Impala Linear Corporation ILC 6370/71 SOT-89 Step up Switching Regulator with Shutdown Features General Description 50mA boost converter in 5-lead SOT-89 package. Only 3 external components are needed to complete the switcher design, and frequency options of 50, 100, and 180kHz gives the designer the ability to trade off system needs with switcher design size. 87% max duty cycle gives conversion efficiencies of 85%. Standard voltage options of 2.5V, 3.3V, and 5.0V at ±2.5% accuracy feature on-chip phase compensation and softstart design. ILC6371 drives an external transistor for higher current switcher design, with all of the features and benefits of the ILC6370. ! 85% efficiency at 50mA ! Start-up voltages as low as 900mV ! ±2.5% accurate outputs ! Complete switcher design with only 3 external components ! 50, 100 and 180kHz switching frequency versions available ! Shutdown to 0.5µA ! External transistor option allows several hundred milliamp switcher design Applications ! Cellular Phones, Pagers ! Portable Cameras and Video Recorders ! Palmtops and PDAs Block Diagram LX VL X LIMI TER V DD Slow Start V OUT BUFFER Vre f V SS P WM Co ntrol led OSC P hase com p 50/ 100/180KHz EXT - CE CHIP ENABLE V DD is i nternall y connected to the VO + UT pi n. Pin-Package Configurations LX V SS 5 4 SOT -89-5 VS S EXT 5 4 SOT -89-5 (TOP VI EW) 1 2 N/C VO UT (TOP VI EW) 3 CE ILC6370 Impala Linear Corporation ILC6370/1 1.3 1 2 N/C VO UT 3 CE ILC6371 (408) 574-3939 Ordering Information* ILC6370CP-25 2.5V±2.5%@50kHz ILC6370CP-25 3.3V±2.5%@50kHz ILC6370CP-50 5.0V±2.5%@50kHz ILC6370BP-25 2.5V±2.5%@100kHz ILC6370BP-33 3.3V±2.5%@100kHz ILC6370BP-50 5.0V±2.5%@100kHz ILC6370AP-25 2.5V±2.5%@180kHz ILC6370AP-33 3.3V±2.5%@180kHz ILC6370AP-50 5.0V±2.5%@180kHz ILC6371CP-25 2.5V±2.5%@50kHz, external xtor ILC6371CP-33 3.3V±2.5%@50kHz, external xtor ILC6371CP-50 5.0V±2.5%@50kHz, external xtor ILC6371BP-25 2.5V±2.5%@100kHz, external xtor ILC6371BP-33 3.3V±2.5%@100kHz, external xtor ILC6371BP-50 5.0V±2.5%@100kHz, external xtor ILC6371AP-25 2.5V±2.5%@180kHz, external xtor ILC6371AP-33 3.3V±2.5%@180kHz, external xtor ILC6371AP-50 5.0V±2.5%@180kHz, external xtor Standard Product offering comes in tape and reel, quantity 1000 per reel, orientation right for SOT-89 www.impalalinear.com July 1999 1 SOT-89 Step up Switching Regulator with Shutdown Absolute Maximum Ratings (TA = 25°C) Parameter VOUT Input Voltage Pin CE Input Voltage Voltage on pin LX Current on pin LX Voltage on pin EXT Current pin EXT Continuous Total Power Dissipation (SOT-89-5) Operating Ambient Temperature Storage Temperature Symbol VOUT VCE VLX ILX VEXT IEXT PD Ratings 12 12 12 400 0.3 ~VOUT +0.3 +50 500 TOPR TSTG Units V V V mA V mA mW ο -30~+80 -40~+125 ο C C Elcetrical Characteristics ILC6370BP-50 VOUT = 5.0V, FOSC = 100kHz, TA = 25°C, Test Circuit of figure 1 Parameter Symbol Output Voltage Input Voltage Oscillation Startup Voltage Operation Startup Voltage Supply Current 1 VOUT VIN VST2 VST1 IDD1 Supply Current 1 IDD2 LX Switch-On Resistance LX Leakage Current Oscillator Frequency Maximum Duty Ratio Satndb-by Current CE "High " Voltage CE "Low " Voltage RSWON ILXL FOSC MAXDTY ISTB VCEH VCEL Conditions Min Typ Max 3.218 3.300 3.383 10 LX :10kΩ Pull-up to.5V, VOUT = VST IOUT +1mA LX :10kΩ Pull-up to.5V, VOUT = 4.5V Open Loop Measurement, VS/D = VIN, VLX =VIN- 0.4V, VOUT = 3V Open Loop Measurement, VOUT = VIN, VLX = 0V Measure Waveform at EXT pin VIN = 3.6V IOUT = 20mA 500 600 55 1.5 86 2.5 0.64 0.85 Ω 2.0 µA 255 300 345 KHz No Load 10 100 17 95 25 Minimum VIN When Vref does not start up Vref rises to 0V from 0.9V 1 6.0 