参数资料
| 型号： | SC190CIMLTRT |
| 厂商： | Semtech |
| 文件页数： | 8/18页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.3A 10MLP |
| 标准包装： | 1 |
| 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： | 2.7 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 300mA |
| 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： | 10-VFDFN 裸露焊盘 |
| 包装： | 标准包装 |
| 供应商设备封装： | 10-MLP（3x3） |
| 产品目录页面： | 1357 (CN2011-ZH PDF) |
| 其它名称： | SC190CIMLDKR |
SC190
POWER MANAGEMENT
Applications Information
The output load in switcher mode has to be reduced to a
load that the LDO regulator can support before switching
between the two modes to minimize output voltage
deviation. The transition from LDO regulator mode to
switcher mode requires the load to be kept at levels the
LDO regulator can support for a given time period after
the MODE pin has been pulled low (see Timing Diagram
on page 7).
Protection Features
The SC190 provides the following protection features:
? Thermal Shutdown
? Current Limit
? Overvoltage Protection
? Soft-Start
Thermal Shutdown
The device has a thermal shutdown feature to protect the
device if the junction temperature exceeds 150°C. In
thermal shutdown the PWM drive is disabled tri-stating
the LX output and the front-end LDO is disabled. The
device will not be enabled again until the temperature
reduces by 10°C. If during this time the output falls by
greater than 60% of its regulation voltage a soft start will
be invoked. Thermal shutdown is not active during LDO
mode in order to minimize supply current.
Current Limit
The part has a number of current limit functions. The Front-
end LDO regulator has a current limit set at approximately
500mA, which will protect the FELDO regulator in the
event of a pulsed short circuit.
The PMOS and NMOS power devices of the buck switcher
stage are protected by current limit functions.
In the case of a short to ground on the output, the part
enters frequency foldback mode which causes the
switching frequency to divide by a factor determined by
the output voltage, stopping the inductor current “stair
stepping.”
The back-end LDO regulator has a current limit feature
which will limit the maximum output current during LDO
regulator mode to 50mA.
Overvoltage Protection
Overvoltage protection is provided on the SC190. In the
event of an overvoltage on the output in switcher mode,
the drive to the PWM stage is disabled and the part will
not resume switching until the output voltage has fallen to
below 2% of the regulation voltage.
Soft-Start
The soft-start mode is enabled after every shutdown cycle
to limit in-rush current. In conjunction with the frequency
foldback this controls the maximum current during the
start-up. The switcher’s PMOS current limit is stepped
from 25%, to 50%, to 75%, and then 100% of its typical
value by the internal oscillator. The oscillator frequency
is stepped by 1 / 8 , 1 / 4 , 1 / 2 and 1 under the control of 4
output voltage thresholds causing modulation of the soft-
start timer (see Current Limit description in the Protection
Features section). As soon as the part reaches regulation,
soft-start mode is disabled.
100 Percent Duty Cycle Operation
The SC190C has a 100% duty cycle mode of operation
to allow the switcher to regulate the output at low input
voltage to high output voltage conditions. As the input
supply drops towards the output voltage, the PMOS on-
time increases linearly until a point where the PMOS
FET is on for 100% of the time. Once the PMOS is on DC
the output voltage will track the input voltage minus the
voltage drop across the PMOS power device according to
the following relationship:
V out = V in – I out ( R dsp + R ind )
V out = Output Voltage
V in = Input Voltage
I out = Output current
R dsp = PMOS switch ON resistance
R ind = Series resistance of the inductor
? 2005 Semtech Corp.
8
www.semtech.com
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