參數(shù)資料
型號(hào)： MAX1800
廠商： Maxim Integrated Products, Inc.
英文描述： Digital Camera Step-Up Power Supply
中文描述： 數(shù)碼相機(jī)升壓型電源
文件頁(yè)數(shù)： 20/24頁(yè)
文件大?。?/td> 461K
代理商： MAX1800
M
Digital Camera Step-Up
Power Supply
20
______________________________________________________________________________________
Applications Information
Using the MAX1801 with the MAX1800
Step-Up Master
The MAX1801 is a slave DC-DC controller that can be
used with the MAX1800 to generate additional output
voltages. It does not generate its own reference or
oscillator. Instead, it uses the reference and oscillator
of the MAX1800 step-up master converter controller
(Figure 1). The MAX1801 controller operation and
design are similar to that for the MAX1800 auxiliary
controllers. For more details, consult the MAX1801 data
sheet.
Using an Auxiliary Controller
in a SEPIC Configuration
Where the battery voltage may be above or below the
required output voltage, a step-up converter or step-
down converter will not be suitable; use a step-up
/step-down converter. One type of step-up/step-down
converter is the single-ended primary inductance con-
verter (or SEPIC) shown in Figure 8. Inductors L1 and
L2 can be separate inductors or can be wound on a
single core and coupled like a transformer. Typically,
using a coupled inductor will improve efficiency since
some power is transferred through the coupling so that
less power passes through coupling capacitor C2.
Likewise, C2 should be a low-ESR type capacitor to
improve efficiency. The ripple current rating must be
greater than the larger of the input and output currents.
The MOSFET (Q1) drain-source voltage rating and the
rectifier (D1) reverse voltage rating must exceed the
sum of the input and output voltages. Other types of
step-up/step-down circuits are a flyback converter and
a step-up converter followed by a linear regulator.
Using an Auxiliary Controller
for a Multi-Output Flyback Circuit
Some applications require multiple voltages from a sin-
gle converter that features a flyback transformer. Figure
9 shows a MAX1800 auxiliary controller in a two-output
flyback configuration. The controller drives an external
MOSFET that switches the transformer primary, and the
two secondaries generate the output voltages. Only a
single positive output voltage can be regulated using
the feedback resistive voltage-divider, so the other volt-
ages are set by the turns ratio of the transformer secon-
daries. The regulation of the other secondary voltages
degrades due to transformer leakage inductance and
winding resistance. Voltage regulation is best when the
load current is limited to a small range. Consult the
transformer manufacturer for the proper design for a
given application.
Using a Charge Pump For
Negative Output Voltages
Negative output voltages can be produced without a
transformer, using a charge-pump circuit with an auxil-
iary controller as shown in Figure 10. When MOSFET
Q1 turns off, the voltage at its drain rises to supply cur-
rent to V
OUT+
. At the same time, C1 charges to the volt-
age at V
OUT+
through D1. When the MOSFET turns on,
C1 discharges through D3, thereby charging C3 to
V
OUT
- minus the drop across D3 to create roughly the
same voltage as V
OUT+
at V
OUT-
but with inverted
polarity. If different magnitudes are required for the
positive and negative voltages, a linear regulator can
be used at one of the outputs to achieve the desired
voltages.
Using the Gain Block
as a Linear Regulator
The gain block at AO can be used with an external P-
channel MOSFET to make a low-dropout linear regula-
tor. The gain block output has push-pull drive, which
makes it suitable to drive a MOSFET gate. The circuit
for this application is shown in Figure 11.
The output voltage is set by the resistive voltage-divider
of R1 and R2. Use 100k
for R2. R1 is:
Q
1
C
C
R
1
- OUTPUT
+ OUTPUT
R
2
R
C
MAIN
IN
COMP
DCON
PART OF
MAX1800
DL
FB
INPUT
1-CELL
LITHIUM-ION
Figure 9. Auxiliary Flyback Configuration
相關(guān)PDF資料
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1800EHJ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1800EHJ-T 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1800EVKIT 功能描述:電源管理IC開發(fā)工具 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
MAX1801EKA 制造商:Maxim Integrated Products 功能描述:DIGITAL CAMERA STEP-UP SLAVE DC-DC - Rail/Tube
MAX1801EKA+ 制造商:Maxim Integrated Products 功能描述:DC DC CNTRLR SGL-OUT STEP UP 2.7V TO 5.5V 8PIN SOT-23 - Rail/Tube
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