LT1614 Inverting 600kHz Switching Regulator U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT ®1614 is a fixed frequency, inverting mode switching reglator that operates from an input voltage as low as 1V. Utilizing a low noise topology, the LT1614 can generate a negative output down to – 24V from a 1V to 5V input. Fixed frequency switching ensures a clean output free from low frequency noise. The device contains a lowbattery detector with a 200mV reference and shuts down to less than 10µA. No load quiescent current of the LT1614 is 1mA and the internal NPN power switch handles a 500mA current with a voltage drop of just 295mV. Better Regulation Than a Charge Pump 0.1Ω Effective Output Impedance – 5V at 200mA from a 5V Input 600kHz Fixed Frequency Operation Operates with VIN as Low as 1V 1mA Quiescent Current Low Shutdown Current: 10µA Low-Battery Detector Low VCESAT Switch: 295mV at 500mA U APPLICATIO S ■ ■ ■ ■ High frequency switching enables the use of small inductors and capacitors. Ceramic capacitors can be used in many applications, eliminating the need for bulky tantalum types. MR Head Bias LCD Bias GaAs FET Bias Positive-to-Negative Conversion The LT1614 is available in 8-lead MSOP or SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO + VIN C1 33µF 100k L2 22µH 5V to – 5V Converter Efficiency 90 VOUT – 5V 200mA SW SHDN LT1614 VC NFB GND 69.8k D1 24.9k + VIN 5V C2 33µF 1nF C1, C2: AVX TAJB336M010 C3: TAIYO YUDEN EMK316BJ105MF D1: MBR0520 L1, L2: MURATA LQH3C220 Figure 1. 5V to – 5V/200mA Converter 1614 TA01 80 EFFICIENCY (%) C3 1µF L1 22µH 70 60 50 40 3 100 10 30 LOAD CURRENT (mA) 300 1614 TA02 1 LT1614 W W W AXI U U ABSOLUTE RATI GS (Note 1) VIN, SHDN, LBO Voltage ......................................... 12V SW Voltage ............................................... – 0.4V to 30V NFB Voltage ............................................................ – 3V VC Voltage ................................................................ 2V LBI Voltage ............................................ 0V ≤ VLBI ≤ 1V Current into FB Pin .............................................. ±1mA Junction Temperature ...........................................125°C Operating Temperature Range LT1614C ................................................. 0°C to 70°C LT1614I ............................................. – 40°C to 85°C Extended Commercial Temperature Range (Note 2) .................. – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER ORDER PART NUMBER TOP VIEW TOP VIEW NFB VC SHDN GND 1 2 3 4 8 7 6 5 LBO LBI VIN SW MS8 PACKAGE 8-LEAD PLASTIC MSOP LT1614CMS8 LT1614IMS8 MS8 PART MARKING TJMAX = 125°C, θJA = 160°C/W LTID LTJB NFB 1 8 LBO VC 2 7 LBI SHDN 3 6 VIN GND 4 5 SW LT1614CS8 LT1614IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 1614 1614I TJMAX = 125°C, θJA = 120°C/W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Commercial Grade 0°C to 70°C. VIN = 1.5V, VSHDN = VIN unless otherwise noted. PARAMETER CONDITIONS MIN Quiescent Current VSHDN = 0V Feedback Voltage NFB Pin Bias Current (Note 3) VNFB = –1.24V Reference Line Regulation 1V ≤ VIN ≤ 2V 2V ≤ VIN ≤ 6V Error Amp Transconductance 2 UNITS mA µA – 1.21 – 1.24 – 1.27 V – 2.5 – 4.5 –7 µA 0.6 0.3 1.1 0.8 %/V %/V 0.92 1 V 6 V ● ∆I = 5µA µmhos 16 100 V/V ● 500 600 ● 73 70 80 80 % % 0.75 1.2 A Maximum Duty Cycle Switch Current Limit (Note 4) 2 10 ● Error Amp Voltage Gain Switching Frequency MAX 1 5 ● Minimum Input Voltage Maximum Input Voltage TYP 750 kHz LT1614 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Commercial Grade 0°C to 