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參數(shù)資料
| 型號： | MAX1776 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 32-Bit Digital Signal Controller with ROM 100-BGA MICROSTAR -40 to 85 |
| 中文描述： | 24V、600mA內(nèi)置開關(guān)、100%占空比、降壓型轉(zhuǎn)換器 |
| 文件頁數(shù)： | 10/13頁 |
| 文件大小： | 740K |
| 代理商： | MAX1776 |
M
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
10
______________________________________________________________________________________
Shutdown (
SHDN
)
A logic low level on
SHDN
shuts down the MAX1776
converter. When in shutdown, the supply current drops
to 3μA to maximize battery life, and the internal P-chan-
nel MOSFET turns off to isolate the output from the input.
The output capacitance and load current determine the
rate at which the output voltage decays. A logic level
high on
SHDN
activates the MAX1776. Do not leave
SHDN
floating. If unused, connect
SHDN
to IN.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the MAX1776. When the junction temperature
exceeds T
J
= +160
°
C, a thermal sensor turns off the
pass transistor, allowing the IC to cool. The thermal sen-
sor turns the pass transistor on again after the IC
’
s junc-
tion temperature cools by 10
°
C, resulting in a pulsed
output during continuous thermal-overload conditions.
Design Information
Output Voltage Selection
The feedback input features dual-mode operation.
Connect FB to GND for the 5.0V preset output voltage.
Alternatively, adjust the output voltage by connecting a
voltage-divider from the output to GND (Figure 4).
Select a value for R2 between 10k
and 100k
.
Calculate R1 with the following equation:
where V
FB
= 1.25V, and V
OUTPUT
may range from
1.25V to V
IN
.
Setting Current Limit
The MAX1776 has an adjustable peak current limit.
Configure this peak current limit by connecting ILIM
and ILIM2 as shown in Table 1.
Choose a current limit that realistically reflects the maxi-
mum load current. The maximum output current is half
of the peak current limit. Although choosing a lower
current limit allows using an inductor with a lower cur-
rent rating, it requires a higher inductance (see
Inductor Selection
) and does little to reduce inductor
package size.
Inductor Selection
When selecting the inductor, consider these four para-
meters: inductance value, saturation rating, series
resistance, and size. The MAX1776 operates with a
wide range of inductance values. For most applica-
tions, values between 10μH and 100μH work best with
the controller
’
s high switching frequency. Larger induc-
tor values will reduce the switching frequency and
thereby improve efficiency and EMI. The trade-off for
improved efficiency is a higher output ripple and slower
transient response. On the other hand, low-value induc-
tors respond faster to transients, improve output ripple,
offer smaller physical size, and minimize cost. If the
inductor value is too small, the peak inductor current
exceeds the current limit due to current-sense com-
parator propagation delay, potentially exceeding the
inductor
’
s current rating. Calculate the minimum induc-
tance value as follows:
(
where t
ON(MIN)
= 1μs.
The inductor
’
s saturation current rating must be greater
than the peak switch current limit, plus the overshoot
due to the 250ns current-sense comparator propaga-
tion delay. Saturation occurs when the inductor
’
s mag-
netic flux density reaches the maximum level the core
can support and the inductance starts to fall. Choose
an inductor with a saturation rating greater than I
PEAK
in the following equation:
I
PEAK
= I
LX(PEAK)
+ (V
IN
- V
OUTPUT
)
250ns / L
L
V
V
I
(MIN) =
IN(MAX)
OUTPUT
ON(MIN)
LX (PEAK
-
)
×
t
)
R1
R2
V
V
1
OUTPUT
FB
-
=
×
Figure 4. Adjustable Output Voltage
IN
GND
LX
FB
OUT
OUTPUT
1.25V TO V
IN
INPUT
4.5V TO 24V
C
IN
D1
L1
C
OUT
R1
R2
ILIM2
ILIM
SHDN
MAX1776
Table 1. Current-Limit Configuration
CURRENT
LIMIT (mA)
ILIM
CONNECTED TO
ILIM2
CONNECTED TO
150
300
600
1200
GND
GND
IN
IN
GND
IN
GND
IN
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1776EUA | 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 安裝風格:SMD/SMT |
| MAX1776EUA+ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 24V 600mA 100% Duty Cycle Step-Down 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 安裝風格:SMD/SMT |
| MAX1776EUA+ | 制造商:Maxim Integrated Products 功能描述:SEMICONDUCTOR ((NW)) |
| MAX1776EUA+ | 制造商:Maxim Integrated Products 功能描述:CONVERTER STEP DOWN 24V 0.6A SMD 制造商:Maxim Integrated Products 功能描述:CONVERTER, STEP DOWN, 24V 0.6A, SMD |
| MAX1776EUA+T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 24V 600mA 100% Duty Cycle Step-Down 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 安裝風格:SMD/SMT |
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