BL8530
PFM STEP-UP DC/DC CONVERTER WITH HIGH EFFICIENCY AND LOW NOISE
OUTLINE：
FEATURES：
The BL8530 series are CMOS-based PFM
step-up DC-DC Converter. The converter can
start up by supply voltage as low as 0.8V, and
capable of delivering maximum 200mA output
current at 3.3V output with 1.8V input Voltage.
Quiescent current drawn from power source is
as low as 7uA. All of these features make
BL8530 series be suitable for the portable
devices, which are supplied by a single battery
to four-cell batteries.
To reduce the noise caused by the switch
regulator, BL8530 is well considerated in circuit
design and manufacture. So that the interferer
to other circuits by the device is reduced
greatly.
BL8530 integrates stable reference
circuits and trimming technology, so it can
afford high precision and low temperature-drift
coefficient of the output voltage.
BL8530 is available in SOT-89-3
、
SOT-23-3 and SOT-23-5 packages which is PB
free. And in 5-pin packages, such as
SOT-23-5, the device can be switch on or off
easily by CE pin, to minimize the standby
supply current.
•
•
•
•
•
•
•
•
•
•
•
Deliver 200mA at 3.3V Output voltage
with 1.8V input Voltage
Low start-up voltage (when the output
current is 1mA)--------------------------0.8V
The converter output voltage can be
adjusted from 2.5V½6.0V(In 0.1V step).
Output voltage accuracy -----------±2％
Low temperature-drift coefficient of the
output voltage------------------±100ppm/℃
Only three external components are
necessary: An inductor, a Schottky diode
and an output filter capacitor
High power conversion efficiency---85％
Low quiescent current drawn from power
source------------------------------------- <7uA
APPLICATIONS
：
Power source for PDA、DSC、MP3
Player、electronic toy and wireless mouse
Power source for a single or dual-cell
battery-powered equipments
Power source for LED
PIN CONFIGURARION：
SELECTION GUIDE：
BL8530--XX
X XX
Package Type：
RN：SOT-23-5
RM：SOT-23-3
SM：SOT-89-3
Function Description：
1
：
Internal Tr. Driver
，
Without Enable circuit
2：Internal Tr. Driver，
With Enable circuit
3
：
External Tr. Driver
，
Without Enable circuit
4：
External Tr. Driver，
With
Enable circuit
Output Voltage：
25……2.5V
30……3.0V
……
60……6.0V (In 0.1V step)
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Ver1.0
1/14
BL8530
PIN DESCRIPTION:
Pin No.
SOT-23-3
1
2
3
－
－
Symbol
Vss（GND）
Vout
Lx（Ext）
NC
CE
Description
Ground pin
Output pin, power supply for
internal circuits
Switching pin
-
Chip enable pin (active high)
SOT-89-3
1
2
3
－
－
SOT-23-5
4
2
5
3
1
PRODUCTOR LIST :
Product Name
BL8530-XX1SM
BL8530-XX1RM
BL8530-XX2RN
BL8530-XX3SM
BL8530-XX3RM
BL8530-XX4RN
BLOCK DIAGRAM：
Output Voltage
XX V
XXV
XX V
XXV
XXV
XXV
Lx Tr. Driver
Internal
Internal
Internal
External
External
External
Chip Enable
No
No
Yes
No
No
Yes
Package
SOT-89-3
SOT-23-3
SOT-23-5
SOT-89-3
SOT-23-3
SOT-23-5
ABSOLUTE MAXIMUM RATINGS
Input voltage range-----------------------------------------------------------------------------------0.3V~12V
Input voltage: Vi(LX) ---------------------------------------------------------------------------------0.3V~(Vout+0.3)
CE pin voltage -----------------------------------------------------------------------------------------0.3V~(Vout+0.3)
Lx pin output current --------------------------------------------------------------------------------0.7A
Maximum power dissipation, Pd T=25°C
SOT-89-3---------------------------------------------------------------------------------------0.5W
SOT-23-5---------------------------------------------------------------------------------------0.15W
SOT-23-3---------------------------------------------------------------------------------------0.15W
Maximum junction temperature ------------------------------------------------------------------150°C
Operating free-air temperature range ---------------------------------------------------------- -20~+80°C
Storage temperature range ----------------------------------------------------------------------- -40~125°C
Lead temperature and time -----------------------------------------------------------------------260°C,10S
2/14
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Ver1.0
BL8530
RECOMMENDED OPERATING CONDITIONS
Input voltage range
Inductor
Input capacitor
Output capacitor
Operating junction temperature
MIN
0.8
10
0
47
-20
NOM
27
≥10
100
MAX
Vout
100
220
85
UNIT
V
µH
µF
µF
℃
*Suggestion：Use
tantalum capacitor to reduce the ripple of the output voltage.
ELECTRICAL CHARACTERISTICS
SYMBOL
ITEM
TEST CONDITIONS
REFERENCE DATA
MIN
TYP.
