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参数资料
| 型号： | RC5057MT |
| 厂商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 中文描述： | SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | SOIC-16 |
| 文件页数： | 7/23页 |
| 文件大小： | 215K |
| 代理商： | RC5057MT |
PRODUCT SPECIFICATION
RC5057
REV. 1.2.0 2/10/00
15
MOSFET Selection
This application requires N-channel Logic Level Enhance-
ment Mode Field Effect Transistors. Desired characteristics
are as follows:
Low Static Drain-Source On-Resistance,
RDS,ON < 20m (lower is better)
Low gate drive voltage, VGS = 4.5V rated
Power package with low Thermal Resistance
Drain-Source voltage rating > 15V.
The on-resistance (RDS,ON) is the primary parameter for
MOSFET selection. The on-resistance determines the power
dissipation within the MOSFET and therefore signicantly
affects the efciency of the DC-DC Converter. For details
and a spreadsheet on MOSFET selection, refer to Applica-
tions Bulletin AB-8.
Inductor Selection
Choosing the value of the inductor is a tradeoff between
allowable ripple voltage and required transient response. The
system designer can choose any value within the allowed
minimum to maximum range in order to either minimize rip-
ple or maximize transient performance. The rst order equa-
tion (close approximation) for minimum inductance is:
where:
Vin = Input Power Supply
Vout = Output Voltage
f = DC/DC converter switching frequency
ESR = Equivalent series resistance of all output capacitors in
parallel
Vripple = Maximum peak to peak output ripple voltage budget.
The rst order equation for maximum allowed inductance is:
where:
Co = The total output capacitance
Ipp = Maximum to minimum load transient current
Vtb = The output voltage tolerance budget allocated to load
transient
Dm = Maximum duty cycle for the DC/DC converter
(usually 95%).
Some margin should be maintained away from both Lmin
and Lmax. Adding margin by increasing L almost always
adds expense since all the variables are predetermined by
system performance except for Co, which must be increased
to increase L. Adding margin by decreasing L can be done
by purchasing capacitors with lower ESR. The RC5057 pro-
vides signicant cost savings for the newer CPU systems
that typically run at high supply current.
RC5057 Short Circuit Current Characteristics
The RC5057 protects against output short circuit by turning
off both the high-side and low-side MOSFETs and resetting
softstart. The short circuit limit is set with the R5 resistor, as
given by the formula
with IDetect ≈ 50A, ISC the desired current limit, and RDS,on
the high-side MOSFET’s on resistance. Remember to make
R5 large enough to include the effects of initial tolerance and
temperature variation on the MOSFET’s RDS,on. However,
the value of R5 should be less than 8.3K. If a greater value
is necessary, a lower RDS,on MOSFET should be used
instead. Alternately, use of a sense resistor in series with the
source of the MOSFET, as shown in Figure 6, eliminates this
source of inaccuracy in the current limit. Note the addition of
the diode, which is necessary for proper operation of this cir-
cuit.
As an example, Figure 5 shows the typical characteristic of
the DC-DC converter circuit with an FDB6030L high-side
MOSFET (RDS = 20m maximum at 25°C * 1.25 at 75°C =
25m
) and a 8.2K R5.
Figure 5. RC5057 Short Circuit Characteristic
The converter exhibits a normal load regulation characteristic
until the voltage across the MOSFET exceeds the internal
short circuit threshold of 50A * 8.2K
= 410mV, which
occurs at 410mV/25m
= 16.4A. (Note that this current limit
level can be as high as 410mV/15m
= 27A, if the MOSFET
Lmin
(Vin – Vout)
f
x
Vout
Vin
x
ESR
Vripple
=
Lmax
(Vin – Vout) Dm Vtb
Ipp2
= 2C0
R5
ISC x RDS, on
IDetect
=
V
OUT
(V)
Output Current (A)
0
5
10
15
20
25
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
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相关代理商/技术参数 |
参数描述 |
|---|---|
| RC5057N | 功能描述:开关变换器、稳压器与控制器 DIP-16 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 |
| RC5058 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:High Performance Programmable Synchronous DC-DC Controller for Multi-Voltage Platforms |
| RC5058M | 功能描述:开关变换器、稳压器与控制器 SOIC-24 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 |
| RC5058MT | 功能描述:开关变换器、稳压器与控制器 SOIC-24 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 |
| RC5060 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:ACPI Switch Controller |
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