4): Bypass. Add an optional capacitor from LDOOUT to BYP to reduce noise at LDOOUT; otherwise leave BYP unconnected. A capacitor also soft-starts the linear regulator. BYP (Pin 4): Bypass. Add an optional capacitor from LDOOUT to BYP to reduce noise at LDOOUT; otherwise leave BYP unconnected. A capacitor also soft-starts the linear regulator. FB (Pin 5): The LT3048 regulates the FB pin to 1.25V. Connect the feedback resistor divider tap to this pin. LDOOUT (Pin 5): LDO Linear Regulator Output. This pin is regulated to a fixed voltage. Bypass to ground with a minimum of 1μF. LDOOUT (Pin 6): LDO Linear Regulator Output. This pin is programmed by the feedback resistor divider. Bypass to ground with a minimum of 1μF. LDOIN (Pin 6): LDO Linear Regulator Input. Normally connected to BSTOUT. Bypass to ground. EN (Pin 7): Enable. Logic input to enable the boost and linear regulator. EN (Pin 7): Enable. Logic input to enable the boost and linear regulator. BSTOUT (Pin 8): Boost Regulator Output. This pin is connected to the internal Schottky diode and is regulated to 1.1V above LDOOUT. Bypass to ground. BSTOUT (Pin 8): Boost Regulator Output. This pin is connected to the internal Schottky diode and is regulated to 1.1V above LDOOUT. Bypass to ground. GND (Exposed Pad Pin 9): The internal boost power switch is connected to the exposed pad. Tie to ground. GND (Exposed Pad Pin 9): The internal boost power switch is connected to the exposed pad. Tie to ground. 8 3048fa For more information www.linear.com/LT3048 LT3048 Series LT3048 BLOCK DIAGRAMS L1 IN C2 C1 2 1 VIN 8 BSTOUT SW Q2 + 1.1V LDOOUT OUT 6 ON OFF 7 EN C4 OSC C3 Q1 – + + BYP R1 4 A1 FB 5 R2 VC + 1.235V GND 3, 9 3048 F01a Figure 1a. LT3048 Block Diagram L1 IN C2 C1 2 1 VIN 8 6 BSTOUT SW LDOIN Q2 + 1.1V LDOOUT OUT 5 ON OFF 7 EN C4 OSC C3 Q1 – + + BYP 4 A1 VC + GND 3, 9 3048 F01b Figure 1b. LT3048-XX Block Diagram 3048fa For more information www.linear.com/LT3048 9 LT3048 Series OPERATION The LT3048 combines a boost regulator with a low dropout linear regulator to produce a programmable output from a lower input voltage. The LT3048-15, LT3048-12, LT3048-5, LT3048-3.3 regulate to 15V, 12V, 5V and 3.3V, respectively. With EN below 0.4V, all circuits are turned off, Q2 disconnects the load from the input, and current consumption is less than 1µA. Driving EN high enables the oscillator and all bias circuits including voltage reference and regulation amplifiers. The boost regulator uses peak current mode operation, providing cycle-by-cycle current regulation and limiting, fast transient response, and good stability. The error amplifier, A1, regulates BSTOUT (and LDOIN) to 1.1V above LDOOUT or VIN, whichever is higher. Regulating 1.1V between LDOIN and LDOOUT allows the linear regulator to provide good transient response and ripple rejection, while maintaining good efficiency. This regulation loop also minimizes total power dissipation in fault conditions. If the output is overloaded, the linear regulator will enter current limit, LDOOUT voltage will decrease. By reducing the boost regulator output voltage, the voltage across Q2 will be reduced, limiting dissipation in Q2. Thermal shutdown provides additional protection. APPLICATIONS INFORMATION Capacitor Selection Inductor Selection A 4.7μF ceramic capacitor should be sufficient for the boost regulator output bypass. Low ESR (equivalent series resistance) ceramic capacitors should be used at the outputs of the regulator to minimize the output ripple voltage. Use only X5R or X7R dielectrics, as these materials retain their capacitance over wider voltage and temperature ranges better than other dielectrics. A 5.6μH inductor will suffice for most LT3048 applications. See Table 2 for recommended inductor values. Smaller value inductors can be used at the cost of reduced maximum load current. Figure 2 shows the maximum load current as a function of output voltage. The inductor’s RMS current rating must be greater than the maximum input current. To keep efficiency high, the DCR (series resistance) should be minimized. Table 3 lists several vendors. Table 1. Ceramic Capacitor Manufacturers MANUFACTURER PHONE WEB Table 2. Recommended Inductor Values Taiyo Yuden (408) 573-4150 www.t-yuden.com PART # INDUCTANCE AVX (803) 448-9411 www.avxcorp.com LT3048 5.6μH www.murata.com LT3048-15 10μH LT3048-12 10μH LT3048-5 4.7μH LT3048-3.3 3.3μH Murata (714) 852-2001 FB Resistor Network The output voltage is programmed with a resistor divider between the output and FB pin. Choose the 1% resistors according to: V R1= R2 OUT − 1 1.235V R2 should be 200k or less to avoid bias current errors. 