10.0 1.8 16.0 Units V V mA µA µA % % % V msec Note: Unless otherwise spcified, VIN = VOUT x 0.6, IOUT = 50mA. See Schematic, figure 1. Impala Linear Corporation ILC6370/1 1.3 (408) 574-3939 www.impalalinear.com July 1999 2 SOT-89 Step up Switching Regulator with Shutdown Electrical Characteristics ILC6370BP-50 VOUT = 5.0V, FOSC = 100kHz, TA = 25°C; Test Circuit of figure 1 Parameter CE “High” Current CE “Low” Current LX Limit Voltage Efficiency Symbol ICEH ICEL VLXLMT EFFI Conditions LX: 10kΩ pull-up to 5V, VCE = VOUT = 4.5V = LX: 10kΩ pull-up to 5V, VOUT 4.5V, VCE = 0V (1) LX: 10kΩ pull-up to 5V, VOUT = 4.5V, FOSC > FOSC x 2 Min Typ Max 0.25 -0.25 1.1 0.7 85 Units µA µ V % 1. Switching frequency determined by delay time of internal comparator to turn LX “OFF,” and minimum “ON” time as determined by MAXDTY spec. Electrical Characteristics ILC6371BP-50 VOUT = 5.0V, FOSC = 100kHz, TA = 25°C; Test Curcuit of figure 2. Parameter Output Voltage Symbol VOUT Input Voltage Oscillation Startup Voltage Supply Current 1 Supply Current 2 EXT “High” On-Resistance VIN VST IDD 1 IDD 2 REXTH EXT “Low” On-Resistance Oscillator Frequency REXTL FOSC Maximum Duty Ratio MAXDTY Stand-by Current CE “High” Voltage ISTB VCEH CE “Low” Voltage VCEL CE “High” Current CE “Low” Current Efficiency Slow Start Time ICEH ICEL EFFI TSS Impala Linear Corporation ILC6370/1 1.3 Conditions Min 4.87 5 EXT: 10kΩ pull-up to 5V, VOUT = VST EXT: 10kΩ pull-up to 5V, VOUT = 4.5V EXT: 10kΩ pull-up to 5V, VOUT = 5.5V EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, VEXT = 4.1V VEXT = 0.4V, VOUT = 5.5V EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, Measuring of EXT pin EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, Measuring of EXT pin EXT: 10kΩ pull-up to 5V, VOUT = 4.5V EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, Existance of LX Oscillation EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, Stopped LX Oscillation EXT: 10kΩ pull-up to 5V, VOUT = VCE = 4.5V EXT: 10kΩ pull-up to 5V, VOUT = 4.5V, VCE = 0V Typ 5.000 Max 5.125 Units V 38.4 6.9 30 10 0.8 64.1 13.8 50 V V µA µA Ω 85 30 100 50 115 Ω kHz 80 87 92 % 0.5 µA V 0.20 V 0.25 -0.25 µA µA % msec 0.75 85 10 (408) 574-3939 www.impalalinear.com July 1999 3 SOT-89 Step up Switching Regulator with Shutdown Applications Circuits CE SD VOUT 3 2 1 L + ILC6370 VIN 4 CL 5 GND Figure 1: Test Circuit L: 100µH (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA735) CL: 16V 47µF (Tantalum Capacitor; NICHICON, F93) CE SD VOUT 3 2 1 L + ILC6371 VIN CL CB 4 5 Tr RB GND Figure 2: Test Circuit L: 100µH (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA735) CL: 16V 47µF (Tantalum Capacitor; NICHICON, F93) RB: 1kΩ CB: 3300pF Tr: 2SC3279, 2SDI628G Electrical Characteristics ILC6370BP-50 VOUT = 5.0V, FOSC = 100kHz, TA = 25°C; Test Circuit of figure 1 Parameter Slow Start Time Impala Linear Corporation ILC6370/1 1.3 Symbol Conditons TSS Min Typ Max msec 10 (408) 574-3939 www.impalalinear.com Units July 1999 4 SOT-89 Step up Switching Regulator with Shutdown Functions and Operation The ILC6370 performs boost DC-DC conversion by controlling the switch element shown in the circuit below. When the switch is closed, current is built up through the inductor. When the switch opens, this current has to go somewhere and is forced through the diode to the output. As this on and off switching continues, the output capacitor voltage builds up due to the charge it is storing from the inductor current. In this way, the output voltage gets boosted relative to the input. The ILC6370 monitors the voltage on the output capacitor to determine