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參數(shù)資料
| 型號： | MAX15003 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Triple-Output Buck Controller with Tracking/Sequencing |
| 中文描述： | 三輸出buck控制器，提供跟蹤/排序功能 |
| 文件頁數(shù)： | 20/32頁 |
| 文件大?。?/td> | 945K |
| 代理商： | MAX15003 |
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M
Triple-Output Buck Controller with
Tracking/Sequencing
20
______________________________________________________________________________________
Setting the Current Limit
Connect a 25k
to 150k
resistor, R
ILIM
, from ILIM to
SGND to program the valley current-limit threshold
(V
CL
) from 50mV to 300mV. ILIM sources 20μA out to
R
ILIM
. The resulting voltage divided by 10 is the valley
current-limit threshold.
The MAX15003 uses a valley current-sense method for
current limiting. The voltage drop across the low-side
MOSFET due to its on-resistance is used to sense the
inductor current. The voltage drop (V
VALLEY
) across the
low-side MOSFET at the valley point and at I
LOAD
is:
R
DS(ON)
is the on-resistance of the low-side MOSFET,
I
LOAD
is the rated load current, and
I
P-P
is the peak-
to-peak inductor current.
The R
DS(ON)
of the MOSFET varies with temperature.
Calculate the R
DS(ON)
of the MOSFET at its operating
junction temperature at full load using the MOSFET
datasheet. To compensate for this temperature varia-
tion, the 20μA ILIM reference current has a temperature
coefficient of 3333ppm/°C. This allows the valley cur-
rent-limit threshold (V
CL
) to track and partially compen-
sate for the increase in the synchronous MOSFET’s
R
DS(ON)
with increasing temperature. Use the following
equation to calculate R
ILIM
:
Figure 4 illustrates the effect of the MAX15003 ILIM ref-
erence current temperature coefficient to compensate
for the variation of the MOSFET R
DS(ON)
over the oper-
ating junction temperature range.
Power MOSFET Selection
When choosing the MOSFETs, consider the total gate
charge, R
DS(ON)
, power dissipation, the maximum drain-
to-source voltage and package thermal impedance. The
product of the MOSFET gate charge and on-resistance is
a figure of merit, with a lower number signifying better
performance. Choose MOSFETs that are optimized for
high-frequency switching applications. The average gate-
drive current from the MAX15003’s output is proportional
to the frequency and gate charge required to drive the
MOSFET. The power dissipated in the MAX15003 is pro-
portional to the input voltage and the average drive cur-
rent (see the Power Dissipationsection).
Compensation Design Guidelines
The MAX15003 uses a fixed-frequency, voltage-mode
control scheme that regulates the output voltage by dif-
ferentially comparing the “sampled” output voltage
against a fixed reference. The subsequent error voltage
that appears at the error amplifier output (COMP) is
compared against an internal ramp voltage to generate
the required duty cycle of the pulse-width modulator. A
second order lowpass LC filter removes the switching
harmonics and passes the DC component of the pulse-
width-modulated signal to the output. The LC filter,
which has an attenuation slope of -40dB/decade, intro-
duces 180° of phase shift at frequencies above the LC
resonant frequency. This phase shift, in addition to the
inherent 180° of phase shift of the regulator’s self-gov-
erning (negative) feedback system, poses the potential
for positive feedback. The error amplifier and its associ-
ated circuitry are designed to compensate for this insta-
bility to achieve a stable closed-loop system.
The basic regulator loop consists of a power modulator
(comprises the regulator’s pulse-width modulator, asso-
ciated circuitry, and LC filter), an output feedback
divider, and an error amplifier. The power modulator
has a DC gain set by V
IN
/ V
RAMP
, with a double pole
and a single zero set by the output inductance (L), the
output capacitance (C
OUT
), and its equivalent series
resistance (ESR). A second, higher frequency zero also
exists, which is a function of the output capacitor’s ESR
and ESL); though only taken into account when using
very high-quality filter components and/or frequencies
of operation.
R
ILIM
RDS ON
ICL MAX
(
IP P
2
T
C
=
(
)
)
.
×
°
(
)
10
20 1061 3 333 103
25
V
R
I
I
VALLEY
DS ON
(
LOAD
P P
2
=
)
×
VALLEY CURRENT-LIMIT THRESHOLD
AND R
DS(ON)
vs. TEMPERATURE
M
TEMPERATURE (
°
C)
V
L
D
130
110
70
90
-10 10
30
50
-30
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
0.5
-50
150
R
DS(ON)
V
ILIM
R
ILIM
= 25.5k
Figure 4. Current-Limit Trip Point and V
RDS(ON)
vs.
Temperature
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| MAX15003ATM+ | 功能描述:DC/DC 開關(guān)控制器 Triple-Out Buck Ctlr w/Track/Sequence 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 |
| MAX15003ATM+T | 功能描述:DC/DC 開關(guān)控制器 Triple-Out Buck Ctlr w/Track/Sequence 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 |
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| MAX15004AAUE/V+T | 功能描述:電流型 PWM 控制器 Flyback/Boost/SEPIC Power-Supply Ctlr 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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