ELM94xxB CMOS PFM step-up DC/DC converter ■General description ELM94xxB 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, ELM94 series is able to acquire constant output voltage higher than input voltage. The standard output voltages are 2.7V, 3.0V, 3.3V, and 5.0V; ELM94 series can also be designed as semi-custom IC within the range of 2.5V to 5.5V by 0.1V step. ■Features • • • • • • • ■Application Output voltage range Low voltage operation Low power operation High efficiency High output voltage accuracy Output current(e.g.) Package : 2.5V to 5.5V (by 0.1V) : Vin≥0.98V (RL=30kΩ) : 12μW (Typ. ELM9430B) : Typ. 80% : ±2.5% : 20mA (When Vin=1.5V, Vout=3.0V) : SOT-89 • Constant voltage source for batteryoperated devices • Constant voltage source for cameras • Portable communication equipments • Local regulator ■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 12 12 200 300 -40 to +85 -55 to +125 Unit V V mA mW °C °C ■Selection guide ELM94xxB-x Symbol a, b Output voltage c Product version d Taping direction ■Pin configuration e.g. : 27: Vout=2.7V 30: Vout=3.0V 33: Vout=3.3V 50: Vout=5.0V B S : Refer to PKG file N : Refer to PKG file ELM94 x x B - x ↑ ↑ ↑ ↑ a b c d SOT-89 (TOP VIEW) Pin No. 1 2 3 6-1 Pin name VSS VOUT LX ELM94xxB CMOS PFM step-up DC/DC converter ■Standard circuit 㪤㪘㪎㪉㪈 㪊㪊㪇㱘㪟 㪣㪯 㪭㫀㫅 㪜㪣㪤㪐㪋㫏㫏㪙 㪭㪦㪬㪫 㪭㫆㫌㫋 㪂 㪭㪪㪪 㪉㪉㱘㪝 ■Block diagram 㪧㪅㪝㪅㪤㪅 㪣㪯 㪭㪦㪬㪫 㪂 㪄 㪭㫉㪼㪽 㪦㫊㪺㫀㫃㫃㪸㫋㫆㫉 㪪㫋㪸㫉㫋㪄㫌㫇 㪭㪪㪪 ■Electrical characteristics Vout=2.7V (ELM9427B) Parameter Input voltage Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Maximum duty ratio Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C Condition Min. Typ. Max. Unit 10 V RL=27kΩ 0.98 V Iout=1mA 0.7 V Iout=100μA, Vin=1.5V 3.5 7.0 μA Iout=1mA, Vin=1.5V 2.63 2.70 2.77 V Vout=2.6V, Vlx=0.4V 80 mA Vout=Vlx=10V 1.0 μA Vout=2.6V 22 35 55 kHz Vout=2.6V, Switch"ON" 45 55 65 % Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C Condition Min. Typ. Max. Unit 10 V RL=30kΩ 0.98 V Iout=1mA 0.7 V Iout=100μA, Vin=1.5V 4.0 8.0 μA Iout=1mA, Vin=1.5V 2.92 3.00 3.08 V Vout=2.9V, Vlx=0.4V 90 mA Vout=Vlx=10V 1.0 μA Vout=2.9V 22 35 55 kHz Vout=2.9V, Switch"ON" 45 55 65 % Vout=3.0V (ELM9430B) Parameter Input voltage Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Maximum duty ratio 6-2 ELM94xxB CMOS PFM step-up DC/DC converter Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C Condition Min. Typ. Max. Unit 10 V RL=33kΩ 0.98 V Iout=1mA 0.7 V Iout=100μA, Vin=1.5V 4.5 9.0 μA Iout=1mA, Vin=1.5V 3.21 3.30 3.39 V Vout=3.2V, Vlx=0.4V 100 mA Vout=Vlx=10V 1.0 μA Vout=3.2V 22 35 55 kHz Vout=3.2V, Switch"ON" 45 55 65 % Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C Condition Min. Typ. Max. Unit 10 V RL=50kΩ 0.98 V Iout=1mA 0.9 V Iout=100μA, Vin=3V 7.0 14.0 μA Iout=1mA, Vin=3V 4.87 5.00 5.13 V Vout=4.8V, Vlx=0.4V 130 mA Vout=Vlx=10V 1.0 μA Vout=4.8V 22 35 58 kHz Vout=4.8V, Switch"ON" 50 60 70 % Vout=3.3V (ELM9433B) Parameter Input voltage Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Maximum duty ratio Vout=5.0V (ELM9450B) Parameter Input voltage Starting voltage Holding voltage Current consumption Output voltage Output current of LX pin Leakage current of LX pin Oscillating frequency Maximum duty ratio ■Marking SOT-89 㪸 㪹 a : the integer digit of the output voltage Mark 2 3 Vout 2.