10 Table 3. Inductor Manufacturers VENDOR URL Coilcraft www.coilcraft.com Sumida www.sumida.com Toko www.toko.com Würth Elektronik www.we-online.com 3048fa For more information www.linear.com/LT3048 LT3048 Series APPLICATIONS INFORMATION 45 L = 5.6µH DCR = 120mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 40 LOAD CURRENT (mA) 35 30 C1 C2 GUARANTEED 25 20 15 L1 10 5 0 0 2 4 6 8 10 12 14 16 18 20 22 LDOOUT VOLTAGE (V) C4 C3 3048 F02 Figure 2. LT3048 Typical and Guaranteed Load Current vs. Output Voltage Reducing Output Noise With A Bypass Capacitor The LT3048 relies on the power supply rejection of the linear regulator to reduce switching regulator noise at LDOOUT. The linear regulator also contributes thermal noise to the output. The thermal noise can be reduced, and transient response improved, by adding a capacitor between LDOOUT and BYP. A typical value is 1nF. This capacitor increases start-up time of the regulator. Recommended PCB Layout Figure 3 shows the recommended layout for LT3048 circuits. Most important is careful placement of the BSTOUT bypass capacitor C2. High frequency AC current flows in a loop formed by C2, internal power transistor Q1 and boost diode D2. Keep this loop small. Also be sure to place an unbroken ground plane below this loop, on the highest copper layer below the surface. This prevents the AC loop from coupling to LDOOUT and other nearby circuitry. Keep the SW node as small as possible. LDO Stability and Output Capacitance The LT3048 linear regulator requires an output capacitor for stability. It is designed to be stable with most low ESR capacitors (typically ceramic, tantalum or low ESR electrolytic). A minimum output capacitor of 1μF with an ESR of 1Ω or less is recommended to prevent oscillations. Larger values of output capacitance decrease peak 3048 F03 Figure 3. Recommended PCB Layout deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3048, increase the effective output capacitor value. Give consideration to the use of ceramic capacitors as they are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specified with EIA codes of Z5U, Y5V, X5R and X7R. Typical voltage and temperature coefficients are shown in Figures 4 and 5. The X5R and X7R dielectrics have more stable characteristics and are most suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. Care still must be exercised when using X5R and X7R capacitors; the codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors can be significant enough to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as case size increases, but expected capacitance at operating voltage should be verified. 3048fa For more information www.linear.com/LT3048 11 LT3048 Series APPLICATIONS INFORMATION Wide Input Voltage Applications 40 The LT3048 can be used in wide input voltage applications. The input supply voltage to the LT3048 must be between 2.7V and 4.8V and capable of at least 10mA. The inductor can run off a separate voltage supply (PVIN). This technique allows the output to be powered from 1V to 23V (see Figure 6). CHANGE IN VALUE (%) 20 X5R 0 –20 –40 Y5V –60 –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF –100 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 3048 F04 Figure 4. Ceramic Capacitor Temperature Characteristics 20 SW IN 2.7V TO 4.8V 1µF VIN BSTOUT 4.7µF OUT 5V LDOUT 301k LT3048 1nF FB BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF 0 CHANGE IN VALUE (%) 5.6µH PVIN 1V TO 23V 100k OFF ON X5R EN GND BYP 1µF 3048 F06 –20 –40 Figure 6. Connecting the Inductor to a Separate Voltage Supply –60 Y5V –80 –100 0 2 4 6 8 10 12 DC BIAS VOLTAGE (V) 14 16 3048 F05 Figure 5. Ceramic Capacitor DC Bias Characteristics Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress. In a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients. 