MIC2295 High Power Density 1.2A Boost Regulator General Description Features The MIC2295 is a 1.2Mhz, PWM dc/dc boost switching regulator available in low profile Thin SOT23 and 2mm x 2mm MLF package options. High power density is achieved with the MIC2295’s internal 34V / 1.2A switch, allowing it to power large loads in a tiny footprint. • • • • • • • • • • • • • The MIC2295 implements constant frequency 1.2MHz PWM current mode control. The MIC2295 offers internal compensation that offers excellent transient response and output regulation performance. The high frequency operation saves board space by allowing small, low-profile external components. The fixed frequency PWM scheme also reduces spurious switching noise and ripple to the input power source. The MIC2295 is available in a low-profile Thin SOT23 5-lead package and a 2mm x2mm 8-lead MLF leadless package. The 2mm x 2mm MLF package option has an output over-voltage protection feature. The MIC2295 has an operating junction temperature range of –40°C to +125°C. 10µH VIN 10µH 1-Cell Li Ion 3V to 4.2V C1 2.2µF AGND • • • • • • • • • Organic EL power supplies 3.3V to 5V/500mA conversion TFT-LCD bias supplies Flash LED drivers Positive and negative output regulators SEPIC converters Positive to negative Cuk converters 12V supply for DSL applications Multi-output dc/dc converters R1 100K MIC2295 OVP SW VIN FB EN MIC2295 BMLOVP FB EN 1µF Applications 15V / 200mA SW VIN VIN 1-Cell Li Ion 3V to 4.2V VOUT 15V VOUT 100mA • 2.5V to 10V input voltage range Output voltage adjustable to 34V 1.2A switch current 1.2MHz PWM operation Stable with small size ceramic capacitors High efficiency Low input and output ripple <1mA shutdown current UVLO Output over-voltage protection (MIC2295BML) Over temperature shutdown Thin SOT23-5 package option 2mm x 2mm leadless 8-lead MLF package option –40oC to +125oC junction temperature range R1 100k PGND PGND AGND R2 9.01K R2 9.01K 2.2µF 2.2µF 2mm x 2mm Boost Regulator MLF is a trademark of Amkor Technology. July 2004 M9999-72104 [email protected] or (408) 955-1690 Micrel MIC2295 Ordering Information Output Over Voltage Protection Marking Code* Junction Temperature Range Package Part Number MIC2295BD5 - SVAA -40°C to 125°C Thin SOT23-5 MIC2295YD5 - SVAA -40°C to 125°C Thin SOT23-5 MIC2295BML 34V SXA -40°C to 125°C 2mm x2mm MLF-8L MIC2295YML 34V SXA -40°C to 125°C * Marking codes to be confirmed by Product Engineering. 2mm x2mm MLF-8L Lead Finish Standard Pb-Free Standard Pb-Free Pin Configuration Pin Description MIC2295BD5 Thin SOT-23-5 MIC2295BML 2x2 MLF-8L Pin Name Pin Function 1 2 3 7 6 SW GND FB 4 3 EN 5 2 1 VIN OVP 5 4 8 EP N/C AGND PGND GND Switch Node (Input): Internal power BIPOLAR collector. Ground (Return): Ground. Feedback (Input): 1.24V output voltage sense node. VOUT = 1.24V ( 1 + R1/R2) Enable (Input): Logic high enables regulator. Logic low shuts down regulator. Supply (Input): 2.5V to 10V input voltage. Output Over-Voltage Protection (Input): Tie this pin to VOUT to clamp the output voltage to 34V maximum in fault conditions. Tie this pin to ground if OVP function is not required. No connect. No internal connection to die. Analog ground Power ground Ground (Return). Exposed backside pad. July 2004 M9999-052402 2 (408) 955-1690 Micrel MIC2295 Absolute Maximum Rating (Note 1) Operating Range (Note 2) Supply voltage (VIN) ……………………..… 12V Switch voltage (VSW) …………………… -0.3V to 34V Enable pin voltage (VEN) …………..……..…. -0.3 to VIN FB Voltage (VFB)……...………………………..…………6V Switch Current (ISW) ………………………..…..….. 2.5A Ambient Storage Temperature (TS) …. -65°C to +150°C ESD Rating, Note 3...………………………… ……..2KV Supply Voltage (VIN) …………………..