ILC6390

ILC6390 FAIRCHILD | Alldatasheet

Document overview

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Technical content

Features

• 85% conversion efficiency at 50mA out  Start-up voltages as low as 900mV  ±2.5% accurate outputs  Complete switch design with only 3 external components  Automatically senses load variations to select the optimal duty cycle and extend conversion efficiency over a wide range  External transistor configuration to run as switcher controller  Shutdown to 0.5µA

Applications

 Cellular phones, pagers  Cameras, video recorders  Palmtops and PDAs

Description

50 mA boost converter using Pulse Frequency Modulation, or PFM, technique, in 5-lead SOT-89 or a 5-lead SOT-23 package. Only 3 external components are needed to complete the switcher design. The ILC6390 automatically senses load variations to choose between 55% and 75% duty cycles. Normal operation is 55% duty at 155kHz; when load currents exceed the internal comparator trip point, a “turbo mode” kicks in to provide extended on-time switching (75% duty at 100kHz oscillation). Requiring only 30µA of supply current, the ILC6390 achieves efficiencies as high as 85% at 5V yet shuts down to 0.5µA max. Standard voltages offered are 2.5, 3.3, and 5.0V and is available in both a 5 lead SOT-23 and 5 lead SOT-89 package for small footprint applications. In addition, the ILC6391 is configured to drive an external transistor to achieve higher power levels. ILC6390CM L V IN GNDCE SD C L V OUT ILC6390CP 123 CE V OUT C L L SD V IN GND ILC6391CM 123 CE V OUT C L L SD V IN GND R Tr ILC6391CP 123 CE V OUT C L L SD V IN GND C B R B Tr Figures 1 & 2 L: 100µH (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA 735) C L: 16V 47µF (Tantalum Capacitor; NICHICON, f93) Figures 3 & 4 L: 47µH (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA735) C L: 16V 47µF (Tantalum Capacitor; NICHICON, F93) RB: 1kΩ CB: 3300pF Tr: 2SC3279, 2SDI628G Typical Applications ILC6390/91 SOT-89 Step-Up PFM Switcher with Auto-Load Sense ©2001 Fairchild Semiconductor Corporation

©2001 Fairchild Semiconductor Corporation Pin Assignments Internal Block Diagram Absolute Maximum Ratings (A = 25°C) Parameter Symbol Ratings Units VOUT Input Voltage V OUT 12 V Voltage on pin LX VLX 12 V Current on pin LX ILX 400 mA Voltage on pin EXT V EXT VSS -0.3~VOUT +0.3 V Current on pin EXT I EXT ±50 mA CE Input Voltage V CE 12 V VDD Input Voltage V DD 12 V Continuous Total Power Dissipation P D ( S OT-2 5 ) PD ( S OT-8 9 ) 150 500 mW Operating Ambient Temperature T opr -30~+80 °C Storage Temperature T stg -40~+125 °C ILC6390CM ILC6390CP 123 SOT-25 (TOP VIEW) L X V SS CE V DD N/C V SS LX SOT-89-5 (TOP VIEW) 123 N/C V OUT CE ILC6391CM 123 SOT-25 (TOP VIEW) L X V SS CE V DD N/C ILC6391CP V SS L X SOT-89-5 (TOP VIEW) 123 N/C V OUT CE V OUT V DD VREF 4~5mV 2-STEP PFM CONTROLLED OSC 100/155kHz VLX LIMITER BUFFER V SS LX EXT CE CHIP ENABLE

©2001 Fairchild Semiconductor Corporation Note: 2. “Supply Current 1” is the supply current while the oscillator is continuously oscillating. In actual operation the oscillator periodically operates which results in less average power consumption. The current that is actually provided by external VIN source is represented by “No-Load Input Current.” 3. The switching frequency is determined by the delay time of the internal comparator and MFO1, which sets the min. on-time Parameter Symbol Conditions Min. Typ. Max. Units Output Voltage V OUT Test Circuit Figures 1 & 2 4.875 5.000 5.125 V Input Voltage V IN 10 V Oscillation Startup Voltage VST IOUT = 1mA 0.80 0.9 V Oscillation Hold Voltage V HLD IOUT = 1mA 0.70 V NO-Load Input Current I IN IOUT = 0mA (Note1) 5.3 10.6 µA Supply Current 1 (Note 2) I DD 1V OUT = 4.75V 31.7 63.4 µA Supply Current 2 V OUT = 5.5V 2.4 4.8 µA LX Switch-On Resistance R SWON VOUT = 4.75V, VLX = 0.4 2.8 4.3 Ω LX Leakage Current I LXL No external components, VOUT = VLX = 10V 1.0 µA Duty Ratio 1 DUTY 1 V OUT = 4.75V, Measuring of LX waveform 70 75 80 % Duty Ratio 2 DUTY 2 V OUT = 4.75V, Measuring of LX on- time 50 55 60 % Maximum Oscillation Freq. 1 MFO 1 VOUT = 4.75V, 75% duty 85 100 115 kHz Maximum Oscillation Freq. 2 MFO 2 VOUT = 4.75V, 55% duty 153 180 207 kHz Stand = by Current I STB VOUT = 4.75V 0.5 µA CE “High” Voltage V CEH VOUT = 4.75V, Existence of LX Oscillation 0.75 V CE “Low” Voltage V CEL VOUT = 4.75V, Disappearance of LX Oscillation 0.20 V CE “High” Current I CEH VCE = VOUT x 0.95 0.25 µA CE “Low” Current I CEL VOUT = 4.75V, VCE = 0V -0.25 µA LX Limit Voltage V LXLMT VOUT = 4.75V, fOSC > MFO x 2 (Note 3) 0.7 1.1 V Efficiency EFFI Test Circuit Figures 1 & 2 85 %

