LT8410/LT8410-1 Ultralow Power Boost Converter with Output Disconnect DESCRIPTION FEATURES n n n n n n n n n n n n n Ultralow Quiescent Current 8.5μA in Active Mode 0μA in Shutdown Mode Comparator Built into SHDN pin Low Noise Control Scheme Adjustable FB reference voltage Wide Input Range: 2.5V to 16V Wide Output Range : Up to 40V Integrated Power NPN Switch 25mA Current Limit (LT8410) 8mA Current Limit (LT8410-1) Integrated Schottky Diode Integrated Output Disconnect High Value (12.4M/0.4M) Feedback Resistors Integrated Built in Soft-Start (Optional Capacitor from VREF to GND) Overvoltage Protection for CAP and VOUT pins Tiny 8-Pin 2mm × 2mm DFN package The LT®8410/LT8410-1 are ultralow power boost converters with integrated power switch, Schottky diode and output disconnect circuitry. The parts control power delivery by varying both the peak inductor current and switch offtime. This control scheme results in low output voltage ripple as well as high efficiency over a wide load range. The quiescent current is a low 8.5μA, which is further reduced to 0μA in shutdown. The internal disconnect circuitry allows the output voltage to be blocked from the input during shutdown. High value (12.4M/0.4M) resistors are integrated on chip for output voltage detection, significantly reducing input referred quiescent current. The LT8410/-1 also features a comparator built into the SHDN pin, over voltage protection for the CAP and VOUT pins, built in soft-start and comes in a tiny 8-pin 2mm × 2mm DFN package. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. APPLICATIONS n n Sensor Power RF Mems Relay Power General Purpose Bias TYPICAL APPLICATION Output Voltage Ripple vs Load Current General Purpose Bias with Wide Input Voltage Efficiency vs Load Current 10 VIN 2.5V to 16V VIN = 3.6V 2.2μF 0.1μF SW CAP VCC VOUT VOUT = 16V LT8410 VREF 0.1μF* SHDN 604K GND 0.1μF FBP 412K *HIGHER VALUE CAPACITOR IS REQUIRED WHEN THE VIN IS HIGHER THAN 5V 8410-1 TA01a VOUT PEAK-TO-PEAK RIPPLE (mV) 100μH CHIP ENABLE 100 VIN = 12V 90 8 EFFICIENCY (%) n 6 4 2 0 0.01 VIN = 5V 80 VIN = 3.6V 70 60 50 0.1 1 LOAD CURRENT (mA) 10 8410-1 TA02 40 0.01 0.1 1 10 LOAD CURRENT (mA) 100 8410-1 TA03 84101f 1 LT8410/LT8410-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VCC Voltage ................................................ –0.3V to 16V SW Voltage ................................................ –0.3V to 40V CAP Voltage ............................................... –0.3V to 40V VOUT Voltage .............................................. –0.3V to 40V SHDN Voltage ............................................ –0.3V to 16V VREF Voltage.............................................. –0.3V to 2.5V FBP Voltage .............................................. –0.3V to 2.5V Maximum Junction Temperature .......................... 125°C Operating Temperature Range (Note 2)..–40°C to 125°C Storage Temperature Range...................