- 您现在的位置：买卖IC网 > PDF目录13060 > LTC3876IUHF#PBF (Linear Technology)IC CTLR DC/DC DDR DUAL 38-QFN PDF资料下载
参数资料
| 型号： | LTC3876IUHF#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 35/48页 |
| 文件大小： | 0K |
| 描述： | IC CTLR DC/DC DDR DUAL 38-QFN |
| 标准包装： | 52 |
| 应用： | 控制器，DDR，DDR2，DDR3 |
| 输入电压： | 4.5 V ~ 38 V |
| 输出数： | 2 |
| 输出电压： | 可调 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 38-WFQFN 裸露焊盘 |
| 供应商设备封装： | 38-QFN（5x7） |
| 包装： | 管件 |
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页第31页第32页第33页第34页当前第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页
LTC3876
APPLICATIONS INFORMATION
The DTR comparator output is overridden by reverse
inductor current detection (I REV ) and overvoltage (OV)
condition. This means BG will be turned off when SENSE +
is higher than SENSE – (i.e., inductor current is positive),
as long as the OV condition is not present. When inductor
current drops to zero and starts to reverse, BG will turn
back on in forced continuous mode (e.g., the MODE/
PLLIN pin tied to INTV CC , or an input clock is present),
even if DTR is still below half INTV CC . This is to allow the
inductor current to go negative to quickly pull down the
V OUT overshoot. Of course, if the MODE/PLLIN pin is set
to discontinuous mode (i.e., tied to SGND), BG will stay
off as inductor current reverse, as it would with the DTR
feature disabled.
Note that it is expected that this DTR feature will cause
additional loss on the bottom MOSFET, due to its body
diode conduction. The bottom FET temperature may be
higher with a load of frequent and large load steps. This
is an important design consideration. Experiments on the
demo board shows a 20°C increase when a continuous
100% to 50% load step pulse train with 50% duty cycle
and 100kHz frequency is applied to the output.
If not needed, this DTR feature can be disabled by tying
the DTR pin to INTV CC , or simply leave the DTR pin open
so that an internal 2.5A current source will pull itself up
to INTV CC .
Efficiency Considerations
The percent efficiency 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 efficiency and which change would
produce the most improvement. Percentage efficiency
can be expressed as:
%Efficiency = 100% – (L1% + L2% + L3% + ...)
where L1%, L2%, etc. are the individual losses as a per-
centage of input power. Although all dissipative elements
in the circuit produce power losses, several main sources
usually account for most of the losses in LTC3876 circuits:
1. I 2 R loss. These arise from the DC resistances of the
MOSFETs, inductor, current sense resistor and is the ma-
jority of power loss at high output currents. In continu-
ous mode the average output current flows though the
inductor L, but is chopped between the top and bottom
MOSFETs. If the two MOSFETs have approximately the
same R DS(ON) , then the resistance of one MOSFET can
simply be summed with the inductor’s DC resistances
(DCR) and the board traces to obtain the I 2 R loss. For
example, if each R DS(ON) = 8mΩ, R L = 5mΩ, and R SENSE
= 2mΩ the loss will range from 15mW to 1.5W as the
output current varies from 1A to 10A. This results in loss
from 0.3% to 3% a 5V output, or 1% to 10% for a 1.5V
output. Efficiency varies as the inverse square of V OUT
for the same external components and output power
level. The combined effects of lower output voltages
and higher currents load demands greater importance
of this loss term in the switching regulator system.
2. Transition loss. This loss mostly arises from the brief
amount of time the top MOSFET spends in the satura-
tion (Miller) region during switch node transitions. It
depends upon the input voltage, load current, driver
strength and MOSFET capacitance, among other fac-
tors, and can be significant at higher input voltages or
higher switching frequencies.
3. DRV CC current. This is the sum of the MOSFET driver
and INTV CC control currents. The MOSFET driver cur-
rents result 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 DRV CC to ground. The resulting dQ/dt is a
current out of DRV CC that is typically much larger than
the controller I Q current. In continuous mode,
I GATECHG = f ? (Qg (TOP) + Qg (BOT) ),
where Qg (TOP) and Qg (BOT) are the gate charges of the
top and bottom MOSFETs, respectively.
Supplying DRV CC power through EXTV CC could save
several percents of efficiency, especially for high V IN
applications. Connecting EXTV CC to an output-derived
3876f
35
相关PDF资料 |
PDF描述 |
|---|---|
| VI-JTZ-CZ-B1 | CONVERTER MOD DC/DC 2V 10W |
| HSM12DRTS | CONN EDGECARD 24POS DIP .156 SLD |
| LTC1263IS8#TRPBF | IC DC/DC CONV FLASHMEM 12V 8SOIC |
| C0603X7R1C151K | CAP CER 150PF 16V 10% X7R 0201 |
| VI-JTX-CZ-B1 | CONVERTER MOD DC/DC 5.2V 25W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3878EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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 |
| LTC3878EGN#PBF | 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR CTRL SSOP-16 |
| LTC3878EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC3878IGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC3878IGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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。