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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
* * * * * * * 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) : Vin0.98V (RL=30k) : 12W (Typ. ELM9430B) : Typ. 80% : 2.5% : 20mA (When Vin=1.5V, Vout=3.0V) : SOT-89
Application
* 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 c d Output voltage Product version Taping direction 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 abc d
Pin configuration
SOT-89 (TOP VIEW)
Pin No. 1 2 3 Pin name VSS VOUT LX
6-1
ELM94xxB CMOS PFM step-up DC/DC converter
Standard circuit
Block diagram
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=330H, D=MA721, C=22F, Vss=0V, Top=25C Condition Min. Typ. Max. Unit 10 V RL=27k 0.98 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 3.5 7.0 A 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 A Vout=2.6V 22 35 55 kHz Vout=2.6V, Switch"ON" 45 55 65 % L=330H, D=MA721, C=22F, Vss=0V, Top=25C Condition Min. Typ. Max. Unit 10 V RL=30k 0.98 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 4.0 8.0 A 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 A 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 Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty
6-2
ELM94xxB CMOS PFM step-up DC/DC converter
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 Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty L=330H, D=MA721, C=22F, Vss=0V, Top=25C Condition Min. Typ. Max. Unit 10 V RL=33k 0.98 V Iout=1mA 0.7 V Iout=100A, Vin=1.5V 4.5 9.0 A 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 A Vout=3.2V 22 35 55 kHz Vout=3.2V, Switch"ON" 45 55 65 %
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 Symbol Vin Vst Vhold Iss Vout Ilx Ilxl Fosc Duty
L=330H, D=MA721, C=22F, Vss=0V, Top=25C Condition Min. Typ. Max. Unit 10 V RL=50k 0.98 V Iout=1mA 0.9 V Iout=100A, Vin=3V 7.0 14.0 A Iout=1mA, Vin=3V 4.87 5.00 5.13 V Vout=4.8V, Vlx=0.4V 130 mA Vout=Vlx=10V 1.0 A Vout=4.8V 22 35 58 kHz Vout=4.8V, Switch"ON" 50 60 70 %
Marking
SOT-89
a : the integer digit of the output voltage Mark 2 3 Vout 2.*V 3.*V Vout *.0V *.1V *.2V *.3V *.4V Mark 4 5 Vout 4.*V 5.*V Vout *.5V *.6V *.7V *.8V *.9V
b : the decimal digit of the output voltage Mark 0 1 2 3 4 Mark 5 6 7 8 9
c : Assembly lot No. 0 to 9 d : Assembly lot No. A to Z (excepted I, O, X)
6-3
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
Vout - Vin
100
EFFICIENCY-Vin Vin ,VRp-p RIPPLE VOLTAGE-Vin
Efficiency EFFICIENCY
(Iout =1mA) 250 200 150
3
90 80 70 60 50
2
Iout =1mA 3mA 10mA
RIPPLE VOLTAGE VRp-p
100 50 0
1
0
1
Vin (V)
2
0
1
Vin (V)
2
Vout - Vin
100
EFFICIENCY-Vin Vin ,VRp-p (Iout =1mA) RIPPLE VOLTAGE-Vin
EFFICIENCY Efficiency
250 200 150
3
90 80 70 60 50
2
Iout =1mA 3mA 10mA
RIPPLE VOLTAGE VRp-p
100 50 0
1
0
1
Vin (V)
2
3
0
1
Vin (V)
2
3
6-5
RIPPLE VRp-p (mV)(mV) VOLTAGE
Efficiency (%) EFFICIENCY (%)
Vout (V)
VRp-p (mV) RIPPLE VOLTAGE (mV)
Efficiency (%) EFFICIENCY (%)
Vout (V)
ELM94xxB CMOS PFM step-up DC/DC converter
Vout - Vin
100
EFFICIENCY-Vin Vin ,VRp-p RIPPLE VOLTAGE-Vin (Iout =1mA)
EFFICIENCY Efficiency
250 200 150
3 Iout =1mA
90 80 70 60
3mA 2 10mA
VRp-p RIPPLE VOLTAGE
100 50 0
1
0
1
Vin (V)
2
3
50
0
1
Vin (V)
2
3
Vout - Vin
100
EFFICIENCY-Vin ,VRp-p - Vin (Iout =1mA) RIPPLE VOLTAGE-Vin
EFFICIENCY Efficiency
500 400 300
5 Iout =1mA 3mA 4 10mA
90 80 70 60 50
VRp-p RIPPLE VOLTAGE
200 100 0
3
0
1
Vin (V)
2
3
0
1
2
Vin (V)
3
4
5
6-6
VRp-p (mV) RIPPLE VOLTAGE (mV)
Efficiency (%) EFFICIENCY (%)
Vout (V)
RIPPLE VOLTAGE (mV) VRp-p (mV)
EFFICIENCY (%) Efficiency (%)
Vout (V)

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