–65°C to 150°C TOP VIEW SHDN 1 8 FBP VCC 2 9 7 VREF GND 3 6 CAP SW 4 5 VOUT DC PACKAGE 8-PIN (2mm s 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 88°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 LT8410EDC#PBF LT8410EDC#TRPBF LDQR 8-Lead (2mm × 2mm) Plastic DFN – 40°C to 125°C LT8410IDC#PBF LT8410IDC#TRPBF LDQR 8-Lead (2mm × 2mm) Plastic DFN – 40°C to 125°C LT8410EDC-1#PBF LT8410EDC-1#TRPBF LFCC 8-Lead (2mm × 2mm) Plastic DFN – 40°C to 125°C LT8410IDC-1#PBF LT8410IDC-1#TRPBF LFCC 8-Lead (2mm × 2mm) Plastic DFN – 40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard 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/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN =3.0V, VSHDN =VIN unless otherwise noted. (Note 2) PARAMETER CONDITIONS MIN Minimum Operating Voltage TYP MAX 2.2 2.5 V 16 V Maximum Operating Voltage l Reference Voltage VREF Current Limit 1.220 (Note 3) VREF Discharge Time VREF Line Regulation Quiescent Current 1.235 1.255 l l Quiescent Current in Shutdown VSHDN = 0V Quiescent Current from VOUT and CAP VOUT = 16V Minimum Switch Off Time After Start-Up (Note 4) During Start-Up (Note 4) Switch Current Limit LT8410 LT8410-1 l l 20 6 V 10 μA 70 μS 0.01 Not Switching UNITS %/V 8.5 12 0 1 μA μA 3 μA 240 600 nS nS 25 8 30 10 mA mA 84101f 2 LT8410/LT8410-1 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN =3.0V, VSHDN =VIN unless otherwise noted. (Note 2) PARAMETER CONDITIONS Switch VCESAT LT8410, ISW = 10mA LT8410-1, ISW = 4mA Switch Leakage Current VSW = 5V Schottky Forward Voltage IDIODE = 10mA Schottky Reverse Leakage VCAP – VSW = 5 VCAP – VSW = 40 PMOS Disconnect Current Limit LT8410 LT8410-1 PMOS Disconnect VCAP – VOUT IOUT = 1mA MIN TYP 150 100 FBP Pin Bias Current VFBP = 0.5V, Current Flows Out of Pin l SHDN Minimum Input Voltage High SHDN Rising l 0 1 μA 650 850 mV 0 0 0.5 1 μA μA 14 2.5 19 4 25 5 mA mA 31.6 31.85 32.2 1.3 30 1.30 1.45 1.20 SHDN Input Voltage High Hysteresis 0.08 (Note 3) 0.1 SHDN Input Voltage Low SHDN Pin Bias Current VSHDN = 3V VSHDN = 16V 400 200 0 1 2 LOAD CURRENT (mA) 3 8410-1 G01 VCC = 3.6V VOUT = 16V FIGURE 4 CIRCUIT 0.4 V 1 3 μA μA 40 0.2 0 –0.2 30 20 10 –0.4 –0.6 0.3 50 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE CHANGE (%) SWITCHING FREQUENCY (kHz) 600 μA VOUT vs FBP Voltage 0.6 VCC = 3.6V VOUT = 16V FIGURE 4 CIRCUIT 0.14 TA = 25°C, unless otherwise noted. Load Regulation 1000 V the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: See applications section for more information. Note 4: Start-up mode occurs when VOUT is less than VFBP • 64/3. TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency vs Load Current nA mV 0 2 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 LT8410/LT8410-1 are guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over 0 mV 60 SHDN Hysteresis Current UNITS mV mV 50 l VOUT Resistor Divider Ratio 800 MAX 0 1 2 LOAD CURRENT (mA) 3 8410-1 G02 0 0 0.5 1 1.5 FBP VOLTAGE (V) 2 8410-1 G03 84101f 3 LT8410/LT8410-1 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Temperature Quiescent Current – Not Switching 1 VCC = 3.6V, VOUT = 16V LOAD = 0.5mA FIGURE 4 CIRCUIT 10 0.5 0.25 0 – 0.25 – 0.5 QUIESCENT CURRENT (μA) 10 QUIESCENT CURRENT (μA) 0.75 OUTPUT VOLTAGE CHANGE (%) Quiescent Current vs Temperature 12 8 6 4 2 – 0.75 8 6 4 2 VCC = 3.6V –1 – 40 0 40 80 TEMPERATURE (°C) 0 120 0 4 8 12 VCC VOLTAGE (V) 8410-1 G04 0 –40 16 10 SHDN Current vs SHDN Voltage 1000 2.5 2 VCC = 3.6V SHDN PIN BIAS CURRENT (μA) QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) VCC = 3.6V 4 120 8410-1 G06 Quiescent Current in Regulation with No Load 6 40 80 TEMPERATURE (°C) 8410-1 G05 Quiescent Current vs SHDN Voltage 8 0 100 2 1.5 1 0.5 0 VCC = 3.6V 0 0 1 2 3 SHDN VOLTAGE (V) 4 10 5 0 10 20 30 OUTPUT VOLTAGE (V) 8410-1 G07 24 13 16 VREF Voltage vs Temperature VCC = 3.6V VOUT = 16V FIGURE 5 CIRCUIT 1.234 VREF VOLTAGE (V) 28 8 12 SHDN VOLTAGE (V) 1.235 15 PEAK INDUCTOR CURRENT (mA) PEAK INDUCTOR CURRENT (mA) 40 32 4 8410-1 G09 Peak Inductor Current vs Temperature (LT8410-1) VCC = 3.6V VOUT = 16V FIGURE 4 CIRCUIT 0 8410-1 G08 Peak Inductor Current vs Temperature (LT8410) 36 –0.5 40 1.233 11 1.232 9 1.231 7 VCC = 3.6V 20 – 40 0 40 80 TEMPERATURE (°C) 120 8410-1 G10 5 –40 0 40 80 TEMPERATURE (°C) 120 8410-1 G11 1.23 –40 0 40 80 TEMPERATURE (°C) 120 8410-1 G12 84101f 4 LT8410/LT8410-1 TYPICAL PERFORMANCE CHARACTERISTICS LT8410 Switching Waveform at 0.5mA Load LT8410 Switching Waveform at No Load VOUT VOLTAGE 2mV/DIV AC COUPLED VOUT VOLTAGE 10mV/DIV AC COUPLED SW VOLTAGE 10V/DIV SW VOLTAGE 10V/DIV INDUCTOR CURRENT 10mA/DIV INDUCTOR CURRENT 20mA/DIV VCC = 3.6V VOUT = 16V 50μs/DIV 8410-1 G13 2μs/DIV VCC = 3.6V VOUT = 16V LT8410 Switching Waveform at 3mA Load 8410-1 G14 UVLO vs Temperature 2.6 VOUT VOLTAGE 10mV/DIV AC COUPLED UVLO VOLTAGE (V) 2.4 SW VOLTAGE 10V/DIV INDUCTOR CURRENT 20mA/DIV VCC = 3.6V VOUT = 16V 500ns/DIV VCC RISING 2.2 VCC FALLING 2 1.8 1.6 8410-1 G15 1.4 –40 0 40 80 TEMPERATURE (°C) 120 8410-1 G16 SHDN Minimum Input Voltage High vs Temperature Line Regulation 1.5 0.3 0.25 1.4 SHDN MINIMUM INPUT VOLTAGE HIGH (V) OUTPUT VOLTAGE CHANGE (%) VOUT = 16V 0.2 0.15 0.1 SHDN FALLING 1.2 1.1 0.05 0 SHDN RISING 1.3 0 4 8 12 VCC VOLTAGE (V) 16 8410-1 G17 1 –40 0 40 80 TEMPERATURE (°C) 120 8410-1 G18 84101f 5 LT8410/LT8410-1 TYPICAL PERFORMANCE CHARACTERISTICS Output Disconnect PMOS Current vs CAP to VOUT Voltage Difference LT8410 Start-Up Waveforms Without Capacitor at VREF Pin 25 SHDN VOLTAGE 5V/DIV VCAP = 16V LT8410 PMOS CURRENT (mA) 20 INDUCTOR CURRENT 20mA/DIV 15 CAP VOLTAGE 5V/DIV VOUT VOLTAGE 5V/DIV 10 LT8410-1 5 VCC = 3.6V VOUT = 16V 0 0 200μs/DIV 8410-1 G20 4 8 12 16 CAP TO VOUT VOLTAGE DIFFERENCE (V) 8410-1 G19 LT8410 Start-Up Waveforms With 0.1μF Capacitor at VREF Pin LT8410 Transient Response 0.5mA→1.5mA→0.5mA Load Pulse SHDN VOLTAGE 5V/DIV VOUT VOLTAGE 200mV/DIV AC COUPLED INDUCTOR CURRENT 20mA/DIV INDUCTOR CURRENT 20mA/DIV LOAD CURRENT 0.5mA/DIV CAP VOLTAGE 5V/DIV VOUT VOLTAGE 5V/DIV VCC = 3.6V VOUT = 16V 2ms/DIV 8410-1 G21 VCC = 3.6V VOUT = 16V 2ms/DIV 8410-1 G22 SW Saturation Voltage vs Switch Current (LT8410) 300 SWITCH VCESAT (mV) 250 200 150 100 50 0 0 5 10 15 20 SWITCH CURRENT (mA) 25 8410-1 G24 84101f 6 LT8410/LT8410-1 PIN FUNCTIONS SHDN (Pin 1): Shutdown Pin. This pin is used to enable/ disable the chip. Drive below 0.3V to disable the chip. Drive above 1.4V to activate the chip. Do not float this pin. VCC (Pin 2): Input Supply Pin. Must be locally bypassed to GND. See typical applications section. VREF (Pin 7): Reference Pin. Soft-start can be achieved by placing a capacitor from this pin to GND. This cap will be discharged for 70μs (typical) at the beginning of start-up and then be charged to 1.235V