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参数资料
| 型号： | LTC1878EMS8#TR |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 6 V |
| 输入电压： | 2.65 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 550kHz |
| 电流 - 输出： | 600mA |
| 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： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-MSOP |
| 其它名称： | LTC1878EMS8TR |
LTC1878
OPERATIO
Dropout Operation
When the input supply voltage decreases toward the
output voltage, the duty cycle increases toward the maxi-
mum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one
cycle until it reaches 100% duty cycle. The output voltage
will then be determined by the input voltage minus the
voltage drop across the internal P-channel MOSFET and
the inductor.
Low Supply Operation
The LTC1878 is designed to operate down to an input
supply voltage of 2.65V although the maximum allowable
output current is reduced at this low voltage. Figure 1
shows the reduction in the maximum output current as a
function of input voltage for various output voltages.
Another important detail to remember is that at low input
supply voltages, the R DS(ON) of the P-channel switch
increases. Therefore, the user should calculate the power
dissipation when the LTC1878 is used at 100% duty cycle
with a low input voltage (see Thermal Considerations in
the Applications Information section).
Slope Compensation and Inductor Peak Current
Slope compensation provides stability in constant fre-
quency architectures by preventing subharmonic oscilla-
tions at high duty cycles. It is accomplished internally by
adding a compensating ramp to the inductor current
signal at duty cycles in excess of 40%. As a result, the
maximum inductor peak current is reduced for duty cycles
> 40%. This is shown in the decrease of the inductor peak
current as a function of duty cycle graph in Figure 2.
1200
1000
L = 10 μ H
V OUT = 1.5V
1100
1000
V IN = 3.3V
800
V OUT = 3.3V
900
600
V OUT = 2.5V
800
400
200
700
0
2.5
3.5
4.5 5.5 6.5
7.5
600
0
20
40
60
80
100
INPUT VOLTAGE (V)
1878 F01
Figure 1. Maximum Output Current vs Input Voltage
APPLICATIO S I FOR ATIO
The basic LTC1878 application circuit is shown on the first
page. External component selection is driven by the load
requirement and begins with the selection of L followed by
C IN and C OUT .
Inductor Value Calculation
The inductor selection will depend on the operating fre-
quency of the LTC1878. The internal nominal frequency is
550kHz, but can be externally synchronized from 400kHz
to 700kHz.
8
DUTY CYCLE (%)
1878 F02
Figure 2. Maximum Inductor Peak Current vs Duty Cycle
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. However, oper-
ating at a higher frequency generally results in lower
efficiency because of increased internal gate charge losses.
The inductor value has a direct effect on ripple current. The
ripple current ? I L decreases with higher inductance or
frequency and increases with higher V IN or V OUT .
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1878EMS8TRPBF | 制造商:Linear Technology 功能描述: |
| LTC1879EGN | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP 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 |
| LTC1879EGN#PBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP 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 |
| LTC1879EGN#TR | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP 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 |
| LTC1879EGN#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1.2A 16SSOP 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 |
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