參數(shù)資料
型號： MAX8543
廠商： Maxim Integrated Products, Inc.
英文描述： Dual J-K Negative-Edge-Triggered Flip-Flops With Clear And Preset 16-CDIP -55 to 125
中文描述： 降壓型控制器，具有預(yù)偏置啟動、無損檢測、同步整流和OVP
文件頁數(shù)： 20/27頁
文件大?。?/td> 399K
代理商： MAX8543
M
S tep-Down Controllers with Prebias S tartup,
Lossless S ensing, S ync hronization, and OV P
20
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2)
If the resulting value of R
ILIM
is negative, either
increase P
FB
or choose a low-side MOSFET with a
lower R
DS(ON)
. The latter is preferred as it increas-
es the efficiency and results in a lower short-circuit
current.
To set the constant current limit for the latch-up mode,
only R
ILIM
is used. The equation for R
ILIM
below sets
the current-limit threshold at 1.2 times the maximum-
rated output current:
Similarly, I
VALLEY
is the value of the inductor valley
current at maximum load, R
DS(ON)
is the maximum on-
resistance of the low-side MOSFET at the highest oper-
ating junction temperature.
Peak Current Limit
Peak inductor current-limit threshold (V
TH
) has four
possible settings through ILIM (MAX8543) or ILIM1
(MAX8544) as shown in
Table
3 below. The resulting
current limit is calculated as:
where R
DC
is either the DC resistance of the inductor or
the value of the optional current-sense resistor.
Note that V
ILIM
is a logic-level setting, and can allow a
variation of ±0.1 x V
VL
without affecting V
TH
. To ensure
maximum output current, use the minimum value of V
TH
from each setting, and the maximum R
DC
values at the
highest expected operating temperature. The DC resis-
tance of the inductor’s copper wire has a +0.22%/°C
temperature coefficient.
To use the DC resistance of the output inductor for cur-
rent sensing, an RC circuit is added (see Figure 7). The
RC time constant is set to be twice the inductor (L / R
DC
)
time constant. Pick the value of R4 in the range of 470
to 2k
, and then calculate the capacitor value from: C9
= 2L / (R
DC
×
R4). Add a resistor (R5) equal in value to
R4 to the CS- connection to minimize input-offset error.
The equivalent current-sense resistance is equal to the
DC resistance of the inductor (R
DC
).
To use a current-sense resistor, connect the resistor as
shown in Figure 8. Since most current-sense resistors
have inductance, the RC circuit is also required
and is calculated in the same manner as inductor
current sensing. Place C11 close to CS+ and CS- pins
to decouple the high-frequency noise pickup. Place
C10 (same value as C9) across R5 to aid in short-
circuit recovery.
I
V
R
I
LIM
TH
DC
P P
2
=
R
I
R
A
ILIM
VALLEY
DS ON
(
=
×
1.
1
)
μ
Table 3. ILIM Current-Limit Threshold
Settings
V
ILIM
RECOMMENDED
ILIM CONNECTION
V
TH
MIN
(mV)
V
TH
TYP
(mV)
V
TH
MAX
(mV)
0
GND
38.5
50
56.5
1/3 V
VL
Voltage-divider:
100k
from ILIM/ILIM1 to GND
200k
from ILIM/ILIM1 to VL
85.0
100
115.0
2/3 V
VL
Voltage-divider:
200k
from ILIM/ILIM1 to GND
100k
from ILIM/ILIM1 to VL
127.5
150
172.5
V
VL
VL
170.0
200
230.0
MAX8543/
MAX8544
C9
V
OUT
R4
R5
R3
L1
LX
CS-
CS+
C11
C10
Figure 8. Using a Current-Sense Resistor
MAX8543/
MAX8544
C9
V
OUT
R4
R5
L1
LX
CS-
CS+
C11
C10
Figure 7. Inductor R
DC
Current Sensing
相關(guān)PDF資料
PDF描述
MAX8544 Dual J-K Negative-Edge-Triggered Flip-Flops With Clear And Preset 20-LCCC -55 to 125
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MAX8556 3-Line To 8-Line Decoders/Demultiplexers 16-CFP -55 to 125
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX8543EEE 功能描述:DC/DC 開關(guān)控制器 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
MAX8543EEE+ 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX8543EEE+T 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX8543EEE-T 功能描述:DC/DC 開關(guān)控制器 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
MAX8544EEP 功能描述:DC/DC 開關(guān)控制器 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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