70°C. VIN = 1.5V, VSHDN = VIN unless otherwise noted. PARAMETER CONDITIONS Switch VCESAT Shutdown Pin Current MIN TYP MAX UNITS ISW = 500mA (25°C, 0°C) ISW = 500mA (70°C) 295 350 400 mV mV VSHDN = VIN VSHDN = 0V 10 –5 20 – 10 µA µA 200 210 215 mV mV V LBI Threshold Voltage ● 190 185 LBO Output Low ISINK = 10µA 0.1 0.25 LBO Leakage Current VLBI = 250mV, VLBO = 5V 0.01 0.1 µA LBI Input Bias Current (Note 5) VLBI = 150mV 10 50 nA Low-Battery Detector Gain 1MΩ Load 1000 Switch Leakage Current VSW = 5V 0.01 3 TYP MAX 1 5 2 10 V/V µA Industrial Grade – 40°C to 85°C. VIN = 1.5V, VSHDN = VIN unless otherwise noted. PARAMETER CONDITIONS MIN Quiescent Current VSHDN = 0V Feedback Voltage mA µA ● – 1.21 – 1.24 – 1.27 V ● –2 – 4.5 – 7.5 µA 1V ≤ VIN ≤ 2V 2V ≤ VIN ≤ 6V 0.6 0.3 1.1 0.8 %/V %/V – 40°C 85°C 1.1 0.8 1.25 1.0 V V NFB Pin Bias Current (Note 3) VNFB = – 1.24V Reference Line Regulation Minimum Input Voltage Maximum Input Voltage Error Amp Transconductance UNITS 6 ● ∆I = 5µA Error Amp Voltage Gain V 16 µmhos 100 V/V Switching Frequency ● 500 600 Maximum Duty Cycle ● 70 80 % 0.75 1.2 A Switch Current Limit (Note 4) 750 kHz Switch VCESAT ISW = 500mA (– 40°C) ISW = 500mA (85°C) 250 330 350 400 mV mV Shutdown Pin Current VSHDN = VIN VSHDN = 0V 10 –5 20 – 10 µA µA LBI Threshold Voltage 200 220 mV LBO Output Low ISINK = 10µA 0.1 0.25 V LBO Leakage Current VLBI = 250mV, VLBO = 5V 0.1 0.3 µA 5 30 ● 180 LBI Input Bias Current (Note 5) VLBI = 150mV Low-Battery Detector Gain 1MΩ Load 1000 Switch Leakage Current VSW = 5V 0.01 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1614C is guaranteed to meet specified performance from 0°C to 70°C and is designed, characterized and expected to meet these extended temperature limits, but is not tested at – 40°C and 85°C. The LT1614I is guaranteed to meet the extended temperature limits. nA V/V µA 3 Note 3: Bias current flows out of NFB pin. Note 4: Switch current limit guaranteed by design and/or correlation to static tests. Duty cycle affects current limit due to ramp generator. Note 5: Bias current flows out of LBI pin. 3 LT1614 U W TYPICAL PERFOR A CE CHARACTERISTICS Shutdown Pin Bias Current vs Input Voltage Quiescent Current in Shutdown 10 10 8 8 LBI Bias Current vs Temperature 16 6 4 2 LBI BIAS CURRENT (nA) SHDN BIAS CURRENT (µA) QUIESCENT CURRENT (µA) 14 6 4 12 10 8 6 4 2 2 0 0 1 2 3 INPUT VOLTAGE (V) 4 0 5 0 1 2 3 INPUT VOLTAGE (V) 4 1614 G01 –25 0 50 25 TEMPERATURE (°C) 75 1614 G02 Switch VCESAT vs Current Oscillator Frequency vs Input Voltage 210 TA = 25°C 100 1614 G03 LBI Reference vs Temperature 500 900 208 300 200 100 800 206 204 FREQUENCY (kHz) REFERENCE VOLTAGE (mV) 400 VCESAT (mV) 0 –50 5 202 200 198 196 194 25°C 85°C 700 –40°C 600 500 192 0 0 100 500 200 300 400 SWITCH CURRENT (mA) 190 –50 600 –25 25 50 0 TEMPERATURE (°C) 75 –1.245 5 5 –1.240 VIN = 3V 1 0 –40 VIN = 5V –20 0 20 40 TEMPERATURE (°C) 60 80 1614 G07 *Includes diode leakage –1.235 4 VNFB (V) NFB PIN BIAS CURRENT (µA) QUIESCENT CURRENT (mA) 6 2 5 VNFB vs Temperature 6 3 4 1614 G06 NFB Pin Bias Current vs Temperature VIN = 1.25V 3 1614 G05 Quiescent Current vs Temperature* 4 2 1 INPUT VOLTAGE (V) 1614 G04 4 400 100 3 –1.230 –1.225 2 –1.220 1 0 –50 –1.215 –25 0 25 50 TEMPERATURE (°C) 75 100 1614 G08 –1.210 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1614 G09 LT1614 U U U PIN FUNCTIONS NFB (Pin 1): Negative Feedback Pin. Reference voltage is – 1.24V. Connect resistive divider tap here. The suggested value for R2 is 24.9k. Set R1 and R2 according to: R1 = GND (Pin 4): Ground. Connect directly to local ground plane. SW (Pin 5): Switch Pin. Minimize trace area at this pin to keep EMI down. | VOUT | – 1.24 1.24 + 4.5 • 10 – 6 R2 VIN (Pin 6): Supply Pin. Must have 1µF ceramic bypass capacitor right at the pin, connected directly to ground. VC (Pin 2): Compensation Pin for Error Amplifier. Connect a series RC from this pin to ground. Typical values are 100kΩ and 1nF. Minimize trace area at VC. LBI (Pin 7): Low-Battery Detector Input. 