how much and how often to drive the switch. In general, the switching characteristic is determined by the output voltage desired and the current required by the load. Specifically the energy transfer is determined by the power stored in the coil during each switching cycle. PL = ƒ(tON, VIN) The ILC6370 and ILC6371 use a PWM or Pulse Width Modulation technique. The parts come in one of three fixed internal frequencies: 50, 100, or 180kHz. The switches are constantly driven at these frequencies. The control circuitry varies the power being delivered to the load by varying the on-time, or duty cycle, of the switch. Since more on-time translates to higher current build up in the inductor, the maxmim duty cycle of the switch determines the maximum load current that the device can support. The ILC6370 and ILC6371 both support up to 87% duty cycles, for maximum usable range of load currents. There are two key advantages of PWM type controllers. First, because the controller automatically varies the duty cycle of the switche’s on-time in response to changing load conditions, the PWM controller will always have an optimized waveform for a steady-state load. This translates to very good efficiency at high currents and minimal ripple on the output. [Ripple is due to the output cap constanty accepting and storing the charge recieved from the inductor, and delivering charge as required by the load. The “pumping” action of the switch produces a sawtooth-shaped voltage as seen by the output.] The other key advatage of the PWM type controllers is that the radiated noise due to the swtiching transients will always occur at the (fixed) switching frequency. Many applications do not care much about switching noise, but certain types of applications, especially communication equipment, need to minimze the high frequency interference within their system as much as is possible. Using a boost converter requires a certain amount of higher frequency noise to be generated; using a PWM converter makes that noise highly predictable; thus easier to filter out. There are downsides of PWM approaches, especially at very low currents. Because the PWM technique relies on constant switching and varying duty cycle to match the load conditions, there is Impala Linear Corporation ILC6370/1 1.3 (408) 574-3939 some point where the load current gets to small to be handled efficiently. If the ILC6370 had an ideal switch, this would not be such a problem. But an actual switch consumes some finite amount of current to switch on and off; at very low current this can be of the same magnitude as the load current itself, driving switching efficiencies down to 50% and below. The other limitation of PWM techniques is that, while the fundamental switching frequency is easier to filter out since it’s constant, the higher order harmonics of PWM will be present and may have to be filtered out as well. Any filtering rquirements will vary by application and by actual system design and layout, so generalizations in this area are difficult, at best. [For other boost converter techniques, please see the ILC6380/81 and ILC6390/91 data sheets.] However, PWM control for boost DC-DC conversion is widely used, especially in audio-noise sensitive applications or applications requiring strict filtering of the high frequency components. Impala’s products give very good efficiencies of 85% at 50mA output (5V operation), 87% maximum duty cycles for high load conditions, while maintaining very low shutdown current levels of 0.5µA. The only difference between the ILC6370 and ILC6371 parts is that the 6371 is configured to