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| 型号： | LTC3865EFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 27/38页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38TSSOP |
| 特色产品： | LTC3865 Dual Synchronous Controllers |
| 标准包装： | 50 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 880kHz |
| 占空比： | 95% |
| 电源电压： | 4.5 V ~ 38 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 ~ 125°C |
| 封装/外壳： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3865/LTC3865-1
APPLICATIONS INFORMATION
The I TH series R C -C C ?lter sets the dominant pole-zero
loop compensation. The values can be modi?ed slightly
(from 0.5 to 2 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 selected
because the various types and values determine the loop
gain and phase. An output current pulse of 20% to 80%
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 without break-
ing the feedback loop. Placing a power MOSFET directly
across the output capacitor and driving the gate with an
appropriate signal generator is a practical way to produce
a realistic load step condition. The initial output voltage
step resulting from the step change in output current may
not be within the bandwidth of the feedback loop, so this
signal cannot be used to determine phase margin. This
is why it is better to look at the I TH pin signal which is in
the feedback loop and is the ?ltered and compensated
control loop response. The gain of the loop will be in-
creased by increasing R C and the bandwidth of the loop
will be increased by decreasing C C . If R C is increased by
the same factor that C C is decreased, the zero frequency
will be kept the same, thereby keeping the phase shift the
same in the most critical frequency range of the feedback
loop. The output voltage settling behavior is related to the
stability of the closed-loop system and will demonstrate
the actual overall supply performance.
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
alter its delivery of current quickly enough to prevent this
sudden step change in output voltage if the load switch
resistance is low and it is driven quickly. If the ratio of
C LOAD to C OUT is greater than 1:50, the switch rise time
should be controlled 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.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the IC. These items are also illustrated graphically in the
layout diagram of Figure 12. Figure 13 illustrates the
current waveforms present in the various branches of
the 2-phase synchronous regulators operating in the
continuous mode. Check the following in your layout:
1. Are the top N-channel MOSFETs M1 and M3 located
within 1 cm of each other with a common drain con-
nection at C IN ? Do not attempt to split the input de-
coupling for the two channels as it can cause a large
resonant loop.
2. Are the signal and power grounds kept separate? The
combined IC signal ground pin and the ground return
of C INTVCC must return to the combined C OUT (–) ter-
minals. The V OSENSE and I TH traces should be as short
as possible. The path formed by the top N-channel
MOSFET, Schottky diode and the C IN capacitor should
have short leads and PC trace lengths. The output
capacitor (–) terminals should be connected as close
as possible to the (–) terminals of the input capacitor
by placing the capacitors next to each other and away
from the Schottky loop described above.
3. Do the LTC3865 V OSENSE pins connect to the (+) terminals
of C OUT ? The connections between the V OSENSE pins
and C OUT should not be along the high current input
feeds from the input capacitor(s).
4. Are the SENSE + and SENSE – leads routed together with
minimum PC trace spacing? The ?lter capacitor between
SENSE + and SENSE – should be as close as possible
to the IC. Ensure accurate current sensing with Kelvin
connections at the sense resistor or inductor, whichever
is used for current sensing.
5. Is the INTV CC decoupling capacitor connected close to
the IC, between the INTV CC and the power ground pins?
This capacitor carries the MOSFET drivers current peaks.
An additional 1μF ceramic capacitor placed immediately
next to the INTV CC and PGND pins can help improve
noise performance substantially.
3865fb
27
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3865EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3865EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-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) |
| LTC3865EUH-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3865EUH-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-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) |
| LTC3865IFE#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:2,500 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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