200mV reference. Voltage on LBI must stay between ground and 700mV. Float this pin if not used. SHDN (Pin 3): Shutdown. Ground this pin to turn off switcher. Must be tied to VIN (or higher voltage) to enable switcher. Do not float the SHDN pin. LBO (Pin 8): Low-Battery Detector Output. Open collector, can sink 10µA. A 1MΩ pull-up is recommended. Float this pin if not used. The low-battery detector is disabled when SHDN is low. LBO is high-Z in this state. W BLOCK DIAGRAM VIN 6 VIN R5 40k R6 40k + SHDN VC gm 2 ERROR AMPLIFIER A1 + SHUTDOWN – Q1 Q2 ×10 LBI – R4 140k NFB LBO 8 – 200mV A4 SW COMPARATOR – 1 VOUT + 7 ENABLE BIAS R3 30k RAMP GENERATOR R1 (EXTERNAL) + Σ + DRIVER FF A2 5 Q3 Q R + S + NFB R2 (EXTERNAL) 3 A=3 600kHz OSCILLATOR 0.15Ω – 4 GND 1614 BD Figure 2. Block Diagram 5 LT1614 U OPERATIO The LT1614 combines a current mode, fixed frequency PWM architecture with a –1.23V reference to directly regulate negative outputs. Operation can be best understood by referring to the block diagram of Figure 2. Q1 and Q2 form a bandgap reference core whose loop is closed around the output of the converter. The driven reference point is the lower end of resistor R4, which normally sits at a voltage of –1.23V. As the load current changes, the NFB pin voltage also changes slightly, driving the output of gm amplifier A1. Switch current is regulated directly on a cycle-to-cycle basis by A1’s output. The flip-flop is set at the beginning of each cycle, turning on the switch. When the summation of a signal representing switch current and a ramp generator (introduced to avoid subharmonic oscillations at duty factors greater than 50%) exceeds the VC signal, comparator A2 changes stage, resetting the flipflop and turning off the switch. Output voltage decreases (the magnitude increases) as switch current is increased. The output, attenuated by external resistor divider R1 and R2, appears at the NFB pin, closing the overall loop. Frequency compensation is provided externally by a series RC connected from the VC pin to ground. Typical values are 100k and 1nF. Transient response can be tailored by adjustment of these values. As load current is decreased, the switch turns on for a shorter period each cycle. If the load current is further decreased, the converter will skip cycles to maintain output voltage regulation. C2 1µF L1 If D2 is replaced by an inductor, as shown in Figure 4, a higher performance solution results. This converter topology was developed by Professor S. Cuk of the California Institute of Technology in the 1970s. A low ripple voltage results with this topology due to inductor L2 in series with the output. Abrupt changes in output capacitor current are eliminated because the output inductor delivers current to the output during both the off-time and the on-time of the LT1614 switch. With proper layout and high quality output capacitors, output ripple can be as low as 1mVP–P. The operation of Cuk’s topology is shown in Figures 5 and␣ 6. During the first switching phase, the LT1614’s switch, represented by Q1, is on. There are two current loops in operation. The first loop begins at input capacitor