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参数资料
| 型号： | LTC3547EDDB-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ .3A DL 8DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 5.5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 2.25MHz |
| 电流 - 输出： | 300mA |
| 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-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-DFN（3x2） |
LTC3547
APPLICATIO S I FOR ATIO
Ef?ciency Considerations
The percent ef?ciency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the ef?ciency and which change would
produce the most improvement. Percent ef?ciency can
be expressed as:
% Ef?ciency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc., are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, four sources usually account for the losses in
LTC3547 circuits: 1) V IN quiescent current, 2) switching
losses, 3) I 2 R losses, 4) other system losses.
1) The V IN current is the DC supply current given in the
Electrical Characteristics which excludes MOSFET
driver and control currents. V IN current results in a
small (<0.1%) loss that increases with V IN , even at
no load.
2) The switching current is the sum of the MOSFET driver
and control currents. The MOSFET driver current re-
sults from switching the gate capacitance of the power
MOSFETs. Each time a MOSFET gate is switched from
low to high to low again, a packet of charge dQ moves
from V IN to ground. The resulting dQ/dt is a current out
of V IN that is typically much larger than the DC bias cur-
rent. In continuous mode, I GATECHG = f O (Q T + Q B ), where
Q T and Q B are the gate charges of the internal top and
bottom MOSFET switches. The gate charge losses are
proportional to V IN and thus their effects will be more
pronounced at higher supply voltages.
3) I 2 R losses are calculated from the DC resistances of
the internal switches, R SW , and external inductor,
R L . In continuous mode, the average output current
?ows through inductor L, but is “chopped” between
the internal top and bottom switches. Thus, the series
resistance looking into the SW pin is a function of both
top and bottom MOSFET R DS(ON) and the duty cycle
(DC) as follows:
R SW = (R DS(ON)TOP ) ? (DC) + (R DS(ON)BOT ) ? (1 – DC)
(5)
The R DS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Character-
istics curves. Thus, to obtain I 2 R losses:
I 2 R losses = I OUT2 ? (R SW + R L )
4) Other “hidden” losses, such as copper trace and in-
ternal battery resistances, can account for additional
ef?ciency degradations in portable systems. It is very
important to include these “system” level losses in
the design of a system. The internal battery and fuse
resistance losses can be minimized by making sure that
C IN has adequate charge storage and very low ESR at
the switching frequency. Other losses, including diode
conduction losses during dead-time, and inductor
core losses, generally account for less than 2% total
additional loss.
3547fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3548 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous,400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous, Fixed Output 2.25MHz Step-Down DC/DC Regulator |
| LTC3548-2 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous, Fixed/Adjustable Output, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548A | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548AEDD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
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