ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com■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 toacquire constant output voltage higher than input voltage. The standard output voltages are 2.7V, 3.0V, 3.3V, and5.0V; 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: 2.5V to 5.5V (by 0.1V)• Low voltage operation: Vin≥0.98V(RL=30kΩ)• Low power operation: Typ.12μW(ELM9430B)• High efficiency: Typ.80%• High output voltage accuracy : ±2.5%• Output current(e.g.): 20mA(Vin=1.5V, Vout=3.0V)• Package: 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

SymbolVlxVoutIlx
PdTopTstg

Limit
1212200500-40 to +85-55 to +125

Unit
VVmA
mW°C°C■Selection guide
ELM94xxB-x
Symbola, b

Output voltagecProduct version

dTaping 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.
123

Pin name
VSS
VOUT
LX

Rev.1.0
1/6

ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com■Standard circuit■Block diagram+ -■Electrical characteristics
Vout=2.7V(ELM9427B)

L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C
SymbolCondition
Min.
Typ.
Max.
Unit
Vin
10V
Vst RL=27kΩ
0.98
VVhold Iout=1mA
0.7
VIss
Iout=100μA, Vin=1.5V
3.5
7.0μA
Vout Iout=1mA, Vin=1.5V
2.63
2.70
2.77
VIlxVout=2.6V, Vlx=0.4V
80mA
Ilxl Vout=Vlx=10V
1.0μA
Fosc Vout=2.6V
223555
kHzDuty Vout=2.6V, Switch"ON"
4555
65%

Vout=3.0V(ELM9430B)

L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C
SymbolCondition
Min.
Typ.
Max.
Unit
Vin
10V
Vst RL=30kΩ
0.98VVhold Iout=1mA
0.7
V
Iss
Iout=100μA, Vin=1.5V
4.0
8.0μA
Vout Iout=1mA, Vin=1.5V
2.92
3.00
3.08
VIlx
Vout=2.9V, Vlx=0.4V
90mA
Ilxl Vout=Vlx=10V
1.0μA
Fosc Vout=2.9V223555
kHz
Duty Vout=2.9V, Switch"ON"
4555
65%

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
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

Rev.1.0
2/6

ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com

Vout=3.3V(ELM9433B)

L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C
SymbolCondition
Min.
Typ.
Max.
Unit
Vin10V
Vst RL=33kΩ
0.98
VVhold Iout=1mA
0.7
V
Iss
Iout=100μA, Vin=1.5V
4.5
9.0μA
Vout Iout=1mA, Vin=1.5V
3.21
3.30
3.39
VIlx
Vout=3.2V, Vlx=0.4V
100mA
Ilxl Vout=Vlx=10V
1.0μA
Fosc Vout=3.2V
223555kHz
Duty Vout=3.2V, Switch"ON"455565%

Vout=5.0V(ELM9450B)

L=330μH, D=MA721, C=22μF, Vss=0V, Top=25°C
SymbolCondition
Min.
Typ.
Max.
Unit
Vin10V
Vst RL=50kΩ
0.98VVhold Iout=1mA
0.9
VIss
Iout=100μA, Vin=3V
7.0
14.0μA
Vout Iout=1mA, Vin=3V
4.87
5.00
5.13
VIlx
Vout=4.8V, Vlx=0.4V
130mA
Ilxl Vout=Vlx=10V
1.0μA
Fosc Vout=4.8V
223558kHz
Duty Vout=4.8V, Switch"ON"
5060
70%

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

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■MarkingSOT-89

a : the integer digit of the output voltage
MarkVout
MarkVout
22.*V
44.*V
33.*V
55.*V
b : the decimal digit of the output voltage
MarkVout
MarkVout
05*.0V
*.5V
1.1V
6*
*.6V
2
7*.2V
*.7V
38*.3V
*.8V
4.4V
9*
*.9V
c : Assembly lot No.

0 to 9d : Assembly lot No.

A to Z (excepted I, O, X)

Rev.1.0
3/6

ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com■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 islow, 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 isacquired as follows:
1) Output current of DC/DC converter
The current from output terminal (VOUT) of the circuit is:
Vin 2
Iout = K
Duty=50%
8 • L • Fosc • (Vout-Vin) *K: the efficiency of whole circuit (≈75% to ≈85%)2) Remedies for noiseThis 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.

Rev.1.0
4/6

ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com■Typical characteristics� �������������������������������������������������������������

Efficiency (%)(%)
EFFICIENCY

100

Vout (V)3

Iout =1mA

23mA
10mA

10

1Efficiency
EFFICIENCY

90

200

80

150
VRp-p
RIPPLEVOLTAGE701005060502Vin (V)(Iout =1mA)
2500102Vin (V)VRp-p (mV)(mV)RIPPLE VOLTAGE

EFFICIENCY-Vin
�,VRp-p - Vin
RIPPLE VOLTAGE-Vin

Vout - Vin� �������������������������������������������������������������

Efficiency(%)(%)
EFFICIENCY

100

Vout (V)3

Iout =1mA

23mA
10mA

101Vin (V)2

EFFICIENCY
Efficiency

90200

80150
RIPPLEVOLTAGE
VRp-p

70

10060
50

3250

5001Vin (V)23(mV)(mV)RIPPLE VRp-p
VOLTAGEEFFICIENCY-Vin
�,VRp-p - Vin (Iout =1mA)
RIPPLE VOLTAGE-Vin

Vout - Vin

0Rev.1.05/6ELM94xxB CMOS PFM step-up DC/DC converter
http://www.elm-tech.com

� �������������������������������������������������������������

EFFICIENCY
Efficiency (%)(%)

1003Vout (V)Iout =1mA3mA

210mA

EFFICIENCY
Efficiency

90200
15080
VRp-p
RIPPLEVOLTAGE

70

100

60
101Vin (V)

250

3250

RIPPLE VOLTAGE
VRp-p (mV)(mV)EFFICIENCY-Vin
�,VRp-p - Vin
RIPPLE VOLTAGE-Vin (Iout =1mA)

Vout - Vin

5001Vin (V)230� �������������������������������������������������������������
EFFICIENCY-Vin
�,VRp-p - Vin (Iout =1mA)
RIPPLE VOLTAGE-Vin

Vout - VinVout (V)

5Iout =1mA3mA

4310mA

01Vin (V)2

EFFICIENCY
Efficiency

9040080300
VRp-p
RIPPLEVOLTAGE

70200

6050

3500

100

0123Vin (V)45

VRp-p (mV)(mV)RIPPLE VOLTAGE

Efficiency(%)
EFFICIENCY(%)

1000

Rev.1.06/6