C1, flows through L1, Q1 and back to C1. The second loop flows from output capacitor C3, through L2, C2, Q1 and back to C3. The output current from RLOAD is supplied by L2 and C3. The voltage at node SW is VCESAT and at node SWX the voltage is –(VIN + |VOUT|). Q1 must conduct both L1 and L2 current. C2 functions as a voltage level shifter, with an approximately constant voltage of (VIN + |VOUT|) across it. D2 C2 1µF L1 L2 VIN + D1 VIN C1 –VOUT LT1614 R1 SHDN NFB VC 10Ok GND VIN GND C3 R2 10k 1nF 1614 F03 Figure 3. Direct Regulation of Negative Output Using Boost Converter with Charge Pump NFB VC 10Ok 1nF –VOUT R1 SHDN C3 R2 10k SW LT1614 C1 SHUTDOWN + SHUTDOWN D1 + SW + VIN 6 The LT1614 can work in either of two topologies. The simpler topology appends a capacitive level shift to a boost converter, generating a negative output voltage, which is directly regulated. The circuit schematic is detailed in Figure 3. Only one inductor is required, and the two diodes can be in a single SOT-23 package. Output noise is the same as in a boost converter, because current is delivered to the output only during the time when the LT1614’s internal switch is on. 1614 F04 Figure 4. L2 Replaces D2 to Make Low Output Ripple Inverting Topology. Coupled or Uncoupled Inductors Can Be Used. Follow Phasing If Coupled for Best Results LT1614 U OPERATIO When Q1 turns off during the second phase of switching, the SWX node voltage abruptly increases to (VIN + |VOUT|). The SW node voltage increases to VD (about 350mV). Now current in the first loop, begining at C1, flows through L1, C2, D1 and back to C1. Current in the second loop flows from C3 through L2, D1 and back to C3. Load current continues to be supplied by L2 and C3. rents are dumped into the ground plane as drawn in Figures 4, 5 and 6. This single layout technique can virtually eliminate high frequency “spike” noise so often present on switching regulator outputs. Output ripple voltage appears as a triangular waveform riding on VOUT. Ripple magnitude equals the ripple current of L2 multiplied by the equivalent series resistance (ESR) of output capacitor C3. Increasing the inductance of L1 and L2 lowers the ripple current, which leads to lower output voltage ripple. Decreasing the ESR of C3, by using ceramic or other low ESR type capacitors, lowers output ripple voltage. Output ripple voltage can be reduced to arbitrarily low levels by using large value inductors and low ESR, high value capacitors. An important layout issue arises due to the chopped nature of the currents flowing in Q1 and D1. If they are both tied directly to the ground plane before being combined, switching noise will be introduced into the ground plane. It is almost impossible to get rid of this noise, once present in the ground plane. The solution is to tie D1’s cathode to the ground pin of the LT1614 before the combined cur–(VIN + VOUT) VCESAT L1 SW C2 L2 SWX VIN –VOUT D1 Q1 + C1 C3 RLOAD + 1614 F05 Figure 5. Switch-On Phase of Inverting Converter. L1 and L2 Current Have Positive dI/dt VIN + VOUT+ VD L1 SW VD C2 L2 SWX VIN –VOUT Q1 + D1 C1 C3 RLOAD + 1614 F06 Figure 6. Switch-Off Phase of Inverting Converter. L1 and L2 Current Have Negative dI/dt 7 LT1614 U OPERATIO Transient Response The inverting architecture of the LT1614 can generate a very low ripple output voltage. Recently available high value ceramic capacitors can be used successfully in LT1614 designs. The addition of a phase lead capacitor, CPL, reduces output perturbations due to load steps when lower value ceramic capacitors are used and connected