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參數(shù)資料
| 型號： | MAX1904ETJ |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 500kHz Multi-Output, Low-Noise Power-Supply Controllers for Notebook Computers |
| 中文描述： | 0.2 A DUAL SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, QCC32 |
| 封裝： | 5 X 5 MM, 0.80 MM, MO-220WHHD-2, TQFN-32 |
| 文件頁數(shù)： | 21/33頁 |
| 文件大?。?/td> | 649K |
| 代理商： | MAX1904ETJ |
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M
500kHz Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
______________________________________________________________________________________
21
connected but no battery is installed. V
IN(MAX)
must not
exceed 30V.
Minimum Input (Battery) Voltage, V
IN(MIN)
.This should
be taken at full load under the lowest battery condi-
tions. If V
IN(MIN)
is less than 4.2V, use an external cir-
cuit to externally hold V
L
above the V
L
undervoltage
lockout threshold. If the minimum input-output differ-
ence is less than 1.5V, the filter capacitance required to
maintain good AC load regulation increases (see the
Low-Voltage Operation
section).
Inductor Value
The exact inductor value isn
’
t critical and can be freely
adjusted to make trade-offs between size, cost, and
efficiency. Lower inductor values minimize size and
cost, but reduce efficiency due to higher peak-current
levels. The smallest inductor is achieved by lowering
the inductance until the circuit operates at the border
between continuous and discontinuous mode. Further
reducing the inductor value below this crossover point
results in discontinuous-conduction operation even at
full load. This helps lower output-filter capacitance
requirements, but efficiency suffers due to high I
2
R
losses. On the other hand, higher inductor values mean
greater efficiency, but resistive losses due to extra wire
turns will eventually exceed the benefit gained from
lower peak-current levels. Also, high inductor values
can affect load-transient response (see the V
SAG
equa-
tion in the
Low-Voltage Operation
section). The equa-
tions that follow are for continuous-conduction
operation, since the MAX1901/MAX1902/MAX1904 are
intended mainly for high-efficiency, battery-powered
applications. Discontinuous conduction doesn
’
t affect
normal idle-mode operation.
Three key inductor parameters must be specified:
inductance value (L), peak current (I
PEAK
), and DC
resistance (R
DC
). The following equation includes a
constant (LIR) which is the ratio of inductor peak-to-
peak AC current to DC load current. A higher LIR value
allows smaller inductance, but results in higher losses
and higher ripple. A good compromise between size
and losses is found at a 30% ripple-current to load-cur-
rent ratio (LIR = 0.3), which corresponds to a peak-
inductor current 1.15 times higher than the DC load
current.
(
× ×
(
)
where:
f = switching frequency, normally 333kHz or
500kHz
I
OUT
= maximum DC load current
LIR = ratio of AC to DC inductor current, typi-
cally 0.3; should be >0.15
The nominal peak-inductor current at full load is 1.15
I
OUT
if the above equation is used; otherwise, the peak
current can be calculated by:
The inductor
’
s DC resistance should be low enough that
R
DC
I
PEAK
< 100mV, as it is a key parameter for effi-
ciency performance. If a standard off-the-shelf inductor is
not available, choose a core with an LI
2
rating greater
than L
I
PEAK
2
and wind it with the largest-diameter wire
that fits the winding area. Ferrite core material is strongly
preferred. Shielded-core geometries help keep noise,
EMI, and switching-waveform jitter low.
Current-Sense Resistor Value
The current-sense resistor value is calculated accord-
ing to the worst-case low current-limit threshold voltage
(from the
Electrical Characteristics
) and the peak
inductor current:
Use I
PEAK
from the second equation in the
Inductor
Value
section.
Use the calculated value of R
SENSE
to size the MOS-
FET switches and specify inductor saturation-current
ratings according to the worst-case high current-limit
threshold voltage:
Low-inductance resistors, such as surface-mount
metal-film, are recommended.
Input-Capacitor Value
The input filter capacitor is usually selected according
to input ripple current requirements and voltage rating,
rather than capacitor value. Ceramic capacitors or
Sanyo OS-CON capacitors are typically used to handle
the power-up surge-currents, especially when connect-
ing to robust AC adapters or low-impedance batteries.
RMS input ripple current (I
RMS
) is determined by the
input voltage and load current, with the worst case
occurring at V
IN
= 2
V
OUT
:
I
mV
R
PEAK MAX
SENSE
(
)
=
120
R
mV
I
SENSE
PEAK
=
80
I
I
V
V
V
f
L
V
PEAK
LOAD
OUT
× ×
2
IN MAX
×
OUT
IN MAX
(
=
+
(
)
(
(
)
)
-
L
V
V
V
V
f
I
LIR
OUT
IN MAX
(
OUT
×
IN MAX
OUT
=
)
)
-
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參數(shù)描述 |
|---|---|
| MAX1904ETJ+ | 功能描述:DC/DC 開關(guān)控制器 500kHz Multi-Output Power-Supply 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(fēng)格: 封裝 / 箱體:CPAK |
| MAX1904ETJ+T | 功能描述:DC/DC 開關(guān)控制器 500kHz Multi-Output Power-Supply 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(fēng)格: 封裝 / 箱體:CPAK |
| MAX1904ETJ-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 |
| MAX1906EVKIT | 功能描述:電源管理IC開發(fā)工具 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| MAX1906SEEE | 功能描述:電池管理 RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
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