AP5101SG-13

AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Description The AP5101 is a current mode step-down converter with a built-in power MOSFET to enable smallest solution size power conversion. With the low series resistance power switch it enables a constant output current of up to 1.5A over a wide input supply range. The load and line regulation has excellent response time over the operating input voltage and temperature range. Pin Assignments ( Top View ) SW 1 8 7 6 5 GND BST COMP FB IN 2 EN GND 3 4 N EW PRODUCT The AP5101 is self protected, through a cycle-by-cycle current limiting algorithm and an on chip thermal protection. The AP5101 will provide the voltage conversion with a low count of widely available standard external components. The AP5101 is available in SO-8 package. SO-8 Features • • • • • • • • • • • • VIN 4.75 to 22V 1.5A Peak Output Current Stable with Low ESR Ceramic Output Capacitors External compensation Up to 92% Efficiency 0.1µA Shutdown Mode Fixed 1.4MHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Output Adjustable from 0.81V to 15V SO-8: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1) Applications • • • • Distributed Power Systems Battery Charger Pre-Regulator for Linear Regulators WLED Driver Note: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html. Typical Application Circuit Input 4.75V to 22V C1 2 IN BST SW C4 7 1 L1 Output 3.3V 1.5A ON OFF 3 EN AP5101 5 FB GND COMP R1 D1 4,8 6 C3 R3 R2 C2 Figure 1 Typical Application Circuit AP5101 Document number: DS32258 Rev. 1 - 2 1 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Typical Application Circuit (continiued) C4 10nF Input 4.75V to 22V C1 10uF/25V CERAMIC R4 100k 2 IN EN 7 BST SW N EW PRODUCT 3 1 L1 4.7uH R1 49.9k 1% C2 22µF/6.3V CERAMIC X2 Output 3.3V 1.5A AP5101 GND 4,8 FB COMP 6 5 C3 3nF R3 5.6k D1 B340A R2 16.2k 1% Figure 2. 1.4MHz, 3.3V Output at 1.5A Step-Down Converter AP5101 Document number: DS32258 Rev. 1 - 2 2 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Pin Descriptions ( Top View ) SW 1 8 7 6 5 GND BST COMP FB IN 2 EN GND 3 4 N EW PRODUCT SO-8 Pin Name SW IN Pin Number 1 2 Descriptions Switch Output. This is the reference for the floating top gate driver. Supply Voltage. The AP5101 operates from a +4.75V to +22V unregulated input. A decoupling capacitor C1 is required to prevent large voltage spikes from appearing at the input. Place this capacitor near the IC. On/Off Control Input. Do not leave this pin floating. To turn the device ON, pull EN above 1.2V and to turn it off pull below 0.4V. If enable/disable is not used, connect a 100kΩ resistor between EN to VIN. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into the part. Feedback. To set the output voltage, connect this pin to the output resistor divider or directly to VOUT. To prevent current limit run away during a current limit condition, the frequency foldback comparator lowers the oscillator frequency when the FB voltage is below 400mV. Compensation. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND. Bootstrap. To form a boost circuit, a capacitor is connected between SW and BST pins to form a floating supply across the power switch driver. This capacitor is needed to drive the power switch’s gate above the supply voltage. Typical values for CBST range from 0.1uF to 1uF. Ground. This pin is the voltage reference for the regulated output voltage. All control circuits are referenced to this pin. For this reason care must be taken in its layout. EN 3 GND 4 FB 5 COMP 6 BST 7 GND 8 AP5101 Document number: DS32258 Rev. 1 - 2 3 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Absolute Maximum Ratings (Note 2) Symbol VIN VSW VBS Parameter Supply Voltage Switch Voltage Boost Voltage All Other Pins Storage Temperature Junction Temperature Lead Temperature Rating 26 –0.3 to VIN + 0.3 VSW + 6 –0.3 to +6 -65 to +150 +150 +260 2 200 Unit V V V V °C °C °C kV V N EW PRODUCT TST TJ TL ESD Susceptibility HBM Human Body Model MM Machine Model Note: 2. Exceeding these ratings may damage the device. Thermal Resistance (Note 3) Symbol θJA θJC Note: Parameter Junction to Ambient Junction to Case Rating 120 15 Unit °C/W °C/W 3. Test condition for SO-8: Measured on approximately 1” square