in parallel with feedback resistor R1. Figure 7 shows an LT1614 inverting converter with resistor loads RL1 and RL2. RL1 is connected across the output, while RL2 is switched in externally via a pulse generator. Output voltage waveforms are pictured in subsequent figures, illustrating the performance of output capacitor type. Figure 8 shows the output voltage with a 50mA to 200mA load step, using an AVX TAJ “B” case 33µF tantalum capacitor at the output. Output perturbation is approximately 250mV as the load changes from 50mA to 200mA. Steady-state ripple voltage is 40mVP–P, due to L1’s ripple current and C3’s ESR. Figure 9 pictures the output voltage and switch pin voltage at 500ns per division. Note the absence of high frequency spikes at the output. This is easily repeatable with proper layout, described in the next section. In Figure 10, output capacitor C3 is replaced by a ceramic unit. These large value capacitors have ESR of 2mΩ or less and result in very low output ripple. A 1nF capacitor, CPL, connected across R1 reduces output perburbation due to load step. This keeps the output voltage within 5% of steady-state value. Figure 11 pictures the output and switch nodes at 500ns per division. Output ripple is about 5mVP-P. Again, good layout is essential to achieve this low noise performance. Layout The LT1614 switches current at high speed, mandating careful attention to layout for best performance. You will not get advertised performance with careless layout. Figure␣ 12 shows recommended component placement. Follow this closely in your printed circuit layout. The cut ground copper at D1’s cathode is essential to obtain the low noise achieved in Figures 10 and 11’s oscillographs. Input bypass capacitor C1 should be placed close to the LT1614 as shown. The load should connect directly to output capacitor C2 for best load regulation. You can tie the local ground into the system ground plane at C3’s ground terminal. COMPONENT SELECTION C2 1µF L1 22µH VIN 5V Inductors L2 22µH D1 SHDN + R1 69.8k LT1614 C1 CPL 1nF NFB VC GND RC –VOUT SW RL1 100Ω C3 R2 24.9k RL2 33Ω + VIN CC C1: AVX TAJB226M010 C2: TAIYO YUDEN LMK212BJ105MG C3: AVX TAJB336M006 OR MURATA (SEE TEXT) D1: MBR0520 L1, L2: MURATA LQH3C220 Figure 7. Switching RL2 Provides 50mA to 200mA Load Step for LT1614 5V to – 5V Converter 8 1614 F07 Each of the two inductors used with the LT1614 should have a saturation current rating (where inductance is approximately 70% of zero current inductance) of approximately 0.4A or greater. If the device is used in “charge pump” mode, where there is only one inductor, then its rating should be 0.75A or greater. DCR of the inductors should be 0.4Ω or less. 22µH inductors are called out in the applications schematics because these Murata units are physically small and inexpensive. Increasing the inductance will lower ripple current, increasing available output current. A coupled inductor of 33µH, such as Coiltronics CTX33-2, will provide 290mA at – 5V from a 5V input. Inductance can be reduced if operating from a supply voltage below 3V. Table 1 lists several inductors that will work with the LT1614, although this is not an exhaustive list. There are many magnetics vendors whose components are suitable. LT1614 U OPERATIO VOUT 100mV/DIV AC COUPLED ILOAD VOUT 20mV/DIV AC COUPLED VSW 5V/DIV 200mA 50mA 500µs/DIV 500ns/DIV 1614 F08 Figure 8. Load Step Response of LT1614 with 33µF Tantalum Output Capacitor Figure 9. 