- 您现在的位置：买卖IC网 > PDF目录1831 > LTC3772EDDB#TRPBF (Linear Technology)IC REG CTRLR BUCK PWM CM 8-DFN PDF资料下载
参数资料
| 型号： | LTC3772EDDB#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 8-DFN |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 占空比： | 100% |
| 电源电压： | 2.75 V ~ 9.8 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
LTC3772
APPLICATIO S I FOR ATIO
V OUT = 0 . 8 V ? ? 1 + B ?
For ceramic capacitor, use X7R or X5R types, do not use
Y5V. The choices include Murata GRM series, TDK C2012
and Taiyo-Yuden JMK series.
Setting Output Voltage
The LTC3772 output voltages are each set by an external
feedback resistor divider carefully placed across the out-
put as shown in Figure 3. The regulated output voltage is
determined by:
? R ?
? R A ?
To improve the frequency response, a feed-forward capaci-
tor, C FF , may be used. Great care should be taken to route
the V FB line away from noise sources, such as the inductor
or the SW line.
V OUT
LTC3772
R B C FF
3
V FB
R A
3772 F03
Figure 3. Setting Output Voltage
Efficiency Considerations
The efficiency of a switching regulator is equal to the out-
put power divided by the input power times 100%. It is often
useful to analyze individual losses to determine what is
limiting the efficiency and which change would produce the
most improvement. Efficiency can be expressed as:
Efficiency = 100% – ( η 1 + η 2 + η 3 + ...)
where η 1, η 2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC3772 circuits: 1) LTC3772 DC bias current,
2) MOSFET gate charge current, 3) I 2 R losses and 4) volt-
age drop of the output diode.
1. The V IN current is the DC supply current, given in the
electrical characteristics, that excludes MOSFET driver
and control currents. V IN current results in a small loss
which increases with V IN .
2. MOSFET gate charge current results from switching the
gate capacitance of the power MOSFET. 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 supply current. In continuous
mode, I GATECHG = (f)(dQ).
3. I 2 R losses are predicted from the DC resistances of the
MOSFET, inductor and current shunt. In continuous
mode the average output current flows through L but is
“chopped” between the P-channel MOSFET (in series
with R SENSE ) and the output diode. The MOSFET R DS(ON)
plus R SENSE multiplied by duty cycle can be summed with
the resistances of L and R SENSE to obtain I 2 R losses.
4. The output diode is a major source of power loss at high
currents and gets worse at high input voltages. The diode
loss is calculated by multiplying the forward voltage
times the diode duty cycle multiplied by the load current.
For example, assuming a duty cycle of 50% with a Schot-
tky diode forward voltage drop of 0.4V, the loss increases
from 0.5% to 8% as the load current increases from 0.5A
to 2A.
5. Transition losses apply to the external MOSFET and
increase at higher operating frequencies and input volt-
ages. Transition losses can be estimated from:
Transition Loss = 2(V IN ) 2 I O(MAX) C RSS (f)
Other losses including C IN and C OUT ESR dissipative losses,
and inductor core losses, generally account for less than
2% total additional loss.
Foldback Current Limiting
As described in the Output Diode Selection, the worst-case
dissipation occurs with a short-circuited output when the
diode conducts the current limit value almost continuously.
3772f
13
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3773EUHF#PBF | IC REG CTRLR BUCK PWM CM 38-QFN |
| LTC3775EMSE#PBF | IC REG CTRLR BUCK PWM VM 16-MSOP |
| LTC3776EGN#TRPBF | IC CNTRLR SYNC DUAL 24-SSOP |
| LTC3778EF#PBF | IC REG CTRLR BUCK PWM CM 20TSSOP |
| LTC3780IUH#PBF | IC REG CTRLR BST PWM CM 32-QFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3772ETS8 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 |
| LTC3772ETS8#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 |
| LTC3772ETS8#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 T/R |
| LTC3772ETS8#TRM | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 T/R |
| LTC3772ETS8#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM TSOT23-8 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
发布紧急采购，3分钟左右您将得到回复。