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 5lead 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 • • • • • • • • • • • • • • Applications • • • • • • • • • R1 49.9k 2.2µF AGND L1 10µH PGND VOUT 5V/500mA MIC2295 BD5 MIC2295BML SW VIN OVP FB EN C1 2.2µF 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 VOUT 15V/100mA 10µH VIN 1-Cell Li Ion 3V to 4.2V 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 <1µA 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 R2 4.53K VIN 1-Cell Li Ion C1 2.2µF VIN SW EN FB GND R1 10k 10µF R2 3.3k MLF and MicroLeadFrame is a trademark of Amkor Technology Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com April 2005 M9999-042605 (408) 955-1690 Micrel, Inc. MIC2295 Ordering Information Part Number Marking Code Standard Lead-Free Output Over Voltage Protection Standard Lead-Free Junction Temperature Range Package MIC2295BD5 MIC2295YD5 — SVAA SVAA -40°C to 125°C Thin SOT23-5 MIC2295BML MIC2295YML 34V SXA SXA -40°C to 125°C 2mm x2mm MLF-8L Pin Configuration Pin Description MIC2295BD5 MIC2295BML Thin SOT-23-5 2x2 MLF-8L 1 7 SW 2 — GND 3 6 FB Feedback (Input): 1.24V output voltage sense node. VOUT = 1.24V ( 1 + R1/R2) 4 3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator. 5 2 VIN Supply (Input): 2.5V to 10V input voltage. Pin Name Pin Function Switch Node (Input): Internal power BIPOLAR collector. Ground (Return): Ground. — 1 OVP 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. — 5 N/C No connect. No internal connection to die. — 4 AGND Analog ground — 8 PGND Power ground — EP GND April 2005 Ground (Return). Exposed backside pad. 2 M9999-042605 (408) 955-1690 Micrel, Inc. MIC2295 Absolute Maximum Rating (1) Operating Range (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(3) ................................................................. 2KV Supply Voltage (VIN).......................................... 2.5V to 10V Junction Temperature Range (TJ)..............-40°C to +125°C Package Thermal Impedance θJA 2x2 MLF-8 lead ............................................93°C/W θJA Thin SOT-23-5 lead ...................................256°C/W Electrical Characteristics TA=25oC, VIN =VEN = 3.6V, VOUT = 15V, IOUT = 40mA, unless otherwise noted. Bold values indicate -40°C ≤ TJ ≤ 125°C. Symbol Parameter Condition Min VIN Supply Voltage Range 2.5 VUVLO Under-Voltage Lockout 1.8 IVIN Quiescent Current VFB = 2V (not switching) (4) ISD Shutdown Current VEN = 0V VFB Feedback Voltage (+/-1%) 1.227 (+/-2%) (Over Temp) 1.215 IFB Units 10 V 2.1 2.4 V 2.8 5 mA 0.1 1 µA 1.24 1.252 1.265 VFB = 1.24V -450 Line Regulation 3V ≤ VIN ≤ 5V 0.04 Load Regulation 5mA ≤ IOUT ≤ 40mA Maximum Duty Cycle ISW Switch Current Limit Note 5 VSW Switch Saturation Voltage ISW Switch Leakage Current VEN Enable Threshold IEN Enable Pin Current fSW Oscillator Frequency VOVP Output over-voltage protection TJ Over-Temperature Threshold Shutdown 2. 3. 4. 5. Max Feedback Input Current DMAX Notes: 1. Typ V nA 1 % 1.5 % 85 90 % 1.2 1.7 A ISW = 1.2A 600 mV VEN = 0V, VSW = 10V 0.01 TURN ON 5 1.5 TURN OFF 0.4 VEN = 10V MIC2295BML only Hysteresis µA V 20 40 µA 1.05 1.2 1.35 MHz 30 32 34 V 150 °C 10 °C 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, θ 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. April 2005 3 M9999-042605 (408) 955-1690 Micrel MIC2295 Typical Characteristics C3 MIC2295 -5V Output 80 L1 VIN = 5V 75 70 65 C1 1 F/ 6.3V 60 55 50 1uF/16V 5 1 VIN SW 4 EN C2 4.7uF/ 6.3V OVP FB Vin=5V 40 CMHSH5-2L MIC2295BML Vin=4V 45 VOUT = -5V @ 0.15A L2 3 R1 10K GND Vin=5.5V 2 35 R3 10K 