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参数资料
| 型号： | MAX1639 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | High-Speed Step-Down Controller with Synchronous Rectification for CPU Power |
| 中文描述： | 高速、同步整流、降压型控制器，用于CPU电源 |
| 文件页数： | 11/13页 |
| 文件大小： | 108K |
| 代理商： | MAX1639 |
M
High-S peed S tep-Down Controller with
S ync hronous Rec tific ation for CPU Power
______________________________________________________________________________________
11
where f is the switching frequency, between 300kHz
and 1MHz; I
OUT
is the maximum DC load current; and
LIR is the ratio of AC to DC inductor current (typically
0.3). The exact inductor value is not critical and can be
adjusted to make trade-offs among size, transient
response, cost, and efficiency. Although lower inductor
values minimize size and cost, they also reduce efficien-
cy due to higher peak currents. In general, higher
inductor values increase efficiency, but at some point
resistive losses due to extra turns of wire exceed the
benefit gained from lower AC current levels. Load-
transient response can be adversely affected by
high inductor values, especially at low (V
IN
- V
OUT
)
differentials.
The peak inductor current at full load is 1.15 x I
OUT
if
the previous equation is used; otherwise, the peak cur-
rent can be calculated using the following equation:
The inductor’s DC resistance is a key parameter for effi-
cient performance, and should be less than the current-
sense resistor value.
Calc ulating the Current-S ense
Resistor V alue
Calculate the current-sense resistor value according to
the worst-case minimum current-limit threshold voltage
(from the Electrical Characteristics) and the peak
inductor current required to service the maximum load.
Use I
PEAK
from the equation in the section Specifying
the Inductor
The high inductance of standard wire-wound resistors
can degrade performance. Low-inductance resistors,
such as surface-mount power metal-strip resistors, are
preferred. The current-sense resistor’s power rating
should be higher than the following:
In high-current applications, connect several resistors
in parallel as necessary to obtain the desired resis-
tance and power rating.
S elec ting the Output Filter Capac itor
Output filter capacitor values are generally determined
by effective series resistance (ESR) and voltage-rating
requirements, rather than by the actual capacitance
value required for loop stability. Due to the high switch-
ing currents and demanding regulation requirements in
a typical MAX1639 application, use only specialized
low-ESR capacitors intended for switching-
regulator applications, such as AVX TPS, Kemet T510,
Sprague 595D, Sanyo OS-CON, or Sanyo GX series. Do
not use standard aluminum-electrolytic capacitors,
which can cause high output ripple and instability due
to high ESR. The output voltage ripple is usually domi-
nated by the filter capacitor’s ESR, and can be approxi-
mated as I
RIPPLE
x R
ESR
. To ensure stability, the
capacitor must meet both minimum capacitance and
maximum ESR values as given in the following equa-
tions:
Compensating the Feedbac k Loop
The feedback loop needs proper compensation to pre-
vent excessive output ripple and poor efficiency
caused by instability. Compensation cancels unwanted
poles and zeros in the DC-DC converter’s transfer func-
tion that are due to the power-switching and filter ele-
ments with corresponding zeros and poles in the
feedback network. These compensation zeros and
poles are set by the compensation components CC1,
CC2, and RC1. The objective of compensation is to
ensure stability by ensuring that the DC-DC converter’s
phase shift is less than 180° by a safe margin, at the
frequency where the loop gain falls below unity.
Canceling the Sampling Pole
and Output Filter ESR Zero
Compensate the fast-voltage feedback loop by con-
necting a resistor and a capacitor in series from the
CC1 pin to AGND. The pole from CC1 can be set to
cancel the zero from the filter-capacitor ESR. Thus the
capacitor at CC1 should be as follows:
C
V
V
V
V
x R
x f
R
R
OUT
REF
OUT
IN MIN
(
OUT
SENSE
OSC
ESR
SENSE
+
)
>
<
1
I
x R
OUT MAX
(
SENSE
)
2
R
mV
I
SENSE
PEAK
=
85
I
I
V
V
V
f
x L x V
PEAK
OUT
OUT
2
IN MAX
(
OUT
OSC
IN MAX
(
+
)
)
=
(
)
L
V
V
V
V
x f
x I
x LIR
OUT
IN MAX
(
OUT
IN MAX
(
OSC
OUT
)
)
=
(
)
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1639ESE | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1639ESE+ | 功能描述:DC/DC 开关控制器 High Speed Step Down RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1639ESE+T | 功能描述:DC/DC 开关控制器 High Speed Step Down RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1639ESE-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1639EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit the MAX1639 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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