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| 型号： | LTC1878EMS8#TR |
| 厂商： | Linear Technology |
| 文件页数： | 13/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 6 V |
| 输入电压： | 2.65 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 550kHz |
| 电流 - 输出： | 600mA |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-MSOP |
| 其它名称： | LTC1878EMS8TR |
LTC1878
APPLICATIO S I FOR ATIO
L =
V OUT ? 1 ? OUT ?
( f ) ( ? I L )
?
V IN ?
Asecond,moreseveretransientiscausedbyswitchingin
loads with large (>1 μ F) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
with C OUT , causing a rapid drop in V OUT . No regulator can
deliver enough current to prevent this problem if the load
switch resistance is low and it is driven quickly. The only
solution is to limit the rise time of the switch drive so that
the load rise time is limited to approximately (25 ? C LOAD ).
Thus, a 10 μ F capacitor charging to 3.3V would require a
250 μ s rise time, limiting the charging current to about
130mA.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1878. These items are also illustrated graphically in
Design Example
As a design example, assume the LTC1878 is used in a
single lithium-ion battery-powered cellular phone applica-
tion. The input voltage will be operating from a maximum
of 4.2V down to about 2.7V. The load current requirement
is a maximum of 0.3A but most of the time it will be in
standby mode, requiring only 2mA. Efficiency at both low
and high load currents is important. Output voltage is
2.5V. With this information we can calculate L using
equation (1),
1 ? V ?
(3)
Substituting V OUT = 2.5V, V IN = 4.2V, ? I L =120mA and
f = 550kHz in equation (3) gives:
? 1 ?
? = 15 . 3 μ H
thelayoutdiagramofFigure7.Checkthefollowinginyour
layout:
1. Are the signal and power grounds segregated? The
L =
2 . 5 V ?
550 kHz ( 120 mA ) ?
2 . 5 V ?
4 . 2 V ?
R 2 = ? OUT ? 1 ? R 1 = 875 . 5 k ; use 8 87k
LTC1878 signal ground consists of the resistive
divider, the optional compensation network (R C and
C C1 ) and C C2 . The power ground consists of the (–)
plate of C IN , the (–) plate of C OUT and Pin 4 of the
LTC1878. The power ground traces should be kept
short, direct and wide. The signal ground and power
ground should converge to a common node in a star-
ground configuration.
2. Does the V FB pin connect directly to the feedback
resistors? The resistive divider R1/R2 must be con-
nected between the (+) plate of C OUT and signal ground.
3. Does the (+) plate of C IN connect to V IN as closely as
possible? This capacitor provides the AC current to the
internal power MOSFETs.
4. Keep the switching node SW away from sensitive small
A 15 μ H inductor works well for this application. For best
efficiency choose a 1A inductor with less than 0.25 ?
series resistance.
C IN will require an RMS current rating of at least 0.15A at
temperature and C OUT will require an ESR of less than
0.25 ? . In most applications, the requirements for these
capacitors are fairly similar.
For the feedback resistors, choose R1 = 412k. R2 can
then be calculated from equation (2) to be:
? V ?
? 0 . 8 ?
Figure 8 shows the complete circuit along with its effi-
ciency curve.
signal nodes.
13
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| LTC1878EMS8TRPBF | 制造商:Linear Technology 功能描述: |
| LTC1879EGN | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1879EGN#PBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LTC1879EGN#TR | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1879EGN#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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