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PDF BL8531 Data sheet ( Hoja de datos )
| Número de pieza | BL8531 | |
| Descripción | High Efficiency Low Noise PFM Step-up DC/DC Converter | |
| Fabricantes | SHANGHAI BELLING | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de BL8531 (archivo pdf) en la parte inferior de esta página. Total 10 Páginas | ||
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DESCRIPTION
BL8531
High Efficiency Low Noise PFM Step-up DC/DC Converter
FEATURES
BL8531 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
5.5uA. All of these features make BL8531 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, BL8531 is well considerate in circuit
design and manufacture. So that the interferer to
other circuits by the device is reduced greatly.
BL8531 integrates stable reference circuits and
trimming technology, so it can afford high
precision and low temperature-drift coefficient of
the output voltage.
BL8531 is available in SOT-89-3, SOT-23-3, SOT-
23-5 and TO-92 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
Output voltage can be adjusted from 2.5V～
6.0V (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-------------------------------------<5.5uA
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
TYPICAL APPLICATION
ELECTRICAL CHARACTERISTICS
BLL585031
BL8531CC3TR33 Output Voltage VS. Output Current
Vin=0.9V
Vin=1.5V
Vin=2.5V
Vin=1.0V
Vin=1.8V
Vin=1.2V
Vin=2.0V
3.35
3.30
3.25
3.20
3.15
3.10
3.05
3.00
0
50 100 150 200 250 300 350 400 450 500
Output Current(mA)
www.belling.com.cn
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1 page  
BL8531
SELECTION 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.
Before discussion，we define
D Vout Vin .
Vout
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.
L min D(1 D)2 RL
2f
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，the efficiency
of DC-DC converter will drop greatly, and the DC-
DC circuit will not be stable.
Secondly, consider the ripple of the output
voltage,
I D Vin
Lf
Im ax Vin DVin
(1 D)2 RL 2Lf
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 affect efficiency greatly.
Suppose ESR value of inductor is rL，Rload is load
resistor，then the energy can be calculated by
following expression:
rL
Rload (1 D) 2
For example: input 1.5V, output is 3.0V,
Rload=20Ω, rL=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.
CAPACITOR SELECTION
Ignore ESR of capacitor，the ripple of output
voltage is:
r Vout D
Vout Rload 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 RESR
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.
www.belling.com.cn
5
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| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet BL8531.PDF ] | |
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