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參數(shù)資料
| 型號： | NX2117ACUTR |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO10 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 12/14頁 |
| 文件大?。?/td> | 405K |
| 代理商： | NX2117ACUTR |
NX2116/2116A/2116B/2117/2117A
7
Rev. 3.0
03/14/06
pacitors, both terms in equation (3) need to be evalu-
ated to determine the overall ripple. Usually when this
type of capacitors are selected, the amount of capaci-
tance per single unit is not sufficient to meet the tran-
sient specification, which results in parallel configura-
tion of multiple capacitors .
For example, one 100uF, X5R ceramic capacitor
with 2m
ESR is used. The amount of output ripple is
=
×+
××
=
RIPPLE
2.56A
V
2m
2.55A
8 600kHz 100uF
10.4mV
Although this meets DC ripple spec, however it
needs to be studied for transient requirement.
Based On Transient Requirement
Typically, the output voltage droop during transient
is specified as:
DROOP
TRAN
V
<V
@ step load
DI
STEP
During the transient, the voltage droop during the
transient is composed of two sections. One Section is
dependent on the ESR of capacitor, the other section is
a function of the inductor, output capacitance as well as
input, output voltage. For example, for the overshoot,
when load from high load to light load with a
DI
STEP
transient load, if assuming the bandwidth of system is
high enough, the overshoot can be estimated as the fol-
lowing equation.
2
OUT
overshoot
step
OUT
V
ESRI
2LC
=
×
+
×τ
××
...(6)
where
τ is the a function of capacitor, etc.
crit
step
OUT
crit
OUT
0
ifLL
LI
ESR C
ifLL
V
≤
×
τ=
×≥
...(7)
where
OUT
EE
OUT
crit
step
ESR C
V
ESRCV
L
II
×
××
==
...(8)
where ESR
E and CE represents ESR and capaci-
tance of each capacitor if multiple capacitors are used
in parallel.
The above equation shows that if the selected out-
put inductor is smaller than the critical inductance, the
voltage droop or overshoot is only dependent on the ESR
of output capacitor. For low frequency capacitor such
as electrolytic capacitor, the product of ESR and ca-
pacitance is high and
crit
LL
≤
is true. In that case, the
transient spec is dependent on the ESR of capacitor.
In most cases, the output capacitors are multiple
capacitors in parallel. The number of capacitors can be
calculated by the following
E
step
2
OUT
tran
E
tran
ESRI
V
N
V
2L CV
×
=
+
×τ
× ×
×
...(9)
where
crit
step
E
crit
OUT
0
ifLL
LI
ESR
C
ifLL
V
≤
×
τ=
×≥
...(10)
For example, assume voltage droop during tran-
sient is 100mV for 9A load step.
If the POSCAP 2R5TPE220MC(220uF, 12m
) is
used, the critical inductance is given as
EE
OUT
crit
step
ESRCV
L
I
12m
220 F 1.8V
0.56H
9A
××
==
×
=
The selected inductor is 1uH which is bigger than
critical inductance. In that case, the output voltage tran-
sient not only dependent on the ESR, but also capaci-
tance.
number of capacitors is
step
EE
OUT
LI
ESRC
V
1 H
9A
12m
220 F
2.36us
1.8V
×
τ =
×
=
×
=
E
step
2
OUT
tran
E
tran
2
ESRI
V
N
V
2L CV
12m
9A
100mV
1.8V
(2.36us)
2 1 H 220 F 100mV
1.3
×
=
+
×τ
× ×
×
=+
×
× ×
×
=
The number of capacitors has to satisfied both ripple
and transient requirement. Overall, we can choose N=2.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NX2117CUTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT, POWER GOOD & OVER VOLTAGE |
| NX2119 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119A | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119ACSTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119ACUTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
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