with a 10μA current source. GND (Pin 3 and Pin 9): Ground. Tie directly to local ground plane. Pin 9 is floating but must be grounded for proper shielding. FBP(Pin 8): Positive Feedback Pin. This pin is the error amplifier’s positive input terminal. To achieve the desired output voltage, choose the FBP pin voltage (VFBP) according to the following formula: SW (Pin 4): Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. VFBP = VOUT / 31.85 VOUT (Pin 5): Drain of Output Disconnect PMOS. Place a bypass capacitor from this pin to GND. For protection purposes, the output voltage can not exceed 40V even if VFBP is driven higher than VREF . CAP (Pin 6): This is the cathode of the internal Schottky Diode. Place a bypass capacitor from this pin to GND. BLOCK DIAGRAM VCC SHDN VOUT CAP SW 2 1 5 6 4 ENABLE CHIP MAX 10μA + 12.4M 1.235V + – VREF 400K – 7 1.235V DISCHARGE CONTROL TIMING AND PEAK CURRENT CONTROL FB FBP 1.235V SWITCH CONTROL – + 8 OUTPUT DISCONNECT CONTROL VC + + – 9 3 GND GND 84101f 7 LT8410/LT8410-1 OPERATION The LT8410 series utilizes a variable peak current, variable off-time control scheme to provide high efficiency over a wide output current range. The operation of the part can be better understood by referring to the Block Diagram. The part senses the output voltage by monitoring the internal FB node, and servoing the FB node voltage to be equal to the FBP pin voltage. The chip integrates an accurate high value resistor divider (12.4M/0.4M) from the VOUT pin. The output voltage is set by the FBP pin voltage, which in turn is set by an external resistor divider from the VREF pin. The FBP pin voltage can also be directly biased with an external reference, allowing full control of the output voltage during operation. 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 ensure that the inductor current remains under control The LT8410 series also has a PMOS output disconnect switch. The PMOS switch is turned on when the part is enabled via the SHDN pin. When the part is 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 differences between the LT8410 and LT8410-1 are the SW current limit and the output disconnect PMOS current limit. For the LT8410, the SW current limit and PMOS current limit are approximately 25mA and 19mA respectively, while those of the LT8410-1 are approximately 8mA and 4mA respectively. APPLICATIONS INFORMATION Inductor Selection Several inductors that work well with the LT8410 and LT8410-1 are listed in Table 1. The tables are not complete, and 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, as many different sizes and shapes are available. Inductors with a value of 47μH or higher are recommended for most LT8410 series designs. Inductors with low core losses and small DCR (copper wire resistance) are good choices for LT8410 series applications. For full output power, the inductor should have a saturation current rating higher than the peak inductor current. The peak inductor current can be calculated as: VIN • 150 • 10 – 6 mA L where the worst case ILIMIT is 30mA and 10mA for LT8410 and LT8410-1 respectively. L is the inductance value in Henrys and VIN is the input voltage to the boost circuit. IPK = ILIMIT + Table 1. Recommended