- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄383334 > MAX1977 (Maxim Integrated Products, Inc.) High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers PDF資料下載
參數(shù)資料
| 型號： | MAX1977 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| 中文描述： | 高效率、四路輸出、主電源控制器，用于筆記本電腦 |
| 文件頁數(shù)： | 26/32頁 |
| 文件大?。?/td> | 497K |
| 代理商： | MAX1977 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁當前第26頁第27頁第28頁第29頁第30頁第31頁第32頁
M
High-Effic ienc y, Quad Output, Main Power-
S upply Controllers for Notebook Computers
26
______________________________________________________________________________________
When using low-capacity filter capacitors such as
polymer types, capacitor size is usually determined by
the capacity required to prevent V
SAG
and V
SOAR
from
tripping the undervoltage and overvoltage fault latches
during load transients in ultrasonic mode .
For low input-to-output voltage differentials (V
IN
/V
OUT
<2),
additional output capacitance is required to maintain sta-
bility and good efficiency in ultrasonic mode.
The amount of overshoot due to stored inductor energy
can be calculated as:
where I
PEAK
is the peak inductor current.
S tability Considerations
Stability is determined by the value of the ESR zero
(f
ESR
) relative to the switching frequency (f). The point
of instability 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.
Low-ESR capacitors (especially polymer or tantalum),
in widespread use at the time of publication, typically
have ESR zero frequencies lower than of 30kHz. In the
design example used for inductor selection, the ESR
needed to support a specified ripple voltage is found
by the equation:
where LIR is the inductor ripple current ratio and I
LOAD
is the average DC load. Using a LIR = 0.35 and an
average load current of 5A, the ESR needed to support
50mV
P-P
ripple is 28m
.
Do not place high-value ceramic capacitors directly
across the fast-feedback inputs (OUT_ to GND for inter-
nal feedback, FB_ divider point for external feedback)
without taking precautions to ensure stability. Large
ceramic capacitors can have a high-ESR zero frequency
and cause erratic, unstable operation. Adding a discrete
resistor or placing the capacitors a couple of inches
downstream from the junction of the inductor and OUT_
may improve stability.
Unstable operation manifests itself in two related but
distinctly different ways: double pulsing and fast-feed-
back loop instability. Noise on the output or insufficient
ESR may cause double pulsing. Insufficient ESR does
not allow the amplitude of the voltage ramp in the output
signal to be large enough. The error comparator mistak-
enly triggers a new cycle immediately after the 350ns
minimum off-time period has expired. Double pulsing
results in increased output ripple, and can indicate the
presence of loop instability caused by insufficient ESR.
Loop instability results in oscillations or ringing at the
output after line or load perturbations, causing the out-
put voltage to fall below the tolerance limit.
The easiest method for checking stability is to apply a
very fast zero-to-max load transient (refer to the
MAX1999 EV kit data sheet) and observe the output
voltage-ripple envelope for overshoot and ringing.
Monitoring the inductor current with an AC current
probe may also provide some insight. Do not allow
more than one cycle of ringing of under- or overshoot
after the initial step response.
Input Capac itor S elec tion
The input capacitors must meet the input ripple current
(I
RMS
) requirement imposed by the switching current.
The MAX1777/MAX1977/MAX1999 dual switching regu-
lators operate at different frequencies. This interleaves
the current pulses drawn by the two switches and
reduces the overlap time where they add together. The
input RMS current is much smaller in comparison than
with both SMPSs operating in phase. The input RMS cur-
rent varies with load and the input voltage.
The maximum input capacitor RMS current for a single
SMPS is given by:
when V+ = 2 x V
OUT_
(D = 50%), I
RMS
has maximum
current of I
LOAD
/2.
The ESR of the input capacitor is important for deter-
mining capacitor power dissipation. All the power
(I
2RMS
x ESR) heats up the capacitor and reduces effi-
ciency. Nontantalum chemistries (ceramic or OS-CON)
are preferred due to their low ESR and resilience to
power-up surge currents. Choose input capacitors that
exhibit less than +10°C temperature rise at the RMS
input current for optimal circuit longevity. Place the
drains of the high-side switches close to each other to
share common input bypass capacitors.
I
I
V
V
V
V
RMS
LOAD
OUT
OUT
≈
+
(
)
+
_
_
ESR
V
LIR
I
RIPPLE P P
×
LOAD
(
)
=
f
R
C
ESR
ESR
OUT
=
×
×
1
2
π
f
ESR
≤π
f
V
L
×
I
C
V
SOAR
PEAK
×
OUT
=
×
_
2
2
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX1999 | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| MAX1977EEI | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| MAX1999EEI | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| MAX1778 | 32-Bit Digital Signal Controller with ROM 100-LQFP -40 to 85 |
| MAX1880 | Quad-Output TFT LCD DC-DC Converters with Buffer |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1977EEI | 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 |
| MAX1977EEI+ | 功能描述:DC/DC 開關(guān)控制器 Quad Out Main Power Supply Controller 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 |
| MAX1977EEI+T | 功能描述:DC/DC 開關(guān)控制器 Quad Out Main Power Supply Controller 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 |
| MAX1977EEI-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 |
| MAX1977EEI-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。