- 您现在的位置：买卖IC网 > PDF目录1832 > LTC3836EUFD#TRPBF (Linear Technology)IC REG CTRLR BUCK PWM CM 28-QFN PDF资料下载
参数资料
| 型号： | LTC3836EUFD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/30页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 28-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 825kHz |
| 占空比： | 97% |
| 电源电压： | 2.75 V ~ 4.5 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： | 28-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页当前第22页第23页第24页第25页第26页第27页第28页第29页第30页
LTC3836
APPLICATIONS INFORMATION
Ef?ciency Considerations
The 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 ef?ciency and which change would produce the
most improvement. 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, ?ve main sources usually account for most of
the losses in LTC3836 circuits: 1) LTC3836 DC bias cur-
rent, 2) MOSFET gate charge current, 3) I 2 R losses, and
4) transition losses.
1) The V IN (pin) current is the DC supply current, given
in the electrical characteristics, excluding MOSFET
driver currents. V IN current results in a small loss that
increases with V IN .
2) MOSFET gate charge current results 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 SENSE + to ground.
The resulting dQ/dt is a current out of SENSE + , which
is typically much larger than the DC supply current. In
continuous mode, I GATECHG = f ? Q P .
3) I 2 R losses are calculated from the DC resistances of the
MOSFETs and inductor. In continuous mode, the average
output current ?ows through L but is “chopped” between
the top MOSFET and the bottom MOSFET. The MOSFET
R DS(ON) s multiplied by duty cycle can be summed with
the resistance of L to obtain I 2 R losses.
4) Transition losses apply to the top MOSFET and increase
with higher operating frequencies and input voltages.
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.
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V OUT immediately shifts by an amount
equal to ( ? I LOAD )(ESR), where ESR is the effective series
resistance of C OUT . ? I LOAD also begins to charge or dis-
charge C OUT , which generates a feedback error signal. The
regulator loop then returns V OUT to its steady-state value.
During this recovery time, V OUT can be monitored for
overshoot or ringing. OPTI-LOOP ? compensation allows
the transient response to be optimized over a wide range
of output capacitance and ESR values.
The I TH series R C -C C ?lter (see Functional Diagram) sets
the dominant pole-zero loop compensation. The I TH external
components shown in the Typical Application on the front
page of this data sheet will provide an adequate starting point
for most applications. The values can be modi?ed slightly
(from 0.2 to 5 times their suggested values) to optimize
transient response once the ?nal PC layout is done and
the particular output capacitor type and value have been
determined. The output capacitors need to be decided upon
because the various types and values determine the loop
feedback factor gain and phase. An output current pulse of
20% to 100% of full load current having a rise time of 1μs to
10μs will produce output voltage and I TH pin waveforms that
will give a sense of the overall loop stability. The gain of the
loop will be increased by increasing R C , and the bandwidth
of the loop will be increased by decreasing C C . The output
voltage settling behavior is related to the stability of the
closed-loop system and will demonstrate the actual overall
supply performance. For a detailed explanation of optimiz-
ing the compensation components, including a review of
control loop theory, refer to Application Note 76.
A second, more severe transient is caused by switching
in loads with large (>1μF) 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 10μF capacitor would require a 250μs rise time,
limiting the charging current to about 200mA.
3836fb
22
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3838IFE#TRPBF | IC REG CTRLR BUCK PWM CM 38TSSOP |
| LTC3839EUH#PBF | IC REG CTRLR BUCK PWM CM 32-QFN |
| LTC3850IGN-2#TRPBF | IC REG CTRLR BUCK PWM CM 28-SSOP |
| LTC3850IGN#PBF | IC REG CTRLR BUCK PWM CM 28-SSOP |
| LTC3851EGN#PBF | IC REG CTRLR BUCK PWM CM 16-SSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3838EFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3838EFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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) |
| LTC3838EUHF#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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) |
| LTC3838EUHF#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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) |
| LTC3838EUHF-1#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38QFN 制造商:Linear Technology 功能描述:BUCK DUAL CNTRL 4.5-38V 2MHZ 38QFN 制造商:Linear Technology 功能描述:BUCK, DUAL, CNTRL, 4.5-38V, 2MHZ, 38QFN 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, DUAL, BUCK, ADJ, QFN-38, Primary Input Voltage:38V, No. of Outputs:2, Output Current:25A, No. of Pins:38, Operating Temperature Min:-40C, Operating Temperature Max:125C, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential |
发布紧急采购，3分钟左右您将得到回复。