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参数资料
| 型号： | TC115301EMT |
| 元件分类： | 稳压器 |
| 英文描述： | 0.4 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | SOT-89, 5 PIN |
| 文件页数： | 7/12页 |
| 文件大小： | 148K |
| 代理商： | TC115301EMT |
4
PFM/PWM Step-up DC/DC Converter
TC115
TC115-1 4/26/99
2001 Microchip Technology Inc.
DS21361A
APPLICATIONS
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.
Inductor Selection
Selecting the proper inductor value is a trade-off be-
tween physical size and power conversion requirements.
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 increse the
start-up time slightly.
Practical inductor values, therefore, range from 50
H to
300
H. Inductors with a ferrite core (or equivalent) are
recommended. For highest efficiency, use an inductor with
a series resistance less than 20 m
.
DETAILED DESCRIPTION
The TC115 is a combination PFM/PWM step-up (boost)
regulator. It is particularly useful in 1, 2, and 3 cell applica-
tions where the required output current is 140 mA or less,
and size/cost issues are a concern. The device operates in
PWM mode when the output load is sufficient to demand a
10% (or greater) duty cycle. While in PWM mode, the TC115
behaves as any other PWM switching regulator, to a guar-
anteed maximum duty cycle of 92%. At low output loads (i.e.
output loads requiring < 10% duty cycle to support); the
TC115 automatically switches to pulse frequency modula-
tion (PFM) operating mode with a fixed duty cycle of 25%,
max, (17%, typical). While in PFM mode, the inductor is
modulated with individual fixed width pulses only as needed
to maintain output voltage. This action reduces supply
current, thereby improving power efficiency at low output
loads.
Input Power and Sensing
The TC115 is powered from the PS input, which
must be
connected to the regulated output as shown in Figure 1. PS
also senses output voltage for closed-loop regulation. Start-
up current is furnished through the inductor when input
voltage is initially applied. This action starts the oscillator,
causing the voltage at the PS input to rise, bootstrapping the
regulator into full operation.
Output Diode
For best results, use a Schottky diode such as the
MA735, 1N5817, EC10 or equivalent. Connect the diode
between the PS and LX pins as close to the IC as possible.
Do not use ordinary rectifier diodes since the higher thresh-
old voltages reduce efficiency.
Low Power Shutdown Mode
The TC115 enters a low power shutdown mode when
SHDN is brought low. While in shutdown, the oscillator is
disabled and the internal switch is shut off. Normal regulator
operation resumes when SHDN is brought high. SHDN may
be tied to the input supply if not used.
Note: Because the
TC115 uses an external diode, a leakage path between the
input voltage and the output node (through the inductor and
diode) exists while the regulator is in shutdown. Care must
be taken in system design to assure the input supply is
isolated from the load during shutdown.
Behavior When VIN is Greater Than the
Factory-Programmed VOUT Setting
The TC115 is designed to operate as a step-up regula-
tor only. As such, VIN is assumed to always be less than the
Figure 1. TC115 Typical Application
factory-programmed VOUT setting (VR). Operating the TC115
with VIN > VR causes regulating action to be suspended (and
corresponding supply current reduction to 9
A, typical) until
VIN is again less than VR. While regulating action is sus-
pended, VIN is connected to VOUT through the series combi-
nation of the inductor and Schottky diode. Care must be
taken to add the appropriate isolation (MOSFET output
switch or post LDO with shutdown) during system design if
this VIN/VOUT leakage path is problematic.
C1
L1
5
4
TC115
1
3
2
SHDN
PS
NC
C2
D1
GND
LX
VOUT
VIN
OFF ON
(Tie to VIN or VOUT
if not used)
+
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC115301EMTTR | 功能描述:开关变换器、稳压器与控制器 PFM/PWM Step-Up 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 |
| TC115331ECT | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PFM/PWM Step-Up DC/DC Converter |
| TC115331EMTTR | 功能描述:开关变换器、稳压器与控制器 PFM/PWM Step-Up 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 |
| TC115501ECT | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PFM/PWM Step-Up DC/DC Converter |
| TC115501EMTTR | 功能描述:开关变换器、稳压器与控制器 PFM/PWM Step-Up 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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