AME5244 AME | Alldatasheet
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Rev. A.03 40V CC/CV Buck Converter n General Description The AME5244 is a specific 40V HV buck converter that operates in either CV/CC mode supports an output volt- age range of 0.8V to 12V and support constant output current at 200KHz switching frequency. Protection features include under voltage protection, over voltage protection, current limit, thermal shutdown, and short circuit protection. The device is available in SOP-8/PP package with exposed pa d for low thermal resistance. n Features n Application l Car Charger l Wall Adapter l 40V Maximum Rating for Input Power l 200KHz Switching Frequency l CC/CV Mode Function l Internal Soft Start l UVP, Input/Output OVP, OTP, SCP l Available in SOP-8/PP Package l RoHS Compliant and Halogen Free n Functional Block Diagram n Typical Application AME5244-AZAADJ-24 EMI Control PWM Controller GNDCOMP IN FB CC Control 0.8V BS SW Oscillator Vref & S/D Control AME5244 47uH SW FB GND R3 8.2K C4 3.3nF COMP IN 22nF VIN= 8V~40V BS 110K 20K VBUS GND 47uF 10W 470uF SK Optional
Rev. A.03 40V CC/CV Buck Converter n Pin Configuration SOP-8/PP Top View AME5244-AZAADJ 1. IN 2. COMP 3. NC 4. NC 5. FB 6. GND 7. SW 8. BS * Die Attach: Conductive Epoxy n Pin Description 1 32 4 GND 5678 Pin No. Pin Name Pin Description 1 IN Input power. 2 COMP Compensation Node. 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 Ground.
Rev. A.03 40V CC/CV Buck Converter n Ordering Information Number of Pins Package Type Pin Configuration AME5244 - x x x xxx - xx Output Voltage Special Feature Special Feature A 1. IN Z: SOP/PP A: 8 ADJ: Adjustable 10 (SOP-8/PP) 2. COMP 24 3. NC 4. NC 5. FB 6. GND 7. SW 8. BS Pin Configuration Package Type Number of Pins Output Voltage
Rev. A.03 40V CC/CV Buck Converter n Absolute Maximum Ratings n Recommended Operating Conditions Parameter Symbol Rating Unit Input Voltage VIN 8 to 40 Output Voltage VOUT 0.8 to 12 Junction Temperature Range TJ -40 to +125 Ambient Temperature Range TA -40 to +85 oC V n Thermal Information * Measure qJC on backside center of molding compound if IC has no tab. ** MIL-STD-202G 210F Parameter Package Die Attach Symbol Maximum Unit Thermal Resistance* (Junction to Case) qJC 19 Thermal Resistance (Junction to Ambient) qJA 84 Power Dissipation PD 1450 mW 260 oCLead Temperature ( soldering 10 sec)** Conductive Epoxy oC / W SOP-8/PP Maximum Unit -0.3V to 40 V -1 to VIN +1 V VSW - 0.3 to VSW + 7 V -0.3V to 7 V 2000 V 150 oC -65 to +150 oC HBM 2 kV MM 150 V ESD Classification Storage Temperature Input Voltage Parameter Switch Voltage Boost Switch Voltage All Other Pins Electrostatic Discharge (HBM) Junction Temperature
Rev. A.03 40V CC/CV Buck Converter n Electrical Specifications Typical values VIN=12V with typical TA=25oC, unless otherwise specified. Parameter Symbol Test Condition Min Typ Max Units Input Voltage Operating Range VIN 8 40 V VIN UVLO Rising Threshold Voltage VUVLO Input Voltage Rising 7 V VIN UVLO Hysteresis VUVLO_YHS Input Voltage Falling 1 V Standby Current VOUT=5V, No load 3 mA Feedback Voltage VFB 0.8 V Feedback Voltage Accuracy DVFB -1.5 +1.5 % Internal Soft Start Time TSS 10 mS Hith Site Switch ON-Resistance RDS(ON)_HI 120 mW Max. Duty Cycle DMAX 85 % Switching Frequency fOSC VFB=0.8V 175 200 225 KHz AME5244-AZAADJ-10 1.6 A AME5244-AZAADJ-24 2.7 A Thermal Shutdown TSD 150 oC Thermal Shutdown Hysteresis DTSD 20 oC Output OVP VOV-OUT VOUT x 1.06 VOUT x 1.16 V Input OVP VOV-IN 32 35 40 V Input OVP Hysteresis 2 V Short Current Limit 2 A ICCConstant Current