MUM
2.45
2.5
2.55
2.646
2.7
2.754
2.94
3.0
3.06
3.234
3.3
3.366
3.528
3.6
3.672
3.92
4.0
4.08
4.9
5.0
5.1
5.88
6.0
6.12
12
12
15
UNIT
Vout
Output Voltage
V
Vin
Iin
Vstart
Vhold
Input Voltage
Input Current
Iout=0mA，
Vin=Vout*0.6
Iout=1mA，
Vin：0→2V
Iout=1mA，
Vin：2→0V
V
uA
V
V
Start-up voltage
Hold-on voltage
Quiescent
current drawn
from power
source
Switch ON
Resistance
LX leakage
current
CE “H”
threshold
voltage
CE “H”
threshold
voltage
Oscillator
frequency
Oscillator duty
cycle
Efficiency
0.8
0.6
external
Vout
0.7
0.9
I
DD
Rswon
I
LXleak
V
CEH
V
CEL
Fosc
Maxdty
η
Without
components,
=Vout×1.05
4
7
uA
Ω
uA
V
0.4
Vout=Vlx=6V
V
CE
：0→2V
V
CE
：
2→0V
LX on “L” side
Vout=Vout*0.96
On（Vlx“L”
）side
300
70
0.6
0.9
0.3
350
75
85
0.5
0.5
0.6
400
80
V
Khz
％
％
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Ver1.0
3/14
BL8530
NOTE：
1、 Diode：Schottky type, such as：1N5817,1N5819,1N5822
2、 Inductor：27uH(R<0.5Ω)
3、 Capacitor：100uF(Tantalum type)
TYPICAL APPLICATIONS：
DETAILED DESCRIPTION
The BL8530 series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up
DC-DC converter. Only three external components are necessary: an inductor, a output filter
capacitor and a schottky diode. And the converter’s low noise and low ripple output voltage can be
adjusted from 2.5V to 5.0V, 0.1V step. By using the depletion technics, the quiescent current drawn
from power source is lower than 7uA. The high efficiency device consists of resistors for output
voltage detection and trimming, a start-up voltage circuit, an oscillator, a reference circuit, a PFM
control circuit, a switch protection circuit and a driver transistor.
The PFM control circuit is the core of the BL8530 IC. This block controls power switch on duty
cycle to stabilize output voltage by calculating results of other blocks which sense input voltage,
output voltage, output current and load conditions. In PFM modulation system, the frequency and
pulse width is fixed. The duty cycle is adjusted by skipping pulses, so that switch on-time is changed
based on the conditions such as input voltage, output current and load. The oscillate block inside
BL8530 provides fixed frequency and pulse width wave.
The reference circuit provides stable reference voltage to output stable output voltage. Because
internal trimming technology is used, The chip output change less than ±2%. At the same time，the
problem of temperature-drift coefficient of output voltage is considered in design,
so
temperature-drift coefficient of output voltage is less than 100ppm/℃。
High-gain differential error amplifier guarantees stable output voltage at difference input voltage
and load. In order to reduce ripple and noise, the error amplifier is designed with high band-with.
Though at very low load condition, the quiescent current of chip do effect efficiency certainly.
The four main energy loss of Boost structure DC-DC converter in full load are the ESR of inductor,
the voltage of Schottky diode, on resistor of internal N-channel MOSFET and its driver. In order to
improve the efficiency, BL8530 integrates low on-resistor N-channel MOSFET and well design driver
circuits. The switch energy loss is limited at very low level.
SELECTION OF THE EXTERNAL COMPONENTS
Thus it can be seen, the inductor and schottky diode affect the conversion efficiency greatly.
The inductor and the capacitor also have great influence on the output voltage ripple of the converter.
So it is necessary to choose a suitable inductor, a capacitor and a right schottky diode, to obtain high
efficiency, low ripple and low noise.
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Ver1.0
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Before discussion，we define
D
≡
Vout
−
Vin
.
Vout
BL8530
（1）Inductor
Selection
Above all, we should define the minimum value of the inductor that can ensure the boost
DC-DC to operate in the continuous current-mode condition.
D
(1
−
D
)
2
R
L
L
min
≥
2
f
The above expression is got under conditions of continuous current mode, neglect Schottky
diode’s voltage, ESR of both inductor and capacitor. The actual value is greater that it. If inductor’s
value is less than
Lmin，
efficiency of DC-DC converter will drop greatly, and the DC-DC circuit will
the
not be stable.
Secondly, consider the ripple of the output voltage,
∆
I
=
D
•
Vin
Lf
Vin
DVin
+
Im
ax
=
2
Lf
(1
−
D
)
2
R
L
If inductor value is too small, the current ripple through it will be great. Then the current through
diode and power switch will be great. Because the power switch on chip is not ideal switch, the
energy of switch will improve. The efficiency will fall.
Thirdly，in general, smaller inductor values supply more output current while larger values start
up with lower input voltage and acquire high efficiency.
An inductor value of 3uH to 1mH works well in most applications. If DC-DC converter delivers
large output current (for example: output current is great than 50mA), large inductor value is
recommended in order to improve efficiency. If DC-DC must output very large current at low input
supply voltage, small inductor value is recommended.
The ESR of inductor will effect efficiency greatly. Suppose ESR value of inductor is r
L
，R
load
is
load resistor，then the energy can be calculated by following expression
：
∆
η
≈
r
L
R
load
(1
−
D
)
2
For example: input 1.5V, output is 3.0V, R
load
=20Ω, r
L
=0.5Ω, The energy loss is 10%.
Consider all above，inductor value of 47uH、ESR<0.5Ω is recommended in most applications.
Large value is recommended in high efficiency applications and smaller value is recommended
（2）Capacitor
Selection
Ignore ESR of capacitor，the ripple of output voltage is:
r
=
D
∆
Vout
=
Vout
R
load
Cf
So large value capacitor is needed to reduce ripple. But too large capacitor value will slow
down system reaction and cost will improve. So 100uF capacitor is recommended. Larger
capacitor value will be used in large output current system. If output current is small (<10mA),
small value is needed.
Consider ESR of capacitor，ripple will increase：
r
'
=
r
+
Im
ax
•
R
ESR
Vout
When current is large, ripple caused by ESR will be main factor. It may be greater than 100mV。
The ESR will affects efficiency and increase energy loss. So low-ESR capacitor (for example:
tantalum capacitor) is recommend or connect two or more filter capacitors in parallel.
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Ver1.0
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