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| 型号： | TC126301ECT |
| 元件分类： | 稳压器 |
| 英文描述： | 0.4 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PDSO5 |
| 封装： | EIAJ, SC-74A, SOT-23A, 5 PIN |
| 文件页数： | 8/12页 |
| 文件大小： | 524K |
| 代理商： | TC126301ECT |
2007 Microchip Technology Inc.
DS21372D-page 5
TC125/TC126
4.0
APPLICATIONS
4.1
Input Bypass Capacitors
Adding an input bypass capacitor reduces peak current
transients drawn from the input supply and reduces the
switching noise generated by the regulator. The source
impedance of the input supply determines the size of
the capacitor that should be used.
4.2
Inductor Selection
Selecting the proper inductor value is a trade-off
between physical size and power conversion require-
ments. Lower value inductors cost less, but result in
higher ripple current and core losses. They are also
more prone to saturate since the coil current ramps to
a higher value. Larger inductor values reduce both
ripple current and core losses, but are larger in physical
size and tend to increase the start-up time slightly. The
recommended inductor value for use with the TC125/
126 is 100
μH. Inductors with a ferrite core (or equiva-
lent) are recommended. For highest efficiency, use an
inductor with a series resistance less than 20 m
Ω.
4.3
Internal Transistor Switch Current
Limiting
The peak switch current is equal to the input voltage
divided by the RDSON of the internal switch. The
internal transistor has absolute maximum current rating
of 400 mA with a design limit of 350 mA. A built-in
oscillator frequency doubling circuit guards against
high switching currents. Should the voltage on the LX
pin rise above 1.1V, max while the internal N-channel
switch is ON, the oscillator frequency automatically
doubles to minimize ON time. Although reduced, switch
current still flows because the regulator remains in
operation. Therefore, the LX input is not internally
current limited and care must be taken never to exceed
the 350 mA maximum limit. Failure to observe this will
result in damage to the regulator.
4.4
Output Diode
For best results, use a Schottky diode such as the
MA735, 1N5817, MBR0520L or equivalent. Connect
the diode between the PS and LX pins (TC125) or
SENSE and LX pins (TC126) as close to the IC as
possible. (Do not use ordinary rectifier diodes since the
higher threshold voltages reduce efficiency.)
4.5
Output Capacitor
The effective series resistance of the output capacitor
directly affects the amplitude of the output voltage
ripple. (The product of the peak inductor current and
the ESR determines output ripple amplitude.) There-
fore, a capacitor with the lowest possible ESR should
be selected. Smaller capacitors are acceptable for light
loads or in applications where ripple is not a concern.
The Sprague 595D series of tantalum capacitors are
among the smallest of all low ESR surface mount
capacitors
available.
lists
suggested
components and suppliers.
4.6
Board Layout Guidelines
As with all inductive switching regulators, the TC125/
126 generate fast switching waveforms that radiate
noise. Interconnecting lead lengths should be
minimized to keep stray capacitance, trace resistance,
and radiated noise as low as possible. In addition, the
GND pin, input bypass capacitor, and output filter
capacitor ground leads should be connected to a single
point. The input capacitor should be placed as close to
power and ground pins of the TC125/126 as possible.
TABLE 4-1:
SUGGESTED COMPONENTS AND SUPPLIERS
Type
Inductors
Capacitors
Diodes
Surface Mount
Sumida
CD54 Series
CDR125 Series
Coiltronics
CTX Series
Murata
LQN6C Series
Matsuo
267 Series
Murata
GRM200 Series
Sprague
595D Series
Nichicon
F93 Series
Nihon
EC10 Series
Matsushita
MA735 Series
Through-Hole
Sumida
RCH855 Series
RCH110 Series
Renco
RL1284-12
Sanyo
OS-CON Series
Nichicon
PL Series
ON Semiconductor
1N5817-1N5822
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| TC126301ECTTR | 功能描述:开关变换器、稳压器与控制器 PFM Step-up DC/DC RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
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| TC1263-2.5VAT | 功能描述:低压差稳压器 - LDO 500mA Fixed Out Adj 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 |
| TC1263-2.5VET | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:500 mA, Fixed-Output, CMOS LDO with Shutdown |
| TC1263-2.5VETTR | 功能描述:低压差稳压器 - LDO 500mA Fixed Out Adj 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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