33µF “B” Case Tantalum Capacitor Has ESR Resulting in 40mVP-P Voltage Ripple at Output with 200mA Load VOUT 100mV/DIV AC COUPLED VOUT 10mV/DIV AC COUPLED 200mA VSW 5V/DIV ILOAD 1614 F09 50mA 500µs/DIV 500ns/DIV 1614 F10 Figure 10. Replacing C3 with 22µF Ceramic Capacitor Lowers Output Voltage Ripple. 1nF Phase-Lead Capacitor in Parallel with R1 Lowers Transient Excursion 1614 F11 Figure 11. 22µF Ceramic Capacitor at Output Reduces Output Ripple Voltage C1 + SHUTDOWN R1 R2 RC CC 1 8 2 7 3 6 4 5 VIN L1 D1 + GND C3 C2 1614 F12 L2 VOUT Figure 12. Suggested Component Placement. Note: Cut in Ground Copper at D1’s Cathode 9 LT1614 U OPERATIO Capacitors As described previously, ceramic capacitors can be used with the LT1614. For lower cost applications, small tantalum units can be used. A value of 22µF is acceptable, although larger capacitance values can be used. ESR is the most important parameter in selecting an output capacitor. The “flying” capacitor (C2 in the schematic figures) should be a 1µF ceramic type. An X5R or X7R dielectric should be used to avoid capacitance decreasing severely with applied voltage. The input bypass capacitor is less critical, and either tantalum or ceramic can be used with little trade-off in circuit performance. Some capacitor types appropriate for use with the LT1614 are listed in Table 2. Diodes A Schottky diode is recommended for use with the LT1614. The Motorola MBR0520 is a very good choice. Where the input to output voltage differential exceeds 20V, use the MBR0530 ( a 30V diode). Table 1. Inductor Vendors VENDOR PHONE URL PART COMMENT Sumida (847) 956-0666 www.sumida.com CLS62-22022 CD43-470 22µH Coupled 47µH Murata (404) 436-1300 www.murata.com LQH3C-220 22µH, 2mm Height Coiltronics (407) 241-7876 www.coiltronics.com CTX20-1 20µH Coupled, Low DCR Table 2. Capacitor Vendors 10 VENDOR PHONE URL PART COMMENT Taiyo Yuden (408) 573-4150 www.t-yuden.com Ceramic Caps X5R Dielectric AVX (803) 448-9411 www.avxcorp.com Ceramic Caps Tantalum Caps Murata (404) 436-1300 www.murata.com Ceramic Caps LT1614 U U W U APPLICATIONS INFORMATION Shutdown Pin 3.3V R1 The LT1614 has a Shutdown pin (SHDN) that must be grounded to shut the device down or tied to a voltage equal or greater than VIN to operate. The shutdown circuit is shown in Figure 13. VIN LBI LT1614 1M + LBO R2 100k – 200mV INTERNAL REFERENCE GND Note that allowing SHDN to float turns on both the startup current (Q2) and the shutdown current (Q3) for VIN > 2VBE. The LT1614 doesn’t know what to do in this situation and behaves erratically. SHDN voltage above VIN is allowed. This merely reverse-biases Q3’s base emitter junction, a benign condition. The low-battery detector is disabled when SHDN is low. VLB – 200mV 2µA Figure 14. Setting Low-Battery Detector Trip Point 200k VIN 2N3906 Q3 SHDN R1 = 1614 F14 VIN R2 400k TO PROCESSOR LBO LT1614 VREF 200mV SHUTDOWN CURRENT 10k 200k LBI + GND 10µF 1614 F15 START-UP CURRENT Figure 15. Accessing 200mV Reference Q2 Q1 Figure 13. Shutdown Circuit Low-Battery Detector The LT1614’s low-battery detector is a simple PNP input gain stage with an open collector NPN output. The negative input of the gain stage is tied internally to a 200mV reference. The positive input is the LBI pin. Arrangement as a low-battery detector is straightforward. Figure 14 details hookup. R1 and R2 need only be low enough in value so that the bias current of the LBI pin doesn’t cause large errors. For R2, 100k is adequate. The 200mV reference can also be accessed as shown in Figure 15. The lowbattery detect is not operative when the device is shut down. Coupled Inductors The applications shown in this data sheet use two uncoupled inductors because the Murata units specified are small and inexpensive. This topology can also be used with a coupled inductor as shown in Figure 16. Be sure to get the phasing right. L1A 10µH VIN 5V + VIN C1 33µF 100k C3 1µF • • L1B 10µH VOUT – 5V 200mA SW SHDN LT1614 VC NFB GND 69.8k D1 24.9k + 1614 F13 C2 33µF 1nF C1, C2: AVX TAJB336M010 C3: AVX 1206CY106 D1: MBR0520 L1: COILTRONICS CTX10-1 1614 F16 Figure 16. 