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參數(shù)資料
| 型號： | MAX770CPA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
| 中文描述： | SWITCHING CONTROLLER, 300 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | PLASTIC, DIP-8 |
| 文件頁數(shù)： | 16/20頁 |
| 文件大?。?/td> | 204K |
| 代理商： | MAX770CPA |
M
The standard operating circuits use a 22μH inductor.
If a different inductance value is desired, select L
such that:
V
IN
(max) x t
ON
(min)
L
≥
——————————
I
LIM
/2
Larger inductance values tend to increase the start-up
time slightly, while smaller inductance values allow the
coil current to ramp up to higher levels before the
switch turns off, increasing the ripple at light loads.
Inductors with a ferrite core or equivalent are recom-
mended; powder iron cores are not recommended for
use with high switching frequencies. Make sure the
inductor’s saturation current rating (the current at which
the core begins to saturate and the inductance starts to
fall) exceeds the peak current rating set by R
SENSE
.
However, it is generally acceptable to bias the inductor
into saturation by approximately 20% (the point where
the inductance is 20% below the nominal value). For
highest efficiency, use a coil with low DC resistance,
preferably under 20m
. To minimize radiated noise,
use a toroid, a pot core, or a shielded coil.
Table 2 lists inductor suppliers and specific recom-
mended inductors.
Power T ransistor S elec tion
Use an N-channel MOSFET power transistor with the
MAX770/MAX771/MAX772 (Figure 8a).
Use an N-FET whenever possible with the MAX773. An
NPN transistor can be used, but be extremely careful
when determining the base current (see NPN
Transistors section). An NPN transistor is not recom-
mended when using the shunt regulator.
N-Channel MOSFETs
To ensure the external N-channel MOSFET (N-FET) is
turned on hard, use logic-level or low-threshold
N-FETs when the input drive voltage is less than 8V. This
applies even in bootstrapped mode, to ensure start-up.
N-FETs provide the highest efficiency because they do
not draw any DC gate-drive current, but they are typi-
cally more expensive than NPN transistors. When using
an N-FET with the MAX773, connect EXTH and EXTL to
the N-FET’s gate (Figure 8b).
When selecting an N-FET, three important parameters
are the total gate charge (Q
g
), on resistance (r
DS(ON)
),
and reverse transfer capacitance (C
RSS
).
Q
g
takes into account all capacitances associated with
charging the gate. Use the typical Q
g
value for best
results; the maximum value is usually grossly over-
specified since it is a guaranteed limit and not the mea-
sured value. The typical total gate charge should be
50nC or less. With larger numbers, the EXT pins may
not be able to adequately drive the gate. The EXT
rise/fall time with various capacitive loads as shown in
the Typical Operating Characteristics.
5V /12V /15V or Adjustable, High-Efficiency,
Low I
Q
, Step-Up DC-DC Controllers
16
______________________________________________________________________________________
MAX770
MAX771
MAX772
N
EXT
CS
R
SENSE
MAX773
NPN
EXTH
EXTL
CS
L
R
SENSE
R
BASE
I
C(PEAK)
I
B
Figure 8a. Use an N-Channel MOSFET with the
MAX770/MAX771/MAX772
Figure 8b. Using an N-Channel MOSFET with the MAX773
Figure 8c. Using an NPN Transistor with the MAX773
MAX773
N
EXTH
EXTL
CS
L
R
SENSE
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX770CSA | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
| MAX770EPA | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
| MAX770ESA | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
| MAX770MJA | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
| MAX771CPA | 5V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX770CPA+ | 功能描述:DC/DC 開關(guān)控制器 5/12/15/AdjV Step Up DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX770CSA | 功能描述:DC/DC 開關(guān)控制器 5/12/15/AdjV Step Up DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX770CSA+ | 功能描述:DC/DC 開關(guān)控制器 5/12/15/AdjV Step Up DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX770CSA+ | 制造商:Maxim Integrated Products 功能描述:IC STEP-UP DC/DC CONTROLLER 8-SOIC |
| MAX770CSA+T | 功能描述:DC/DC 開關(guān)控制器 5/12/15/AdjV Step Up DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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