- 您现在的位置：买卖IC网 > PDF目录15303 > LTC3778EF#TR (Linear Technology)IC REG CTRLR BUCK PWM CM 20TSSOP PDF资料下载
参数资料
| 型号： | LTC3778EF#TR |
| 厂商： | Linear Technology |
| 文件页数： | 12/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 电源电压： | 4 V ~ 36 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： | 20-TSSOP（0.173"，4.40mm 宽） |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC3778EFTR |
LTC3778
APPLICATIO S I FOR ATIO
load current increases. By lengthening the on-time slightly
as current increases, constant frequency operation can be
maintained. This is accomplished with a resistive divider
from the I TH pin to the V ON pin and V OUT . The values
required will depend on the parasitic resistances in the
specific application. A good starting point is to feed about
25% of the voltage change at the I TH pin to the V ON pin as
shown in Figure 3a. Place capacitance on the V ON pin to
this requires a large inductor. There is a tradeoff between
component size, efficiency and operating frequency.
A reasonable starting point is to choose a ripple current
that is about 40% of I OUT(MAX) . The largest ripple current
occurs at the highest V IN . To guarantee that ripple current
does not exceed a specified maximum, the inductance
should be chosen according to:
? ? ?
L = ?
? ?
V IN ( MAX ) ?
filterouttheI TH variationsattheswitchingfrequency.The
resistor load on I TH reduces the DC gain of the error amp
and degrades load regulation, which can be avoided by
V OUT
? f ? I L ( MAX ) ? ?
1 ?
V OUT ?
?
using the PNP emitter follower of Figure 3b.
R VON1
30k
Once the value for L is known, the type of inductor must be
selected. A variety of inductors designed for high current,
V OUT
R VON2
100k
R C
C C
C VON
0.01 μ F
V ON
LTC3778
I TH
3778 F03a
low voltage applications are available from manufacturers
such as Sumida, Panasonic, Coiltronics, Coilcraft and
Toko.
Schottky Diode D1 Selection
R VON1
3k
(3a)
The Schottky diode D1 shown in Figure 1 conducts during
the dead time between the conduction of the power
MOSFET switches. It is intended to prevent the body diode
V OUT
INTV CC
10k
Q1
2N5087
R VON2
10k
C VON
0.01 μ F
R C
C C
V ON
LTC3778
I TH
3778 F03b
of the bottom MOSFET from turning on and storing charge
during the dead time, which can cause a modest (about
1%) efficiency loss. The diode can be rated for about one
half to one fifth of the full load current since it is on for only
a fraction of the duty cycle. In order for the diode to be
(3b)
Figure 3. Correcting Frequency Shift with Load Current Changes
Inductor Selection
Given the desired input and output voltages, the inductor
value and operating frequency determine the ripple
current:
effective, the inductance between it and the bottom MOS-
FET must be as small as possible, mandating that these
components be placed adjacently. The diode can be omit-
ted if the efficiency loss is tolerable.
C IN and C OUT Selection
The input capacitance C IN is required to filter the square
wave current at the drain of the top MOSFET. Use a low
ESR capacitor sized to handle the maximum RMS current.
? I L = ? OUT ? ? 1 ? OUT ?
? V ? ? V ?
? f L ? ? V IN ?
I RMS ? I OUT ( MAX )
V OUT
V IN
V IN
V OUT
–1
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors and output voltage
ripple. Highest efficiency operation is obtained at low
This formula has a maximum at V IN = 2V OUT , where
I RMS = I OUT(MAX) / 2. This simple worst-case condition is
frequency with small ripple current. However, achieving
3778f
12
相关PDF资料 |
PDF描述 |
|---|---|
| VE-JW4-EY-F4 | CONVERTER MOD DC/DC 48V 50W |
| VI-JWB-EW-F1 | CONVERTER MOD DC/DC 95V 100W |
| H2BXT-10112-B8-ND | JUMPER-H1500TR/A3048B/X 12" |
| ESC19DREI-S93 | CONN EDGECARD 38POS .100 EYELET |
| TVX2G4R7MCD | CAP ALUM 4.7UF 400V 20% AXIAL |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3780EG | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP |
| LTC3780EG#PBF | 功能描述:IC REG CTRLR BST PWM CM 24-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 |
| LTC3780EG#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP T/R |
| LTC3780EG#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 24-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: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 |
| LTC3780EGPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller SSOP24 |
发布紧急采购，3分钟左右您将得到回复。