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| 型号： | NCP1550SN25T1G |
| 厂商： | ON Semiconductor |
| 文件页数： | 13/17页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 5TSOP |
| 产品变化通告： | Product Obsolescence 01/Jul/2009 |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 690kHz |
| 占空比： | 100% |
| 电源电压： | 2.45 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 ~ 85°C |
| 封装/外壳： | 6-TSOP（0.059"，1.50mm 宽）5 引线 |
| 包装： | 剪切带 (CT) |
| 其它名称： | NCP1550SN25T1GOSCT |
NCP1550
DETAILED OPERATING DESCRIPTION
Detailed Operating Description
The NCP1550 series are step?down (Buck) DC?DC
controllers designed primarily for use in portable
applications powered by battery cells. With an appropriate
external P?channel MOSFET connected, the device can
provide up to 2 A loading current with high conversion
efficiency. The NCP1550 series using an unique control
scheme combines the advantages of Pulse?Frequency?
Modulation (PFM) that can provide excellent efficiency
even at light loading conditions and Constant?Frequency
Pulse?Width?Modulation that can achieve high efficiency
and low output voltage ripple at heavy loads. The NCP1550
working at high switching frequency makes it possible to use
small size surface mount inductor and capacitors to reduce
PCB area and provide better interference handling for noise
sensitive applications. The simplified functional blocks of
the device are shown in Figure 1 and descriptions for each
of the functions are given below.
The Internal Oscillator
An oscillator that governs the switching of a PWM control
cycles is required. NCP1550 have an internal Fixed?
Frequency oscillator. The oscillator frequency is trimmed to
600 kHz with an accuracy of ± 15%. All other timing signals
needed for operation are derived from this oscillator signal.
Voltage Reference and Soft?Start
An internal high accuracy voltage reference is included in
NCP1550. This reference voltage is connected to the
inverting input terminal of the error amplifier, A1, which
compared with portion of the output voltage, V OUT derived
from an integrated voltage divider with precise trimming to
give the required output voltage at ± 2% accuracy. NCP1550
also comes with a built?in soft?start circuit that controls the
ramping up of the internal reference voltage during the
power?up of the converter. This function effectively enables
the output voltage to rise gradually over the specified
soft?start time, 8 msec typical. This prevents the output
voltage from overshooting during startup of the converter.
Voltage Mode Pulse?Width?Modulation (PWM)
Control Scheme
For normal operation, NCP1550 is working in
Constant?Frequency Pulse?Width?Modulation (PWM)
Voltage Mode Control. The controller operates with the
internal oscillator, which generates the required ramp
function to compare with the output of the error amplifier, A1.
The error amplifier compares the internally divided?down
voltage at its output. This error voltage is compared with the
ramp function to generate the control pulse to drive the
external power switch. On a cycle?by?cycle basis, the
greater the error voltage, the longer the switch is held on.
Hence, corresponding corrective action will be made to keep
the output voltage within regulation. Constant?Frequency
PWM reduces output voltage ripple and noise, which is one
of the important characteristics for noise sensitive
communication applications. The high switching frequency
allows small size surface mount components to improve
layout compactness and reduce PC board area, and eliminate
audio and emission interference.
Power?Saving Pulse?Frequency?Modulation (PFM)
Control Scheme
While the loading is decreasing, the converter enters the
Discontinuous Conduction Mode (DCM) operation, which
means the inductor current will decrease to zero before the
next switching cycle starts. In DCM operation, the ON time
for each switching cycle will decrease significantly when
the output current decreases. In order to maintain a high
conversion efficiency even at light load conditions, the ON
time for each switching cycle is closely monitored and for
any ON time smaller than the preset value, 320 nsec, the
switching pulse will be skipped. As a result, when the
loading current is small, the converter will be operating in a
“Constant ON time (320 nsec nominal), variable OFF time”
Pulse?Frequency Modulation (PFM) mode. This innovative
control scheme improves the conversion efficiency for the
system at light load and standby operating conditions hence
extend the operating life of the battery.
Low Power Shutdown Mode
NCP1550 can be disabled whenever the CE pin (Pin 1) is
tied to GND. In shutdown, the internal reference, oscillator,
control circuitry, driver and internal feedback voltage
divider are turned off and the output voltage falls to 0 V.
During the shutdown mode, as most of the internal functions
are stopped and current paths are cut?off, the device
consume extremely small current in this condition.
Under?Voltage Lockout (UVLO)
To prevent operation of the P?Channel MOSFET below
safe input voltage levels, an Undervoltage Lockout is
incorporated into the NCP1550. When the input supply
voltage drops below approximately 2.2 V, the comparator,
CP1 will turn?off the control circuitry and shut the converter
down.
output voltage with the voltage reference to produce an error
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| NCP1550SN27T1 | 功能描述:直流/直流开关转换器 1.8V 2A Buck PWM/PFM RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| NCP1550SN27T1G | 功能描述:直流/直流开关转换器 1.8V 2A Buck PWM/PFM w/Enable Soft Start RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| NCP1550SN30T1 | 功能描述:直流/直流开关转换器 1.8V 2A Buck PWM/PFM RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| NCP1550SN30T1G | 功能描述:直流/直流开关转换器 1.8V 2A Buck PWM/PFM w/Enable Soft Start RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| NCP1550SN33T1 | 功能描述:直流/直流开关转换器 1.8V 2A Buck PWM/PFM RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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