參數(shù)資料
型號(hào)： MAX1845ETX
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類(lèi)： 穩(wěn)壓器
英文描述： Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit
中文描述： DUAL SWITCHING CONTROLLER, 620 kHz SWITCHING FREQ-MAX, QCC36
封裝： 6 X 6 MM, 0.80 MM, MO220WJJD-1, TQFN-36
文件頁(yè)數(shù)： 18/27頁(yè)
文件大?。?/td> 543K
代理商： MAX1845ETX
M
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
18
______________________________________________________________________________________
Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite
cores are often the best choice, although powdered
iron is inexpensive and can work well at 200kHz. The
core must be large enough not to saturate at the peak
inductor current (I
PEAK
):
I
PEAK
= I
LOAD(MAX)
+ [(LIR / 2)
I
LOAD(MAX)
]
Transient Response
The inductor ripple current also impacts transient-
response performance, especially at low V
IN
- V
OUT
dif-
ferentials. Low inductor values allow the inductor
current to slew faster, replenishing charge removed
from the output filter capacitors by a sudden load step.
The amount of output sag is also a function of the maxi-
mum duty factor, which can be calculated from the on-
time and minimum off-time:
I
C
DUTY V
F
×
×
2
where:
where minimum off-time = 400ns typ (Table 4).
The amount of overshoot during a full-load to no-load
transient due to stored inductor energy can be calculat-
ed as:
V
SOAR
= L
I
PEAK
2
/ (2 C
OUT
V
OUT
)
where I
PEAK
is the peak inductor current.
Determining the Current Limit
For most applications, set the MAX1845 current limit by
the following procedure:
1) Determine the minimum (valley) inductor current
(IL
(MIN)
) under conditions when V
IN
is small, V
OUT
is
large, and load current is maximum. The minimum
inductor current is I
LOAD
minus half the ripple cur-
rent (Figure 4).
2) The sense resistor determines the achievable cur-
rent-limit accuracy. There is a trade-off between cur-
rent-limit accuracy and sense-resistor power
dissipation. Most applications employ a current-
sense voltage of 50mV to 100mV. Choose a sense
resistor such that:
R
SENSE
= Current-Limit Threshold Voltage / I
L(MIN)
Extremely cost-sensitive applications that do not
require high-accuracy current sensing can use the on-
resistance of the low-side MOSFET switch in place of
the sense resistor by connecting CS_ to LX_ (Figure
7a). Use the worst-case value for R
DS(ON)
from the
MOSFET data sheet, and add a margin of 0.5%/
°
C for
the rise in R
DS(ON)
with temperature. Use the calculat-
ed R
DS(ON)
and I
L(MIN)
from step 1 above to determine
the current-limit threshold voltage. If the default 50mV
threshold is unacceptable, set the threshold value as in
step 2 above.
In all cases, ensure an acceptable current limit consid-
ering current-sense and resistor accuracies.
Output Capacitor Selection
The output filter capacitor must have low enough ESR to
meet output ripple and load-transient requirements, yet
have high enough ESR to satisfy stability requirements.
Also, the capacitance value must be high enough to
absorb the inductor energy going from a full-load to no-
load condition without tripping the OVP circuit.
For CPU core voltage converters and other applications
where the output is subject to violent load transients,
the output capacitor
’
s size depends on how much ESR
is needed to prevent the output from dipping too low
under a load transient. Ignoring the sag due to finite
capacitance:
In non-CPU applications, the output capacitor
’
s size
depends on how much ESR is needed to maintain an
acceptable level of output voltage ripple:
R
V
I
LIR
ESR
P P
LOAD MAX
≤
×
(
)
R
V
I
ESR
DIP
(
LOAD MAX
≤
)
DUTY
K (V
+ 0.075V) V
+ 0.075V) V
K (V
+ min off-time
OUT
IN
OUT
OUT
=
V
L
-
V
SAG
LOAD MAX
IN MIN
(
OUT
=
×
(
)
(
)
(
)
)
2
LX
DL
CS
MAX1845
LX
DL
CS
MAX1845
b)
a)
Figure 7. Current-Sense Configurations
相關(guān)PDF資料
PDF描述
MAX1848 Replaced by TMS320VC5506 : DSP (DSP Only) for Embedded V90 Modem Solution [Not Recommended For New Designs (NRND)] 144-LQFP
MAX1848ETA Replaced by TMS320VC5506 : DSP (DSP Only) for Embedded V90 Modem Solution [Not Recommended For New Designs (NRND)] 144-BGA MICROSTAR
MAX1848EKA White LED Step-Up Converter in SOT23
MAX1855 Fixed-Point Digital Signal Processor 352-FC/CSP 0 to 0
MAX1854EEG High-Speed, Adjustable, Synchronous Step-Down Controllers with Integrated Voltage Positioning
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1845ETX+ 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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
MAX1845ETX+T 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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
MAX1845ETX-T 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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
MAX1845ETX-TG068 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1845EVKIT 功能描述:電源管理IC開(kāi)發(fā)工具 Evaluation Kit for the MAX1845 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*