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參數(shù)資料
| 型號： | MAX17004AETJ+ |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3.3 A DUAL SWITCHING CONTROLLER, 575 kHz SWITCHING FREQ-MAX, QCC32 |
| 封裝： | 5 X 5 MM, 0.80 MM HEIGHT, LEAD FREE, MO-220WHHD-2, QFN-32 |
| 文件頁數(shù)： | 21/36頁 |
| 文件大?。?/td> | 611K |
| 代理商： | MAX17004AETJ+ |
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MAX17003A/MAX17004A
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
28
______________________________________________________________________________________
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 VSAG and VSOAR 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 VSAG and VSOAR 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 section).
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:
where:
For a typical 300kHz application, the ESR zero frequen-
cy must be well below 95kHz, preferably below 50kHz.
Tantalum and OSCON 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 25mVP-P ripple is
25mV/1.5A = 16.7m
Ω. One 220F/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% (VOUT/VIN
≥ 50%), the output ripple volt-
age should not be greater than twice the internal slope-
compensation voltage:
VRIPPLE ≤ 0.02 x VOUT
where VRIPPLE equals
ΔIINDUCTOR x RESR. The worst-
case ESR limit occurs when VIN = 2 x VOUT, so the
above equation can be simplified to provide the follow-
ing boundary condition:
RESR ≤ 0.04 x L x fSW
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 and cycle
skipping resulting in lower frequency operation.
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 com-
parator into triggering too early or into skipping a cycle.
Cycle skipping 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 oscillations at the output after line or load
steps. Such perturbations 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 may help to simultaneously moni-
tor the inductor current with an AC current probe. Do
not allow more than three cycles of ringing after the ini-
tial step-response under/overshoot.
f
RC
ESR
ESR OUT
=
1
2
π
f
ESR
OSC
≤
π
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX17004AETJ+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX17004ETJ+ | 功能描述:電壓模式 PWM 控制器 Quad Out Main Power Supply Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MAX17004ETJ+T | 功能描述:電壓模式 PWM 控制器 Quad Out Main Power Supply Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MAX17005AETP+ | 功能描述:電池管理 1.2MHz High-Perf Charger 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 |
| MAX17005AETP+T | 功能描述:電池管理 1.2MHz High-Perf Charger 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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