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參數(shù)資料
| 型號： | MAX845 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Isolated Transformer Driver for PCMCIA Applications(750mW,隔離變壓器驅動器) |
| 中文描述： | 隔離型、變壓器驅動器，適用于PCMCIA設計 |
| 文件頁數(shù)： | 5/16頁 |
| 文件大?。?/td> | 230K |
| 代理商： | MAX845 |
_______________Detailed Desc ription
The MAX845 is a transformer driver specifically
designed to provide isolated power for PCMCIA and
other height- and/or space-sensitive applications. It
drives a center-tapped transformer primary from a 5V
or 3.3V DC power supply. The secondary can be
wound to provide any isolated DC voltage needed at
power levels up to 750mW.
The 450kHz minimum switching frequency allows the
use of very thin transformers, making the MAX845 ideal
for PCMCIA and other space-limited applications. The
MAX845 is designed to drive a single transformer less
than 0.09 inches (2.3mm) in height, including package.
Further reduction down to 0.050 inches (1.27mm) can
be achieved using a transformer without a package.
The MAX845 consists of an RC oscillator driving a pair
of N-channel power switches. The oscillator runs at
double the output frequency, driving a toggle flip-flop
to ensure 50% duty cycle to each of the switches.
Internal circuitry ensures break-before-make action
between the two switches.
A low-current shutdown mode disables all internal cir-
cuitry, including the oscillator and both power switches.
Drive the shutdown pin (SD) high to shut down the part;
drive SD low for normal operation. The SD pin has no
internal default condition and must not be allowed to
float.
Most MAX845 applications will operate at high frequen-
cies. The frequency-select pin (FS) is pulled high or left
open (FS is internally pulled up to V
CC
) to operate at a
minimum of 450kHz. Pulling FS low selects the low-fre-
quency state.
T heory of Operation
Figure 2 shows the MAX845 driving both a TGM-010P3
transformer with a center-tapped primary, and a sec-
ondary with a voltage-doubler rectifier topology. All of the
transformers driven by the MAX845 must have a center
tap with V
IN
applied. Whenever one of the MAX845 out-
puts (D1 or D2) goes low, the other goes to approximate-
ly double the supply voltage. A voltage is induced in the
secondary and the rectifier diodes steer the currents into
the appropriate output capacitor. On alternate half
cycles, each capacitor is charged. The output voltage is
the sum of the voltages from each output capacitor. This
topology yields the simplest and smallest transformer
because the least number of secondary turns is required
for a given voltage.
__________Applic ations Information
With the MAX845 transformer driver, designers have
the advantages of push/pull converter topology in
space-sensitive applications. The push/pull DC-DC
converter topology allows isolated multiple outputs,
step-up/step-down or inverted outputs, easier filtering
on the input and the output, and lower overall noise.
Isolated Power for PCMCIA Applic ations
Medical instrumentation, modems, and LAN-interface
cards often require isolated power supplies. One of the
best switching-regulator topologies for this application
is the push/pull forward-converting DC-DC power sup-
ply shown in Figures 3 and 4. Because the transformer
works in the forward mode (rather than the flyback
mode), its core does not store energy and, therefore,
can be small. Input and output capacitors can be small
because of the high-frequency and continuous-current
waveforms.
M
Isolated Transformer Driver
for PCMCIA Applic ations
_______________________________________________________________________________________
5
MAX845
D1
D2
FS
GND2
GND1
V
CC
FREQUENCY
SELECT
C2
C3
C1
OUTPUT
5V @ 150mA
5V
N
N
Q
Q
OSC
F / F
V
IN
SD
ON / OFF
400kHz/
700kHz
T
ISO
GND
V
CC
CR1
CR2
Figure 2. Detailed Block Diagram
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX845C/D | 功能描述:功率驅動器IC Isolated Transformer Driver PCMCIA RoHS:否 制造商:Micrel 產品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時間: 下降時間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| MAX845C/D+ | 功能描述:功率驅動器IC RoHS:否 制造商:Micrel 產品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時間: 下降時間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| MAX845CSA | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX845ESA | 功能描述:功率驅動器IC RoHS:否 制造商:Micrel 產品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時間: 下降時間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| MAX845ESA/GH9 | 功能描述:功率驅動器IC RoHS:否 制造商:Micrel 產品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時間: 下降時間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
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