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参数资料
| 型号： | LTC3728IG |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.209 INCH, PLASTIC, SSOP-28 |
| 文件页数： | 9/36页 |
| 文件大小： | 1661K |
| 代理商： | LTC3728IG |
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LTC3728
17
3728fg
APPLICATIONS INFORMATION
which are highest at high input voltages. For VIN < 20V
the high current efciency generally improves with larger
MOSFETs, while for VIN > 20V the transition losses rapidly
increase to the point that the use of a higher RDS(ON)device
with lower CRSS actually provides higher efciency. The
synchronous MOSFET losses are greatest at high input
voltage when the top switch duty factor is low or during
a short-circuit when the synchronous switch is on close
to 100% of the period.
The term (1 +
δ) is generally given for a MOSFET in the
form of a normalized RDS(ON) vs Temperature curve, but
δ = 0.005/°C can be used as an approximation for low
voltage MOSFETs. CRSS is usually specied in the MOSFET
characteristics. The constant k = 1.7 can be used to esti-
mate the contributions of the two terms in the main switch
dissipation equation.
The Schottky diode D1 shown in Figure 1 conducts dur-
ing the dead time between the conduction of the two
power MOSFETs. This prevents the body diode of the
bottom MOSFET from turning on, storing charge during
the dead time and requiring a reverse recovery period
that could cost as much as 3% in efciency at high VIN.
A 1A to 3A Schottky is generally a good compromise for
both regions of operation due to the relatively small aver-
age current. Larger diodes result in additional transition
losses due to their larger junction capacitance. Schottky
diodes should be placed in parallel with the synchronous
MOSFETs when operating in pulse-skip mode or in Burst
Mode operation.
CIN and COUT Selection
The selection of CIN is simplied by the multiphase ar-
chitecture and its impact on the worst-case RMS current
drawn through the input network (battery/fuse/capacitor).
It can be shown that the worst case RMS current occurs
when only one controller is operating. The controller with
the highest (VOUT)(IOUT) product needs to be used in the
formula below to determine the maximum RMS current
requirement. Increasing the output current, drawn from
the other out-of-phase controller, will actually decrease the
input RMS ripple current from this maximum value (see
Figure 4). The out-of-phase technique typically reduces
the input capacitor’s RMS ripple current by a factor of
30% to 70% when compared to a single phase power
supply solution.
The type of input capacitor, value and ESR rating have
efciency effects that need to be considered in the selec-
tion process. The capacitance value chosen should be
sufcient to store adequate charge to keep high peak
battery currents down. 20μF to 40μF is usually sufcient
for a 25W output supply operating at 200kHz. The ESR of
the capacitor is important for capacitor power dissipation
as well as overall battery efciency. All of the power (RMS
ripple current ESR) not only heats up the capacitor but
wastes power from the battery.
Medium voltage (20V to 35V) ceramic, tantalum, OS-CON
and switcher-rated electrolytic capacitors can be used
as input capacitors, but each has drawbacks: ceramic
voltage coefcients are very high and may have audible
piezoelectric effects; tantalums need to be surge-rated;
OS-CONs suffer from higher inductance, larger case size
and limited surface-mount applicability; electrolytics’
higher ESR and dryout possibility require several to be
used. Multiphase systems allow the lowest amount of
capacitance overall. As little as one 22μF or two to three
10μF ceramic capacitors are an ideal choice in a 20W to
35W power supply due to their extremely low ESR. Even
though the capacitance at 20V is substantially below their
rating at zero-bias, very low ESR loss makes ceramics
an ideal candidate for highest efciency battery operated
systems. Also consider parallel ceramic and high quality
electrolytic capacitors as an effective means of achieving
ESR and bulk capacitance goals.
In continuous mode, the source current of the top N-channel
MOSFET is a square wave of duty cycle VOUT/VIN.Toprevent
large voltage transients, a low ESR input capacitor sized for
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3728IG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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: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 |
| LTC3728IG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP 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: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 |
| LTC3728IUH#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® 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 |
| LTC3728IUH#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: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 |
| LTC3728LCGN | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:否 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: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 |
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