drive an external transistor as the switch element. Since larger transistors can be selected for this element, higher effective loads can be regulated. Start-up Mode The ILC6370 has an internal soft-start mode which suppresses ringing or overshoot on the output during start-up. The following diagram illustrates this start-up condition’s typical performance VOUT MIN VIN - Vf T SOFT-START (~10msec) t=0 External Components and Layout Consideration The ILC6370 is designed to provide a complete DC-DC convertor solution with a minmum of external components. Ideally, only three externals are required: the inductor, a pass diode, and an output capacitor. The inductor needs to be of low DC Resistance type, typically 1Ω value. Toroidal wound inductors have better field containment (less high frequency noise radiated out) but tend to be more expensive. Some manufacturers like Coilcraft have new bobbin-wound inductors with shielding included, which may be an ideal fit for these applications. Contact the manufacturer for more information. The inductor size needs to be in the range of 47µH to 1mH. In general, larger inductor sizes deliver less current, so the load current wil determine the inductor size used. www.impalalinear.com July 1999 5 SOT-89 Step up Switching Regulator with Shutdown For load currents higher than 10mA, use an inductor from 47µH to 100µH. [The 100µH inductor shown in the data sheet is the most typical used for this application.] For load currents of around 5mA, such as pagers, use an indcutor in the range of 100µH to 330µH. 220µH is the most typical value used here. For lighter loads, an inductor of up to 1mH can be used. The use of a larger inductor will increase overall conversion efficiency, due to the reduction in switching currents through the device. For the ILC6371, using an external transistor, the use of a 47µH inductor is recommended based on our experience with the part. Note that these values are recommended for both 50kHz and 100kHz operation. If using the ILC6370 or ILC6371 at 180kHz, the inductor size can be reduced to approximately half of these stated values. The capacitor should, in general, always be tantalum type, as tantalum has much better ESR and temperature stability than other capacitor types. NEVER use electrolytics or chemical caps, as the C-value changes below 0°C so much as to make the overall design unstable. Different C-values will directly impact the ripple seen on the output at a given load current, due to the direct charge-to-voltage relationship of this element. Different C-Values will also indirectly affect system reliability, as the lifetime of the capacitor can be degraded by constant high current influx and outflux. Running a capacitor near its maximum rated voltage can deteriorate lifetime as well; this is especially true for tantalum caps which are particularly sensitive to overvoltage conditions. In general, this capacitor should always be 47µF, Tantalum, 16V rating. Impala Linear Corporation ILC6370/1 1.3 (408) 574-3939 The diode must be of shottkey type for fast recovery and minimal loss. A diode rated at greater than 200mA and maximum voltage greater than 30V is recommended for the fastest switching time and best reliability over time. Different diodes may introduce different level of high frequency switching noise into the output waveform, so trying out several sources may make the most sense for your system. For the ILC6371, much of the component selection is as described above, with the addition of the external NPN transistor and the base drive network. The transistor needs to be of NPN type, and