ELM650DA CC/CV Mode 36V step down 2A DC/DC converter ■General description ELM650DA is a step down switching regulator, which has a built-in 40V P-channel power MOSFET for delivering output current. ELM650A is designed to allow for operating a wide supply voltage range from 8V to 36V and capable of delivering 2A output current. ELM650DA features programmable CV/CC mode control functions, the CV mode (Constant Voltage) function to provide a regulated voltage output and the CC mode (Constant Current) function provide a current limitation function, it is suitable for the DC/DC switching power applications when requested the current limitation function. ■Features ■Application • • • • • • • • • • • • • • • • CC/CV mode control Soft start function for start-up Output over-voltage protection Over temperature protection Fold back short-circuit protection High efficiency operation Input voltage range Input voltage surge Fixed operating frequency Voltage reference accuracy Current limit accuracy Package Car charger Portable charger applications DC/DC converters with current limited General purpose CV/CC power supply : 8V to 36V : 40V : 100kHz : ±1% : ±4% : SOP-8 ■Maximum absolute ratings Parameter VCC to GND LX to VCC VSEN to GND ISEN+ to GND ISEN- to GND OVP to GND COMP to GND Output current Power dissipation at Ta <60 °C Operationg temperature Storage temperature range Symbol Vcc LX Vsen ISEN+ ISENOVP COMP Icc Pd Top Tstg Limit -0.3 to +40.0 +0.3 to -40.0 -0.3 to +7.0 -0.3 to +7.0 -0.3 to +7.0 -0.3 to +7.0 -0.3 to +7.0 3 0.75 -40 to +85 -60 to 150 Caution:Permanent damage to the device may occur when ratings above maximum absolute ones are used. Unit V V V V V V V A W °C °C ■Selection guide ELM650DA-N Symbol a b c Package Product version Taping direction D: SOP-8 A N: Refer to PKG file ELM650DA - N ↑↑ ↑ ab c * Taping direction is one way. 10 - 1 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter ■Pin configuration SOP-8(TOP VIEW) 1 8 2 7 3 6 4 5 Pin No. 1 2 3 4 5 6 7 8 Pin name GND VSEN ISENISEN+ LX VCC OVP COMP Pin description GND The voltage sense input The current sense negative input The current sense positive input Regulator output The input supply voltage The over-voltage sense input The E/A output pin for frequency compensation ■Block diagram COMP 8 OVP LX VCC 7 6 1.18V 5 Reference Generator + OTP RAMP 1.18V + Error + Amp. - - Control logic PWM Comp. Gate DRV Soft start + Current Amp. 0.4V - - + Vss 1 2 3 4 GND VSEN ISEN- ISEN+ 10 - 2 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter ■Standard circuit U1 6 Vin 7 + C1 8 R1 C3 1 C4 VCC LX OVP ISEN+ COMP ISENGND L1 5 R2 Vout C5 4 D1A 3 VSEN 2 + C2 R3 R5 R4 R6 ELM650DA GND ■Functional descriptions 1. CV/CC mode control ELM650DA provides CV/CC function. The CV (constant voltage) function is implemented to deliver a regulated output voltage for the output terminal, and the CC (constant current) function is to limit output current to be a limited value to prevent the device damaged due to output short circuit or over current condition. 2. Soft start function ELM650DA is composed of built-in internal soft start function to prevent a large surge current happening when during start-up period due to the surge current charging output filter capacitors. 3. Output over-voltage protection ELM650DA provides output over-voltage protection function. When output over-voltage happens, ELM650DA shuts down and recovers to normal state automatically if output over-voltage is released. 4. Output short-circuit protection ELM650DA provides output short-circuit protection function. When output short-circuit happens, ELM650DA shuts down and recovers to normal state automatically if output short-circuit is released. ■Marking SOP-8 Mark 650 a to o 10 - 3 Content Product No.code Assembly lot No. Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter ■Electrical characteristics Vin=12V, Iout=1.0A, Top=25°C, unless otherwise specified Condition Min. Typ. Max. Unit Parameter Symbol Input voltage section Input voltage Vin Input no load current Ino-load Iout=0A Oscillator section Operating frequency Fosc Duty cycle range Duty Error amplifier section Reference voltage of Vvsen the voltage error amplifier Reference voltage of Visen the current error amplifier Tran conductance of Gmerr error amplifier Output over voltage protection section Reference voltage of Vovp the over voltage comparator Output short circuit protection section Reference voltage of the Vscp short circuit fold back comparator MOSFET section Drain-source breakdown voltage V(br)dss Vgs=0V, Iout=250µA Drain-source on-state resistance Rds (on) Vin=24V, Iout=1A 8 36 10 V mA 90 110 95 kHz % 1.168 1.180 1.192 V 107.5 112.0 116.5 mV 150 1.145 1.180 µA/V 1.215 0.4 V V -40 V mΩ 200 ■Application circuits U1 L1 Vin 6 7 GND 8 1 R1 + + C1 C3 C2 C10 C4 C5 VCC LX OVP ISEN+ COMP ISENGND L2 5 R5 R3 4 C8 R4 3 1 R6 R8 R7 R9 3 R10 L3 2 Vout+ 4 Vout- LED VSEN 2 ELM650DA R2 C6 D1 C9 + C7 L4 10 - 4 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter BOM list for application circuits Device C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 D1 L1 L2 L3 L4 LED R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 U1 Description Input ECAP, 47µF/35V, 6.3*7mm Input ECAP, 100µF/35V, 6.3*7mm MLCC, 0603, X7R MLCC, 0603, X7R MLCC, 0603, NPO MLCC, 0805, X7R Output ECAP, 220µF/6.3V, 6.3φ*7mm MLCC, 0603, X7R MLCC, 0603, X7R MLCC, 0603, X7R Schottky diode, SMB, 40V/5A DR Choke, 4φ*6mm Power inductor, T- 5052B, L= 100µH wire=0.65 T Core, 6*3*3, 0.5φ*2C*3Ts SMD bead core , 0805, 220Ω 3000mA LED, GREEN Chip R , 0603 , 5% Chip R , 0805 , 5% Chip R , 0603 , 5% Chip R , 0603 , 5% Chip R , 1206 , 1% Chip R , 0603 , 1% Chip R , 0603 , 1% Chip R , 0603 , 5% Chip R , 0603 , 5% Chip R , 0603 , 5% Buck controller, CC/CV function, Vin 8~36V, SOP-8 Value 47µF/35V 100µF/35V 104 473 47pF 102 220µF/6.3V NA 104 104 SB54 15µH 100µH 22µH BEAD LED 100K 10R 51R 51R 0.045R 390K 118K 470R 120R 1K ELM650DA Q'ty 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ■Application notes 1. Output voltage setting Figure 1 shows the connections for setting the output voltage value. Typically, selecting the proper ratio of the two feedback resistors Rvsen1 and Rvsen2 by using Rvsen2 ≈ 118kΩ and determining Vsen from the following equation: Rvsen1 = Rvsen2 ( Vout / 1.18V - 1 ) Vout RVsen1 ELM650DA Vsen RVsen2 Fig-1: Output voltage setting 10 - 5 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter 2. CC current setting The constant current value of ELM650DA is set by a Rs resistor which is connected between Isen+ and Isenpin. The output current of CC mode and Rs resistor are set by the following equation: Rs = 0.112 / ICC Rs ELM650DA Icc Vout Isen+ Isen- Fig-2 : Constant current mode setting When output voltage is set over 6V, the voltage of the V(Isen+), V(Isen-) should be set under 6V by the following equation: Visen± = (1/ks) Vout ≤ 6V, ks = (Rs1 + Rs2) / Rs2 = (Rs3 + Rs4) / Rs4 Also ks = (Rs1 + Rs2) / Rs2, and Rs = ks × 0.112/Icc at this time. Rs Rs1 Isen+ IsenRs2 Vout Rs3 Rs4 Fig-3 : Constant current mode setting ( At Vout ≥ 6V ) 3. Input capacitor selection The bulk input capacitor selection is based on the voltage rating, the RMS current carrying capability, and the required input voltage ripple. The capacitor voltage rating is recommended with 1.5 times for the maximum input voltage as conservative guideline, depending on the application condition. The capacitor RMS current rating is considered for stress condition, and the trapezoid current waveform as the simplified formula is described: Irms = Iout(max) * √ ( Vout / Vin ) Vin = input voltage ; Vout = output voltage ; Iout(max) = maximum output current. The capacitor values with respect to the required input voltage ripple if neglect ESR is described: C = Iout(max) * ΔT / ΔV ΔT = capacitor supplied charging time ; ΔV = allowable input voltage ripple. 10 - 6 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter 4. Output rectifier selection The output rectifier is selected by the consideration of the reverse voltage rating, the current rating’ and the reverse recovery time and forward voltage drop for the power loss. The reverse voltage rating should be at least 1.25 times the maximum input voltage for the consideration of voltage arc. The current rating should be larger than the maximum inductor current. The diode conduction loss is due to the forward conduction and is described: Pcond = Iout(max) * Vf * ( 1 - Vout / Vin ) Vin = input voltage ; Vout = output voltage ; Iout(max) = maximum output current ; Vf = diode forward voltage. The diode reverse recovery loss is due to the reverse recovery from the forward conduction to the reverse blocking state, and is described: Prr = Qrr * Vin / Tsw Vin = input voltage ; Qrr = diode reverse recovery charge ; Tsw = switching period. 