©2001 Fairchild Semiconductor Corporation Note: 1. “Supply Current 1” is the supply current while the oscillator is continuously oscillating. In actual operation the oscillator periodically operates which results in less average power consumption. Parameter Symbol Conditions Min. Typ. Max. Units. Output Voltage V OUT Test Circuit Figures 3 & 4 4.875 5.000 5.125 V Input Voltage V IN 10 V Operation Startup Voltage V ST IOUT = 1mA 0.80 0.9 V Operation Hold Voltage V ST IOUT = 1mA 0.70 V Supply Current 1 (Note 1) IDD 1V OUT = 4.75V 31.7 63.4 µA Supply Current 2 I DD 2V OUT = 5.5V 2.4 4.8 µA EXT “High” On-Resistance R EXTH VOUT = 4.75V, VEXT = VOUT -0.4 50 75 Ω EXT “Low” On-Resistance R EXTL VOUT = 4.75V, VEXT = 0.4 50 75 Ω Duty Ratio 1 DUTY 1 V OUT = 4.75V, Measuring of EXT waveform 70 75 80 % Duty Ratio DUTY 2 V IN = VOUT x 0.95, IOUT = 1mA, Measuring of EXT High State 50 55 60 % Maximum Oscillation Freq. 1 MFO 1 VOUT = 4.75V, 75% duty 85 100 115 kHz Maximum Oscillation Freq. 2 MFO 2 VIN = VOUT x 0.95, 55% duty 153 180 207 kHz Stand = by Current I STB VOUT = 4.75V 0.5 µA CE “High” Voltage V CEH VOUT = 4.75V, Existence of EXT Oscillation 0.75 V CE “Low” Voltage I CEL VOUT = 4.75V, Disappearance of EXT Oscillation 0.20 V CE “High” Current I CEH VCE = VOUT = 4.75V 0.25 µA CE “Low” Current V OUT = 4.75, VCE = 0V -0.25 µA Efficiency EFFI Test Circuit Figures 3 & 4 85 %