*V 3.*V Mark 4 5 Vout 4.*V 5.*V b : the decimal digit of the output voltage 㪺 㪻 Mark 0 1 2 3 4 Vout *.0V *.1V *.2V *.3V *.4V c : Assembly lot No. 0 to 9 d : Assembly lot No. A to Z (excepted I, O, X) 6-3 Mark 5 6 7 8 9 Vout *.5V *.6V *.7V *.8V *.9V ELM94xxB CMOS PFM step-up DC/DC converter ■External parts To design DC/DC converter with ELM94 series, coil, diode, and capacitor are necessary. (Refer to 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 ELM94 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 ELM94 series, ELM recommends schottoky diodes. 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 ELM94 series. For ELM94 series, ELM recommends Aluminum electrolytic or Tantalum capacitor. ■Design of DC/DC converter In DC/DC converter which consists of ELM94 series and above-mentioned external parts, the output is acquired as follows: 1) Output current of DC/DC converter The current from output terminal (Vout) of the circuit is: Vin 2 Iout = K 8 • L • Fosc • (Vout-Vin) * Duty=50% 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 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. 6-4 ELM94xxB CMOS PFM step-up DC/DC converter ■Typical characteristics 䊶 㪭㫆㫌㫋㪔㪉㪅㪎㪭㩷㩿㪜㪣㪤㪐㪋㪉㪎㪙㪀㩷㩷㩷㩷㩷㩿㪫㫆㫇㪔㪉㪌㷄㪃㩷㪣㪔㪊㪊㪇㱘㪟㪃㩷㪛㪔㪤㪘㪎㪉㪈㪃㩷㪚㪔㪉㪉㱘㪝㪀㩷 Efficiency (%) (%) EFFICIENCY 100 Vout (V) 3 Iout =1mA 2 3mA 10mA 1 0 1 Efficiency EFFICIENCY 90 200 150 80 RIPPLE VOLTAGE VRp-p 70 100 50 60 50 2 Vin (V) (Iout =1mA) 250 0 1 0 2 Vin (V) VRp-p (mV)(mV) RIPPLE VOLTAGE EFFICIENCY-Vin ǯ,VRp-p - Vin RIPPLE VOLTAGE-Vin Vout - Vin 䊶 㪭㫆㫌㫋㪔㪊㪅㪇㪭㩷㩿㪜㪣㪤㪐㪋㪊㪇㪙㪀㩷㩷㩷㩷㩷㩿㪫㫆㫇㪔㪉㪌㷄㪃㩷㪣㪔㪊㪊㪇㱘㪟㪃㩷㪛㪔㪤㪘㪎㪉㪈㪃㩷㪚㪔㪉㪉㱘㪝㪀㩷 Efficiency(%) (%) EFFICIENCY 100 Vout (V) 3 Iout =1mA 2 3mA 10mA 1 0 1 Vin (V) 2 EFFICIENCY Efficiency 90 200 80 150 RIPPLE VOLTAGE VRp-p 70 100 60 50 3 6-5 250 50 0 1 Vin (V) 2 3 0 (mV)(mV) RIPPLE VRp-p VOLTAGE EFFICIENCY-Vin ǯ,VRp-p - Vin (Iout =1mA) RIPPLE VOLTAGE-Vin Vout - Vin ELM94xxB CMOS PFM step-up DC/DC converter 䊶 㪭㫆㫌㫋㪔㪊㪅㪊㪭㩷㩿㪜㪣㪤㪐㪋㪊㪊㪙㪀㩷㩷㩷㩷㩷㩿㪫㫆㫇㪔㪉㪌㷄㪃㩷㪣㪔㪊㪊㪇㱘㪟㪃㩷㪛㪔㪤㪘㪎㪉㪈㪃㩷㪚㪔㪉㪉㱘㪝㪀㩷 EFFICIENCY Efficiency (%) (%) 100 3 Vout (V) Iout =1mA 3mA 2 10mA EFFICIENCY Efficiency 90 200 80 150 VRp-p RIPPLE VOLTAGE 70 100 60 1 0 1 Vin (V) 2 50 3 250 50 0 1 Vin (V) 2 3 RIPPLE VOLTAGE VRp-p (mV)(mV) EFFICIENCY-Vin ǯ,VRp-p - Vin RIPPLE VOLTAGE-Vin (Iout =1mA) Vout - Vin 0 䊶 㪭㫆㫌㫋㪔㪌㪅㪇㪭㩷㩿㪜㪣㪤㪐㪋㪌㪇㪙㪀㩷㩷㩷㩷㩷㩿㪫㫆㫇㪔㪉㪌㷄㪃㩷㪣㪔㪊㪊㪇㱘㪟㪃㩷㪛㪔㪤㪘㪎㪉㪈㪃㩷㪚㪔㪉㪉㱘㪝㪀㩷 EFFICIENCY-Vin ǯ,VRp-p - Vin (Iout =1mA) RIPPLE VOLTAGE-Vin Vout - Vin Vout (V) 5 Iout =1mA 3mA 4 3 10mA 0 1 Vin (V) 2 6-6 EFFICIENCY Efficiency 90 400 80 300 VRp-p RIPPLE VOLTAGE 70 200 60 50 3 500 100 0 1 2 3 Vin (V) 4 5 0 VRp-p (mV)(mV) RIPPLE VOLTAGE Efficiency (%) EFFICIENCY (%) 100