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BL8534 Schematic ( PDF Datasheet ) - Belling

Teilenummer BL8534
Beschreibung High Efficiency Low Noise PFM Step-up DC/DC Converter
Hersteller Belling
Logo Belling Logo 




Gesamt 11 Seiten
BL8534 Datasheet, Funktion
BL8534
High Efficiency Low Noise PFM Step-up DC/DC Converter
DESCRIPTION
BL8534 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 20uA. All of these features make
BL8534 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, BL8534 is well considerated in
circuit design and manufacture. So that the
interferer to other circuits by the device is
reduced greatly.
BL8534 integrates stable reference circuits
and trimming technology, so it can afford high
precision and low temperature-drift coefficient
of the output voltage.
BL8534 is available in SOT-89-3, SOT-23-3,
SOT-23-5 and TO-92 packages that are 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.
FEATURES
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
to 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
Low quiescent current drawn from power
source-------------------------------------<20uA
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
BLLC83503040CC3TR33
4
3
BL8534
2
VIN=1.2V
VIN=1.5V
1 VIN=2V
VIN=2.5V
VIN=3V
0
0 200 400 600 800
Output Current(mA)
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1
Free Datasheet http://www.datasheet4u.com/






BL8534 Datasheet, Funktion
BL8534
I = DVIN
Lf
I MAX
=
VIN
(1D)2 RL
+
DVIN
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.
Thirdlyin 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
rLRload is load resistorthen the energy can
be calculated by following expression
η
Rload
rL
(1
D)2
For example: input 1.5V, output is 3.0V,
Rload=20, rL=0.5, the energy loss is 10%.
Consider all aboveinductor value of 47uH
ESR<0.5is recommended in most
applications. Large value is recommended in
high efficiency applications and smaller value
is recommended
CAPACITOR SELECTION
Ignore ESR of capacitorthe 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 + I MAX RESR
VOUT
When current is large, ripple caused by ESR
will be main factor. It may be greater than
100mVThe ESR will affect efficiency and
increase energy loss. So low-ESR capacitor
(for example: tantalum capacitor) is
recommend or connects two or more filter
capacitors in parallel.
DIODE SELECTION
Rectifier diode will affects efficiency greatly
Though a common diode (such as 1N4148)
will work well for light load it will reduce
about 5%~10% efficiency for heavy load
For optimum performance, a Schottky diode
(such as 1N5817 1N5819 1N5822) is
recommended.
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6
Free Datasheet http://www.datasheet4u.com/

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