©2001 Fairchild Semiconductor Corporation The ILC6390 performs boost DC-DC conversion by control- ling 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 ILC6390 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. P L = ƒ(tON , VIN) The ILC6390 and ILC6391 use a PFM or Pulse Frequency Modulation technique. In this technique, the switch is always turned on for a fixed period of time, corresponding to a fixed switching frequency at a predefined duty cycle. For the ILC6390 this value is 3.55msec on time, corresponding to 55% duty cycle at 155kHz. Because the inductor value, capacitor size, and switch on-time and frequency are all fixed, the ILC6390 in essence delivers the same amount of power to the output during each switching cycle. This in turn creates a constant output voltage ramp which is dependent on the output load requirement. In this mode, the only differ- ence between the PFM and PWM techniques is the duty cycle of the switch. Once the output voltage reaches the set point, the ILC6390 will shut off the switch oscillator and wait until the output voltage drops low again, at which point it will re-start the oscillator. As you can see in the diagram, the PFM boost converter actually skips pulses as a way of varying the amount of power being delivered to the output. Because of this, PFM is sometimes called “Pulse Skipping Modulation.” The chief advantage of using a PFM technique is that, at low currents, the switcher is able to maintain regulation without constantly driving a switch on and off. This power savings can be 5mA or more for the ILC6390 versus the ILC6370, and at very light loads this current difference can make a noticeable impact on overall efficiency. However, because the ILC6390 will skip pulses based on load current, the effective frequency of switching may well drop into the audio band. This means that the radiated noise of the ILC6390 may interfere with the audio channel of the system and additional filtering may be necessary. In addi- tion, because the PFM on-time is fixed, it usually has higher output ripple voltage than the PWM switcher, which dynam- ically changes the on-time to match the load current require- ments. [Ripple is due to the output cap constantly accepting and storing the charge received from the inductor, and deliv- ering charge as required by the load. The “pumping” action of the switch produces a sawtooth-shaped voltage as seen by the output.] On the plus side, because pulses are skipped, overtone con- tent of the frequency noise is lower than in a PWM configu- ration. The sum of these characteristics for PFM converters makes it the ideal choice for low-current or ultra-long runt- ime applications, where overall conversion efficiency at low currents is of primary concern. [For other conversion tech- niques, please see the ILC6370/71 and ILC6380/81 datasheets.] Dual-Step Mode The ILC6390 and ILC6391 have one other unique feature, that being to automatically switch to a second switching scheme in the presence of heavy output loading. As we men- tioned, the standard switching scheme for these parts is a 3.55msec, 155kHz, 55% duty cycle part. However, if the device detects that the output load increases beyond a set point (as seen by the voltage drop on the output capacitor), it switches in a 7.5msec, 100kHz, 75% duty cycle “turbo mode” specifically to keep up with the increased load demand. This switchover is seamless to the user, but will result in a change in the output ripple voltage characteristic of the DC-DC converter. PFM converters are widely used in portable consumer appli- cations not requiring a high current level and relatively unaf- fected by audio noise. Applications such as pagers and PDAs, which need to operate in stand-by for extended peri- ods of time, gravitate toward the advantages of PFM since maximum run-time is a chief differentiating element. The ILC6390 addresses this low-current requirement, and addi- tionally offers a “turbo” mode which maintains output regu- lation in the presence of heavier-than-normal load currents, and maintains 0.5mA shutdown currents. The only difference between the ILC6390 and ILC6391 parts is that the 6391 is configured to drive an external tran- sistor as the switch element. Since larger transistors can be selected for this element, higher effective loads can be regu- lated. V SET V OUT Switch Waveform

©2001 Fairchild Semiconductor Corporation External Components and Layout Consideration The ILC6390 is designed to provide a complete DC-DC con- verter solution with a minimum of external components. Ide- ally, only three externals are required: the inductor, a pass diode, and an output capacitor. The inductor needs to be of low DC Resistance type, typi- cally 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 47mH to 1mH. In general, larger inductor sizes deliver less current, so the load current will determine the inductor size used. For load currents higher than 10mA, use an inductor from 47mH to 100mH. [The 100mH inductor shown in the datasheet is the most typical used for this application.] For load currents of around 5mA, such as pagers, use an inductor in the range of 100mH to 330mH. 220mH 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 effi- ciency, due to the reduction in switching currents through the device. For the ILC6391, using an external transistor, the use of a 47mH inductor is recommended based on our experience with the part. 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 over- voltage conditions. In general, then, this capacitor should always be 47mF, Tan- talum, 16V rating. The diode must be of shottkey type for fast recovery and minimal loss. A diode rated at greater than 200mA and max- imum voltage greater than 30V is recommended for the fast- est switching time and best reliability over time. Different diodes may introduce different levels of high frequency switching noise into the output waveform, so trying out sev- eral sources may make the most sense for your system. For the IL6391, much of the component selection is as described above, with the addition of the external NPN tran- sistor and the base drive network. The transistor needs to be of NPN type, and should be rated for currents of 2A or more. [This translates to lower effective on resistance and, there- fore, higher overall efficiencies.] The base components should remain at 1kΩ and 3300pF; 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 perfor- mance 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 eliminate ground bounce problems. It is also critical that the ground pin of C L and the VSS pin of the device be the same point 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 guidelines can sim- plify the task by avoiding some of the more common mis- takes made in these cases. Once actual performance is completed, though, be sure to double-check the design on actual manufacturing prototype product to verify that noth- ing has changed which can affect the performance.

