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参数资料
| 型号： | NCP1117DT19RKG |
| 厂商： | ON SEMICONDUCTOR |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | 1.0 A Low−Dropout Positive Fixed and Adjustable Voltage Regulators |
| 中文描述： | 1.9 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PSSO2 |
| 封装： | LEAD FREE, DPAK-3 |
| 文件页数： | 8/17页 |
| 文件大小： | 178K |
| 代理商： | NCP1117DT19RKG |
NCP1117, NCV1117
http://onsemi.com
8
APPLICATIONS INFORMATION
Introduction
The NCP1117 features a significant reduction in dropout
voltage along with enhanced output voltage accuracy and
temperature stability when compared to older industry
standard threeterminal adjustable regulators. These
devices contain output current limiting, safe operating area
compensation and thermal shutdown protection making
them designer friendly for powering numerous consumer
and industrial products. The NCP1117 series is pin
compatible with the older LM317 and its derivative device
types.
Output Voltage
The typical application circuits for the fixed and
adjustable output regulators are shown in Figures 20 and 21.
The adjustable devices are floating voltage regulators. They
develop and maintain the nominal 1.25 V reference voltage
between the output and adjust pins. The reference voltage is
programmed to a constant current source by resistor R1, and
this current flows through R2 to ground to set the output
voltage. The programmed current level is usually selected to
be greater than the specified 5.0 mA minimum that is
required for regulation. Since the adjust pin current, I
adj
, is
significantly lower and constant with respect to the
programmed load current, it generates a small output
voltage error that can usually be ignored. For the fixed
output devices R1 and R2 are included within the device and
the ground current I
gnd
, ranges from 3.0 mA to 5.0 mA
depending upon the output voltage.
External Capacitors
Input bypass capacitor C
in
may be required for regulator
stability if the device is located more than a few inches from
the power source. This capacitor will reduce the circuit’s
sensitivity when powered from a complex source impedance
and significantly enhance the output transient response. The
input bypass capacitor should be mounted with the shortest
possible track length directly across the regulator’s input
and ground terminals. A 10 F ceramic or tantalum
capacitor should be adequate for most applications.
Figure 20. Fixed Output Regulator
1
2
Output
3
Input
NCP1117
XTXX
+
+
C
out
C
in
I
gnd
Frequency compensation for the regulator is provided by
capacitor C
out
and its use is mandatory to ensure output
stability. A minimum capacitance value of 4.7 F with an
equivalent series resistance (ESR) that is within the limits of
0.25
to 2.2
is required. The capacitor type can be
ceramic, tantalum, or aluminum electrolytic as long as it
meets the minimum capacitance value and ESR limits over
the circuit’s entire operating temperature range. Higher
values of output capacitance can be used to enhance loop
stability and transient response with the additional benefit of
reducing output noise.
Figure 21. Adjustable Output Regulator
1
2
Output
3
Input
NCP1117
XTA
+
+
C
out
C
in
I
adj
R2
+
C
adj
V
ref
R1
Vout
Vref 1
R2
R1
IadjR2
The output ripple will increase linearly for fixed and
adjustable devices as the ratio of output voltage to the
reference voltage increases. For example, with a 12 V
regulator, the output ripple will increase by 12 V/1.25 V or
9.6 and the ripple rejection will decrease by 20 log of this
ratio or 19.6 dB. The loss of ripple rejection can be restored
to the values shown with the addition of bypass capacitor
C
adj
, shown in Figure 21. The reactance of C
adj
at the ripple
frequency must be less than the resistance of R1. The value
of R1 can be selected to provide the minimum required load
current to maintain regulation and is usually in the range of
100 to 200 .
Cadj
1
2
frippleR1
The minimum required capacitance can be calculated
from the above formula. When using the device in an
application that is powered from the AC line via a
transformer and a full wave bridge, the value for C
adj
is:
fripple
120 Hz, R1
120
The value for C
adj
is significantly reduced in applications
where the input ripple frequency is high. If used as a post
regulator in a switching converter under the following
conditions:
, then Cadj
11.1 F
fripple
Figures 10 and 11 shows the level of ripple rejection that
is obtainable with the adjust pin properly bypassed.
50 kHz, R1
120
, then Cadj
0.027 F
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相关代理商/技术参数 |
参数描述 |
|---|---|
| NCP1117DT20 | 功能描述:低压差稳压器 - LDO 2.0V 1A Positive RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCP1117DT20G | 功能描述:低压差稳压器 - LDO 2.0V 1A Positive RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCP1117DT20RK | 功能描述:低压差稳压器 - LDO 2.0V 1A Positive RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCP1117DT20RKG | 功能描述:低压差稳压器 - LDO 2.0V 1A Positive RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCP1117DT25 | 功能描述:低压差稳压器 - LDO 2.5V 1A Positive RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
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