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| 型号： | LX1660CD-TR |
| 厂商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.5 A SWITCHING CONTROLLER, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, SOIC-16 |
| 文件页数： | 2/15页 |
| 文件大小： | 376K |
| 代理商： | LX1660CD-TR |
A D V ANCED PWM C ONTROLLER
LX1660/1661
PRODUCT DA T ABOOK 1996/1997
Copyright 1998
Rev. 1.1a 10/25/2004
10
P RODUCTION D ATA S HEET
USING THE LX1660/61 DEVICES
The LX1660/61 devices are very easy to design with, requiring
only a few simple calculations to implement a given design. The
following procedures and considerations should provide effective
operation for virtually all applications. Refer to the Application
Information section for component reference designators.
SELECTING BETWEEN THE LX1660 AND THE LX1661
In order to provide maximum user versatility, the Advanced PWM
Controller is offered in two versions: the LX1660 and the LX1661.
The LX1661 has a 40mV offset built-in which compensates for
the current sense resistor voltage drop.
This allows optimal
transient response for high-speed systems, such as Pentium Pro
processor power supplies. Overall system design could be more
economical with the LX1661, since output capacitance require-
ments could be eased.
The LX1660 provides a very accurate DC set-point, since the
40mV offset is not included in the device. This device is good for
critical DC applications, such as core power in slower micropro-
cessors and related systems.
See "Theory Of Operation" section earlier in this data sheet.
OUTPUT INDUCTOR
The output inductor should be selected to meet the requirements
of the output voltage ripple in steady-state operation and the
inductor current slew-rate during transient.
The peak-to-peak output voltage ripple is:
V
RIPPLE = ESR * IRIPPLE
where,
I
RIPPLE =
*
I
RIPPLE is the inductor ripple current, L is the output inductor
value and ESR is the Effective Series Resistance of the output
capacitor.
I
RIPPLE should typically be in the range of 20% to 40% of the
maximum output current. Higher inductance results in lower
output voltage ripple, allowing slightly higher ESR to satisfy the
transient specification. Higher inductance also slows the inductor
current slew rate in response to the load-current step change,
I,
resulting in more output-capacitor voltage droop. The inductor-
current slew rates at rise and fall edges are:
T
RISE = L * I / (VIN - VOUT )
and,
T
FALL = L * I / VOUT
When using electrolytic capacitors, the capacitor voltage
droop is usually negligible, due to the large capacitance.
INPUT INDUCTOR
In order to supply faster transient load changes, a smaller output
inductor is needed. However, reducing the size of the output
inductor will result in a higher ripple voltage on the input supply.
This noise on the 5V rail can affect other system components, such
as graphic cards. In this case, it is recommended that a 1 - 1.5H
inductor is used on the input to the regulator, to filter the ripple
on the 5V supply. Ensure that this inductor has the same current
rating as the output inductor.
OUTPUT CAPACITOR
The output capacitor is sized to meet ripple and transient
performance specifications. Effective Series Resistance (ESR) is a
critical parameter. When a step load current occurs, the output
voltage will have a step that equals the product of the ESR and the
current step,
I. In an advance microprocessor power supply, the
output capacitor is usually selected for ESR instead of capacitance
or RMS current capability.
A capacitor that satisfies the ESR
requirement usually has a larger capacitance and current capabil-
ity than strictly needed. The allowed ESR can be found by:
ESR * (I
RIPPLE + I) < VEX
where I
RIPPLE is the inductor ripple current, I is the maximum
load current step change, and V
EX is the allowed output voltage
excursion in the transient. Adaptive voltage positioning increases
the value ofV
EX, allowing a higher ESR value and reducing the cost
of the output capacitor.
Typically, the positioning voltage is 40mV, using the LX1661,
and the transient tolerance is 100mV, resulting in a V
EX of 140mV
(See Figure 3). The LX1660 does not have the positioning voltage
offset, so V
EX is 100mV maximum.
Electrolytic capacitors can be used for the output capacitor, but
are less stable with age than tantalum capacitors. As they age, their
ESR degrades, reducing the system performance and increasing
the risk of failure.
It is recommended that multiple parallel
capacitors be used, so that, as ESR increases with age, overall
performance will still meet the processor's requirements.
There is frequently strong pressure to use the least expensive
components possible, however, this could lead to degraded long-
term reliability, especially in the case of filter capacitors. Linfinity's
demonstration boards use Sanyo MV-GX filter capacitors, which
are aluminum electrolytic, and have demonstrated reliability. The
Oscon series from Sanyo generally provides the very best
performance in terms of long term ESR stability and general
reliability, but at a substantial cost penalty. The MV-GX series
provides excellent ESR performance at a reasonable cost. Beware
of off-brand, very low-cost filter capacitors, which have been
shown to degrade in both ESR and general electrolytic character-
istics over time.
V
IN - VOUT
f
SW * L
V
OUT
V
IN
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相关代理商/技术参数 |
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| LX1660CN | 功能描述:IC PWM MONO SWITCHING REG 16DIP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,000 系列:- 应用:电源，ICERA E400，E450 输入电压:4.1 V ~ 5.5 V 输出数:10 输出电压:可编程 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:42-WFBGA，WLCSP 供应商设备封装:42-WLP 包装:带卷 (TR) |
| LX1661 | 制造商:MICROSEMI 制造商全称:Microsemi Corporation 功能描述:ADVANCED PWM CONTROLLER |
| LX1661CD | 功能描述:IC PWM MONO SWITCHING REG 16SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,000 系列:- 应用:电源，ICERA E400，E450 输入电压:4.1 V ~ 5.5 V 输出数:10 输出电压:可编程 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:42-WFBGA，WLCSP 供应商设备封装:42-WLP 包装:带卷 (TR) |
| LX1661CN | 功能描述:IC PWM MONO SWITCHING REG 16DIP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,000 系列:- 应用:电源，ICERA E400，E450 输入电压:4.1 V ~ 5.5 V 输出数:10 输出电压:可编程 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:42-WFBGA，WLCSP 供应商设备封装:42-WLP 包装:带卷 (TR) |
| LX1662 | 制造商:MICROSEMI 制造商全称:Microsemi Corporation 功能描述:SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC |
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