5V to – 5V Converter with Coupled Inductor 11 LT1614 U TYPICAL APPLICATIO S 5V to – 15V/80mA DC/DC Converter C1 1µF L1 22µH VIN + 100k VOUT –15V 80mA SW SHDN LT1614 NFB VC 22µF L2 22µH GND 255k D1 + VIN 5V 24.9k 10µF 25V 1nF C1: 25V, Y5V D1: MBR0520 L1, L2: MURATA LQH3C220 1614 TA05 5V to – 15V Converter Efficiency 80 EFFICIENCY (%) 75 70 65 60 55 50 1 10 LOAD CURRENT (mA) 100 1614 TA06 12 LT1614 U TYPICAL APPLICATIO S 3.3V to – 3.1V/200mA DC/DC Converter C1 1µF L1 22µH VIN 22µF 100k VOUT – 3.1V 200mA SW SHDN LT1614 VC + L2 22µH GND 18.7k D1 FB 22µF + VIN 3.3V 12.7k 1nF C1: AVX1206CY106 D1: MBR0520 L1, L2: MURATA LQH3C220 1614 TA03 3.3V to – 3.1V Converter Efficiency 80 EFFICIENCY (%) 70 60 50 40 30 20 3 10 30 100 LOAD CURRENT (mA) 300 1614 TA04 13 LT1614 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 8 7 6 5 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.006 ± 0.004 (0.15 ± 0.102) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 14 0.118 ± 0.004* (3.00 ± 0.102) 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) MSOP (MS8) 1098 1 2 3 4 LT1614 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC 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. SO8 1298 15 LT1614 U TYPICAL APPLICATIO S 5V to – 5V Converter Uses All Ceramic Capacitors C3 1µF L1 22µH VIN 3V TO 5V VIN 100k VOUT – 5V 200mA SW SHDN LT1614 VC NFB GND C1 4.7µF L2 22µH 1nF 69.8k D1 C2 10µF 24.9k 1nF C1: TAIYO YUDEN LMK316BJ475ML C2: TAIYO YUDEN JMK316BJ106ML C3: TAIYO YUDEN EMK316BJ105MF D1: MOTOROLA MBR0520 L1, L2: MURATA LQH3C220 OR SUMIDA CD43-220 1614 TA07 Efficiency vs Load Current 80 VIN = 3V VOUT = –5V 75 EFFICIENCY (%) 70 65 60 55 50 45 40 1 10 LOAD CURRENT (mA) 100 1614 TA08 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC®1174 High Efficiency Step-Down and Inverting DC/DC Converter Selectable IPEAK = 300mA or 600mA LT1307 Single Cell Micropower 600kHz PWM DC/DC Converter 3.3V at 75mA from 1 Cell, MSOP Package LT1308 Single Cell High Current Micropower 600kHz Boost Converter 5V at 1A from a Single Li-Ion Cell, SO-8 Package LT1316 Micropower Boost DC/DC Converter Programmable Peak Current Limit, MSOP Package LT1317 Micropower 600kHz PWM DC/DC Converter 2 Cells to 3.3V at 200mA, MSOP Package LTC1474 Low Quiescent Current High Efficiency DC/DC Converter IQ = 10µA, Programmable Peak Current Limit, MSOP LT1610 1.7MHz Single Cell Micropower DC/DC Converter 5V at 200mA from 3.3V, MSOP Package LT1611 Inverting 1.4MHz Switching Regulator in 5-Lead SOT-23 – 5V at 150mA from 5V Input, Tiny SOT-23 Package LT1613 1.4MHz Switching Regulator in 5-Lead SOT-23 5V at 200mA from 3.3V Input, Tiny SOT-23 Package LT1615 Micropower Constant Off-Time DC/DC Converter in 5-Lead SOT-23 20V at 12mA from 2.5V, Tiny SOT-23 Package LT1617 Micropower Inverting DC/DC Converter in 5-Lead SOT-23 –15V at 12mA from 2.5V, Tiny SOT-23 Package LT1930 1.2MHz Boost DC/DC Converter in 5-Lead SOT-23 5V at 480mA from 3.3V Input, VOUT Up to 34V LT1931 1.2MHz Inverting DC/DC Converter in 5-Lead SOT-23 –5V at 350mA from 5V Input, 1mVP-P Output Ripple 16 Linear Technology Corporation sn1614 1614fs LT/TP 1000 4K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1998