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参数资料
| 型号： | LTC3828EUH#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 590kHz |
| 占空比： | 99.4% |
| 电源电压： | 4.5 V ~ 28 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： | 32-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3828
APPLICATIONS INFORMATION
Synchronous Switch Duty Cycle =
V IN – V OUT
V IN
the relatively small average current. Larger diodes result
in additional transition losses due to their larger junction
capacitance.
( I MAX DS ( ON ) +
) 2 ( 1 + δ ) R
P MAIN =
? ( f )
+
? V – V V
The MOSFET power dissipations at maximum output
current are given by:
V OUT
V IN
? ? 2 ? ?
( V IN ) 2 ? I MAX ? ( R DR )( C MILLER ) ?
? 1 1 ?
? INTVCC THMIN THMIN ?
C IN and C OUT Selection
The selection of C IN is simpli?ed 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 (V OUT )(I OUT ) product needs to be used in the
formula below to determine the maximum RMS current
requirement. Increasing the output current, drawn from
( ) ( 1 + δ ) R DS ( ON )
P SYNC =
V IN – V OUT
V IN
I MAX
2
the other out-of-phase controller, will actually decrease the
input RMS ripple current from this maximum value (see
Figure 3). The out-of-phase technique typically reduces
where δ is the temperature dependency of R DS(ON) and
R DR (approximately 2Ω) is the effective driver resistance
at the MOSFET’s Miller threshold voltage. V THMIN is the
typical MOSFET minimum threshold voltage.
Both MOSFETs have I 2 R losses while the topside N-channel
equation includes an additional term for transition losses,
which are highest at high input voltages. For V IN < 12V
the high current ef?ciency generally improves with larger
MOSFETs, while for V IN ≥ 12V the transition losses rapidly
increase to the point that the use of a higher R DS(ON) device
with lower C MILLER actually provides higher ef?ciency. 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 R DS(ON) vs Temperature curve, but
δ = 0.005/°C can be used as an approximation for low
voltage MOSFETs.
The Schottky diode D1 shown in Figure 1 conducts during
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 ef?ciency at high V IN . A 1A to 3A Schottky is generally
a good compromise for both regions of operation due to
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
ef?ciency effects that need to be considered in the selec-
tion process. The capacitance value chosen should be
suf?cient to store adequate charge to keep high peak
battery currents down. 20μF to 40μF is usually suf?cient
for a 25W output supply operating at 260kHz. The ESR of
the capacitor is important for capacitor power dissipation
as well as overall battery ef?ciency. 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 coef?cients 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
3828fc
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| LTC3829EFE#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® 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 |
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| LTC3829EUHF#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) |
| LTC3829EUHF#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: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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