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参数资料
| 型号： | MAX1802EHJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 26/28页 |
| 文件大小： | 0K |
| 描述： | IC PWR SPLY STEP DOWN 32-TQFP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 360 |
| 应用： | 控制器，数字式相机 |
| 输入电压： | 2.5 V ~ 11 V |
| 输出数： | 5 |
| 输出电压： | 1.25 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-TQFP |
| 供应商设备封装： | 32-TQFP（5x5） |
| 包装： | 托盘 |
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Digital Camera Step-Down
Power Supply
converter is the SEPIC, shown in Figure 9. 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
INPUT
1 CELL
Li+
some power is transferred through the coupling, so less
power passes through the coupling capacitor (C2).
Likewise, C2 should have low ESR to improve efficien-
MAIN
L1
L2
cy. 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)
ON
DCON
C2
D1
OUTPUT
3.3V
reverse-voltage rating must exceed the sum of the
EXT
Q1
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.
MAX1802
FB
R1
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 10 shows a MAX1802 auxiliary controller in a
two-output flyback configuration. The controller drives
an external MOSFET that switches the transformer pri-
mary, and the two secondaries generate the outputs.
COMP
R C
G C
R2
Only a single positive output voltage can be regulated
using the feedback resistive voltage-divider, so the
other voltages are set by the turns ratio of the trans-
former secondaries. The regulation of the other sec-
ondary 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 11. 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
Figure 9. Auxiliary Controller, SEPIC Configuration
Conductors carrying discontinuous currents should be
kept as short as possible. Conductors carrying high
currents should be made as wide as possible. A sepa-
rate low-noise ground plane containing the reference
and signal grounds should only connect to the power-
ground plane at one point to minimize the effects of
power-ground currents.
Keep the voltage feedback network very close to the
IC, preferably within 0.2in (5mm) of the FB_ pin. Nodes
with high dv/dt (switching nodes) should be kept as
small as possible and should stay away from high-
impedance nodes such as FB_ and COMP_.
Refer to the MAX1802EVKIT evaluation kit manual for a
full PC board example.
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
voltage.
Designing a PC Board
A good PC board layout is important to achieve optimal
performance from the MAX1802. Good design reduces
excessive conducted and/or radiated noise, both of
which are undesirable.
TRANSISTOR COUNT: 7740
Chip Information
26
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1802EHJ+ | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1802EHJ+T | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1802EHJ-T | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1804EUB | 功能描述:电流和电力监控器、调节器 RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
| MAX1804EUB+ | 功能描述:电流和电力监控器、调节器 Feedback Integrator for Power Supply RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
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