參數(shù)資料
型號(hào)： MAX1904ETJ
廠(chǎng)商： MAXIM INTEGRATED PRODUCTS INC
元件分類(lèi)： 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(yè)數(shù)： 22/33頁(yè)
文件大?。?/td> 649K
代理商： MAX1904ETJ
M
500kHz Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
22
______________________________________________________________________________________
Therefore, when V
IN
is 2 x V
OUT
:
Bypassing V+
Bypass the V+ input with a 4.7μF tantalum capacitor
paralleled with a 0.1μF ceramic capacitor, close to the
IC. A 10
series resistor to V
IN
is also recommended.
Bypassing VL
Bypass the VL output with a 4.7μF tantalum capacitor
paralleled with a 0.1μF ceramic capacitor, close to the
device.
Output-Filter Capacitor Value
The output-filter capacitor values are generally deter-
mined by the ESR and voltage-rating requirements,
rather than actual capacitance requirements for loop sta-
bility. In other words, the low-ESR electrolytic capacitor
that meets the ESR requirement usually has more output
capacitance than is required for AC stability. Use only
specialized low-ESR capacitors intended for switching-
regulator applications, such as AVX TPS, Sanyo
POSCAP, or Kemet T510. To ensure stability, the capaci-
tor must meet both minimum capacitance and maximum
ESR values as given in the following equations:
V
V
OUT
OUT
×
These equations are worst case, with 45
°
of phase mar-
gin to ensure jitter-free, fixed-frequency operation and
provide a nicely damped output response for zero to
full-load step changes. Some cost-conscious designers
may wish to bend these rules with less-expensive
capacitors, particularly if the load lacks large step
changes. This practice is tolerable if some bench test-
ing over temperature is done to verify acceptable noise
and transient response.
No well-defined boundary exists between stable and
unstable operation. As phase margin is reduced, the
first symptom is a bit of timing jitter, which shows up as
blurred edges in the switching waveforms where the
scope won
’
t quite sync up. Technically speaking, this
jitter (usually harmless) is unstable operation, since the
duty factor varies slightly. As capacitors with higher
ESRs are used, the jitter becomes more pronounced, and
the load-transient output-voltage waveform starts looking
ragged at the edges. Eventually, the load-transient wave-
form has enough ringing on it that the peak noise levels
exceed the allowable output-voltage tolerance. Note that
even with zero phase margin and gross instability pre-
sent, the output-voltage noise never gets much worse
than I
PEAK
R
ESR
(under constant loads).
The output-voltage ripple is usually dominated by the
filter capacitor
’
s ESR, and can be approximated as
I
RIPPLE
R
ESR
. There is also a capacitive term, so the
full equation for ripple in continuous-conduction mode
is V
NOISE (p-p)
= I
RIPPLE
[R
ESR
+ 1/(2
π
f
C
OUT
)]. In idle mode, the inductor current becomes
discontinuous, with high peaks and widely spaced
pulses, so the noise can actually be higher at light load
(compared to full load). In idle mode, calculate the out-
put ripple as follows:
Transformer Design
(for Auxiliary Outputs Only)
Buck-plus-flyback applications, sometimes called
“
cou-
pled-inductor
”
topologies, need a transformer to gener-
ate multiple output voltages. Performing the basic
electrical design is a simple task of calculating turns
ratios and adding the power delivered to the secondary
to calculate the current-sense resistor and primary
inductance. However, extremes of low input-output dif-
ferentials, widely different output loading levels, and
high turns ratios can complicate the design due to par-
asitic transformer parameters such as interwinding
capacitance, secondary resistance, and leakage
inductance. For examples of what is possible with real
world transformers, see the Maximum V
DD
Output
Current vs. Input Voltage graph in the
Typical
Operating Characteristics
.
Power from the main and secondary outputs is combined
to get an equivalent current referred to the main output
voltage (see the
Inductor Value
section for parameter
definitions). Set the current-sense resistor value at 80mV
/ I
TOTAL
.
V
R
R
L
V
V
V
R
C
NOISE P P
ESR
SENSE
OUT
×
IN
OUT
SENSE
OUT
(
)
.
.
[ /
1
/(
)]
-
-
=
×
+
×
×
+
0 025
0 0003
1
2
C
V
V
R
f
R
R
V
V
REF
OUT
IN MIN
×
SENSE
ESR
SENSE
OUT
REF
>
+
<
×
(
/
)
(
)
1
I
I
RMS
LOAD
2
=
I
I
V
V
V
V
RMS
LOAD
OUT
IN
OUT
IN
=
×
(
)
-
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MAX1904ETJ+ 功能描述:DC/DC 開(kāi)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(kāi)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(kāi)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(kāi)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(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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(kāi)發(fā)工具 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
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