AME 40V CC/CV Buck Converter AME5244 n General Description n Typical Application The AME5244 is a specific 40V HV buck converter that operates in either CV/CC mode supports an output voltage range of 0.8V to 12V and support constant output current at 200KHz switching frequency. R4 C3 10Ω 22nF VIN= 8V~40V Protection features include under voltage protection, over voltage protection, current limit, thermal shutdown, and short circuit protection. The device is available in IN D1 SK R1 34 110K AME5244 C4 3.3nF COMP VBUS C2 470uF FB GND R2 20K C5 Optional R3 8.2K GND n Features 40V Maximum Rating for Input Power 200KHz Switching Frequency CC/CV Mode Function Internal Soft Start UVP, Input/Output OVP, OTP, SCP Available in SOP-8/PP Package RoHS Compliant and Halogen Free SW C1 47uF SOP-8/PP package with exposed pad for low thermal resistance. l l l l l l l L1 47uH BS AME5244-AZAADJ-24 n Functional Block Diagram IN Oscillator n Application Vref & S/D Control l Car Charger l Wall Adapter EMI Control BS PWM Controller SW 0.8V CC Control FB COMP Rev. A.03 GND 1 AME 40V CC/CV Buck Converter AME5244 n Pin Configuration SOP-8/PP Top View 8 7 6 AME5244-AZAADJ 1. IN 2. COMP 3. NC 4. NC 5. FB 6. GND 7. SW 8. BS 5 GND 1 2 3 4 * Die Attach: Conductive Epoxy n Pin Description 2 Pin No. Pin Name Pin Description 1 IN 2 COMP 3, 4 NC No connection. 5 FB Feedback Input. 6 GND Ground. 7 SW Power Switching Output 8 BS High Side. Gate Drive Boost Input. 9 Exposed Pad Input power. Compensation Node. Ground. Rev. A.03 AME 40V CC/CV Buck Converter AME5244 n Ordering Information AME5244 - x x x xxx - xx Special Feature Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration A (SOP-8/PP) Rev. A.03 1. IN 2. COMP 3. NC 4. NC 5. FB 6. GND 7. SW 8. BS Package Type Z: SOP/PP Number of Pins A: 8 Output Voltage ADJ: Adjustable Special Feature 10 24 3 AME 40V CC/CV Buck Converter AME5244 n Absolute Maximum Ratings Parameter Maximum Unit Input Voltage -0.3V to 40 V Switch Voltage -1 to VIN +1 V VSW - 0.3 to VSW + 7 V -0.3V to 7 V Electrostatic Discharge (HBM) 2000 V Junction Temperature 150 o Storage Temperature -65 to +150 o Boost Switch Voltage All Other Pins ESD Classification C C HBM 2 kV MM 150 V n Recommended Operating Conditions Parameter Symbol Rating VIN 8 to 40 VOUT 0.8 to 12 Junction Temperature Range TJ -40 to +125 Ambient Temperature Range TA -40 to +85 Input Voltage Output Voltage Unit V o C n Thermal Information Parameter Package Die Attach Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Maximum θJ C 19 Unit o SOP-8/PP Conductive Epoxy Power Dissipation Lead Temperature ( soldering 10 sec)** 4 Symbol * Measure θJC on backside center of molding compound if IC has no tab. ** MIL-STD-202G 210F C/W θJA 84 PD 1450 260 mW o C Rev. A.03 AME 40V CC/CV Buck Converter AME5244 n Electrical Specifications Typical values VIN=12V with typical TA=25oC, unless otherwise specified. Parameter Input Voltage Operating Range VIN UVLO Rising Threshold Voltage VIN UVLO Hysteresis Symbol VIN Feedback Voltage Accuracy Min Typ 8 Max Units 40 V 7 V VUVLO Input Voltage Rising VUVLO_YHS Input Voltage Falling 1 V VOUT=5V, No load 3 mA 0.8 V Standby Current Feedback Voltage Test Condition VFB ∆VFB -1.5 +1.5 % TSS 10 mS RDS(ON)_HI 120 mΩ Max. Duty Cycle DMAX 85 % Switching Frequency fOSC Constant Current ICC Thermal Shutdown TSD Internal Soft Start Time Hith Site Switch ON-Resistance Thermal Shutdown Hysteresis VFB=0.8V 175 VOV-OUT Input OVP VOV-IN 225 KHz AME5244-AZAADJ-10 1.6 A AME5244-AZAADJ-24 2.7 A ∆TSD Output OVP 200 150 o C 20 o C VOUT x 1.06 32 35 VOUT x 1.16 V 40 V Input OVP Hysteresis 2 V Short Current Limit 2 A Rev. A.03 5 AME 40V CC/CV Buck Converter AME5244 n Detailed Description Under Voltage Lockout (UVLO) The AME5244 incorporates an under voltage lockout circuit to keep the device disabled when VIN (the input voltage) is below the UVLO rising threshold voltage. Once the UVLO rising threshold voltage is reached,the device start-up begins. The device operates until VIN falls below the UVLO falling threshold voltage. The typical hysteresis in the UVLO comparator is 1V. Over Voltage Protection The AME5244 has input and output over-voltage protections. The thresholds of input and output OVP circuit include are typicapl 35V and minimum 106% x VOUT, respectively. Once the input voltage or output voltage is higher than the threshold, the high-side MOSFET is turned off. When the input voltage or output voltage drops lower than the threshold, the high-side MOSFET will be enabled again. Over Current Protection The AME5244 cycle-by-cycle limits the peak inductor current to protect embedded switch from dameage. Highside switch current limiting is implemented by monitoring the current through the high side MOSFET. Thermal Shutdown The AME5244 