30 0 100 200 300 Output Current L1 = Murata LQH32CN4R7M23 L2 = Murata LQH32CN4R7M23 C4 1uF/ 6.3V MIC6211 + - R2 2.49K Sumida CDRH4D18 4.7µH 15V Short circuit protected Boost 85 80 75 1-Cell Li Ion 70 10µF/ 6.3V 4 5 1 VIN SW EN 0.1uF/ 6.3V 160K MIC2295 FB Vin=2.5 V Vin=3V 65 VOUT = 15V / 50mA GND 2 4.7µF/ 25V 3 10K 60 0 20 40 60 80 OUTPUT CURRENT (mA) April 2005 100 CIN = JMK212BJ106MG (Taiyo Yuden) 4 M9999-042605 (408) 955-1690 Micrel MIC2295 VIN = 3.3V to 5.5V 78 C1 F/ 6.3V 72 70 5 1 SW 66 MBRX140 4.7uH L2 VOUT = 5V @ 0.3A C4 470pF/ 10V R1 43.2K MIC2295BML 4 EN Vin=3V Vin=3.5V Vin=4V Vin=5V Vin=5.5V 68 1uF/16V VIN 76 74 C3 L1 4.7uH MIC2295 SEPIC 5V Output FB C2 4.7uF/ 6.3V 3 GND 2 R2 14.3K 64 0 50 100 150 200 250 OUTPUT CURRENT (mA) L1 = Murata LQH32CN4R7M23 L2 = Murata LQH32CN4R7M23 5V MIC2295 SEPIC with on coupled inductor C3 1µF/16V L1 4.7µH VIN = 3.5V to 5.5V 80 VIN 70 60 55 SW 4 FB GND 45 50 100 150 200 250 C2 4.7µF 6.3V R2 14.3k L1 = Sumida CL5DS 1 1/HP 30 0 3 2 Vin=2.5 V Vin=3.3 V Vin=5V 35 C4 470pF 10V R1 43.2k EN 50 40 VOUT = 5V @ 0.3A MIC2295BML C1 4.7µF 6.3V 65 L1 4.7µH 1 5 75 MBRX140 300 LOAD CURRENT (mA MIC2295 12V output Efficiency Input Voltage vs. Supply Voltage Max Duty Cycle vs Input Voltage 90 85 80 100 1.5 95 1.3 90 75 1.1 85 0.9 70 Vin=3.3V Vin=4.2V Vin=3.6V 65 80 0.7 75 0.5 60 70 50 100 150 200 2.5 2.5 OUTPUT CURRENT (mA) Switch Voltage vs. Supply Voltage 250 85 200 80 150 75 100 70 50 65 4.5 6.5 Input Voltage (V) April 2005 8.5 7 8.5 10 Vin=3.3V Vin=4V Vin=4.2V 60 0 50 100 150 OUTPUT CURRENT (mA) 5 200 4 5.5 7 8.5 10 SUPPLY VOLTAGE (V) Feedback Voltage vs. Temperature MIC2295 15V output Efficiency 90 2.5 5.5 SUPPLY VOLTAGE (V) 300 0 4 FEEDBACK VOLTAGE (V) 0 1.30 1.28 1.26 1.24 1.22 1.20 1.18 1.16 1.14 1.12 1.10 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) M9999-042605 (408) 955-1690 Micrel MIC2295 1.2 1.1 1.0 0.9 0.8 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) FEEDBACK CURRENT (nA) 700 Load Regulation 12.15 12.1 12.05 12 11.95 11.9 V 11.85 11.8 0 IN 25 = 3.6V 50 75 100 125 150 LOAD (mA) 100 MAXIMUM DUTY CYCLE (%) 1.3 12.2 OUTPUT VOLTAGE (V) FREQUENCY (MHz) 1.4 Frequency vs. Temperature Maximum Duty Cycle vs. Supply Voltage 98 96 94 92 90 88 86 84 82 80 2.5 4 5.5 7 8.5 SUPPLY VOLTAGE (V) 10 FB Pin Current vs. Temperature 600 500 400 300 200 100 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) April 2005 6 M9999-042605 (408) 955-1690 Micrel MIC2295 Functional Characteristics Switching Waveforms 3.2V 12VOUT 150mA Load Time (400µs/div) OUTPUT VOLTAGE (50mV/div) Output Voltage Inductor Current (10µH) SWITCH SATURATION (5V/div) INPUT VOLTAGE (2V/div) 4.2V INDUCTOR CURRENT (500mA/div) OUTPUT VOLTAGE (1mV/div) AC-Coupled Line Transient Response 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.) April 2005 7 M9999-042605 (408) 955-1690 Micrel MIC2295 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 the output of the VIN FB 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 voltage-loop 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 EN OVP* 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 April 2005 8 M9999-042605 (408) 955-1690 Micrel MIC2295 Application 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. VIN L1 10mH D1 VOUT MIC2288BML VIN C1 2.2µF SW OVP EN R1 C2 10µF FB GND GND R2 GND Figure 2 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). Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator; V D = 1− IN 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. 