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参数资料
| 型号： | LM3350MMX/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHED CAPACITOR CONVERTER, 1100 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | MINI, SO-8 |
| 文件页数： | 8/10页 |
| 文件大小： | 278K |
| 代理商： | LM3350MMX/NOPB |
Detailed Operation
OPERATING PRINCIPLE
The LM3350 is a charge-pump voltage converter that pro-
vides a voltage conversion ratio of 3/2 in step-up mode and
a conversion ratio of 2/3 in the step-down mode. Thus it can
be used in the step-down mode to provide a 3.3V output
from a regulated 5V input or in the step-up mode to provide
a 5V output from a regulated 3.3V input. Other values of
input voltages can be used as long as they are within the
limits.
The LM3350 contains an array of CMOS switches which are
operated in a certain sequence to provide the step-up or
step-down of the input supply. An internal RC oscillator
provides the timing signals.
Energy transfer and storage are provided by four inexpen-
sive ceramic capacitors. The selection of these capacitors is
explained in the Capacitor Selection section under Applica-
tion Information.
STEP-UP APPLICATIONS NEED AN EXTRA DIODE
The LM3350 is biased from pin V
high. Thus for step-up
applications, an external Schottky diode (D1) is needed to
supply power to V
high during startup (See Figure 2). Note
that during shutdown, this diode will provide a DC path from
V
in to Vout. The load may therefore continue to draw current
from the input voltage source. This Schottky diode is not
required for step-down applications (See Figure 3).
SHUTDOWN MODE
When ENABLE is a logic low (ground), the LM3350 enters a
low power shutdown mode. In this mode, all circuitry is
disabled and therefore, all switching action stops. During
shutdown, the current consumption drops to 250 nA (typical).
When ENABLE is a logic high, (i.e. 3.3V for step-up mode
and 5.0V for step-down mode), the LM3350 returns to nor-
mal operation.
Application Information
CAPACITOR SELECTION
The LM3350 requires four capacitors: an input bypass ca-
pacitor (connected between V
in and ground), an output hold
capacitor (connected between V
out and ground), and two
sampling capacitors (C1 and C2 in Figures 2, 3). 0.33 F
(±20%) ceramic chip type capacitors are recommended for
all four capacitors. The usable operating frequency should
be greater than 5 MHz for all capacitors.
The input bypass capacitor (C
in) is the least critical. Its value
should be at least that of the sampling capacitors.
While the recommended sampling capacitor values are 0.33
F, other values may be selected. Values other than 0.33 F
affect maximum output current rating and efficiency. Figure 1
shows typical output impedance (Z
out)
versus capacitor
value.
The output hold capacitor value determines the output ripple.
Increasing the value of the hold capacitor decreases the
ripple. The value of this capacitor (C
out) can be calculated
(approximately) based on the output ripple (
V
out) require-
ments from:
where I
load is the load current and fO is the oscillator fre-
quency.
In order to ensure superior performance over the entire
operating temperature range, capacitors made of X7R di-
electric material are suggested. However, capacitors made
of other dielectric materials that still meet the ±20% specifi-
cation over the entire temperature range can also be used.
PRECAUTIONS
The LM3350 is not short circuit protected.
10000211
A. Step-Up Mode
10000212
B. Step-Down Mode
FIGURE 1. Z
out vs. C
LM3350
www.national.com
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3351 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Switched Capacitor Voltage Converter |
| LM3351A WAF | 制造商:Texas Instruments 功能描述: |
| LM3351AM E WAF | 制造商:Texas Instruments 功能描述: |
| LM3351MM | 功能描述:IC REG MULTI CONFIG 50MA 8-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:3.3V 输入电压:4.5 V ~ 24 V PWM 型:- 频率 - 开关:- 电流 - 输出:125mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-6 包装:Digi-Reel® 供应商设备封装:SOT-6 其它名称:MAX1836EUT33#TG16DKR |
| LM3351MM/NOPB | 功能描述:IC REG MULTI CONFIG 50MA 8-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:3.3V 输入电压:4.5 V ~ 24 V PWM 型:- 频率 - 开关:- 电流 - 输出:125mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-6 包装:Digi-Reel® 供应商设备封装:SOT-6 其它名称:MAX1836EUT33#TG16DKR |
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