of 1 oz copper. Recommended Operating Conditions (Note 4) Symbol VIN TA VOUT Note: Parameter Supply Voltage Operating Ambient Temperature Range Output Voltage Min 4.75 -40 0.81 Max 22 +85 15 Unit V °C V 4. The device function is not guaranteed outside of the recommended operating conditions. AP5101 Document number: DS32258 Rev. 1 - 2 4 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Electrical Characteristics (VIN = 12V, TA = +25°C, unless otherwise noted) Symbol VFB IFB R DS(ON) Parameter Feedback Voltage Feedback Current Switch-On Resistance (Note 5) Switch Leakage Current Limit (Note 5) Current Sense Transconductance Output Current to Comp Pin Voltage Error Amplifier Voltage Gain (Note 5) Error Amplifier Transconductance Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (Note 5) Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Low Voltage EN Input High Voltage EN Input Current IS IQ Note: Test Conditions 4.75V ≤ VIN ≤ 22V VFB = 0.8V VEN = 0V, VSW = 0V Min 0.790 Typ. 0.810 0.1 0.35 2.5 1.3 400 Max 0.830 Unit V µA Ω µA A A/V V/V uA/V 10 N EW PRODUCT GCS AVEA GEA fSW ΔIC = ±10μA VFB = 0.6V VFB = 0V VFB = 0.6V 1.1 850 1.4 500 65 100 4.0 100 0.4 1.2 1.7 tON MHz kHz % ns V mV V V µA µA µA mA °C 3.8 4.2 Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown (Note 5) VEN = 2V VEN = 0V VEN = 0V VEN = 2V, VFB = 1V 2.1 0.1 0.1 0.5 150 1.0 0.7 5. Guaranteed by design AP5101 Document number: DS32258 Rev. 1 - 2 5 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Typical Performance Characteristics VIN =12V, VOUT =3.3V, L =4.7uH, C1=10uF, C2=22uF, Ta=+25•C, unless otherwise noted. Steady State Test IOUT=0.5A Load Transient Test IOUT=0.2A to 0.8A. Step at 0.8A/us N EW PRODUCT Time- 1us/div Start-up Through Enable (No Load) Time- 100us/div Start-up through Enable (IOUT=1A, resistive load) Time- 50us/div Shutdown Through Enable (No Load) Time- 50us/div Shutdown Through Enable (IOUT=1A, resistive) Time- 50us/div Time- 50us/div AP5101 Document number: DS32258 Rev. 1 - 2 6 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Typical Performance Characteristics (continued) VIN =12V, VOUT =3.3V, L =4.7uH, C1=10uF, C2=22uF, Ta=+25•C, unless otherwise noted. Short Circuit Entry Short Circuit Recovery N EW PRODUCT Time- 50us/div Current Sense Transconductance (Gcs) Gcs= 1.5A/(comp2-comp1)=1.5A/(1.8-0.65) =1.3A/V Time- 100us/div Time- 2us/div AP5101 Document number: DS32258 Rev. 1 - 2 7 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Applications Information Operation The AP5101 is a current mode control, asynchronous buck regulator. Current mode control assures excellent line and load regulation and a wide loop bandwidth for fast response to load transients. Figure. 3 depicts the functional block diagram of AP5101. The operation of one switching can be explained as follows. At the beginning of each cycle, HS (high-side) MOSFET is off. The EA output voltage is higher than the current sense amplifier output, and the current comparator’s output is low. The rising edge of the 1.4MHz oscillator clock signal sets the RS Flip-Flop. Its output turns on HS MOSFET. N EW PRODUCT When the HS MOSFET is on, inductor current starts to increase. The Current Sense Amplifier senses and amplifies the inductor current. Since the current mode control is subject to sub-harmonic oscillations that peak at half the switching frequency, Ramp slope compensation is utilized. This will help to stabilize the power supply. This Ramp compensation is summed to the Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the sum of the Current Sense Amplifier output and the Slope Compensation signal exceeds the EA output voltage, the RS FlipFlop is reset and HS MOSFET is turned off. The external Schottky rectifier diode (D1) conducts the inductor current. For one whole switching cycle, if the sum of the Current Sense Amplifier output and the Slope Compensation signal does not exceed the EA output, then the falling edge of the oscillator clock resets the Flip-Flop. The output of the Error Amplifier increases when feedback voltage (VFB) is lower than the reference voltage of 0.81V. This also increases the inductor current as it is proportional to the EA voltage. IN 2 CURRENT SENSE AMPLIFIER REGULATOR 7 EN 3 