- 您现在的位置：买卖IC网 > PDF目录4957 > LTC1624CS8#PBF (Linear Technology)IC REG CTRLR BST FLYBK INV 8SOIC PDF资料下载
参数资料
| 型号： | LTC1624CS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK INV 8SOIC |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 225kHz |
| 占空比： | 95% |
| 电源电压： | 3.5 V ~ 36 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1333 (CN2011-ZH PDF) |
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页当前第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
LTC1624
APPLICATIO N S I N FOR M ATIO N
what is limiting the efficiency and which change would
produce the most improvement. Percent efficiency can be
expressed as:
%Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percentage
of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC1624 circuits:
1. LTC1624 V IN current
2. I 2 R losses
3. Topside MOSFET transition losses
4. Voltage drop of the Schottky diode
1. The V IN current is the sum of the DC supply current I Q ,
given in the Electrical Characteristics table, and the
MOSFET driver and control currents. The MOSFET
driver 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 INTV CC to ground. The
resulting dQ/dt is a current out of V IN which 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 internal
bottom side MOSFETs.
By powering BOOST from an output-derived source
(Figure 10 application), the additional V IN current
resulting from the topside driver will be scaled by a
factor of (Duty Cycle)/(Efficiency). For example, in a
20V to 5V application, 5mA of INTV CC current results in
approximately 1.5mA of V IN current. This reduces the
midcurrent loss from 5% or more (if the driver was
powered directly from V IN ) to only a few percent.
2. 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 topside main MOSFET/current
shunt and the Schottky diode. The resistances of the
topside MOSFET and R SENSE multiplied by the duty
cycle can simply be summed with the resistance of L to
obtain I 2 R losses. (Power is dissipated in the sense
resistor only when the topside MOSFET is on. The I 2 R
loss is thus reduced by the duty cycle.) For example, at
50% DC, if R DS(ON) = 0.05 ? , R L = 0.15 ? and R SENSE =
0.05 ? , then the effective total resistance is 0.2 ? . This
results in losses ranging from 2% to 8% for V OUT = 5V
as the output current increases from 0.5A to 2A. I 2 R
losses cause the efficiency to drop at high output
currents.
3. Transition losses apply only to the topside MOSFET(s),
and only when operating at high input voltages (typically
20V or greater). Transition losses can be estimated
from:
Transition Loss = 2.5(V IN ) 1.85 (I MAX )(C RSS )(f)
4. The Schottky 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 drop times the diode duty cycle multiplied by
the load current. For example, assuming a duty cycle of
50% with a Schottky diode forward voltage drop of
0.5V, the loss is a relatively constant 5%.
As expected, the I 2 R losses and Schottky diode loss
dominate at high load currents. 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 DC (resistive) 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 discharge C OUT which generates a feedback
error signal. The regulator loop then acts to return V OUT to
its steady-state value. During this recovery time V OUT can
be monitored for overshoot or ringing that would indicate
a stability problem. The I TH external components shown in
the Figure 1 circuit will provide adequate compensation for
most applications.
A second, more severe transient, is caused by switching in
loads with large (>1 μ F) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
11
相关PDF资料 |
PDF描述 |
|---|---|
| GCM30DTKN-S288 | CONN EDGECARD 60POS .156 EXTEND |
| UCD1V331MNL1GS | CAP ALUM 330UF 35V 20% SMD |
| RSC19DRTN-S734 | CONN EDGECARD 38POS DIP .100 SLD |
| UCD1J680MNL1GS | CAP ALUM 68UF 63V 20% SMD |
| GCM30DTKH-S288 | CONN EDGECARD 60POS .156 EXTEND |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1624IS8 | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1624IS8#PBF | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC 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 |
| LTC1624IS8#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LTC1624IS8#TR | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1624IS8#TRPBF | 功能描述:IC REG CTRLR BST FLYBK INV 8SOIC 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
发布紧急采购，3分钟左右您将得到回复。