參數(shù)資料
型號(hào)： MAX1537A
廠商： Maxim Integrated Products, Inc.
英文描述： High-Efficiency, 5x Output, Main Power-Supply Controllers for Notebook Computers
中文描述： 高效率、5路輸出、主電源控制器，用于筆記本電腦
文件頁(yè)數(shù)： 31/38頁(yè)
文件大?。?/td> 1427K
代理商： MAX1537A
M
High-Efficiency, 5x Output, Main Power-Supply
Controllers for Notebook Computers
______________________________________________________________________________________
31
energy while transitioning from full-load to no-load con-
ditions without tripping the overvoltage fault protection.
When using high-capacitance, low-ESR capacitors (see
the
Output-Capacitor Stability Considerations
section),
the filter capacitor’s ESR dominates the output voltage
ripple. So the output capacitor’s size depends on the
maximum ESR required to meet the output voltage rip-
ple (V
RIPPLE(P-P)
) specifications:
In idle mode, the inductor current becomes discontinu-
ous, with peak currents set by the idle-mode current-
sense threshold (V
IDLE
= 0.2V
LIMIT
). In idle mode, the
no-load output ripple can be determined as follows:
The actual capacitance value required relates to the
physical size needed to achieve low ESR, as well as to
the chemistry of the capacitor technology. Thus, the
capacitor is usually selected by ESR and voltage rating
rather than by capacitance value (this is true of tanta-
lums, OS-CONs, polymers, and other electrolytics).
When using low-capacity filter capacitors, such as
ceramic capacitors, size is usually determined by the
capacity needed to prevent V
SAG
and V
SOAR
from
causing problems during load transients. Generally,
once enough capacitance is added to meet the over-
shoot requirement, undershoot at the rising load edge
is no longer a problem (see the V
SAG
and V
SOAR
equa-
tions in the
Transient Response
section). However, low-
capacity filter capacitors typically have high-ESR zeros
that may affect the overall stability (see the
Output-
Capacitor Stability Considerations
).
Output-Capacitor Stability Considerations
Stability is determined by the value of the ESR zero rel-
ative to the switching frequency. The boundary of insta-
bility is given by the following equation:
For a typical 300kHz application, the ESR zero frequency
must be well below 95kHz, preferably below 50kHz.
Tantalum and OS-CON capacitors in widespread use at
the time of publication have typical ESR zero frequen-
cies of 25kHz. In the design example used for inductor
selection, the ESR needed to support 25mV
P-P
ripple is
25mV / 1.5A = 16.7m
Ω
. One 220μF/4V Sanyo polymer
(TPE) capacitor provides 15m
Ω
(max) ESR. This results
in a zero at 48kHz, well within the bounds of stability.
For low-input-voltage applications where the duty cycle
exceeds 50% (V
OUT
/ V
IN
≥
50%), the output ripple volt-
age should not be greater than twice the internal slope-
compensation voltage:
V
RIPPLE
≤
0.02 x V
OUT
where V
RIPPLE
equals
Δ
I
INDUCTOR
x R
ESR
. The worst-
case ESR limit occurs when V
IN
= 2 x V
OUT
, so the
above equation can be simplified to provide the follow-
ing boundary condition:
R
ESR
≤
0.04 x L x f
OSC
Do not put high-value ceramic capacitors directly
across the feedback sense point without taking precau-
tions to ensure stability. Large ceramic capacitors can
have a high-ESR zero frequency and cause erratic,
unstable operation. However, it is easy to add enough
series resistance by placing the capacitors a couple of
inches downstream from the feedback sense point,
which should be as close as possible to the inductor.
Unstable operation manifests itself in two related but
distinctly different ways: short/long pulses or cycle skip-
ping resulting in a lower switching frequency. Instability
occurs due to noise on the output or because the ESR
is so low that there is not enough voltage ramp in the
output voltage signal. This “fools” the error comparator
into triggering too early or skipping a cycle. Cycle skip-
ping is more annoying than harmful, resulting in nothing
worse than increased output ripple. However, it can
indicate the possible presence of loop instability due to
insufficient ESR. Loop instability can result in oscilla-
tions at the output after line or load steps. Such pertur-
bations are usually damped, but can cause the output
voltage to rise above or fall below the tolerance limits.
The easiest method for checking stability is to apply a
very fast zero-to-max load transient and carefully
observe the output-voltage-ripple envelope for over-
shoot and ringing. It can help to simultaneously monitor
the inductor current with an AC-current probe. Do not
allow more than one cycle of ringing after the initial
step-response under/overshoot.
Input Capacitor Selection
The input capacitor must meet the ripple current
requirement (I
RMS
) imposed by the switching currents.
For an out-of-phase regulator, the total RMS current in
the input capacitor is a function of the load currents, the
input currents, the duty cycles, and the amount of over-
lap as defined in Figure 10.
f
f
where f
R
C
ESR
OSC
π
ESR
ESR
OUT
≤
=
π
1
2
V
V
R
R
RIPPLE P P
IDLE
ESR
SENSE
(
)
=
V
R
LIR
RIPPLE P P
ESR LOAD MAX
(
)
(
)
=
相關(guān)PDF資料
PDF描述
MAX1533 High-Efficiency, 5x Output, Main Power-Supply Controllers for Notebook Computers
MAX1533ETJ High-Efficiency, 5x Output, Main Power-Supply Controllers for Notebook Computers
MAX1537ETX High-Efficiency, 5x Output, Main Power-Supply Controllers for Notebook Computers
MAX153MJP 1Msps, レP-Compatible, 8-Bit ADC with 1レA Power-Down
MAX153EWP 1Msps, レP-Compatible, 8-Bit ADC with 1レA Power-Down
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1537AETX+ 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1537ETX 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel
MAX1537ETX-T 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel
MAX1537EVKIT 制造商:Maxim Integrated Products 功能描述:MAIN POWER SUPPLY CONTROLLER FOR NOTEBOOK - Bulk
MAX1538ETI 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
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

*
*
*