…… 2.5V to 10V Junction Temperature Range (TJ) …… -40°C to +125°C Package Thermal Impedance JA 2x2 MLF-8L lead …………………… 93°C/W JA ThinSOT23-5 lead …………………… 256°C/W Electrical Characteristics T =25 C, V A indicate -40°C TJ 125°C. Parameter Supply Voltage Range Under-Voltage Lockout Quiescent Current Shutdown Current Feedback Voltage Symb ol VIN VUVLO IVIN ISD VFB o IN =VEN = 3.6V, VOUT = 15V, IOUT = 40mA, unless otherwise noted. Bold values Condition 2.5 1.8 VFB = 2V (not switching) VEN = 0V. Note 4. (+/-1%) (+/-2%) (Over Temp) Feedback Input Current Min 1.22 7 1.21 5 Typ 2.1 2.8 0.1 10 2.4 5 1 1.24 1.252 V -450 Line Regulation 3V VIN 5V 0.04 Load Regulation 5mA IOUT 40mA Maximum Duty Cycle DMAX Switch Current Limit Switch Saturation Voltage Switch Leakage Current ISW VSW ISW Enable Threshold VEN Enable Pin Current Oscillator Frequency Output over-voltage protection Over-Temperature Threshold Shutdown IEN fSW Note 1: Note 2: Note 3: Note 4: Note 5: VOVP Tj Note 5 ISW = 1.2A VEN = 0V, VSW = 10V TURN ON TURN OFF VEN = 10V MIC2295BML only nA 1 % 1.5 % 85 90 % 1.2 1.7 600 0.01 5 A mV mA 20 1.2 32 0.4 40 1.35 34 1.5 1.05 30 150 10 Hysteresis Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(Max), the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. This device is not guaranteed to operate beyond its specified operating rating. IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF. ISD = IVIN. Guaranteed by design July 2004 M9999-052402 3 V V mA mA 1.265 VFB = 1.24V IFB Max Unit s (408) 955-1690 V mA MHz V °C °C Micrel MIC2295 Typical Characteristics 5V MIC2295 SEPIC with one coupled inductor MIC2295 SEPIC 5V Output Switch Voltage vs. Supply Voltage 80 78 300 75 250 Switch Voltage (mV) 70 65 74 EFICIENCY (%) EFFICIENCY (%) 76 72 70 Vin=3V Vin=3.5V Vin=4V Vin=5V Vin=5.5V 68 66 60 55 50 45 Vin=2.5 V Vin=3.3 V Vin=5V 40 35 200 150 100 50 30 64 0 0 50 100 150 200 50 100 250 OUTPUT CURRENT (mA) 1.3 80 250 0 2.5 300 85 1.1 0.9 0.5 2.5 5.5 7 8.5 10 90 5.5 7 8.5 10 12.2 OUTPUT VOLTAGE (V) EFFICIENCY (%) 75 70 Vin=2.5 V Vin=3V 65 60 60 0 50 100 150 200 0 OUTPUT CURRENT (mA) Feedback Voltage vs. Temperature 1.20 1.18 1.16 1.14 1.12 1.10 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 40 60 80 1.4 150 200 100 12 11.95 11.9 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) VIN = 3.6V 11.85 11.8 0 1.4 1.2 1.0 Load Regulation 12.1 Current Limit vs. Temperature July 2004 100 12.05 OUTPUT CURRENT (mA) CURRENT LIMIT (A) 1.30 1.28 1.26 1.24 1.22 20 50 12.15 FREQUENCY (MHz) EFFICIENCY (%) 65 FEEDBACK VOLTAGE (V) 0 OUTPUT CURRENT (mA) 80 Vin=3.3V Vin=4.2V Vin=3.6V Vin=3.3V Vin=4V Vin=4.2V 60 4 85 70 70 65 85 75 75 15V Short circuit protected Boost MIC2295 12V output Efficiency 80 80 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) 8.5 MIC2295 15V output Efficiency 75 4 6.5 90 0.7 70 2.5 4.5 Input Voltage (V) EFFICIENCY (%) 95 FREQUENCY (MHz) DUTY CYCLE 100 1.5 85 200 Input Voltage vs. Supply Voltage Max Duty Cycle vs Input Voltage 90 150 LOAD CURRENT (mA) 25 50 75 100 125 150 LOAD (mA) Frequency vs. Temperature 1.3 1.2 1.1 1.0 0.9 0.8 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) M9999-052402 4 (408) 955-1690 90 88 86 84 82 80 2.5 Maximum Duty Cycle vs. Supply Voltage 700 4 5.5 7 8.5 SUPPLY VOLTAGE (V) FB Pin Current vs. Temperature 99 MAXIMUM DUTY CYCLE (%) 100 98 96 94 92 MIC2295 FEEDBACK CURRENT (nA) MAXIMUM DUTY CYCLE (%) Micrel 600 500 400 300 200 100 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 10 97 95 93 91 89 87 VIN = 3.6V 85 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Switching Waveforms 4.2V 3.2V 12VOUT 150mA Load Time (400µs/div) OUTPUT VOLTAGE (50mV/div) Output Voltage Inductor Current (10µH) SWITCH SATURATION (5V/div) INDUCTOR CURRENT (500mA/div) OUTPUT VOLTAGE (1mV/div) AC-Coupled Line Transient Response INPUT VOLTAGE (2V/div) Maximum Duty Cycle vs. Temperature VSW 3.6VIN 12VOUT 150mA Time (400ns/div) Enable Characteristics LOAD CURRENT OUTPUT VOLTAGE (2V/div.) (5V/div.) VIN = 3.6V VIN=3.6V 3.6VIN 12VOUT 150mA Load TIME (400µs/div.) July 2004 M9999-052402 5 (408) 955-1690 Micrel MIC2295 the output of the slope compensation ramp generator. This summed current-loop signal is fed to one of the inputs of the PWM generator. The gm error amplifier measures the feedback voltage through the external feedback resistors and amplifies the error between the detected signal and the 1.24V reference voltage. The output of the gm error amplifier provides the voltage-loop signal that is fed to the other input of the PWM generator. When the current-loop signal exceeds the voltageloop signal, the PWM generator turns off the bipolar output transistor. The next clock period initiates the next switching cycle, maintaining constant frequency current-mode PWM control. Functional Description The MIC2295 is a high power density, PWM dc/dc boost regulator. The block diagram is shown in Figure 1. The MIC2295 is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, PWM