MIC2296 High Power Density 1.2A Boost Regulator General Description Features The MIC2296 is a 600kHz, PWM dc/dc boost switching regulator available in a 2mm x 2mm MLF® package option. High power density is achieved with the MIC2296’s internal 34V / 1.2A switch, allowing it to power large loads in a tiny footprint. The MIC2296 is a version of the MIC2295 1.2MHz, PWM dc/dc boost switching regulator, that offers improved efficiency resulting from 600kHz operation. The MIC2296 implements constant frequency 600kHz PWM current mode control. The MIC2296 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 MIC2296 is available in a low-profile Thin SOT23 5pin package and a 2mm x2mm 8-pin MLF® leadless package. The 2mm x 2mm MLF® package option has an output over-voltage protection feature. The MIC2296 has an operating junction temperature range of –40°C to +125°C • • • • • • • • • • • • • 2.5V to 10V input voltage range Output voltage adjustable to 34V 1.2A switch current 600kHz PWM operation Stable with small size ceramic capacitors High efficiency Low input and output ripple <1µA shutdown current UVLO Output over-voltage protection (MIC2296BML) Over temperature shutdown 2mm x 2mm leadless 8-pin MLF® package option –40oC to +125oC junction temperature range Applications • • • • • • • • Organic EL power supplies 3.3V to 5V/500mA conversion TFT-LCD bias supplies Positive and negative output regulators SEPIC converters Positive to negative Cuk converters 12V supply for DSL applications Multi-output dc/dc converters L1 10µH VOUT 15V/100mA 10µH VOUT 5V/400mA 1000 pF VIN 1-Cell Li Ion 3V to 4.2V C1 2.2µF MIC2296BML SW VIN OVP FB EN AGND PGND MIC2296 BD5 R1 10k R2 901 2.2µF VIN 1-Cell Li Ion C1 2.2µF VIN SW EN FB GND R1 10k 10µF R2 3.3k MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2010 M9999-011310 Micrel, Inc. MIC2296 Ordering Information Part Number Marking Code Standard Lead-Free Output Over Voltage Protection Lead-Free Junction Temp. Range Package Standard MIC2296BML MIC2296YML 34V WDA WDA -40°C to 125°C 8-Pin 2mm x2mm MLF® MIC2296BD5* MIC2296YD5* - WDAA WDAA -40°C to 125°C 5-Pin Thin SOT-23 * Contact factory for availability. Pin Configuration FB GND SW 1 3 2 4 EN 5 VIN OVP 1 8 PGND VIN 2 7 SW EN 3 6 FB AGND 4 5 NC TSOT-23-5 (BD5) EP 8-pin MLF® (BML) Pin Description MIC2296BD5 MIC2296BML Thin SOT-23-5 2x2 MLF-8L Pin Name — 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 2 VIN Supply (Input): 2.5V to 10V input voltage. 4 3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator. — 4 AGND — 5 N/C No connect. No internal connection to die. 3 6 FB Feedback (Input): 1.24V output voltage sense node. VOUT = 1.24V ( 1 + R1/R2) 1 7 SW Switch Node (Input): Internal power BIPOLAR collector. — 8 PGND 2 — GND Ground (Return): Ground. — EP GND Ground (Return). Exposed backside pad. January 2010 Pin Function Analog ground Power ground 2 M9999-011310 Micrel, Inc. MIC2296 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-8L ..................................................93°C/W Electrical Characteristics (4) 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 Typ 2.1 Max Units 10 V 2.4 V IVIN Quiescent Current VFB = 2V (not switching) 2.8 5 mA ISD Shutdown Current VEN = 0V(5) 0.1 1 µA VFB Feedback Voltage 1.24 1.252 IFB Feedback Input Current VFB = 1.24V -450 Line Regulation 3V ≤ VIN ≤ 5V 0.04 Load Regulation 5mA ≤ IOUT ≤ 40mA 0.5 % 90 95 % 1.2 1.7 DMAX Maximum Duty Cycle ISW Switch Current Limit (±1%) 1.227 (±2%) (Over Temp) 1.215 Note 5 1.265 VSW Switch Saturation Voltage ISW = 0.5A 250 ISW Switch Leakage Current VEN = 0V, VSW = 10V 0.01 VEN Enable Threshold TURN ON nA 1 2.5 % A mV 1 1.5 TURN OFF V 0.4 µA V IEN Enable Pin Current VEN = 10V 20 40 µA fSW Oscillator Frequency VIN = 3.6V 525 600 675 kHz VOVP Output over-voltage protection MIC2296BML only 30 32 34 V TJ Over-Temperature Threshold Shutdown Notes: 1. 2. 3. 4. 