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)
: Vin≥0.9V (RL=30kΩ)
: 24μW (Typ. ELM9330xB)
: Typ. 85%
: ±2.5%
: 40mA
(When Vin=1.5V, Vout=3.0V)
: SOT-89, SOT-23
■Application
• Constant voltage source for battery-
operated 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
↑ ↑ ↑ ↑ ↑
a b c 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 feed-
back 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 Iout≤10mA,
please connect tantalum capacitor of 10μF to 47μF 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=330μH, Cin=Cout=22μF, D=MA721, Vss=0V, Top=25°C
Condition
Min. Typ. Max. Unit
RL=30kΩ
0.9
V
Iout=1mA
0.7
V
Iout=100μA, Vin=1.5V
8.0
16.0
μA
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
μA
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=330μH, Cin=Cout=22μF, D=MA721, Vss=0V, Top=25°C
Condition
Min. Typ. Max. Unit
RL=30kΩ
0.9
V
Iout=1mA
0.7
V
Iout=100μA, Vin=1.5V
8.0
16.0
μA
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
μA
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=330μH, Cin=Cout=22μF, D=MA721, Vss=0V, Top=25°C
Condition
Min. Typ. Max. Unit
RL=30kΩ
0.9
V
Iout=1mA
0.7
V
Iout=100μA, Vin=1.5V
8.0
16.0
μA
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
μA
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. Solu-
tion 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.
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