generator, and a 1.2A bipolar output transistor. The oscillator generates a 1.2MHz clock. The clock’s two functions are to trigger the PWM generator that turns on the output transistor, and to reset the slope compensation ramp generator. The current amplifier is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. The output of the current amplifier is summed with VIN FB OVP* EN MIC2295 OVP* SW PWM Generator gm VREF 1.24V Σ 1.2MHz Oscillator Ramp Generator CA GND *OVP available on MLFTM package option only. MIC2295 Block Diagram July 2004 M9999-052402 6 (408) 955-1690 Micrel MIC2295 feedback voltage. As a result the output voltage will climb out of control. This may cause the switch node voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components. To ensure the highest level of protection, the MIC2295 OVP pin will shut the switch off when an over-voltage condition is detected saving itself and other sensitive circuitry downstream. Applications Information DC to DC PWM Boost Conversion The MIC2295 is a constant frequency boost converter. It operates by taking a DC input voltage and regulating a higher DC output voltage. Figure 2 shows a typical circuit. L1 10uH Vin D1 1A/40V Schottky VIN EN Vout Component Selection SW OVP MIC2288BML R1 C2 10uF FB Inductor R2 Inductor selection is a balance between efficiency, stability, cost, size and rated current. For most applications a 10uH is the recommended inductor value. It is usually a good balance between these considerations. Efficiency is affected by inductance value in that larger inductance values reduce the peak to peak ripple current. This has an effect of reducing both the DC losses and the transition losses. GND Gnd Gnd Figure 2. Typical Application regulati Boost regulation is achieved by turning on an internal switch, which draws current through the inductor (L1). When the switch turns off, the inductor’s magnetic field collapses, causing the current to be discharged into the output capacitor through an external Schottkey diode (D1). Voltage regulation is achieved my modulating the pulse width or pulse width modulation (PWM). There is also a secondary effect of an inductors DC resistance (DCR). The DCR of an inductor will be higher for more inductance in the same package size. This is due to the longer windings required for an increase in inductance. Since the majority of input current (minus the MIC2295 operating current) is passed through the inductor, higher DCR inductors will reduce efficiency. Also, to maintain stability, increasing inductor size will have to be met with an increase in output capacitance. This is due to the unavoidable “right half plane zero” effect for the continuous current boost converter topology. The frequency at which the right half plane zero occurs can be calculated as follows; Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator; D =1 Vin Vout The duty cycle required for voltage conversion should be less than the maximum duty cycle of 85%. Also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycle can cause pulse skipping. This is due to the energy stored in the inductor causing the output to overshoot slightly over the regulated output voltage. During the next cycle, the error amplifier detects the output as being high and skips the following pulse. This effect can be reduced by increasing the minimum load or by increasing the inductor value. Increasing the inductor value reduces peak current, which in turn reduces energy transfer in each cycle. Frhpz = Vin 2 Vout L Iout 2 The right half plane zero has the undesirable effect of increasing gain, while decreasing phase. This requires that the loop gain is rolled off before this has significant effect on the total loop response. This can be accomplished by either reducing inductance (increasing RHPZ frequency) or increasing the output capacitor value (decreasing loop gain). Over Voltage Protection For MLF package of MIC2295, there is an over voltage protection function. If the feedback resistors are disconnected from the circuit or the feedback pin is shorted to ground, the feedback pin will fall to ground potential. This will cause the MIC2295 to switch at full duty-cycle in an attempt to maintain the Output Capacitor Output capacitor selection is also a trade-off between performance, size