protects itself from overheating with an internal thermal shutdown circuit. If the junction temperature exceeds the thermal shutdown trip point, the highside MOSFET is turned off. The part is restarted when the junction temperature drops 20oC below the thermal shutdown trip point Setting the Output Voltage The output voltage is using a resistive voltage divider connected from the output voltage to FB. It divides the output voltage down to the feedback voltage by the ratio: VFB = Vout × 6 R2 R1 + R2 the output voltage is: Vout = 0.8 × R1 + R2 R2 Inductor Selection The inductor is required to supply contant current to the load while being driven by the switched input voltage. A larger value inductor will have a larger physical size and higher series resistance. It will result in less ripple current that will in turn result in lower output ripple voltage. Make sure that the peak inductor current is below the maximum switch current limit. Determine inductance is to allow the peak-to-peak ripple current to be approximately 30% of the maximum load current. The inductance value can be calculated by: L= Vout V × 1 − out f s × ∆I L Vin Where fS is the switching frequency, VIN is the input voltage, VOUT is the output voltage, and ∆ΙL is the peakto-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current, calculated by: I LPK = I LOAD + Vout V × 1 − out 2 × fs × L Vin Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI constraints. Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors will also be suggested. Choose X5R or X7R dielectrics when using ceramic capacitors. Rev. A.03 AME 40V CC/CV Buck Converter AME5244 Since the input capacitor (C1) absorbs the input switching current, it requires an adequate ripple current tating. The RMS current in the input capacitor can be esimated by: I C1 = I LOAD × Vout V × 1 − out Vin Vin At VIN=2VOUT, where IC1 = ILOAD/2 is the worst-case condition occurs. For simplification, use an input capacitor with a RMS current rating greater than half of the maximum load current. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. When using electrolytic or tantalum capacitors, a high quality, small ceramic capacitor, i.e. 0.1µF, should be placed as close to the IC as possible. The input voltage ripple for low ESR capacitors can be estimated by: I C1 = I LOAD Vout V × × 1 − out C1× f s Vin Vin Where C1 is the input capacitance value. Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolutic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ∆Vout = Vout V 1 × 1 − out × RESR + fs × L Vin 8× fs × C 2 Where RESR is the equivalent series resistance (ESR) value of the output capacitor and C2 is the output capacitance value. When using ceramic capacitors, the impandance at the switching frequency is dominated by the capacitance which is the main cause for the output voltage ripple. For simplification, the output voltage ripple can be estimated by: ∆Vout = Rev. A.03 Vout V × 1 − out 8× f × L × C2 Vin 2 s When using tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ∆Vout = Vout V × 1 − out × RESR fs × L Vin The characteristics of the output capacitor also affect the stability of the regulation system. Rectifier Diode Use a Schottky diode as the rectifier to conduct current when the High-Side MOSFET is turned off. The Schottky diode must have current rating higher than the maximum output current and a reverse voltage rating higher than the maximum input voltage. Compensation Components AME5244 has current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to govern the characteristics of the control system. The DC gain of the voltage feedback loop is given by: AVDC = RLOAD × GCS × AEA × VFB Vout Where VFB is the feedback voltage (0.8V), AVEA is the error amplifier voltage gain, GCS is the current sense transconducductance and RLOAD is the load resistor value. The system has two poles of importance. One is due to the output capacitor and the load resistor, and the other is due to the compansation capacitor (C4) and the output resistor of the error amplifier. These poles are located at: f P1 = GEA 2 × π × C 4 × AVEA fP2 = 1 2 × π × C 2 × RLOAD 7 AME 40V CC/CV Buck Converter AME5244 Where GEA is the error amplifier transconducductance. The system has one zero of importance, due to the compensation capacitor (C4) and the compensation resistor (R3). This zero is located at: 1 2 × π × C 4 × R3 f Z1 = The system may have another zero of importance, if the output capacitor has a large capacitance and/or a high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at: f ESR = 1 2 × π × C 2 × RESR In this case, a third pole set by the second compensation capacitor (C5) and the compensation resistor (R3) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at: f P3 = 1 2 × π × C 5 × R3 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 important. Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good standard is to set the crossover frequency below one-tenth of the switching frequency. To optimize the compensation components, the following procedure can be used. 2. Choose the compensation capacitor (C4) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero (fZ1) below one-forth of the crossover frequency provides sufficient phase margin. Determine C4 by the floolwing equation: C4 > 4 2 × π × R3 × f c Where R3 is the compensation resistor. 3. Determine if the second compensation capacitor (C5) is required. It is required if the ESR zero of the output capacitor is located at less than half of the switching frequency, or the following relationship is valid: 1 f < s 2 × π × C 2 × RESR 2 If this is the case, then add the second compensation capacitor (C5) to set the pole fP3 at the location of the ESR zero. Determine C5 by the equation: C5 = C 2 × RESR R3 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine R3 by the following equation: R3 = 2 × C 2 × f c Vout 2 × C 2 × 0.1× f c Vout × × < GEA × GCS VFB GEA × GCS VFB Where fC is the desired crossover frequency which is typically below one tenth of the switching frequency. 8 Rev. A.03 AME 40V CC/CV Buck Converter AME5244 PC Board Layout Guidance When laying out the printed circuit board, the following checklist should be uesd to ensure proper operation of the IC. 1) Arrange the power components to reduce the AC loop size consisting of CIN, IN pin, SW pin and the sckottky diode. 2) Place input decoupling ceramic capacitor CIN as close to IN pin as possible. CIN is connected power GND with vias or short and wide path. 3) Return FB and COMP to signal GND pin, and connect the singal GND to power GND at a single point for the best noise immunity. Connect exposed pad to power ground copper area with copper and vias. 4) Use copper plane for power GND for best heat disspation and noise immunity. 5) Please feedback resistor close to FB pin. Top Layer Bottom Layer Rev. A.03 9 AME AME5244 40V CC/CV Buck Converter n Radiated EMI Data (Vertical) n Radiated EMI Data (Horizontal) 10 Rev. A.03 AME 40V CC/CV Buck Converter AME5244 n Characterization Curve Power ON from VIN Efficiency vs. Output Current 100 95 V IN (10V/div) Efficiency (%) 90 85 V OUT (2V/div) 80 75 70 V SW (5V/div) 65 60 0.0 0.5 1.0 1.5 2.0 Time (10.0ms/div) 2.5 Output Current (A) Power Off from VIN I-V Curve 6.0 Output Voltage VOUT (V) 5.0 4.0 3.0 2.0 1.0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 Load Current IOUT (A) Full Load Ripple Load Transient Response VSW (5V/div) VOUT (20mV/div) Time (2.0µ µs/div) Rev. A.03 11 AME 40V CC/CV Buck Converter AME5244 n Characterization Curve (Contd.) Load Transient Response Load Transient Response Input Voltage vs. Constant Current 0A Short Constant Current (A) 2.9 2.7 2.5 2.3 2.1 1.9 1.7 1.5 8 9 10 11 12 13 14 15 Input Voltage (V) 2A Short 12 Rev. A.03 AME 40V CC/CV Buck Converter AME5244 n Characterization Curve VFB VS Temperature Stanby Current vs. Temperature 5.00 Standby Current (mA) 0.82 VFB(V) 0.81 0.80 0.79 0.78 -40 -20 0 20 40 Temperature(°C) 60 80 4.00 3.00 2.00 1.00 0.00 -40 100 Frequency vs. Temperature -20 0 20 40 60 Temperature (°C) 80 100 CC Current vs. Temperature 300 .0 3.60 250 .0 CC Current (A) Frequency (KHz) 3.80 200 .0 150 .0 3.40 3.20 3.00 2.80 2.60 2.40 2.20 100 .0 -40 -20 0 20 40 60 80 100 Temperature (°C) 2.00 -40 -20 0 20 40 60 80 100 Temperature (°C) Input OVP vs. Temperature 40.0 39.0 Input OVP (V) 38.0 37.0 36.0 35.0 34.0 33.0 32.0 31.0 30.0 Rev. A.03 -40 -20 0 20 40 Temperature (°C) 60 80 100 13 AME 40V CC/CV Buck Converter AME5244 n Tape and Reel Dimension SOP-8/PP P PIN 1 W AME AME Carrier Tape, Number of Components Per Reel and Reel Size Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size SOP-8/PP 12.0±0.1 mm 4.0±0.1 mm 2500pcs 330±1 mm n Package Dimension SOP-8/PP TOP VIEW SIDE VIEW D1 E1 E2 E L1 C PIN 1 D e 14 A1 FRONT VIEW A A2 b SYMBOLS MILLIMETERS INCHES MIN MAX MIN MAX A 1.350 1.750 0.053 0.069 A1 0.000 0.250 0.000 0.010 A2 1.250 1.650 0.049 0.065 C 0.100 0.250 0.004 0.010 E 3.750 4.150 0.148 0.163 E1 5.700 6.300 0.224 0.248 L1 0.300 1.270 0.012 0.050 b 0.310 0.510 0.012 0.020 D 4.720 5.120 0.186 0.202 e 1.270 BSC 0.050 BSC θ 0o 8o 0o 8o E2 1.940 2.600 0.076 0.102 D1 1.940 3.500 0.076 0.138 Rev. A.03 www.ame.com.tw E-Mail: [email protected] Life Support Policy: These products of AME, Inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of AME, Inc. AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. AME, Inc. , June 2013 Document: A016A-DS5244-A.03 Corporate Headquarter AME, Inc. 8F, 12, WenHu St., Nei-Hu Taipei 114, Taiwan . Tel: 886 2 2627-8687 Fax: 886 2 2659-2989