shoud be rated for currents of 2A or more. [This translates to lower effective on resistance and, therefore, higher overall efficiencies.] The base components should remain at 1kΩ and 3300kΩ; any changes need to be verified prior to implementation. As for actual physical component layout, in general, the more compact the layout is, the better the overall performance will be. It is important to remember that everything in the circuit depends on a common and solid ground reference. Ground bounce can directly affect the output regulation and presents difficult behavior to predict. Keeping all ground traces wide will elliminate ground bounce problems. It is also critical that the ground pin of CL and VSS pin of the device be the same pin on the board, as this capacitor serves two functions: that of the output load capacitor, and that of the input supply bypass capacitor. Layouts for DC-DC converter designs are critical for overall performance, but following these simple guidlines can simplify the task by avoiding some of the more common mistakes made in these cases. Once actual performance is completed, be sure to double check the design on an actual manufacturing prototype prodcut to verfy that nothing has changed which can affect the performance. www.impalalinear.com July 1999 6 SOT-89 Step up Switching Regulator with Shutdown Typical Performance Characteristics General conditions for all curves OUTPUT VOLTAGE vs. OUTPUT CURRENT ILC6370CP-30 5.4 L = 100µH C = 47µF (Tantalum) 5.2 OUTPUT VOLTAGE VOUT (v) OUTPUT VOLTAGE VOUT (v) 5.4 OUTPUT VOLTAGE vs. OUTPUT CURRENT ILC6370CP-50 5.0 VIN = 2.0V VIN = 3.0V 4.8 VIN = 4.0V 4.6 4.4 VIN = 1.0V 4.4 4.0 L = 100µH C = 47µF (Tantalum) 5.2 5.0 4.8 VIN = 2.0V 4.6 VIN = 1.5V VIN = 1.0V 4.4 4.4 4.0 0 100 200 300 400 0 500 40 80 160 200 EFFICIENCY vs. OUTPUT CURRENT EFFICIENCY vs. OUTPUT CURRENT 100 120 OUTPUT CURRENT IOUT (mA) OUTPUT CURRENT IOUT (mA) ILC6370CP-50 ILC6370CP-30 100 80 80 VIN = 4.0V EFFICIENCY: EFFI (%) EFFICIENCY: EFFI (%) L = 100µH C = 47µF (Tantalum) VIN = 3.0V 60 VIN = 2.0V VIN = 1.0V 40 20 0 VIN = 2.0V 60 VIN = 1.5V VIN = 1.0V 40 20 L = 100µH C = 47µF (Tantalum) 0 0 100 200 300 400 500 0 40 80 OUTPUT CURRENT IOUT (mA) RIPPLE VOLTAGE vs. OUTPUT CURRENT 100 L = 100µH C = 47µF (Tantalum) VIN = 3.0V 80 L = 100µH C = 47µF (Tantalum) VIN = 4.0V RIPPLE Vr (mV p-p) RIPPLE Vr (mV p-p) 200 RIPPLE VOLTAGE vs. OUTPUT CURRENT 100 VIN = 2.0V 60 VIN = .9V 40 80 60 VIN = 1.5V VIN = 2.0V 40 VIN = 1.0V 20 20 0 0 0 100 200 300 400 0 500 50 OUTPUT CURRENT IOUT (mA) INPUT VOLTAGE vs. OUTPUT CURRENT 150 200 INPUT VOLTAGE vs. OUTPUT CURRENT ILC6370CP-30, No Load Current 250 500 200 INPUT CURRENT (µA) 100 400 300 200 L = 100µH RL = 0 C = 47µF (Tantalum) 100 100 OUTPUT CURRENT IOUT (mA) ILC6370CP-50, No Load Current INPUT CURRENT (µA) 160 ILC6370CP-30 ILC6370CP-50 150 100 50 L = 100µH RL = 0 C = 47µF (Tantalum) 0 0 1 2 3 4 1.0 1.2 Impala Linear Corporation 1.4 1.6 1.8 2.0 INPUT VOLTAGE VIN (V) INPUT VOLTAGE VIN (V) ILC6370/1 1.3 120 OUTPUT CURRENT IOUT (mA) (408) 574-3939 www.impalalinear.com July 1999 7 SOT-89 Step up Switching Regulator with Shutdown Typical Performance Characteristics General conditions for all curves START VOLTAGE/HOLD VOLTAGE vs. IOUT TRANSIENT RESPONSE ILC6370CP-50 ILC6370CP-50 1.2 OUTPUT VOLTAGE VOUT (V) 7.0 1.0 VST, VHLD (ςς) VST 0.8 0.6 VHLD 0.4 0.2 L = 100µH C = 47µF (Tantalum) 0 6.0 5.0 4.0 3.0 0 10 20 30 -20 0 OUTPUT CURRENT IOUT (mA) Impala Linear Corporation ILC6370/1 1.3 L = 100µH C = 47µF (Tantallum) VIN = 3.0V IOUT = 1mA~30mA 20 40 60 80 TIME (µsec) (408) 574-3939 www.impalalinear.com July 1999 8