Rev. A.03 40V CC/CV Buck Converter Under Voltage Lockout (UVLO) The AME5244 incorporates an under voltage lockout circuit to keep the device disabled when V IN (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 hyster- esis in the UVLO comparator is 1V. Over Voltage Protection The AME5244 has input and output over-voltage pro- tections. The thresholds of input and output OVP circuit include are typicapl 35V and minimum 106% x VOUT, re- spectively. 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 en- abled again. Over Current Protection The AME5244 cycle-by-cycle limits the peak inductor current to protect embedded switch from dameage. High- side switch current limiting is implemented by monitor- ing the current through the high side MOSFET. Thermal Shutdown The AME5244 protects itself from overheating with an internal thermal shutdown circuit. If the junction tempera- ture exceeds the thermal shutdown trip point, the high- side 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: RR RVV outFB +´= n Detailed Description the output voltage is: Inductor Selection The inductor is required to supply conta nt 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 volt- age. 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 approxi- mately 30% of the maximum load current. The induc- tance value can be calculated by: -´D´= in out Ls out V V If VL 1 Where fS is the switching frequency , VIN is the in put voltage, VOUT is the output voltage, and DIL is the peak- to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak cur- rent, calculated by: 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 discon- tinuous, 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 elec- trolytic capacitors will also be suggested. Choose X5R or X7R dielectrics when using ceramic capacitors. 218.0 R RRVout +´= -´´´+= in out s out LOADLPK V V Lf VII 12
Rev. A.03 40V CC/CV Buck Converter Since the input capacitor (C1) absorbs the input switch- ing current, it requires an adequate ripple current tating. The RMS current in the input capacitor can be esimated by: At VIN=2VOUT, where IC1 = ILOAD/2 is the worst-case con- dition occurs. For simplification, use an input capacitor with a RMS current rating greater than half of the maxi- mum load current. When using ceramic capacitors, make sure that they have enough capacitance to provide suffi- cient charge to prevent excessive voltage ripple at input. When using electrolytic or tantalum capacitors, a high quality, small cera mic capacitor, i.e. 0.1 mF, should be placed as close to the IC as possible. The input voltage ripple for low ESR capacitors can be estimated by: Where C1 is the input capacitance value. Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Cera mic, ta ntalum, or low ESR electrolutic capacitors are recommended. Low ESR ca- pacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: Where RESR is the equivalent series resistance (ESR) value of the output capacitor and C2 is the output capaci- tance value. When using ceramic capacitors, the impandance at the switching frequency is domin ated by the ca pacitance which is the main cause for the output voltage ripple. For simplification, the output voltage ripple can be estimated by: -´´´= in out in out s LOAD C V V V V fC II 11 When using tantalum or ele ctrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: 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 cur- rent when the High-Side MOSFET is turned off. The Schottky diode must have current rating higher than the maximum output current a nd a reverse voltage rating higher than the maximum input voltage. Compensation Components AME5244 has current mode control for easy compen- sation 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 characteris- tics of the control system. The DC gain of the voltage feedback loop is given by: Where VFB is the feedback voltage (0.8V), AVEA is the error amplifier voltage gain, GCS is the current sen se 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: -´´´´=D in out s out out V V CLf VV 128 2 ´´+´ -´´=D 28
11 CfRV
V Lf VV s ESR in out s out out ESR in out s out out RV V Lf VV ´ -´´=D 1 out FB EACSLOADVDC V VAGRA ´´´= -´´= in out in out LOADC V V V VII 11 VEA EA P AC Gf ´´´= 42 p LOAD P RCf ´´´= 22 p
