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| ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter General description ELM93xxxB is CMOS step-up DC/DC converter which consists of reference voltage source, error amplifier, oscillation circuit, start-up circuit, PFM control circuit, switching transistor and output voltage setting resistor. For external parts, coil, diode and capacitor are possible choices; with external parts, ELM93 series is able to acquire constant output voltage higher than input voltage. The standard output voltages are 2.7V, 3.0V, and 3.3V; ELM93 series can also be designed as semi-custom IC within the range of 1.8V to 3.8V by 0.1V step. Features * * * * * * Output voltage range Low voltage operation Low power operation High efficiency High output voltage accuracy Output current (e.g.) : 1.8V to 3.8V (by 0.1V) : Vin0.9V (RL=30k) : 24W (Typ. ELM9330xB) : Typ. 85% : 2.5% : 40mA (When Vin=1.5V, Vout=3.0V) : SOT-89, SOT-23 Application * Constant voltage source for batteryoperated devices * Constant voltage source for cameras * Portable communications equipments * Local regulator * Package Maximum absolute ratings Parameter Apply voltage to LX pin Apply voltage to VOUT pin Output current of LX pin Power dissipation Operating temperature Storage temperature Symbol Vlx Vout Ilx Pd Top Tstg Limit 5 4 200 300 (SOT-89) 200 (SOT-23) -40 to +85 -55 to +125 Unit V V mA mW C C Selection guide ELM93xxxB-x Symbol a, b c d e Output voltage Package Product version Taping direction e.g. : 27: Vout=2.7V 30: Vout=3.0V 33: Vout=3.3V A: SOT-89 B: SOT-23 B S : Refer to PKG file N : Refer to PKG file ELM93 x x x B - x abc d e 8-1 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter Pin configuration SOT-89 (TOP VIEW) SOT-23 (TOP VIEW) Pin No. 1 2 3 Pin name VSS VOUT LX Pin No. 1 2 3 Pin name VSS LX VOUT Standard circuit Cin : The circuit can operate without Cin, but adding Cin to the circuit can lower the feedback noise to the Input; this method is also effective in improving efficiency because input voltage drop during switching can be eased. Under the condition of Iout10mA, please connect tantalum capacitor of 10F to 47F to a coil as close as possible. Block diagram 8-2 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter Electrical characteristics Vout=2.7V (ELM9327xB) Parameter Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Duty ratio Symbol Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330H, Cin=Cout=22F, D=MA721, Vss=0V, Top=25C Condition Min. Typ. Max. Unit RL=30k 0.9 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 8.0 16.0 A Iout=1mA, Vin=1.5V 2.63 2.70 2.77 V Vout=2.6V, Vlx=0.4V 60 mA Vout=3.5V, Vlx=3.5V 1.0 A Vout=2.6V 80 100 120 kHz Vout=2.6V, Switch"ON" 65 75 85 % Vout=3.0V (ELM9330xB) Parameter Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Duty ratio Symbol Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330H, Cin=Cout=22F, D=MA721, Vss=0V, Top=25C Condition Min. Typ. Max. Unit RL=30k 0.9 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 8.0 16.0 A Iout=1mA, Vin=1.5V 2.92 3.00 3.08 V Vout=2.9V, Vlx=0.4V 70 mA Vout=3.5V, Vlx=3.5V 1.0 A Vout=2.9V 80 100 120 kHz Vout=2.9V, Switch"ON" 65 75 85 % Vout=3.3V (ELM9333xB) Parameter Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Duty ratio Symbol Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330H, Cin=Cout=22F, D=MA721, Vss=0V, Top=25C Condition Min. Typ. Max. Unit RL=30k 0.9 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 8.0 16.0 A Iout=1mA, Vin=1.5V 3.21 3.30 3.39 V Vout=3.2V, Vlx=0.4V 80 mA Vout=3.5V, Vlx=3.5V 1.0 A Vout=3.2V 80 100 120 kHz Vout=3.2V, Switch"ON" 65 75 85 % 8-3 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter Marking SOT-89 a : the integer digit of the output voltage Mark 1 2 3 Vout 1.*V 2.*V 3.*V b : the decimal digit of the output voltage Mark 0 1 2 3 4 5 6 7 8 9 Vout *.0V *.1V *.2V *.3V *.4V *.5V *.6V *.7V *.8V *.9V SOT-23 c, d : 50 to 99 (Assembly lot No.) External parts To design DC/DC converters using ELM93 series, coil, diode, and capacitor are necessary. (Refer to the standard circuit configuration.) 