5. Hysteresis 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. Specification for packaged product only. ISD = IVIN. January 2010 3 M9999-011310 Micrel MIC2296 Typical Characteristics 12V Output with L = 4.7µH 84 90 VIN = 4.2V 88 86 84 82 80 VIN = 3.6V 78 76 74 VIN = 3.2V 74 72 0 800 300 290 VIN = 4.2V 72 70 50 100 150 200 250 OUTPUT CURRENT (mA) Frequency vs. Input Voltage VIN = 3.6V VIN = 3.2V 0 100 230 220 210 200 200 400 600 800 1000 OUTPUT CURRENT (mA) 10 Input Voltage (V) Max Duty Cycle vs. Input Voltage 2 1.9 98 600 Switch Saturation Voltage vs. Input Voltage 280 270 260 250 240 82 80 78 76 5V Output with L = 4.7µH Current Limit vs. Input Voltage 1.8 1.7 96 1.6 1.5 400 200 94 1.4 1.3 92 1.2 1.1 10 Load Regulation 12.15 12.1 12.05 12 11.95 11.9 V 11.85 11.8 0 January 2010 IN 25 = 3.6V 50 75 100 125 150 LOAD (mA) 1.30 1.28 5 7.5 INPUT VOLTAGE (V) 1 2.5 10 Feedback Voltage vs. Temperature 700 FEEDBACK CURRENT (nA) OUTPUT VOLTAGE (V) 12.2 5 7.5 INPUT VOLTAGE (V) 90 2.5 FEEDBACK VOLTAGE (V) 0 2.5 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) 4 5 7.5 INPUT 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) M9999-011310 Micrel MIC2296 Functional Characteristics Enable Characteristics Load Current (100mA/div) Enable Voltage (2V/div) Output Voltage (5V/div) Output Voltage (50mV/div) Step Load Response VIN = 3.6V VOUT = 12V IOUT = 150mA TIME (100µs/div) TIME (2µs/div) January 2010 VIN = 3.6V VOUT = 12V IOUT = 50mA to 150mA 5 M9999-011310 Micrel MIC2296 Functional Description The MIC2296 is a high power density, PWM dc/dc boost regulator. The block diagram is shown in Figure 1. The MIC2296 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 600kHz 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* MIC2296 OVP* SW PWM Generator gm VREF 1.24V CA 600kHz Oscillator Ramp Generator GND *OVP available on MLFTM package option only. Figure 1. MIC2296 Block Diagram January 2010 6 M9999-011310 Micrel MIC2296 Application Information voltage condition is detected saving itself and other sensitive circuitry downstream. DC to DC PWM Boost Conversion The MIC2296 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. Component Selection L1 10µH VIN VOUT SW VIN EN U1 MIC2296-BML OVP R1 C2 10µF FB R2 GND GND 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. This causes 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 90%. 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 MIC2296, 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 MIC2296 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 components. To ensure the highest level of protection, the MIC2296 OVP pin will shut the switch off when an overJanuary 2010 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 MIC2296 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 MIC2296. 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 7 Recommended Output Capacitance 10 F 4.7 F 2.2 F M9999-011310 Micrel MIC2296 Diode Selection The MIC2296 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 MIC2296. 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 MIC2296, with short traces for good noise performance. Diode Selection For maximum efficiency, Schottky diode is recommended for use with MIC2296. 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 MIC2296 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 MIC2296 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 MIC2296, 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 MIC2296, 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 MIC2296 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 MIC2296 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 ≤ 5kΩ). Inductor Selection In MIC2296, 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. January 2010 8 M9999-011310 Micrel MIC2296 VIN 3V to 4.2V L1 4.7µH VIN SW OVP EN C2 22µF 6.3V FB R2 1.87k GND C1 2.2µF 10V L1 15µH VIN SW OVP EN R1 31.6k GND C2 4.7µF 16V FB R2 5k GND GND 3VIN to 4.2VOUT @ 400mA VIN 3V to 4.2V VOUT 9V @ 180mA D1 MIC2296BML R1 5.62k GND L1 4.7µH 560 pF 470 pF MIC2296BML C1 4.7µF 6.3V VIN 3V to 4.2V VOUT 5V @ 400mA D1 GND 3VIN - 4.2VIN to 9VOUT @ 180mA L1 15µH VIN 5V VOUT 12V @ 120mA D1 VOUT 24V @160mA D1 1200 pF MIC2296BML C1 2.2µF 10V SW VIN OVP EN MIC2296BML R1 43.2k C2 4.7µF 16V FB GND GND GND 3VIN - 4.2Vin to 12VOUT @ 120mA L1 15µH VIN 3V to 4.2V VIN SW R1 43.2k OVP EN FB GND R2 5k GND C1 2.2µF 10V R2 2.32k C2 2.2µF 25V GND 5VIN to 24VOUT @ 160mA VOUT 24V@80mA D1 1200 pF MIC2296BML C1 2.2µF 10V VIN SW OVP EN C2 2.2µF 25V FB GND GND R1 43.2k R2 2.32k GND 3VIN to 4.2VIN to 24VOUT @ 80mA January 2010 9 M9999-011310 Micrel MIC2296 Package Information 8-Pin Package MLF (ML) 5-Pin Thin SOT-23 (D5) January 2010 10 M9999-011310 Micrel MIC2296 Recommended Land Pattern 8-Pin Package MLF (ML) 5-Pin Thin SOT-23 (D5) January 2010 11 M9999-011310 Micrel MIC2296 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. © 2005 Micrel, Incorporated. January 2010 12 M9999-011310