Inductors for LT8410/-1 PART L (μH) DCR (Ω) SIZE (mm) LQH2MCN680K02 LQH32CN101K53 68 100 6.6 3.5 2.0 × 1.6 × 0.9 Murata 3.2 × 2.5 × 2.0 www.murata.com DO2010-683ML LPS3015-104ML LPS3015-154ML LPS3314-154ML 68 100 150 150 8.8 3.4 6.1 4.1 2.0 × 2.0 × 1.0 Coilcraft 3.0 × 3.0 × 1.4 www.coilcraft.com 3.0 × 3.0 × 1.4 3.3 × 3.3 × 1.3 VENDOR Capacitor Selection The small size and low ESR of ceramic capacitors make them suitable for most LT8410 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 2.2μF or higher input capacitor and a 0.1μF to 1μF output capacitor are sufficient for most applications. Always use a capacitor with a sufficient voltage rating. Many ceramic capacitors rated at 0.1μF to 1μF have greatly reduced capacitance when bias voltages are applied. Be sure to check actual capacitance at the desired output voltage. Generally a 0603 84101f 8 LT8410/LT8410-1 APPLICATIONS INFORMATION or 0805 size capacitor will be adequate. A 0.1μF to 1μF capacitor placed on the CAP node is recommended to filter the inductor current while a 0.1μF to 1μF capacitor placed on the VOUT node will give excellent transient response and stability. To make the VREF pin less sensitive to noise, putting a capacitor on the VREF pin is recommended, but not required. A 47nF to 220nF 0402 capacitor will be sufficient. 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 Manufactures MANUFACTURER PHONE WEBSITE Taiyo Yuden (408) 573-4150 www.t-yuden.com Murata (814) 237-1431 www.murata.com AVX (843) 448-9411 www.avxcorp.com Kemet (408)986-0424 www.kemet.com TDK (847) 803-6100 www.tdk.com 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. No quiescent current will be consumed in the internal feedback resistor divider string during shutdown since the PMOS transistor will be open and the internal feedback resistor divider is connected at the VOUT pin. 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. Maximum Output Load Current The maximum output current of a particular LT8410 series circuit is a function of several circuit variables. The following method can be helpful in predicting the maximum load current for a given circuit: Setting Output Voltage The output voltage is set by the FBP pin voltage, and VOUT is equal to 31.85 • VFBP when the output is regulated, shown in Figure 1. Since the VREF pin provides a good reference (1.235V), the FBP voltage can be easily set by a resistor divider from the VREF pin to ground. The series resistance of this resistor divider should be kept larger than 200KΩ to prevent loading down the VREF pin. The FBP pin can also be biased directly by an external reference. For over voltage protection, the output voltage is limited to 40V. Therefore, if VFBP is higher than 1.235V, the output voltage will stay at 40V. Step 1. Calculate the peak inductor current: IPK = ILIMIT + VIN • 150 • 10 – 6 mA L where ILIMIT is 25mA and 8mA for LT8410 and LT8410-1 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 ) • 200 • 10 – 6 ( = mA 50 where VOUT is the desired output voltage. If the inductor ripple current is less 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. 