12 3048fa For more information www.linear.com/LT3048 LT3048 Series APPLICATIONS INFORMATION LT3048 LT3048 Efficiency 70 5.6µH WE-LHMI4020 SW BSTOUT VIN 1µF 60 4.7µF LDOUT 301k LT3048 1nF FB OUT 5V 30mA 100k OFF ON BYP EN 50 EFFICIENCY (%) IN 2.7V TO 4.8V 1µF GND 40 30 VOUT = 5V L = 5.6µH DCR = 120mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 3048 TA2a 10 0 0 5 10 20 15 LOAD CURRENT (mA) 25 30 3048 TA02b LT3048-15 80 10µH LPS3008-103MLB SW 1µF 70 4.7µF BSTOUT VIN LDOIN LT3048-15 LDOOUT OFF ON 60 BYP EN 1nF GND 3048 TA03a OUT 15V 1µF VIN (V) IOUT (mA) 2.7 19 3.3 22 3.6 24 EFFICIENCY (%) IN 2.7V TO 4.8V LT3048-15: Efficiency 50 40 30 LDOOUT = 15V L = 10µH DCR = 650mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 0 5 0 10 20 15 LOAD CURRENT (mA) 25 3048 TA03b LT3048-12 80 10µH LPS3008-103MR SW 1µF 70 4.7µF BSTOUT VIN LDOIN LT3048-12 LDOOUT OFF ON 60 BYP EN GND 3048 TA04a 1nF OUT 12V 1µF VIN (V) IOUT (mA) 2.7 25 3.3 29 3.6 30 EFFICIENCY (%) IN 2.7V TO 4.8V LT3048-12: Efficiency 50 40 30 VOUT = 12V L = 10µH DCR = 650mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 0 0 5 10 20 15 LOAD CURRENT (mA) 25 30 3048 TA04b 3048fa For more information www.linear.com/LT3048 13 LT3048 Series PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DC8 Package 8-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1939 Rev Ø) Exposed Pad Variation AA 1.8 REF 0.90 REF 0.23 REF 0.85 ±0.05 2.60 ±0.05 PACKAGE OUTLINE 0.335 REF 0.25 ±0.05 0.45 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.00 ±0.05 (4 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 2.00 SQ ±0.05 1.8 REF 5 8 0.23 0.335 REF REF 0.55 ±0.05 PIN 1 NOTCH R = 0.15 (DC8MA) DFN 0113 REV Ø 4 0.200 REF 0.75 ±0.05 1 0.23 ±0.05 0.45 BSC BOTTOM VIEW—EXPOSED PAD 0.00 – 0.05 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 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 14 3048fa For more information www.linear.com/LT3048 LT3048 Series REVISION HISTORY REV DATE DESCRIPTION A 2/15 Clarified to Include All Fixed and Adjustable Output Options PAGE NUMBER 1 − 16 3048fa 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. For more information www.linear.com/LT3048 15 LT3048 Series TYPICAL APPLICATIONS LT3048-5 70 4.7µH LPS3008-472MR 60 SW 1µF 4.7µF BSTOUT VIN 50 LDOIN LT3048-5 LDOOUT OFF ON 1nF BYP EN OUT 5V 1µF 40mA EFFICIENCY (%) IN 2.7V TO 4.8V LT3048-5: Efficiency 40 30 VOUT = 5V L = 4.7µH DCR = 350mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 GND 3048 TA05a 10 0 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 40 3048 TA05b LT3048-3.3 60 3.3µH LPS3008-332MR SW 1µF BSTOUT VIN LDOIN LT3048-3.3 LDOOUT OFF ON 1nF BYP EN 50 4.7µF OUT 3.3V 1µF 40mA EFFICIENCY (%) IN 2.7V TO 4.8V LT3048-3.3: Efficiency GND 40 30 VOUT = 3.3V L = 3.3µH DCR = 285mΩ VIN = 2.7V VIN = 3.3V VIN = 3.6V 20 10 3048 TA06a 0 0 5 10 15 20 25 30 LOAD CURRENT (mA) 35 40 3048 TA06b RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT3460 300mA, 38V ISW, 1.3MHz, High Efficiency Step-Up DC/DC Converter VIN: 2.5V to 16V, VOUT(MAX) = 36V, IQ = 2mA, ISD < 1µA, SC70, ThinSOT™ Package LT3461/LT3461A 300mA, 38V ISW, 1.3MHz, High Efficiency Step-Up DC/DC Converters VIN: 2.5V to 16V, VOUT(MAX) = 38V, IQ = 2.8mA, ISD < 1µA, SC70, ThinSOT Packages LT3464 120mA, 38V ISW, High Efficiency Step-Up DC/DC Converter with Integrated Schottky, Output Disconnect VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA, ThinSOT Package 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 LT1761 20V, 100mA (IOUT) Low Noise LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 20µA, ISD < 1µA, ThinSOT Package LT3009 20V, 20mA (IOUT) Low Noise LDO VIN: 1.6V to 20V, VOUT(MIN) = 0.6V, IQ = 3µA, ISD < 1µA, SC70, 2mm × 2mm DFN-6 Packages 16 3048fa Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LT3048 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT3048 LT 0215 REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2014