and cost. Increasing output capacitance will lead to an improved transient July 2004 M9999-052402 7 (408) 955-1690 Micrel MIC2295 response, but also an increase in size and cost. X5R or X7R dielectric ceramic capacitors are recommended for designs with the MIC2295. Y5V values may be used, but to offset their tolerance over temperature, more capacitance is required. The following table shows the recommended ceramic (X5R) output capacitor value vs. output voltage. Output Voltage <6V <16V <34V D =1 Vin Vout The actual duty-cycle, D, cannot surpass the maximum rated duty-cycle, Dmax. Output Voltage Setting: The following equation can be used to select the feedback resistors R1 and R2 (see figure 1). Recommended Output Capacitance 22uF 10uF 4.7uF Vout R1 = R2 1 1.24V Diode Selection A high value of R2 can increase the whole system efficiency, but the feedback pin input current (IFB) of the gm operation amplifier will affect the output voltage. An R2 value of xx KW is suitable for most applications Inductor Selection: In MIC2295, the switch current limit is 1A. The selected inductor should handle at least 1A current without saturating. The inductor should have a low DC resistor to minimize power losses. The inductor’s value can be 4.7uH to 10uH for most applications. Capacitor Selection: Multi-layer ceramic capacitors are the best choice for input and output capacitors. They offer extremely low ESR, allowing very low ripple, and are available in very small, cost effective packages. X5R dielectrics are preferred. A 4.7uF to 10uF output capacitor is suitable for most applications. Diode Selection: For maximum efficiency, Schottky diode is recommended for use with MIC2295. An optimal component selection can be made by choosing the appropriate reverse blocking voltage rating and the average forward current rating for a given application. For the case of maximum output voltage (34V) and maximum output current capability, a 40V / 1A Schottky diode should be used. Open-Circuit Protection For MLF package option of MIC2295, there is an output over-voltage protection function that clamps the output to below 34V in fault conditions. Possible fault conditions may include: if the device is configured in a constant current mode of operation and the load opens, or if in the standard application the feedback resistors are disconnected from the circuit. In these cases the FB pin will pull to ground, causing the MIC2295 to switch with a high dutycycle. As a result, the output voltage will climb out of regulation, causing the SW pin to exceed its The MIC2295 requires an external diode for operation. A Schottkey diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. Ensure the diode selected can deliver the peak inductor current and the maximum reverse voltage is rated greater than the output voltage. Input Capacitor A minimum 1uF ceramic capacitor is recommended for designing with the MIC2295. Increasing input capacitance will improve performance and greater noise immunity on the source. The input capacitor should be as close as possible to the inductor and the MIC2295, with short traces for good noise performance. Feedback Resistors The MIC2295 utilizes a feedback pin to compare the output to an internal reference. The output voltage is adjusted by selecting the appropriate feedback resistor values. The desired output voltage can be calculated as follows; R1 Vout = Vref + 1 R2 Where Vref is equal to 1.24V. Application Information Duty-Cycle: The MIC2295 is a general-purpose step up DC-DC converter. The maximum difference between the input voltage and the output voltage is limited by the maximum duty-cycle (Dmax) of the converter. In the case of MIC2295, DMAX = 85%. The actual duty cycle for a given application can be calculated as follows: July 2004 M9999-052402 8 (408) 955-1690 Micrel MIC2295 maximum voltage rating and possibly damaging the IC and the external components. To ensure the highest level of safety, the MIC2295 has a dedicated pin, OVP, to monitor and clamp the output voltage in over-voltage conditions. The OVP function is offered in the 2mm x 2mm MLF-8L package option only. To disable OVP function, tie the OVP pin to ground. MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2004 Micrel, Incorporated. July 2004 M9999-052402 9 (408) 955-1690