5. Output inductor selection The output inductor is selected for the trade-offs between the output inductor current ripple, dc resistance for power loss, load transient response time, and the physical size. The output inductor current ripple determines the output voltage ripple requirement, and the inductor’s dc resistance concerns the power loss. The larger the inductor value, the smaller the inductor ripple current, but the slower the transient response time, the larger the inductor dc resistance, and hence the larger the power loss. The inductance value is described: L = Vout * ( 1 - Vout / Vin ) * Tsw / ΔLl Vin = input voltage ; Vout = output voltage ; Tsw = switching period ; ΔLl = inductor ripple current. 6. Output capacitor selection The output capacitor is selected for the trade-offs between output ripple voltage requirement, the output voltage rating, the RMS current rating, the ESR and ESL for the load transient, and the physical size. The capacitor voltage rating is recommended with 1.5 times for the maximum output voltage as conservative guideline. The capacitor RMS current rating is considered for stress condition’ and the trapezoid current waveform as the simplified formula is described: Irms = ΔIL / 2√3 ; ΔIL = inductor ripple current. The output ripple voltage with respect to the capacitor ESR is described: ΔV = ΔI * ( ESR + Tsw / ( 8 * C ) ) ΔI = capacitor ripple current’ which is equivalent to the inductor ripple current ; ESR = capacitor equivalent series resistance ; Tsw = switching period. 7. PC board layout consideration Good PC Board layout is very important in switching converter design. If designed improperly, the PC Board could radiate excessive noise and contribute to the converter instability. 10 - 7 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter Follows below PC board layout guidelines could get better performance: 1) Path A : The Vout- is returned to input bulk capacitor C2, by passing through output capacitor C7. 2) Path B : The output rectifier D1, together with Snubber R2 and C2, are shunt to common ground and returned to input bulk capacitor C2. 3) Path C and D : The decoupling capacitor C11, the compensation network R1, C4, C5, the voltage feedback network R6, R7, C8, and the overvoltage sensing network R8, R9, are connected to IC ground, and returned to input bulk capacitor C2 and output capacitor C7. 4) Path E : Input capacitor C2 is returned to input ground, after all ground networks are following the above paths designed. Fig-4 : PC board layout guidelines U1 L1 Vin 6 7 GND 8 R1 C11 C4 C5 + + C1 C3 C2 VCC LX OVP ISEN+ ELM650DA COMP ISEN- R5 R3 4 C8 R6 LED 1 Vout+ 2 4 C9 R11 R12 2 R13 R15 3 R7 C 1 D1 R2 D R8 1 R10 3 R14 VSEN 2 GND C USB L3 R4 3 C6 E L2 5 B L4 C10 + 4 Vout- R9 C7 D A Fig-5 : The PCB layout of car charger with ELM650DA controller 10 - 8 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter ■Typical characteristics • Vout=5V : Cin=47µF, Cout=220µF, L=100µH, R1=100kΩ, R2=0.0625Ω, R3=390kΩ R4=118kΩ, R5=470Ω, R6=120Ω, C3=0.047µF, C4=47pF, Top=25°C Current Reference-Top 118 Iload=short 115 Vin=24V 116 Current Reference-Vin 116 114 Visen (mV) Visen (mV) 114 112 Vin=12V 110 112 111 110 108 109 -30 1.20 1.19 0 30 Top (�) 60 5 90 Voltage Reference-Top 15 20 Vin (V) 25 30 35 Voltage Reference-Vin 1.200 Iload=1A 10 1.195 Vin=24V 1.190 1.18 Iload=1A Vref (V) Vref (V) Iload=short 113 1.185 1.17 Vin=12V 1.180 1.16 -30 1.175 0 30 Top (�) 60 90 5 10 - 9 10 15 20 Vin (V) 25 30 35 Rev.1.2 ELM650DA CC/CV Mode 36V step down 2A DC/DC converter EFFICIENCY-Iout Vin=12V 80 Vout-Iout 6 5 4 60 Vout (V) EFFICIENCY (%) 100 Vin=24V 40 20 Vin=12V Vin=24V 3 2 1 0 0.001 0.01 0.1 1 0 0.001 10 Iout (A) 0.01 0.1 Iout (A) 1 10 Frequency-Vin 102.0 101.8 101.6 Frequency (kHz) 101.4 101.2 Iload=1A 101.0 100.8 100.6 100.4 100.2 5 10 15 20 Vin (V) 25 30 35 10 - 10 Rev.1.2