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PDF BL8534 Data sheet ( Hoja de datos )
| Número de pieza | BL8534 | |
| Descripción | High Efficiency Low Noise PFM Step-up DC/DC Converter | |
| Fabricantes | Belling | |
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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 page  
BL8534
DETAILED DESCRIPTION
The BL8534 series are boost structure,
voltage-type Pulse-Frequency Modulation
(PFM) step-up DC-DC converter. Only three
external components are necessary: an
inductor, an 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 techniques, 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
BL8534. 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 BL8534 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 amplifiers
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 affect 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, BL8534 integrates low on-
resistor N-channel MOSFET and well design
driver circuits. The switch energy loss is
limited at very low level.
COMPONENTS SELECTION
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 ripple voltage 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.
LMIN
≥
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,
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PACKAGE LINE (Continued)
Package
SOT-89-3 Devices per reel
Package Dimension:
1000Pcs
BL8534
Unit mm
Package
TO-92
Package Dimension:
Devices per Bag 1000Pcs
Unit
mm
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11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet BL8534.PDF ] | |
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