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 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 April 2005 components. To ensure the highest level of protection, the MIC2295 OVP pin will shut the switch off when an overvoltage condition is detected saving itself and other sensitive circuitry downstream. Component Selection Inductor Inductor selection is a balance between efficiency, stability, cost, size and rated current. For most applications a 10µH 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. 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; Frhpz = VIN 2 VOUT × L × IOUT × 2 π 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). Output Capacitor Output capacitor selection is also a trade-off between performance, size and cost. Increasing output capacitance will lead to an improved transient 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 9 Recommended Output Capacitance 10µF 4.7µF 2.2µF M9999-042605 (408) 955-1690 Micrel MIC2295 Diode Selection 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. 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 4.7µF to 10µF output capacitor is suitable for most applications. Input Capacitor A minimum 1µF 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. 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. 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. 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: V D = 1− IN VOUT 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 duty-cycle. As a result, the output voltage will climb out of regulation, causing the SW pin to exceed its 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 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). ⎡V ⎤ R1 = R 2 ⋅ ⎢ OUT − 1⎥ ⎣ 1.24V ⎦ 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. The R2 resistor value must be less than or equal to 5kΩ (R2 ≤ 5 kΩ). Inductor Selection In MIC2295, the switch current limit is 1.2A. The selected inductor should handle at least 1.2A current without saturating. The inductor should have a low DC resistor to minimize power losses. The inductor’s value can be 4.7µH to 10µH for most applications. April 2005 10 M9999-042605 (408) 955-1690 Micrel MIC2295 L1 4.7µH VIN 3V to 4.2V C1 4.7µF 6.3V SW OVP EN FB GND R2 1.87k GND L1 10µH GND C1 2.2µF 10V FB GND R2 5k GND C1 2.2µF 10V C2 4.7µF 16V VIN GND R1 43.2k FB GND GND VIN 3V to 4.2V C2 2.2µF 16V C1 4.7µF 6.3V GND R1 43.2k FB GND OVP EN VOUT 5V @ 400mA D1 SW VIN 470 pF R1 5.62k C2 4.7µF 16V FB R2 1.87k L1 10µH VIN 5V R2 5k C1 2.2µF 10V C2 4.7µF 16V GND VOUT 24V@80mA D1 VIN SW R1 43.2k OVP EN FB GND GND GND R2 5k C2 2.2µF 25V GND 5VIN to 24VOUT @ 80mA 3VIN to 5VIN to 12VOUT @ 300mA April 2005 L1 4.7µH MIC2295BML OVP EN GND 3VIN - 4.2VIN to 5VOUT @ 400mA VOUT 12V @300mA D1 SW R2 5k GND GND MIC2295BML VIN FB C2 4.7µF 16V 3VIN – 5VIN to 12VOUT @ 120mA 3VIN – 5VIN to 12VOUT @ 120mA C1 2.2µF 10V EN GND R2 5k L1 10µH OVP MIC2295BML OVP VIN 3V to 5V R1 43.2k SW VIN GND VOUT 12V @ 120mA D1 SW EN GND VOUT 12V @ 120mA D1 GND MIC2295BML C1 2.2µF 10V L1 10µH VIN 3V to 5V 3VIN - 4.2Vin to 12VOUT @ 120mA VIN 3V to 5V R2 5k MIC2295BML OVP L1 10µH FB C2 4.7µF 16V 3VIN - 4.2VIN to 9VOUT @ 180mA R1 43.2k SW EN EN GND MIC2295BML VIN OVP GND VOUT 12V @ 120mA D1 R1 31.6k SW VIN C1 2.2µF 10V 3.3VIN to 5VOUT @ 400mA VIN 3V to 4.2V VOUT 9V @ 180mA D1 MIC2295BML C2 10µF 16V R1 5.62k L1 10µH VIN 3V to 4.2V 470 pF MIC2295BML VIN VOUT 5V @ 400mA D1 11 M9999-042605 (408) 955-1690 Micrel MIC2295 Package Information 8-Pin Package MLF (ML) MICREL, INC. 2180 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. April 2005 12 M9999-042605 (408) 955-1690