40 OUTPUT VOLTAGE (V) L 30 20 10 Step 3. Calculate the average input current: 0 0 0.5 1 1.5 FBP VOLTAGE (V) 2 8410-1 F01 IIN(AVG) = IPK – IRIPPLE mA 2 Figure 1. FBP to VOUT Transfer Curve 84101f 9 LT8410/LT8410-1 APPLICATIONS INFORMATION Step 4. Calculate the nominal output current: IOUT(NOM) = IIN(AVG) • VIN • 0.7 VOUT mA Step 5. Derate output current: IOUT = IOUT(NOM) • 0.8 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 lower output current capability than predicted by the preceding equations. Inrush Current When VCC is stepped from ground to the operating voltage while the output capacitor is discharged, a high level of inrush current may flow through the inductor and Schottky diode into the output capacitor. Conditions that increase inrush current include a larger more abrupt voltage step at VCC, a larger output capacitor tied to the CAP pin and an inductor with a low saturation current. While the chip is designed to handle such events, the inrush current should not be allowed to exceed 0.3A. For circuits that use output capacitor values within the recommended range and have input voltages of less than 6V, inrush current remains low, posing no hazard to the device. In cases where there are large steps at VCC (more than 6V) and/or a large capacitor is used at the CAP pin, inrush current should be measured to ensure safe operation. Soft-Start The LT8410 series contains a soft-start circuit to limit peak switch currents during start-up. High start-up current is inherent in switching regulators in general since the feedback loop is saturated due to VOUT being far from its final value. The regulator tries to charge the output capacitor as quickly as possible, which results in large peak current. When the FBP pin voltage is generated by a resistor divider from the VREF pin, the start-up current can be limited by connecting an external capacitor (typically 47nF to 220nF) to the VREF pin. When the part is brought out of shutdown, this capacitor is first discharged for about 70μs (providing protection against pin glitches and slow ramping), then an internal 10μA current source pulls the VREF pin slowly to 1.235V. Since the VOUT voltage is set by the FBP pin voltage, the VOUT voltage will also slowly increase to the regulated voltage, which results in lower peak inductor current. The voltage ramp rate on the pin can be set by the value of the VREF pin capacitor. Output Disconnect The LT8410 series has an output disconnect PMOS that blocks the load from the input during shutdown. The maximum current through the PMOS is limited by circuitry inside the chip, helping the chip survive output shorts. SHDN Pin Comparator and Hysteresis Current An internal comparator compares the SHDN pin voltage with an internal voltage reference (1.3V) which gives a precise turn-on voltage level. The internal hysteresis of this turn-on voltage is about 60mV. When the chip is turned on, and the SHDN pin voltage is close to this turn-on voltage, 0.1μA current flows out of the SHDN pin. This current is called SHDN pin hysteresis current, and will go away when the chip is off. By connecting the external resistors as in Figure 2, a user-programmable enable voltage function can be realized. The turn-on voltage for the configuration is: 1.30 • (1 + R1/R2) and the turn-off voltage is: – – (1.24 – R3 • 10 7) • (1 + R1/R2) – (R1 • 10 7) where R1, R2 and R3 are resistance value in Ω. ENABLE VOLTAGE R1 R3 CONNECT TO SHDN PIN R2 Figure 2. Programming Enable Voltage by Using External Resistors 84101f 10 LT8410/LT8410-1 APPLICATIONS INFORMATION Board Layout Considerations As with all switching regulators, careful attention must be paid to the PCB 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 FBP pin and VREF pin are sensitive to noise. Minimize the length and area of all traces to these two pins is recommended. Recommended component placement is shown in Figure 3. VIN SHDN SHDN FBP VCC VREF GND CAP GND SW VOUT 8410-1 F03 CAPACITOR GROUNDS MUST BE RETURNED DIRECTLY TO IC GROUND Figure 3. Recommended Board Layout 84101f 11 LT8410/LT8410-1 TYPICAL APPLICATIONS Efficiency vs Load Current L1 100μH C1 2.2μF 100 SW CAP VCC VOUT C2 0.1μF C3 0.1μF LT8410 VREF SHDN TURN ON/OFF 604K GND VIN = 12V 90 VOUT = 16V EFFICIENCY (%) VIN 2.5V to 16V C4 0.1μF FBP VIN = 5V 80 VIN = 3.6V 70 60 412K 50 C1: 2.2μF, 16V, X5R, 0603 8410-1 TA05 C2: 0.1μF, 25V, X5R, 0603 C3: 0.1μF, 25V, X5R, 0603 * C4: 0.1μF, 16V, X7R, 0402 L1: MURATA LQH32CN101K53 * HIGHER CAPACITANCE VALUE IS REQUIRED FOR C3 WHEN THE VIN IS HIGHER THAN 5V 40 0.01 0.1 1 10 LOAD CURRENT (mA) VIN (V) Figure 4. 16V Output Converter with Wide Input Voltage 16V Output Converter with 2mm x 2mm Inductor 100 8410-1 TA07 IOUT (mA) 3.6 2.2 5 3.6 12 13 L1 68μH C1 2.2μF TURN ON/OFF SW CAP VCC VOUT Efficiency vs Load Current C2 0.1μF 90 VOUT = 16V LT8410 VREF SHDN GND VIN = 12V C3 0.1μF R1 301K VIN = 5V 80 C4 0.1μF EFFICIENCY (%) VIN 2.5V to 16V FBP R2 210K C1: 2.2μF, 16V, X5R, 0603 8410 TA06 C2: 0.1μF, 25V, X5R, 0603 C3: 0.1μF, 25V, X5R, 0603 * C4: 0.1μF, 16V, X7R, 0402 L1: COILCRAFT DO2010-683ML * HIGHER CAPACITANCE VALUE IS REQUIRED FOR C3 WHEN THE VIN IS HIGHER THAN 5V 70 VIN = 3.6V 60 50 40 0.01 0.1 1 10 LOAD CURRENT (mA) 100 8410-1 TA08 LT8410 Maximum Output Current vs Output Voltage RESISTOR DIVIDER FROM VREF R1 (kΩ) / R2 ( kΩ) VIN = 2.8V VIN = 3.6V VIN = 5.0V VIN = 12V 40 NA 0.5 0.7 1.1 3.6 35 110/887 0.7 0.9 1.4 4.4 30 237/768 0.8 1.0 1.5 5.5 25 365/634 1.0 1.4 2.1 7.2 20 487/511 1.4 1.9 2.9 9.7 15 619/383 1.6 2.4 4.0 14 10 750/255 3.3 4.6 7.0 NA 5 866/127 8.0 11 17 NA VOUT (V) MAXIMUM OUTPUT CURRENT (mA) 84101f 12 LT8410/LT8410-1 TYPICAL APPLICATIONS 34V Output Converter with Wide Input Voltage Efficiency vs Load Current 90 L1 150μH C1 2.2μF TURN ON/OFF VIN = 12V SW CAP VCC VOUT 80 C2 0.1μF VOUT = 34V C3 0.1μF LT8410 VREF SHDN 133K GND C4 0.1μF EFFICIENCY (%) VIN 2.5V to 16V VIN = 5V 70 VIN = 3.6V 60 FBP 50 866K C1: 2.2μF, 16V, X5R, 0603 8410-1 TA09 C2: 0.1μF, 100V, X5R, 0603 C3: 0.1μF, 100V, X5R, 0603 * C4: 0.1μF, 16V, X7R, 0402 L1: COILCRAFT LPS3314-154ML * HIGHER CAPACITANCE VALUE IS REQUIRED FOR C3 WHEN THE VIN IS HIGHER THAN 8V 40 0.01 0.1 1 LOAD CURRENT (mA) VIN (V) 10 8410-1 TA10 IOUT (mA) 3.6 0.8 5 1.2 12 4.0 84101f 13 LT8410/LT8410-1 TYPICAL APPLICATIONS Charging Waveforms L1 220μH VIN 2.5V to 16V C1 2.2μF TURN ON/OFF SW CAP VCC VOUT C2 1.0μF SHDN VOLTAGE 2V/DIV VOUT = 16V C3 10000μF LT8410-1 VREF SHDN GND FBP R1 604k C4 0.1μF VOUT VOLTAGE 10V/DIV INPUT CURRENT 5mA/DIV INDUCTOR CURRENT 10mA/DIV R2 412k C1: 