ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■General description ELM600xB is a high efficiency step down DC/DC converter operated with current mode and constant frequency. The internal switch and synchronous rectifier are integrated for high efficiency. External Schottky diodes are not required. The supply current is only 100μA during operation and drops to less than 1μA in shutdown. ELM600xB can supply 1A of load current from 2.5V to 5.5V supply voltage. The switching frequency is set at 1.5MHz, allowing the use of small surface mount inductors and capacitors. It can run 100% duty cycle for low dropout application. The output voltage of ELM600xB is adjustable from the FB pin. ■Features ■Application • • • • • • • • • • • • • • • • • Current mode operation Thermal shutdown protection and short circuit protection Constant frequency : Typ.1.5MHz Output current : 1A High efficiency : Max.95% Shutdown current : Max.1µA(Ven=0V, Vin=5.5V) Supply voltage : 2.5V to 5.5V Low quiescent current : Typ.110µA(Outgoing stopped) Full duty ratio : 0 to 100% (in dropout) Package : DFN6-2x2, TSOT-25 Cellular phone PDA and smart phone MP3 player Digital camera Wireless and DSL card Microcomputer and DSP power supply Portable machine ■Maximum absolute ratings Parameter VIN power supply voltage Apply voltage to SW Apply voltage to EN Apply voltage to FB SW peak current Power dissipation Operating temperature range Storage temperature range Symbol Vin Vsw Ven Vfb Isw Limit -0.3 to +6.0 GND-0.3 to Vin+0.3 GND-0.3 to Vin+0.3 GND-0.3 to Vin+0.3 3.0 (*2) 1000 (DFN6-2x2) (*3) 600 (TSOT-25) (*3) -40 to +85 -65 to +150 Pd Top Tstg Unit V V V V A mW °C °C Caution: * 1. Permanent damage to the device may occur when ratings above maximum absolute ones are used. * 2. Output current must not exceed power dissipation specified in maximum absolute ratings. * 3. Mounted on glass epoxy board (FR-4). (76.2mm×114.3mm×1.6mm : based on EIJ/JEDEC standard size), 2layers, Cu thickness 35μm, Cu area : top side 20%, back side 100%. Rev.1.0 7 - 1 ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■Selection guide ELM600xB-x Symbol a Package b Product version c Taping direction * Taping direction is one way. G: DFN6-2x2 L: TSOT-25 B N: DFN6-2x2(Refer to PKG file) S: TSOT-25(Refer to PKG file) ELM600 x B - x ↑↑ ↑ ab c ■Pin configuration DFN6-2x2(TOP VIEW) DFN6-2x2(BOTTOM VIEW) 6 5 4 46 5 64 4 5 6 1 2 3 31 2 13 3 2 1 Pin No. 1 2 3 4 5 6 Exposed Pad Pin name NC EN VIN SW GND FB NC Pin description No connected. Enable control input Main supply Power switch output Ground Voltage feedback No connected. TSOT-25(TOP VIEW) Pin No. Pin name 1 EN 2 GND 3 SW 4 VIN 5 FB Pin description Enable control input Ground Power switch output Main supply Voltage feedback Rev.1.0 7 - 2 ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■Standard circuit ( Adjustable Output Voltage ) Vin L=2.2µH ● VIN ● C1= 4.7µF C5 SW Vout ● ● GND EN ● ● C6 C4 R2 R3 C2= 10µF ● ELM600xB ● C3 R1 FB ● ● Vin Vout=Vfb × (1+R1/R2) with R1 = 300k for typical application, and C3 should be in the range between 10pF and 47pF for component selection. ■Block diagram VIN Slope Comp Current Sense Amplifier Reference UG + _ 0.6V FB + _ PWM Logic SW PWM Comparator Error Amplifier Oscillator M1 LG M2 Clock DCC Zero-current Comparator + _ EN Shut down control GND Rev.1.0 7 - 3 ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■Electrical characteristics Vin=5V, Vout=1.8V, L=2.2µH, Cout=10µF, Top=25°C, unless otherwise specified Parameter Symbol Test condition Min. Typ. Max. Unit Supply voltage Vin 2.5 5.5 V Output voltage line regulation ∆Vout/∆Vin Vin=2.5V to 5.5V -3 3 %/V Output voltage load regulation Vlr -3 3 % Reference voltage For adjustable Vout 0.588 0.600 0.612 V Vref Output range (adjustable voltage) Vin=2.5V to 5.5V -3 +3 % Vout Shutdown current Is Ven=0V 0.1 1.0 µA Ven=Vin, Vfb=Vref×1.1 110 Quiescent current Iq µA No switching SW leakage current Ileak Ven=0V, Vsw=0V or