REGULATOR OSCILLATOR 1.4MHz/500KHz + S R R Q DRIVER 1 CURRENT LIMIT COMPARATOR GND 4 REFERENCE + + EA FB 5 PWM COMPARATOR 6 ERROR AMPLIFIER Figure 3. Functional Block Diagram AP5101 Document number: DS32258 Rev. 1 - 2 8 of 15 www.diodes.com + RAMP GENERATOR RSEN 25mO BST SW 8 GND COMP July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Applications Information (Continued) Component Selection The output voltage can be adjusted from 0.81V to 15V using an external resistor divider. Table 1 shows a list of resistor selection for common output voltages. Resistor R1 is selected based on a design tradeoff between efficiency and output voltage accuracy. For high values of R1 there is less current consumption in the feedback network. However the trade off is output voltage accuracy due to the bias current in the error amplifier. R2 can be determined by the following equation: ⎛V ⎞ R1 = R 2 × ⎜ OUT − 1⎟ ⎜ 0.81 ⎟ ⎝ ⎠ N EW PRODUCT VOUT (V) 1.8 2.5 3.3 5.0 R1 (kΩ) 80.6 (1%) 49.9 (1%) 49.9 (1%) 49.9 (1%) R2 (kΩ) 64.9 (1%) 23.7 (1%) 16.2 (1%) 9.53 (1%) Table 1. Resistor Selection for Common Output Voltage Compensation Components The AP5101 has an external COMP pin through which system stability and transient response can be controlled. COMP pin is the output of the internal trans-conductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. The DC gain of the voltage feedback loop is given by: A VDC = R LOAD × G CS × A VEA × VFB VOUT Where VFB is the feedback voltage (0.810V), RLOAD is the load resistor value, GCS is the current sense trans-conductance and AVEA is the error amplifier voltage gain. The control loop transfer function incorporates two poles. One is due to the compensation capacitor (C3) and the output resistor of error amplifier, and the other is due to the output capacitor and the load resistor. These poles are located at: fP1 = GEA 2π × C3 × A VEA 1 2π × C2 × RLOAD fP2 = Where GEA is the error amplifier trans-conductance. One zero is present due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at: f Z1 = 1 2π × C3 × R3 AP5101 Document number: DS32258 Rev. 1 - 2 9 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Applications Information (Continued) The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is crucial. A rule of thumb is to set the crossover frequency to below one-tenth of the switching frequency. Use the following procedure to optimize the compensation components: 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation: N EW PRODUCT R3 = 2π × C2 × fc VOUT 2π × C2 × 0.1 × fs VOUT × × < GEA × GCS VFB G ×G VFB EA CS Where fC is the crossover frequency, which is typically less than one-tenth of the switching frequency. 2. Choose the compensation capacitor (C3) to achieve the desired phase margin. Set the compensation zero, fZ1, to below one-fourth of the crossover frequency to provide sufficient phase margin. Determine the C3 value by the following equation: C3 > 2 π × R3 × fc Where R3 is the compensation resistor value. Inductor Calculating the inductor value is a critical factor in designing a buck converter. For most designs, the following equation can be used to calculate the inductor value; V × (VIN − VOUT ) L = OUT VIN × ΔIL × fSW Where ΔIL is the inductor ripple current. And fsw is the buck converter switching frequency. Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from: IL(MAX) = ILOAD + ΔIL 2 Peak current determines the required saturation current rating, which influences the size of the inductor. Saturating the inductor decreases the converter efficiency while increasing the temperatures of the inductor, the MOSFET and the diode. Hence choosing an inductor with appropriate saturation current rating is important. A 1µH to 10µH inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor’s DC resistance should be less than 200mΩ. Use a larger inductance for improved efficiency under light load conditions. AP5101 Document number: DS32258 Rev. 1 - 2 10 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Applications Information (Continued) Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor has to sustain the ripple current produced during the on time on the upper MOSFET. It must hence have a low ESR to minimize the losses. Due to large