Rev. A.03 40V CC/CV Buck Converter Where GEA is the error amplifier transconducductance. The system has one zero of importance, due to the com- pensation capacitor (C4) and the compensation resistor (R3). This zero is located at: 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: In this case, a third pole set by the second compensa- tion 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: The goal of compensation design is to shape the con- verter 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 insta- bility. 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. 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine R3 by the following equation: Where fC is the desired crossover frequency which is typically below one tenth of the switching frequency. 342 RCfZ ´´´= p ESR ESR RCf ´´´= 22 p 352 RCfP ´´´= p 2. Choose the compensation capacitor (C4) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero (fZ1) be- low one-forth of the crossover frequency provides suffi- cient phase margin. Determine C4 by the floolwing equation: 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 le ss than half of the switching frequency, or the following relationship is valid: If this is the case, then add the second compensation capacitor (C5) to set the pole f P3 at the location of the ESR zero. Determine C5 by the equation: FB out CSEA c FB out CSEA c V V GG fC V V GG fCR ´´ ´´= 1.022223 cfRC ´´´> 32 44 p 222 1 s ESR f RC <´´´p 25 R RCC ESR´=
Rev. A.03 40V CC/CV Buck Converter 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 40V CC/CV Buck Converter n Radiated EMI Data (Vertical) n Radiated EMI Data (Horizontal)
Rev. A.03 40V CC/CV Buck Converter n Characterization Curve Efficiency vs. Output Current I-V Curve Power ON from VIN Full Load Ripple Load Transient Response 100 Output Current (A) Efficiency (%) VIN (10V/div) VOUT (2V/div) VSW (5V/div) Time (10.0ms/div) Power Off from VIN 1.0 2.0 3.0 4.0 5.0 6.0 Load Current IOUT (A) Output Voltage VOUT (V) Time (2.0mmmms/div) VOUT (20mV/div) VSW (5V/div)
Rev. A.03 40V CC/CV Buck Converter n Characterization Curve (Contd.) 0A Short 2A Short Input Voltage vs. Constant Current Load Transient Response Load Transient Response 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 8 9 10 11 12 13 14 15 Input Voltage (V) Constant Current (A)
Rev. A.03 40V CC/CV Buck Converter n Characterization Curve Frequency vs. Temperature VFB VS T emperature Stanby Current vs. Temperature 0.78 0.79 0.80 0.81 0.82 -40 -20 0 20 40 60 80 100 Temperature(°C) VFB(V) 0.00 1.00 2.00 3.00 4.00 5.00 -40 -20 0 20 40 60 80 100 Temperature (°C) Standby Current (mA) 100 .0 150 .0 200 .0 250 .0 300 .0 -40 -20 0 20 40 60 80 100 Temperature (°C) Frequency (KHz) Input OVP vs. Temperature 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 -40 -20 0 20 40 60 80 100 Temperature (°C) CC Current (A) CC Current vs. Temperature 30.0 31.0 32.0 33.0 34.0 35.0 36.0 37.0 38.0 39.0 40.0 -40 -20 0 20 40 60 80 100 Temperature (°C) Input OVP (V)
Rev. A.03 40V CC/CV Buck Converter n Tape and Reel Dimension SOP-8/PP Carrier Tape, Number of Components Per Reel a nd Reel Size PIN 1 W PAME AME 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 b e EE2 C FRONT VIEW SIDE VIEWTOP VIEW D A PIN 1 n Package Dimension SOP-8/PP 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 qqqq 0o 8o 0o 8o E2 1.940 2.600 0.076 0.102 D1 1.940 3.500 0.076 0.138 1.270 BSC 0.050 BSC SYMBOLS MILLIMETERS INCHES
Life Support Policy: These products of AME, Inc. are not authorized f or use as critical components in life-support devices or syste ms, without the expre ss written a pproval of the pre sident of AME, Inc. AME, Inc. re serves the right to ma ke changes in the circuitry a nd specifications of its device s and advises its customers to obtain the late st version of releva nt information. ã AME, Inc. , June 2013 Document: A016A-DS5244-A.03 Corporate He adquarter AME, Inc. 8F, 12, WenHu St., Nei-Hu Taipei 114, Taiwan . Tel: 886 2 2627-8687 Fax: 886 2 2659-2989 www.ame.com.tw E-Mail: sales@ame.com.tw