Vin -1 1 µA RdsonP Isw=100mA 250 mΩ PMOSFET on resistance NMOSFET on resistance RdsonN Isw=-100mA 200 mΩ Duty cycle=100% PMOSFET current limit IPcl 2 A Current pulse width<1ms Oscillator frequency Fosc 1.2 1.5 1.8 MHz Thermal shutdown threshold 160 °C Ts EN high level input voltage Venh -40°C ≤ Top ≤ +85°C 1.5 V EN low level input voltage Venl -40°C ≤ Top ≤ +85°C 0.4 V EN input current Ien Ven=0V to Vin -1 1 µA ■Marking DFN6-2x2 Mark a~f Content Assembly lot No. : 0 ~ 9 and A ~ Z TSOT-25 Mark a~e Content Assembly lot No. : 0 ~ 9 and A ~ Z Rev.1.0 7 - 4 ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■Application notes ELM600xB is constant frequency current mode PWM step down converter. ELM600xB is optimized for low voltage, Li-ion battery, powered applications where high efficiency and small size are critical. The device integrates both a main switch and a synchronous rectifier, which provides high efficiency and eliminates an external Schottky diode. ELM600xB can achieve 100% duty cycle. The duty cycle D of a step down converter is defined as: D = Ton × Fosc × 100% ≈ (Vout/Vin) × 100% Where Ton is the main switch on time, Fosc is the oscillator frequency (1.5MHz), Vout is the output voltage and Vin is the input voltage. 1) Current mode PWM control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. ELM600xB switches at a constant frequency (1.5MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the next cycle starts or the inductor current drops to zero. The device skips pulses to improve efficiency at light load. 2) Dropout operation ELM600xB allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. When the duty cycle reaches 100%, the main switch is held on continuously to deliver current to the output up to the P MOSFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. 3) Short circuit protection ELM600xB has short circuit protection. When the output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the P MOSFET current limit. The frequency will return to the normal values once the short circuit condition is removed and the Vout reaches regulated voltage. 4) Maximum load current ELM600xB can operate down to 2.5V input voltage; however the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases. Rev.1.0 7 - 5 ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter http://www.elm-tech.com ■Typical characteristics Iout-Efficiency Iout-Vout Vin=5V, Vout=1.8V 100 1.88 90 1.86 80 1.84 70 Eefficiency (%) Vout (V) 1.90 1.82 1.80 1.78 1.76 60 ���� 50 ���� 40 30 1.74 20 1.72 1.70 0.1 10 0 0.1 1 10 100 1000 10000 Vin=5V 1 10 100 1000 10000 Iout (mA) Iout (mA) Shutdown Startup Vin=5.0V, Vout=1.8V, Iload=1A Vin=5.0V, Vout=1.8V, Iload=1A Vin 5V/div Vin 5V/div Ven 5V/div Ven 5V/div Vout 1V/div Vout 1V/div Isw 1A/div Isw 1A/div 10μs/div 200μs/div Load Transient Output Ripple Vin=5.0V, Vout=1.8V, Iload=0.05A~1A Vin=5.0V, Vout=1.8V, Iload=1A Vout 50mV/div Vout 10mV/div Isw 1A/div 1L 1A/div 500ns/div Short Protection/Current limit Vin=5.0V, Vout=1.8V, Iload=0A~short 7 - 6 200μs/div Rev.1.0 Ven 5V/div Vin 5V/div Vout 1V/div Ven 5V/div Isw 1A/div Vout 1V/div Ven 5V/div Startup Vin=5.0V, Vout=1.8V, Iload=1A Vout 1V/div Vin 5V/div Shutdown Vin=5.0V, Vout=1.8V, Iload=1A Ven ELM600xB 1A 1.5MHz high efficiency synchronous 5V/div Isw PWM step down DC/DC converter Isw 1A/div 1A/div Vout 1V/div 200μs/div Isw 1A/div Vin=5.0V, Vout=1.8V, Iload=0.05A~1A 10μs/div Load Transient Output Ripple Vin=5.0V, Vout=1.8V, Iload=0.05A~1A Vin=5.0V, Vout=1.8V, Iload=1A Vout 10mV/div Vout 50mV/div Isw 1A/div Vout 10mV/div 1L Vout 1A/div 50mV/div 200μs/div 500ns/div 1L 1A/div Short Protection/Current limit Vin=5.0V, Vout=1.8V, Iload=0A~short 500ns/div Vout 1V/div 10μs/div Load Transient Output Ripple Vin=5.0V, Vout=1.8V, Iload=1A 200μs/div Isw 1A/div http://www.elm-tech.com 200μs/div Short Protection/Current limit Vin=5.0V, Vout=1.8V, Iload=0A~short Vout 1V/div Isw 2A/div Isw 2A/div 200μs/div 200μs/div Rev.1.0 7 - 7