dI/dt through the input capacitors, electrolytic or ceramics should be used. If a tantalum must be used, it must be surge protected. Otherwise, capacitor failure could occur. For most applications, a 4.7µF ceramic capacitor is sufficient. N EW PRODUCT Output Capacitor The output capacitor keeps the output voltage ripple small, ensures feedback loop stability and reduces the overshoot of the output voltage. The output capacitor is a basic component for the fast response of the power supply. In fact, during load transient, for the first few microseconds it supplies the current to the load. The converter recognizes the load transient and sets the duty cycle to maximum, but the current slope is limited by the inductor value. Maximum capacitance required can be calculated from the following equation: ΔIinductor 2 ) 2 Co = (Δ V + Vout ) 2 − Vout 2 L(Iout + Where ΔV is the maximum output voltage overshoot. ESR of the output capacitor dominates the output voltage ripple. The amount of ripple can be calculated from the equation below: Vout capacitor = ΔIinductor × ESR An output capacitor with ample capacitance and low ESR is the best option. For most applications, a 22µF ceramic capacitor will be sufficient. External Diode The external diode’s forward current must not exceed the maximum output current. Since power dissipation is a critical factor when choosing a diode, it can be calculated from the equation below: Pdiode = (1 − VOUT ) × IOUT × 0.3V VIN Note: 0.3V is the voltage drop across the Schottky diode. A diode that can withstand this power dissipation must be chosen. PC Board Layout This is a high switching frequency converter. Hence attention must be paid to the switching currents interference in the layout. Switching current from one power device to another can generate voltage transients across the impedances of the interconnecting bond wires and circuit traces. These interconnecting impedances should be minimized by using wide, short printed circuit traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. AP5101 Document number: DS32258 Rev. 1 - 2 11 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Applications Information (Continued) External Bootstrap Diode It is recommended that an external bootstrap diode be added when the input voltage is no greater than 5V or the 5V rail is available in the system. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54. 5V BOOST DIODE N EW PRODUCT BST 7 AP5101 SW 1 10nF Figure 4. External Bootstrap Diode Manufacturer Toko Sumida Wurth Electronics Part Number A921CY-4R7M CDRH4D28C/LD 7440530047 Inductance(µH) 4.7 4.7 4.7 Max DCR (Ω) 0.027 0.036 0.038 Current Rating (A) 1.66 1.50 2.00 Dimensions L x W x H (mm3) 6.0 x 6.3 x 3.0 5.1 x 5.1 x 3.0 5.8 x 5.8 x 2.8 Table 2. Suggested Surface Mount Inductors AP5101 Document number: DS32258 Rev. 1 - 2 12 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Ordering Information AP5101 S G - 13 Package S : SO-8 N EW PRODUCT Device Package Code S Packaging (Note 6) SO-8 Green G : Green Packing 13 : Tape & Reel AP5101SG-13 Note: 13” Tape and Reel Quantity Part Number Suffix 2500/Tape & Reel -13 6. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf. Marking Information ( Top View ) 8 5 Logo Part No AP5101 YY WW X X 1 4 YY : Year : 10, 11, 12~ WW : Week : 01~52; 52 represents 52 and 53 week X : Internal Code G : Green AP5101 Document number: DS32258 Rev. 1 - 2 13 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency Package Outline Dimensions (All Dimensions in mm) 3.85/3.95 5.90/6.10 0.10/0.20 0.254 0.62/0.82 Gauge Plane Seating Plane Detail "A" N EW PRODUCT 7°~9° 1.30/1.50 1.75max. 0.15/0.25 0.35max. 45° 7°~9° Detail "A" 0°/8° 1.27typ 4.85/4.95 0.3/0.5 8x-0.60 5.4 6x-1.27 8x-1.55 Land Pattern Recommendation (Unit: mm) AP5101 Document number: DS32258 Rev. 1 - 2 14 of 15 www.diodes.com July 2010 © Diodes Incorporated AP5101 1.5A Step-Down Converter with 1.4MHz Switching Frequency IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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N EW PRODUCT Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2010, Diodes Incorporated www.diodes.com AP5101 Document number: DS32258 Rev. 1 - 2 15 of 15 www.diodes.com July 2010 © Diodes Incorporated