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| 型号： | LTC1474CMS8 |
| 厂商： | Linear Technology |
| 文件页数： | 10/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.75A 8MSOP |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调 |
| 输入电压： | 3 V ~ 18 V |
| PWM 型： | Burst Mode? |
| 电流 - 输出： | 750mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-MSOP |
LTC1474/LTC1475
APPLICATIO N S I N FOR M ATIO N
? I VIN = ?
? V OUT ? ? V OUT ?
? R 1 + R 2 ? ? ? V IN ? ?
small that this loss is negligible at loads above a
milliamp but at no load accounts for nearly all of the
loss. The second component, the gate charge current,
results from switching the gate capacitance of the
internal P-channel switch. Each time the gate is switched
from high to low to high again, a packet of charge dQ
moves from V IN to ground. The resulting dQ/dt is the
current out of V IN which is typically much larger than the
DC bias current. In continuous mode, I GATECHG = fQ P
where Q P is the gate charge of the internal switch. Both
the DC bias and gate charge losses are proportional to
V IN and thus their effects will be more pronounced at
higher supply voltages.
To minimize no-load supply current, resistor values in the
megohm range should be used. The increase in supply
current due to the feedback resistors can be calculated
from:
?
A 10pF feedforward capacitor across R2 is necessary due
to the high impedances to prevent stray pickup and
improve stability.
V OUT
2. I 2 R losses are predicted from the internal switch,
10pF
R2
inductor and current sense resistor. At low supply
voltages where the switch on-resistance is higher and
the switch is on for longer periods due to higher duty
cycle, the switch losses will dominate. Keeping the peak
LTC1474 V FB
LTC1475
GND
4
1
R1
currents low with the appropriate R SENSE and with
larger inductance helps minimize these switch losses.
At higher supply voltages, these losses are proportional
to load and result in the flat efficiency curves seen in
Figure 1.
3. The catch diode loss is due to the V D I D loss as the diode
conducts current during the off-time and is more pro-
nounced at high supply voltage where the on-time is
short. This loss is proportional to the forward drop.
1474/75 F04
Figure 4. LTC1474/LTC1475 Adjustable Configuration
Low Battery Comparator
The LTC1474/LTC1475 have an on-chip low battery com-
parator that can be used to sense a low battery condition
when implemented as shown in Figure 5. The resistive
divider R3/R4 sets the comparator trip point as follows:
V TRIP = 1 . 23 ? 1 +
However, as discussed in the Catch Diode section,
diodes with lower forward drops often have higher
leakage current, so although efficiency is improved, the
?
?
R 4 ?
R 3 ? ?
no load supply current will increase.
Adjustable Applications
For adjustable versions, the output voltage is programmed
with an external divider from V OUT to V FB (Pin 1) as shown
in Figure 4. The regulated voltage is determined by:
The divided down voltage at the LBI pin is compared to the
internal 1.23V reference. When V LBI < 1.23V, the LBO
output sinks current. The low battery comparator is active
all the time, even during shutdown mode.
V IN
V OUT = 1.23 ? 1+
?
?
R2 ?
R1 ? ?
(4)
R4
LBI
R3
LTC1474/LTC1475
–
+
LBO
1.23V
REFERENCE
1474/75 F05
Figure 5. Low Battery Comparator
10
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| LTC1474CMS8#PBF | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
| LTC1474CMS8#TR | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CMS8#TRPBF | 功能描述:IC REG BUCK ADJ 0.75A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CMS8-3.3 | 功能描述:IC REG BUCK 3.3V 0.75A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CMS8-3.3#PBF | 功能描述:IC REG BUCK 3.3V 0.75A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
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