1) Coil When choosing choke coil, please select that whose core is not magnetically saturated, DC resistance is low, and which has sufficient margin for rated current. For ELM93 series, ELM recommends following coil. * CM-5/CM-5N (Sumida Electric Co., Ltd.) 2) Diode When choosing diode, please select that whose forward voltage is small, switching speed is high and which has sufficient margin for rated current. For ELM93 series, ELM recommends schottoky diodes. 8-4 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter 3) Capacitor When choosing capacitor, please select that which is generally used for smoothing power supply circuit, with comparatively large capacity and whose rated voltage is at least three times larger than rated output voltage of used ELM93 series. For ELM93 series, ELM recommends Aluminum electrolytic or Tantalum capacitor. Under different conditions, such as different input voltage, load current, etc. larger output voltage ripple may happen and thus result in intermittent switching. To solve this, using capacitors with larger capacity can prevent output voltage ripple from becoming larger. Inserting resistor, as shown in the following circuit, may also be effective. Design of DC/DC converter In the DC/DC converter which consists of ELM93 series and above-mentioned external parts, the output is acquired as follows: 1) Output current of DC/DC converter The current from the output terminal (Vout) of the circuit is: 9Vin 2 Iout = K * Duty=75% 32 * L * Fosc * (Vout-Vin) K: the efficiency of whole circuit (75% to 85%) 2) Remedies for noise This DC/DC converter may cause electromagnetic noise due to switching of coil under large current. Solution is necessary especially when the IC is used in wireless devices. To reduce noise, this IC is designed in consideration of the coil switching characteristics. The following methods are also effective to reduce noise. * Use shield-type, or magnetic shield coil. * Locate coil and diode to the LX terminal of IC as close as possible. * Select ground wire as thick and short as possible. * Connect ground wire of circuit to one point. 8-5 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter Typical characteristics * Vout=2.7V (ELM9327xB) Vout - Vin 3.5 3 3.5 3 1.8V (Top=25C, L=330H, D=MA721, Cin=Cout=22F) Vout - Iout Vout (V) Vout (V) 2.5 2 1.5 1 0 Iout=10mA 2.5 2 1.5 1 0.1 Vin=0.9V 1.1V 1.3V 1.5V 3mA 1mA 1 2 1 10 100 Vin (V) Iout (mA) EFFICIENCY - Vin 100 100 90 EFFICIENCY - Iout EFFICIENCY (%) 90 Iout=1mA 80 100 A 70 EFFICIENCY (%) 80 Vin=0.9V 70 60 50 1.1V 1.3V 1.5V 1.8V 60 0 1 2 40 0.1 1 10 100 Vin (V) Iout (mA) VOLTAGE RIPPLE - Vin 100 70 60 Iout(max.) - L VOLTAGE RIPPLE (mV) 80 Iout(max.) (mA) 50 40 30 20 10 1.1V Vin=1.5V 60 40 20 Iout=1mA 1.0V 0.9V 0 1 2 0 200 400 600 800 1000 Vin (V) L ( H) 8-6 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter * Vout=3.0 (VELM9330xB) Vout - Vin 3.5 3 3.5 1.8V 3 1.1V (Top=25C, L=330H, D=MA721, Cin=Cout=22F) Vout - Iout Vout (V) Vout (V) 2.5 2 1.5 1 0 Iout=10mA 2.5 2 1.5 1 0.1 Vin=0.9V 1.3V 1.5V 3mA 1mA 1 2 3 1 10 100 Vin (V) Iout (mA) EFFICIENCY - Vin 100 100 90 EFFICIENCY - Iout EFFICIENCY (%) 90 Iout=1mA 80 EFFICIENCY (%) 80 70 60 Vin=0.9V 1.1V 1.8V 100 A 70 1.5V 50 1.3V 60 0 1 2 3 40 0.1 1 10 100 Vin (V) Iout (mA) VOLTAGE RIPPLE - Vin 100 70 60 Iout(max.) - L VOLTAGE RIPPLE (mV) 80 Iout(max.) (mA) 50 40 30 20 10 1.1V Vin=1.5V 60 40 20 Iout=1mA 1.0V 0.9V 0 1 2 3 0 200 400 600 800 1000 Vin (V) L ( H) 8-7 ELM93xxxB CMOS High efficiency PFM step-up DC/DC converter * Vout=3.3V (ELM9333xB) Vout - Vin 3.5 3 Iout=10mA 3.5 3 1.1V Vin=0.9V 2.5 1.3V 2 1.5 1 0.1 1.5V 1.8V (Top=25C, L=330H, D=MA721, Cin=Cout=22F) Vout - Iout Vout (V) 2.5 3mA 2 1mA 1.5 1 0 Vout (V) 1 2 3 1 10 100 Vin (V) Iout (mA) EFFICIENCY - Vin 100 100 90 EFFICIENCY - Iout EFFICIENCY (%) 90 Iout=1mA 80 100 A 70 EFFICIENCY (%) 80 Vin=0.9V 70 60 1.3V 50 1.1V 1.8V 1.5V 60 0 1 2 3 40 0.1 1 10 100 Vin (V) Iout (mA) VOLTAGE RIPPLE - Vin 100 70 60 Iout(max.) - L VOLTAGE RIPPLE (mV) 80 Iout(max.) (mA) 50 40 30 20 10 1.1V Vin=1.5V 60 40 20 Iout=1mA 1.0V 0.9V 0 1 2 3 0 200 400 600 800 1000 Vin (V) L ( H) 8-8 |
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