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参数资料
| 型号： | LT3742EUF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 560kHz |
| 占空比： | 100% |
| 电源电压： | 4 V ~ 30 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： | 24-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
LT3742
APPLICATIONS INFORMATION
I RMS(CIN) =
? V OUT ? ( V IN – V OUT )
voltages,itisalso3×higherathighinputvoltageswhen
compared to the low C RSS device.
Total gate charge, Q G , is closely related to C RSS . Low
gate charge corresponds to a small value of C RSS . Many
manufacturers have MOSFETs advertised as “low gate
charge” devices (which means they are low C RSS devices)
that are specifically designed for low transition loss, and
are ideal for high input voltage applications.
Input Capacitor Selection
For most applications, 10μF to 22μF of input capacitance
per channel will be sufficient. A small 1μF bypass capacitor
between the V IN and ground pins of the LT3742, placed
close to the device, is also suggested for optimal noise
immunity. Step-down regulators draw current from the
input supply in pulses with very fast rise and fall times.
The input capacitor is required to reduce the resulting
voltage ripple at the LT3742 and to force this very high
frequency switching current into a tight local loop, minimiz-
ing EMI. The input capacitor must have low impedance at
the switching frequency to do this effectively, and it must
have an adequate ripple current rating. With two control-
lers operating at the same frequency but with different
phases and duty cycles, calculating the input capacitor
RMS current is not simple. However, a conservative value
is the RMS input current for the channel that is delivering
the most power (V OUT ? I OUT ):
I OUT
V IN
I RMS(CIN) is largest (I OUT /2) when V IN = 2V OUT (at DC =
50%). As the second, lower power channel draws input
current, the input capacitor’s RMS current actually de-
creases as the out-of-phase current cancels the current
drawn by the higher power channel, so choosing an input
capacitor with an RMS ripple current rating of I OUT,MAX /2
is sufficient.
The combination of small size and low impedance (low
equivalent series resistance, or ESR) of ceramic capacitors
make them the preferred choice. The low ESR results in
very low input voltage ripple and the capacitors can handle
plenty of RMS current. They are also comparatively robust
and can be used at their rated voltage. Use only X5R or
X7R types because they retain their capacitance over wider
voltage and temperature ranges than other ceramics.
An alternative to a high value ceramic capacitor is a lower
value (1μF) along with a larger value (10μF to 22μF) elec-
trolytic or tantalum capacitor. Because the input capacitor
is likely to see high surge currents when the input source
is applied, tantalum capacitors should always be surge
rated. The manufacturer may also recommend operation
below the rated voltage of the capacitor. Be sure to place
the 1μF ceramic as close as possible to the N-channel
power MOSFET.
Output Capacitor Selection
A good starting value for output capacitance is to provide
10μF of C OUT for every 1A of output current. For lower
output voltages (under 3.3V) and for applications needing
the best possible transient performance, the ratio should
be 20μF to 30μF of C OUT for every 1A of output current.
X5R and X7R ceramics are an excellent choice for the
output capacitance. Aluminum electrolytics can be used,
but typically the ESR is too large to deliver low output
voltage ripple. Tantalum and newer, lower ESR organic
electrolytic capacitors are also possible choices, and the
manufactures will specify the ESR. Because the volume of
the capacitor determines the ESR, both the size and value
will be larger than a ceramic capacitor that would give you
similar output ripple voltage performance.
The output capacitor filters the inductor ripple current to
generate an output with low ripple. It also stores energy
in order to satisfy transient loads and to stabilize the
3742fa
16
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| LT3743EFE#PBF | 功能描述:IC LED DVR HP CONST CURR 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C |
| LT3743EFE#PBF | 制造商:Linear Technology 功能描述:IC LED DRIVER BUCK TSSOP-28 |
| LT3743EFE#TRPBF | 功能描述:IC LED DVR SYNC STEPDOWN 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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