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參數(shù)資料
| 型號(hào)： | MAX894LESA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Dual, Current-Limited, High-Side P-Channel Switches with Thermal Shutdown |
| 中文描述： | 0.75 A DUAL SWITCHING CONTROLLER, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁(yè)數(shù)： | 7/8頁(yè) |
| 文件大?。?/td> | 98K |
| 代理商： | MAX894LESA |
M
Dual, Current-Limited, High-S ide P-Channel
S witc hes with T hermal S hutdown
_______________________________________________________________________________________
7
_______________Detailed Desc ription
The MAX894L/MAX895L P-channel MOSFET power
switches limit output current to a user-programmed
level. When the output current is increased beyond the
set current level, the current also increases through the
replica switch (I
OUT
/1050) (MAX895) and through R
SET
(Figure 1). The current-limit error amplifier compares
the voltage across R
SET
to the internal 1.24V reference,
and regulates the current back to the lesser of the pro-
grammed current limit (I
LIMIT
) or the maximum current
limit (I
MAX
).
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
S etting the Current Limit
The MAX894L/MAX895L feature internal current-limiting
circuitry with maximum programmable values (I
MAX
) of
500mA, and 250mA, respectively. For best perfor-
mance, set the current limit (I
LIMIT
) between 0.2I
MAX
≤
I
LIMIT
≤
I
MAX
. This current limit remains in effect
throughout the input supply-voltage range.
Program the current limit with a resistor (R
SET_
) con-
nected from SET_ to ground (Figure 2) as follows:
I
SET
= I
LIMIT
/ I
RATIO
R
SET
= 1.24V / I
SET
= (1.24V x I
RATIO
) / I
LIMIT
where I
LIMIT
is the desired current limit for either switch
and I
RATIO
is the I
OUT
to I
SET
current ratio (1085mA for
the MAX894L and 1050mA for the MAX895L.
S hort-Circ uit Protec tion
The MAX894L/MAX895L are short-circuit-protected
switches. In the event of an output short circuit or cur-
rent-overload condition, the current through either switch
is limited by the internal current-limiting error amplifier to
1.5 x I
LIMIT
. When the fault condition is removed, the
replica error amplifier sets the current limit back to I
LIMIT
.
For a high
V
DS
/
t during an output short-circuit condi-
tion, the switch turns off and disconnects the input supply
from the output. The current-limiting amplifier then slowly
turns the switch on with the output current limited to
1.5 x I
SET
. When the fault condition is removed, the current
limit is set back to I
LIMIT
. Refer to Output Short-Circuit
Fast-Loop Response and Output Short-Circuit Slow-Loop
Response in the Typical Operating Characteristics.
T hermal S hutdown
The MAX894L/MAX895L feature thermal shutdown. The
switch turns off when the junction temperature exceeds
+135°C. Once the device cools by 10°C, the switch turns
back on. If the fault short-circuit condition is not
removed, the switch cycles on and off, resulting in a
pulsed output.
__________Applic ations Information
Input Capac itor
To limit input voltage drop during momentary output
short-circuit conditions, place a capacitor from IN to
GND. A 1
μ
F ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce voltage drop at the input.
Output Capac itor
Connect a 0.1
μ
F capacitor from OUT to GND. This
capacitor prevents inductive parasitics from pulling
OUT negative during turn-off.
Layout and T hermal-Dissipation
Consideration
To take full advantage of the switch-response time to
output short-circuit conditions, it is very important to
keep all traces as short as possible, reducing the effect
of undesirable parasitic inductance. Place input and
output capacitors as close as possible to the device
(no more than 5mm).
Under normal operating conditions, the package can
dissipate and channel heat away. Calculate the maxi-
mum power as follows:
P = I
2LIMITA
x R
ONA
+ I
2LIMITB
x R
ONB
where R
ONA
and R
ONB
are the on-resistances of
switches A and B, respectively.
When one or both outputs are short circuited, the volt-
age drop across the switch equals the input supply.
Hence, the power dissipated across the switch increas-
es, as does the die temperature. If the fault condition is
not removed, the thermal-overload-protection circuitry
turns the switch off until the die temperature falls by
10°C. A ground plane in contact with the device helps
to further dissipate heat.
MAX894L
MAX895L
SET
R
SET
GND
Figure 2. Setting the Current Limit
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX894LESA+ | 功能描述:電源開(kāi)關(guān) IC - 配電 Current-Limited High-Side PCh Switch RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX894LESA+T | 功能描述:電源開(kāi)關(guān) IC - 配電 Current-Limited High-Side PCh Switch RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX894LESA-T | 功能描述:電源開(kāi)關(guān) IC - 配電 Current-Limited High-Side PCh Switch RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| MAX894LESA-TG116 | 制造商:Maxim Integrated Products 功能描述:CURRENT-LIMITED, HIGH-SIDE, P-CHANNEL DUAL SW - Bulk |
| MAX8951EVKIT+ | 制造商:Maxim Integrated Products 功能描述:PWM STEP DOWN CONVERTER - Boxed Product (Development Kits) |
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