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参数资料
| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 34/48页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 30 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3811
APPLICATIONS INFORMATION
moves from DRV CC to ground. The resulting dQ/dt is
a current out of DRV CC that is typically much larger
than the control circuit current. In continuous mode,
I GATECHG = f(Q T + Q B ), where Q T and Q B are the gate
charges of the topside and bottom side MOSFETs.
Supplying DRV CC and INTV CC power through the
EXTV CC switch input from an output-derived source
will scale the V IN current required for the driver and
control circuits by a factor of (Duty Cycle)/(Ef?ciency).
For example, in a 20V input to 2.5V output application,
40mA of DRV CC current results in approximately 5mA
of V IN current. This reduces the mid-current ef?ciency
loss from 10% or more (if the driver was powered
directly from V IN ) to only a few percent.
3. I 2 R losses are predicted from the DC resistances of
the fuse (if used), MOSFET, inductor, current sense
resistor, and input and output capacitor ESR. In
continuous mode the average output current ?ows
through L and R SENSE , but is “chopped” between the
topside MOSFET and the synchronous MOSFET. If the
two MOSFETs have approximately the same R DS(ON) ,
then the resistance of one MOSFET can simply be
summed with the resistances of L, R SENSE and ESR to
obtain I 2 R losses. For example, if each R DS(ON) = 5m Ω ,
R L = 1m Ω , R SENSE = 1.5m Ω and R ESR = 4m Ω (sum
of both input and output capacitance losses), then the
total resistance is 16m Ω . This results in losses ranging
from 5.6% to 8.4% as the output current increases
10% ef?ciency degradation in portable systems. It is very
important to include these “system” level losses during
the design phase. The internal battery and fuse resistance
losses can be minimized by making sure that C IN has ad-
equate charge storage and very low ESR at the switching
frequency. A 25W supply will typically require a minimum of
20μF to 40μF of capacitance having a maximum of 20m Ω to
50m Ω of ESR. The LTC3811 2-phase architecture typically
halves this input capacitance requirement over competing
solutions. Other losses including Schottky conduction
losses during dead-time and inductor core losses generally
account for less than 1% total additional loss.
Feedback Loop Compensation
The LTC3811 incorporates a peak current mode control
topology. Peak current mode control provides excellent
line and load transient response, and inherently provides
the best possible phase-to-phase current sharing in
multiphase applications.
The LTC3811 incorporates a true operational error ampli-
?er in the feedback loop, enabling the user the ?exibility
to place poles and zeros at well de?ned frequencies in
the transfer function, thereby optimizing the loop’s AC
response.
The control-to-output transfer function has a pole at the
origin in order to provide DC regulation, and a pole due
to the load resistance and capacitance at:
from 10A to 15A for a 2.5V output. Ef?ciency varies
as the inverse square of V OUT for the same external
components and output power level. The combined
f P(LOAD) =
1
2 π ? R L ? C L
effects of increasingly lower output voltages and higher
currents required by high performance digital systems
The output decoupling capacitor ESR contributes a zero
to the transfer function at:
is not doubling but quadrupling the importance of loss
terms in the switching regulator system!
4. Transition losses apply only to the topside MOSFET(s),
f Z(ESR) =
1
2 π ? ESR ? C L
and become signi?cant only when operating at high
input voltages (typically 15V or greater). Transition
losses can be estimated from:
The transfer function also has a mathematical double pole at
half the switching frequency due to the sampling nature of
current mode control, although the pole-splitting behavior
? R DR MILLER
Translation Loss = ( V IN )
2 I MAX
2
? C
of the LTC3811’s internal slope compensation reduces the
phase shift for frequencies below f SW /2.
Other “hidden” losses such as copper trace and internal
battery resistances can account for an additional 5% to
For most systems, the simple 2-pole, single-zero response
of a Type-II compensation network (shown in Figure 23)
3811f
34
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
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