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參數(shù)資料
| 型號： | MAX8554 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 4.5V to 28V Input. Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications |
| 中文描述： | 4.5V至28V輸入、同步PWM buck控制器，適合DDR端接和負(fù)載點(diǎn)應(yīng)用 |
| 文件頁數(shù)： | 18/24頁 |
| 文件大小： | 483K |
| 代理商： | MAX8554 |
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors do not corrupt the cur-
rent-sense signals seen by LX and PGND. The IC must
be mounted close to the low-side MOSFET with short,
direct traces making a Kelvin-sense connection to the
source and drain terminals. See the
PC Board Layout
section.
Voltage Positioning
The Quick-PWM control architecture responds virtually
instantaneously to transient load changes and elimi-
nates the control loop delay of conventional PWM con-
trollers. Therefore, a large portion of the voltage
deviation during a step load change is from the ESR
(equivalent series resistance) of the output capacitors.
For DDR termination applications, the maximum
allowed voltage deviation is
±
40mV for any output load
transition from sourcing current to sinking current.
Passive voltage positioning adjusts the converter
’
s out-
put voltage based on its load current to optimize tran-
sient response and minimize the required output
capacitance.
Voltage positioning is implemented by connecting a
low ohmic resistor (R4) as shown in
Figure
2.
MOSFET Drivers
The DH and DL drivers are optimized to drive
MOSFETs that can deliver up to 25A output current. An
adaptive dead-time circuit monitors the DL output and
prevents the high-side MOSFET from turning on until
DL is fully off. There must be a low-resistance, low-
inductance path from the DL driver to the MOSFET gate
in order for the adaptive dead-time circuit to work prop-
erly. Otherwise, the sense circuitry in the MAX8553/
MAX8554 can interpret the MOSFET gate as
“
off
”
while
there is actually still charge left on the gate. Use very
short, wide traces measuring 10 squares to 20 squares
(50 mils to 100 mils wide if the MOSFET is 1in from the
MAX8553/MAX8554). This adaptive dead-time delay is
in addition to a fixed delay of 30ns (typ). The dead time
at the other edge (DH turning off) is determined by a
fixed 32ns (typ) internal delay.
Design Procedure
Setting the Output Voltage
For the MAX8553, the output voltage, V
VTT
, is always
50% of V
REFIN
.
For the MAX8554, the output voltage can be adjusted
from 600mV to 3.5V using a resistive voltage-divider
(R2 and R3 in Figures 1 and 3). To set the voltage,
choose a value for R3 in the range of 1k
to 10k
, then
solve for R2 using the following equation:
where V
FB
is 0.6V.
Inductor Selection
Three key inductor parameters must be specified:
inductance value (L), peak inductor current (I
PEAK
),
and DC resistance (R
DC
). A good compromise
between size and efficiency is to set the inductor peak-
to-peak ripple current equal to 30% of the maximum
load current, thus LIR = 0.3. The switching frequency,
input voltage, output voltage, and selected LIR deter-
mine the inductor value as follows:
(
where f
S
is the switching frequency. The exact inductor
value is not critical and can be adjusted in order to
make trade-offs among size, cost, and efficiency.
Lower inductor values minimize size and cost and also
improve transient response but reduce efficiency and
increase output voltage ripple due to higher peak cur-
rents. Higher inductance increases efficiency by reduc-
ing the RMS current.
Find a low-loss inductor with the lowest possible DC
resistance that fits in the allotted dimensions. The
inductor
’
s current saturation rating must exceed the
L
V
V
V
V
x f x I
x LIR
OUT
IN
OUT
IN
LOAD MAX
=
)
(
)
R
R
V
V
OUT
FB
2
3
=
- 1
M
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
18
______________________________________________________________________________________
TIME
I
I
VALLEY
I
LOAD
I
PEAK
Figure
4. Inductor-Current Waveform
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8554EEE | 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8554EEE+ | 功能描述:電流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8554EEE+T | 功能描述:電流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8554EEE-T | 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MAX8554EVKIT | 功能描述:電流型 PWM 控制器 Evaluation Kit for the MAX8553 MAX8554 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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