©2001 Fairchild Semiconductor Corporation Typical Performance Characteristics General conditions for all curves 2004 0 6 0 80 100 ILC6390CP-30 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) L = 100µH C = 10µF (Tantalum) 100 VIN = 0.9V VIN = 1.2V VIN = 1.5V VIN = 1.8V VIN = 2.0V 2004 0 6 0 80 100 ILC6390CP-30 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) L = 100µH C = 10µF (Tantalum) 100 VIN = 0.9V VIN = 1.2V VIN = 1.5V 1000 200 300 400 500 ILC6391CP-30 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) L = 22µH (CD105) RB = 300 CB = 0 100 VIN = 1.0V VIN = 1.2V VIN = 1.5V VIN = 1.8V 2004 0 6 0 80 100 ILC6390CP-50 Output Voltage vs. Output Current OUTPUT VOLTAGE: V OUT (V) OUTPUT CURRENT I OUT (mA) L = 100µH C = 10µF (Tantalum) 1.0 2.0 3.0 4.0 5.0 6.0 7.0 VIN = 0.9V VIN = 1.2V VIN = 1.5V VIN = 3.0V VIN = 2.0V 2004 0 6 0 80 100 ILC6390CP-50 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) 100 VIN = 2.0V VIN = 3.0V VIN = 1.5V L = 100µH C = 10µF (Tantalum) VIN = 1.2VVIN = 0.9V 2004 0 6 0 80 100 ILC6390CP-30 Output Voltage vs Output Current OUTPUT VOLTAGE: V OUT (V) OUTPUT CURRENT I OUT (mA) 0.5 L = 100µH C = 10µF (Tantalum) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 VIN = 0.9V VIN = 1.2V VIN = 1.5V VIN = 1.8V VIN = 2.0V

©2001 Fairchild Semiconductor Corporation Typical Performance Characteristics General conditions for all curves 2004 0 6 0 80 100 ILC6390CP-50 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) 100 VIN = 2.0V VIN = 3.0V VIN = 1.5V L = 100µH C = 10µF (Tantalum) 2004 0 6 0 80 100 ILC6391CP-50 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) 100 VIN = 2.0V VIN = 3.0V VIN = 1.5V L = 22µH (CD54) R B = 300 C B = 0 VIN = 1.2V 1000 200 300 400 500 ILC6391CP-30 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) 100 VIN = 1.8V VIN = 1.0V VIN = 1.5V L = 22µH (CD105) R B = 300 C B = 0.1µF VIN = 1.2V 2004 0 6 0 80 100 ILC6391CP-30 Output Voltage vs. Output Current OUTPUT VOLTAGE: V OUT (V) OUTPUT CURRENT I OUT (mA) 0.5 L = 22µH (CD105) RB = 300 CB = 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 VIN = 1.0V VIN = 1.2V VIN = 1.5V VIN = 1.8V 2004 0 6 0 80 100 ILC6391CP-30 Output Voltage vs. Output Current OUTPUT VOLTAGE: V OUT (V) OUTPUT CURRENT I OUT (mA) 0.5 L = 22µH (CD105) RB = 300 CB = 0.1µF 1.0 1.5 2.0 2.5 3.0 3.5 4.0 VIN = 1.0V VIN = 1.2V VIN = 1.5V VIN = 1.8V 1000 200 300 400 500 ILC6391CP-30 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) 100 200 300 400 500 VIN = 1.8V VIN = 1.5V L = 22µH (CD105) R B = 300 C B = 0 VIN = 1.2V

©2001 Fairchild Semiconductor Corporation Typical Performance Characteristics General conditions for all curves 1500 300 450 600 750 ILC6391CP-50 Efficiency vs. Output Current EFFICIENCY: EFFI (%) OUTPUT CURRENT I OUT (mA) L = 22µH (CD105) RB = 300 CB = 0.1µF 100 120 VIN = 2.0VVIN = 1.5V VIN = 3.0V 1000 200 300 400 500 ILC6391CP-50 Output Voltage vs. Output Current OUTPUT VOLTAGE: V OUT (V) OUTPUT CURRENT I OUT (mA) L = 22µH (CD54) RB = 300 CB = 0.1µF 1.0 2.0 3.0 4.0 5.0 6.0 7.0 VIN = 2.0V VIN = 1.2V VIN = 1.5V VIN = 3.0V 1500 300 450 600 750 ILC6391CP-50 Output Voltage vs. Output Current OUTPUT VOLTAGE V OUT (V) OUTPUT CURRENT I OUT (mA) L = 22µH (CD105) RB = 300 CB = 0.1µF VIN = 2.0V VIN = 1.5V VIN = 3.0V 1000 200 300 400 500 ILC6391CP-50 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) 100 200 300 400 500 VIN = 3.0V VIN = 2.0V L = 22µH (CD54) R B = 500 C B = 0 VIN = 1.5V 1500 300 450 600 750 ILC6391CP-30 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) 100 200 300 400 500 VIN = 1.8V VIN = 1.5V L = 22µH (CD105) R B = 300 C B = 0.1µF VIN = 1.2V 1500 300 450 600 750 ILC6391CP-50 Ripple Voltage vs. Output Current RIPPLE Vr (mV p-p) OUTPUT CURRENT I OUT (mA) L = 22µH (CD105) RB = 300 CB = 0.1µF 100 200 300 400 500 600 VIN = 2.0V VIN = 1.5V VIN = 3.0V

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