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参数资料
| 型号： | LTC3549EDCB#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.25A 6DFN |
| 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： | 0.61 V ~ 5.5 V |
| 输入电压： | 1.6 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 2.25MHz |
| 电流 - 输出： | 250mA |
| 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-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 6-DFN-EP（2x3） |
LTC3549
APPLICATIO S I FOR ATIO
? V OUT = ? I L ? ESR +
?
8 ? f ? C OUT ?
tions do not offer much relief. Note that the capacitor
manufacturer’s ripple current ratings are often based
on 2000 hours of life. This makes it advisable to further
derate the capacitor, or choose a capacitor rated at a
higher temperature than required. Always consult the
manufacturer if there is any question. The selection of
C OUT is driven by the required effective series resistance
(ESR). Typically, once the ESR requirement for C OUT has
been met, the RMS current rating generally far exceeds
the I RIPPLE(P-P) requirement. The output ripple Δ V OUT
is determined by:
? 1 ?
?
where f = operating frequency, C OUT = output capacitance
and Δ I L = ripple current in the inductor. For a ?xed output
voltage, the output ripple is highest at maximum input
voltage since Δ I L increases with input voltage. Aluminum
electrolytic and dry tantalum capacitors are both available
in surface mount con?gurations. In the case of tantalum,
it is critical that the capacitors are surge tested for use
in switching power supplies. An excellent choice is the
AVX TPS series of surface mount tantalum. These are
specially constructed and tested for low ESR so they give
the lowest ESR for a given volume. Other capacitor types
value, lower cost ceramic capacitors are now available in
smaller case sizes. Their high ripple current, high voltage
rating and low ESR make them ideal for switching regulator
applications. Because the LTC3549’s control loop does not
depend on the output capacitor’s ESR for stable operation,
ceramic capacitors can be used to achieve very low output
ripple and small circuit size.
However, care must be taken when these capacitors are
used at the input and the output. When a ceramic capacitor
is used at the input and the power is supplied by a wall
adapter through long wires, a load step at the output can
induce ringing at the input, V IN . At best, this ringing can
couple to the output and be mistaken as loop instability. At
worst, a sudden inrush of current through the long wires
can potentially cause a voltage spike at V IN , large enough
to damage the part.
When choosing the input and output ceramic capacitors,
choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage charac-
teristics of all the ceramics for a given value and size.
Output Voltage Programming
The output voltage is set by a resistive divider according
to the following formula:
V OUT = 0 . 611 V ? 1 +
includeSanyoPOSCAP,KemetT510andT495series,and
Sprague 593D and 595D series. Consult the manufacturer
for other speci?c recommendations.
?
?
R1 ?
R 2 ? ?
(2)
The external resistive divider is connected to the output,
Using Ceramic Input and Output Capacitors
The LTC3549 typically will require an output capacitor
in the 4.7μF to 10μF range for optimum stability. Higher
V OUT
allowing remote voltage sensing as shown in Figure 1
Table 2 gives 1% resistor values for selected output
voltages.
Table 2. Resistor Values for Selected Output Voltages
LTC3549
V FB
GND
R1
R2
V OUT
0.85V
1.2V
1.5V
1.8V
R1
53.6k
133k
200k
267k
R2
137k
137k
137k
137k
3549 F01
Figure 1. Setting the LTC3549 Output Voltage
3549f
10
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| LTC3550EDHC#PBF | 功能描述:IC CHARGER BATT DUAL 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC3550EDHC#TRPBF | 功能描述:IC CHARGER BATT DUAL 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
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