2.2μF, 16V, X5R, 0603 8410-1 TA10a C2: 1.0μF, 25V, X5R, 0603 * C3: 10000μF, Electrolytic Capacitor C4: 0.1μF, 16V, X7R, 0402 L1: COILCRAFT LPS3008-224ML * HIGHER CAPACITANCE VALUE IS REQUIRED FOR C2 WHEN THE VIN IS HIGHER THAN 12V VIN = 3.6V 20s/DIV 8410-1 G10b Figure 5. Capacitor Charger with the LT8410-1 LT8410-1 Maximum Output Current vs Output Voltage FEEDBACK RESISTOR DIVIDER R1 (kΩ) / R2 ( kΩ) VIN = 2.8V VIN = 3.6V VIN = 5.0V VIN = 12V 40 NA 0.12 0.16 0.24 0.89 35 110/887 0.14 0.19 0.3 1.1 30 237/768 0.18 0.25 0.38 1.5 25 365/634 0.25 0.35 0.55 2 20 487/511 0.34 0.48 0.76 2.9 15 619/383 0.48 0.69 1.1 3.5 10 750/255 0.84 1.2 2.1 NA 5 866/127 2.3 3.3 3.5 NA VOUT (V) MAXIMUM OUTPUT CURRENT (mA) 84101f 14 LT8410/LT8410-1 PACKAGE DESCRIPTION DC Package 8-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1719 Rev Ø) 0.70 p0.05 2.55 p0.05 1.15 p0.05 0.64 p0.05 (2 SIDES) PACKAGE OUTLINE 0.25 p 0.05 0.45 BSC 1.37 p0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED R = 0.05 TYP 2.00 p0.10 (4 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) R = 0.115 TYP 5 8 0.40 p 0.10 0.64 p 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.25 s 45o CHAMFER (DC8) DFN 0106 REVØ 4 0.200 REF 1 0.23 p 0.05 0.45 BSC 0.75 p0.05 1.37 p0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD 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 84101f 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. 15 LT8410/LT8410-1 TYPICAL APPLICATION High Voltage Power Supply Doesn’t Need a Transformer DANGER HIGH VOLTAGE! OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY C3 0.1μF L1 100μH VIN 2.5V to 16V C1 2.2μF C5 0.1μF D1 SW VCC C2 0.1μF CAP VOUT C4 0.1μF LT8410 VREF SHDN TURN ON/OFF GND D3 D4 C6 0.1μF OUTPUT = 100V 0.4mA (VIN = 5V) 1.4mA (VIN = 12V) C7 0.1μF 143K C1: 2.2μF, 16V, X5R, 0603 C2 – C7: 0.1μF, 100V, X5R, 0603 C8: 0.1μF, 16V, X7R, 0402 D1 – D4: ON SEMI RB751S40T1G L1: MURATA LQH32CN101K53 D2 FBP 787K C8 0.1μF 8410-1 TA11 Output Voltage vs FBP Voltage Efficiency vs Load Current 140 90 VIN = 5V VOUT = 100V 120 EFFICIENCY (%) OUTPUT VOLTAGE (V) 80 VIN = 12V 100 80 60 70 VIN = 5V 60 40 50 20 0 0 0.5 1 1.5 FBP VOLTAGE (V) 40 0.01 2 8410-1 TA12 0.1 1 LOAD CURRENT (mA) 10 8410-1 TA13 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS 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 LT3464 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky and PNP Disconnect VIN : 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25μA, ISD < 1μA, ThinSOT™ 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 LT3473/LT3473A 1A (ISW), 1.2MHz, High Efficiency Step-Up DC/DC Converter with Integrated Schottky Diode and Output Disconnect VIN : 2.2V to 16V, VOUT(MAX) = 36V, IQ = 100μA, ISD < 1μA, DFN Package LT3494/LT3494A 180mA/350mA (ISW), High Efficiency, Low Noise Step-Up DC/DC Converter with Output Disconnect VIN : 2.1V to 16V, VOUT(MAX) = 40V, IQ = 65μA, ISD < 1μA, DFN Package LT3495/LT3495B/ 650mA/350mA (ISW), High Efficiency, Low Noise Step-Up LT3495-1/LT3495B-1 DC/DC Converter with Output Disconnect VIN : 2.3 V to 16V, VOUT(MAX) = 40V, IQ = 60μA, ISD < 1μA, DFN Package 84101f 16 Linear Technology Corporation LT 1108 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008