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| 型號： | MAX1540A |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Dual Step-Down Controllers with Saturation Protection, Dynamic Output, and Linear Regulator |
| 中文描述： | 雙路、降壓型控制器，帶有電感飽和保護、動態(tài)輸出和線性穩(wěn)壓器 |
| 文件頁數(shù)： | 28/49頁 |
| 文件大小： | 794K |
| 代理商： | MAX1540A |
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M
Inductor-Saturation Limit
The LSAT connection selects an upper current-sense
limit as the inductor-saturation threshold, or disables
the inductor-saturation protection feature altogether
(LSAT = GND). When enabled, the inductor-saturation
threshold is a multiple of the positive valley current-limit
threshold (Table 5) and tracks the valley current limit
when ILIM is adjusted. The selected inductor-saturation
threshold should give sufficient headroom above the
peak inductor current so switching noise does not acci-
dentally trip the saturation protection. Selecting an
excessively high threshold may allow inductor satura-
tion to go undetected. For an inductor with a low LIR
(the ratio of the inductor ripple current to the designed
maximum load current) near 20%, select the lowest sat-
uration threshold of 1.5 x I
LIM(VAL)
(LSAT = REF). When
using an inductor with a higher LIR, increase the induc-
tor-saturation threshold accordingly.
When inductor-saturation protection is enabled, the
MAX1540A/MAX1541 continuously monitor the inductor
current through the voltage across the current-sense
resistor. When the inductor-saturation threshold is
exceeded, the MAX1540A/MAX1541 immediately turn
off the high-side gate driver and enable a 6μA dis-
charge current on ILIM_ (Figure 7) at the beginning of
the next DH_ on-time. This reduces the voltage on
ILIM_ by
Δ
V
ILIM
where:
where the ILIM saturation fault sink current (I
ILIM(LSAT)
)
is typically 6μA (see the
Electrical Characteristics
table). When using the default 50mV valley current-limit
threshold (ILIM_ = V
CC
), the ILIM_ saturation fault sink
current does not lower the current-limit threshold
(Figure 5).
If the inductor current remains below the saturation
threshold during the next cycle, the controller disables
the ILIM_ discharge current, allowing the ILIM_ voltage
to return to its nominal set point. The inductor should
not remain in saturation once the controller reduces the
valley current limit. If the inductor remains saturated,
the output voltage may drop low enough to trip the
undervoltage fault protection (UVP enabled), causing
the MAX1540A/MAX1541 to set the fault latch and shut
down both outputs. Adding a capacitor from ILIM_ to
GND slows the ILIM_ voltage change by the time con-
stant
τ
= (R
A
|| R
B
) x C
ILIM
, where
τ
is between 5 to 10
switching periods. If the inductor saturation occurs only
during a short load transient, the time constant allows
the power supply to recover before the output voltage
drops below the output undervoltage threshold.
Set
Δ
V
ILIM
to be at least 30% of the ILIM_ set voltage.
Calculate R
A
and R
B
using the equations below:
Inductor-saturation sensing works best when using a cur-
rent-sense resistor in series with the inductor. See the
Setting the Current Limit
section for various current-sense
configurations (Figure 14) and LSAT recommendations.
R
with
set at
R
A
REF
V
ILIM(LSAT)
I
ILIM
V
Δ
ILIM(SET)
V
ILIM
V
Δ
ILIM(SET)
V
B
A
REF
V
ILIM(SET)
V
R
-
=
=
30
1
%
Δ
V
I
ILIM
R +R
B
ILIM(LSAT)
-
R R
=
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
28
______________________________________________________________________________________
MAX1540A
MAX1541
REF
ILIM
6
μ
A
C
REF
TO VALLEY
CURRENT-LIMIT
COMPARATOR
(FIGURE 2)
FROM LSAT
COMPARATOR
AND LOGIC
(FIGURE 2)
C
ILIM
R
B
R
A
Figure 7. Adjustable Current-Limit Threshold
Table 5. LSAT Configuration Table
LSAT
V
CC
Open
REF
GND
INDUCTOR-SATURATION THRESHOLD
2.00 x I
LIM(VAL)
1.75 x I
LIM(VAL)
1.50 x I
LIM(VAL)
Disabled
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1540AETJ+ | 功能描述:DC/DC 開關(guān)控制器 Dual Step-Down Ctlr w/Saturation Prot 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 安裝風格: 封裝 / 箱體:CPAK |
| MAX1540AETJ+T | 功能描述:DC/DC 開關(guān)控制器 Dual Step-Down Ctlr w/Saturation Prot 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 安裝風格: 封裝 / 箱體:CPAK |
| MAX1540ETJ | 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 安裝風格: 封裝 / 箱體:CPAK |
| MAX1540ETJ+ | 功能描述:DC/DC 開關(guān)控制器 Dual Step-Down Ctlr 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 安裝風格: 封裝 / 箱體:CPAK |
| MAX1540ETJ+T | 功能描述:DC/DC 開關(guān)控制器 Dual Step-Down Ctlr 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 安裝風格: 封裝 / 箱體:CPAK |
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