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参数资料
型号： TPS54352PWPG4
厂商： TEXAS INSTRUMENTS INC
元件分类： 稳压器
英文描述： 6.5 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO16
封装： GREEN, PLASTIC, HTSSOP-16
文件页数： 11/35页
文件大小： 858K
代理商： TPS54352PWPG4
TPS54352,TPS54353
TPS54354,TPS54355
TPS54356,TPS54357
SLVS519A MAY 2004 REVISED OCTOBER 2004
www.ti.com
19
INPUT CAPACITORS
The TPS54356 requires an input decoupling capacitor
and, depending on the application, a bulk input capacitor.
The minimum value for the decoupling capacitor, C9, is
10
F. A high quality ceramic type X5R or X7R is
recommended. The voltage rating should be greater than
the maximum input voltage. Additionally some bulk
capacitance may be needed, especially if the TPS54356
circuit is not located within about 2 inches from the input
voltage source. The value for this capacitor is not critical
but it also should be rated to handle the maximum input
voltage including ripple voltage and should filter the output
so that input ripple voltage is acceptable.
This input ripple voltage can be approximated by equation
10:
DV
IN +
I
OUT(MAX)
0.25
CBULK
sw
) I
OUT(MAX)
ESR
(MAX)
Where IOUT(MAX) is the maximum load current, SW is the
switching frequency, CBULK is the bulk capacitor value and
ESRMAX is the maximum series resistance of the bulk
capacitor.
The maximum RMS ripple current also needs to be
checked. For worst case conditions, this can be
approximated by equation 11:
I
CIN +
I
OUT(MAX)
2
In this case the input ripple voltage would be 140 mV and
the RMS ripple current would be 1.5 A. The maximum
voltage across the input capacitors would be VIN max plus
delta VIN/2. The chosen bulk and bypass capacitors are
each rated for 25 V and the combined ripple current
capacity is greater than 3 A, both providing ample margin.
It is very important that the maximum ratings for voltage
and current are not exceeded under any circumstance.
OUTPUT FILTER COMPONENTS
Inductor Selection
To calculate the minimum value of the output inductor, use
equation 12:
L
(MIN) +
V
OUT
V
IN(MAX) *
V
OUT
V
IN(MAX)
K
IND
I
OUT
sw
KIND is a coefficient that represents the amount of inductor
ripple current relative to the maximum output current. For
designs using low ESR output capacitors such as
ceramics, use KIND = 0.3. When using higher ESR output
capacitors, KIND = 0.2 yields better results.
For this design example use KIND = 0.1 to keep the
inductor ripple current small. The minimum inductor value
is calculated to be 17.96
H. The next highest standard
value is 22
H, which is used in this design.
For the output filter inductor it is important that the RMS
current and saturation current ratings not be exceeded.
The RMS inductor current can be found from equation 13:
I
L(RMS) +
I2
OUT(MAX) )
1
12
V
OUT
V
IN(MAX) *
V
OUT
V
IN(MAX)
L
OUT
sw
0.8
2
(13)
and the peak inductor current can be determined with
equation 14:
(14)
I
L(PK) +
I
OUT(MAX) )
V
OUT
V
IN(MAX) *
V
OUT
1.6
V
IN(MAX)
L
OUT
sw
For this design, the RMS inductor current is 3.007 A and
the peak inductor current is 3.15 A. The chosen inductor
is a Coiltronics DR127220 22
H. It has a saturation
current rating of 7.57 A and a RMS current rating of 4 A,
easily meeting these requirements. A lesser rated inductor
could be used if less margin is desired. In general, inductor
values for use with the TPS54356 are in the range of 6.8
H to 47 H.
Capacitor Requirements
The important design factors for the output capacitor are
dc voltage rating, ripple current rating, and equivalent
series resistance (ESR). The dc voltage and ripple current
ratings cannot be exceeded. The ESR is important
because along with the inductor current it determines the
amount of output ripple voltage. The actual value of the
output capacitor is not critical, but some practical limits do
exist.
Consider the relationship between the desired closed loop
crossover frequency of the design and LC corner
frequency of the output filter. In general, it is desirable to
keep the closed loop crossover frequency at less than 1/5
of
the
switching
frequency.
With
high
switching
frequencies such as the 500-kHz frequency of this design,
internal circuit limitations of the TPS54356 limit the
practical maximum crossover frequency to about 70 kHz.
Additionally, the capacitor type and value must be chosen
to work with the internal compensation network of the
TPS5435x family of dc/dc converters. To allow for
adequate phase gain in the compensation network, the LC
corner frequency should be about one decade or so below
the closed loop crossover frequency. This limits the
minimum capacitor value for the output filter to:
C
OUT(MIN) +
1
L
OUT
( K
2
p
CO
) 2
(10)
(11)
(12)
(15)
相关PDF资料
PDF描述
TPS54356MPWPREP 6.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO16
TPS54357MPWPREP 6.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO16
TPS54354MPWPREP 6.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO16
TPS54362QPWPRQ1 8 A SWITCHING REGULATOR, 2200 kHz SWITCHING FREQ-MAX, PDSO20
TPS54373PWP 6 A SWITCHING REGULATOR, 762 kHz SWITCHING FREQ-MAX, PDSO20
相关代理商/技术参数
参数描述
TPS54352PWPR 功能描述:直流/直流开关调节器 4.5 to 20V Inp 3-A Synch PWM Switch RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5
TPS54352PWPRG4 功能描述:直流/直流开关调节器 4.5 to 20V Inp 3-A Synch PWM Switch RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5
TPS54353 制造商:TI 制造商全称:Texas Instruments 功能描述:4.5V TO 20 V INPUT 3-A OUTPUT SYNCHRONOUS PWM SWITCHER WITH INTEGRATED FET
TPS54353-EP 制造商:TI 制造商全称:Texas Instruments 功能描述:4.5-V TO 20-V INPUT, 3-A OUTPUT SYNCHRONOUS PWM SWITCHES
TPS54353MPWPREP 制造商:TI 制造商全称:Texas Instruments 功能描述:4.5-V TO 20-V INPUT, 3-A OUTPUT SYNCHRONOUS PWM SWITCHES
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