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| 型号： | TPS54350PWPR |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 6.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | GREEN, PLASTIC, HTSSOP-16 |
| 文件页数： | 10/32页 |
| 文件大小： | 762K |
| 代理商： | TPS54350PWPR |
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TPS54350
SLVS456C OCTOBER 2003 REVISED OCTOBER 2004
www.ti.com
18
This pole is used to set the overall gain of the compensated
error amplifier and determines the closed loop crossover
frequency. Since R1 is given as 1 k
and the crossover
frequency is selected as 30 kHz, the desired fINT can be
calculated with equation 24:
INT +
10–0.9
CO
2
And the value for C6 is given by equation 25:
C6
+
1
2
pR1
INT
The first zero, fZ1, is located at one half the output filter LC
corner frequency, so R3 can be calculated from:
R3
+
1
pC6
LC
The second zero, fZ2, is located at the output filter LC
corner frequency, so C8 can be calculated from:
C8
+
1
2
pR1
LC
The first pole, fP1, is located to coincide with the output
filter ESR zero frequency. This frequency is given by:
ESR +
1
2
pR
ESR
C
OUT
where RESR is the equivalent series resistance of the
output capacitor.
In this case, the ESR zero frequency is 35.4 kHz, and R5
can be calculated from:
R5
+
1
2
pC8
ESR
The final pole is placed at a frequency above the closed
loop crossover frequency high enough to not cause the
phase to decrease too much at the crossover frequency
while still providing enough attenuation so that there is little
or no gain at the switching frequency. The fP2 pole location
for this circuit is set to 4 times the closed loop crossover
frequency and the last compensation component value C7
can be derived as follows:
C7
+
1
8
pR3
CO
Note that capacitors are only available in a limited range
of standard values, so the nearest standard value has
been chosen for each capacitor. The measured closed
loop response for this design is shown in Figure 5.
BIAS AND BOOTSTRAP CAPACITORS
Every TPS54350 design requires a bootstrap capacitor,
C3 and a bias capacitor, C4. The bootstrap capacitor must
be 0.1
F. The bootstrap capacitor is located between the
PH pins and BOOT pin. The bias capacitor is connected
between the VBIAS pin and AGND. The value should be
1.0
F. Both capacitors should be high quality ceramic
types with X7R or X5R grade dielectric for temperature
stability. They should be placed as close to the device
connection pins as possible.
LOW-SIDE FET
The TPS54350 is designed to operate using an external
low-side FET, and the LSG pin provides the gate drive
output. Connect the drain to the PH pin, the source to
PGND, and the gate to LSG. The TPS54350 gate drive
circuitry is designed to accommodate most common
n-channel FETs that are suitable for this application. The
SWIFT Designer Software can be used to calculate all the
design parameters for low-side FET selection. There are
some simplified guidelines that can be applied that
produce an acceptable solution in most designs.
The selected FET must meet the absolute maximum
ratings for the application:
Drain-source voltage (VDS) must be higher than the
maximum voltage at the PH pin, which is VINMAX + 0.5 V.
Gate-source voltage (VGS) must be greater than 8 V.
Drain current (ID) must be greater than 1.1 x IOUTMAX.
Drain-source on resistance (rDSON) should be as small as
possible, less than 30 m
is desirable. Lower values for
rDSON result in designs with higher efficiencies. It is
important to note that the low-side FET on time is typically
longer than the high-side FET on time, so attention paid to
low-side
FET
parameters
can
make
a
marked
improvement in overall efficiency.
Total gate charge (Qg) must be less than 50 nC. Again,
lower Qg characteristics result in higher efficiencies.
Additionally, check that the device chosen is capable of
dissipating the power losses.
For this design, a Fairchild FDR6674A 30-V n-channel
MOSFET is used as the low-side FET. This particular FET
is specifically designed to be used as a low-side
synchronous rectifier.
POWER GOOD
The TPS54350 is provided with a power good output pin
PWRGD. This output is an open drain output and is
intended to be pulled up to a 3.3-V or 5-V logic supply. A
10-k
, pull-up resistor works well in this application. The
absolute maximum voltage is 6 V, so care must be taken
not to connect this pull-up resistor to VIN if the maximum
input voltage exceeds 6 V.
(25)
(26)
(27)
(28)
(29)
(30)
(31)
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS54350PWPRG4 | 功能描述:开关变换器、稳压器与控制器 4.5 to 20V Inp 3A Step-Down Converter 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 |
| TPS54352 | 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 |
| TPS54352-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 |
| TPS54352MPWPREP | 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 |
| TPS54352PWP | 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 |
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