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参数资料
| 型号： | TPS40074RHL |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 2 A SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PQCC20 |
| 封装： | PLASTIC, QFN-20 |
| 文件页数： | 19/37页 |
| 文件大小： | 448K |
| 代理商： | TPS40074RHL |
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RKFF +
VUVLO(on) * 0.5
0.018 ) 5
RT
(34)
tSTART w 2p
L
CO
(35)
CSS w
12
10*6
0.7
tSTART
(36)
ISCP w
CO VOUT
tSTART
) ILOAD DI
2
(37)
RILIM w
ISCP RDS(on)MAX ) VILIM(min)
ISINK(max)
(38)
ISCP(min) +
ISINK(min) RILIM(min) * VILIM(max)
RDS(on)MIN
(39)
ISCP(max) +
ISINK(max) RILIM(max) * VILIM(min)
RDS(on)MAX
(40)
CILIM(max) +
VO 0.2
VIN RILIM fSW
(41)
TPS40074
SLUS617–APRIL 2005
This equation gives a RKFF value of 136 k. The closest lower standard value should be selected. For this design
and using E24 resistor range 133 k was chosen. This yields a typical start voltage of 8.52 V.
3.2.3 Soft Start Capacitor
It is good practice to limit the rise time of the output voltage. This helps prevent output overshoot and possible
damage to the load. The selection of the soft start time is arbitrary, but it must meet one condition; it should be
greater than the time constant of the output filter, L and CO. This time is given by Equation 35
The soft start time must be greater than 0.281ms. A time of 5 ms was chosen, this time also helps keep the initial
input current during start up low. The value of CSS can be calculated using Equation 36.
CSS should be greater than 0.09 F, a 0.1 F MLCC was chosen. The calculated start time using this capacitor is
5.8 ms.
3.2.4 Short Circuit Protection, RILIM and CILIM
Short circuit protection is programmed using the RILIM resistor. Selection of this resistor depends on the RDS(on) of
the switching MOSFET selected and the required short circuit current trip point, ISCP. The minimum ISCP is limited
by the inductor peak current, the output voltage, the output capacitor and the soft start time. Their relationship is
given by Equation 37. A short circuit current trip point greater than that calculated by this equation should be
used.
The minimum short circuit current trip point for this design is 16.35 A. This value is used in Equation 38 to
calculate the minimum RILIM value.
RILIM is calculated to be 1.14 k . The closest standard value greater than 1.14 k is chose, this is 1.15 k.To
verify that the short circuit current requirements are met the minimum and maximum short circuit current can be
calculated using Equation 39 and Equation 40.
The minimum ISCP is 17.09 A and the maximum is 29.45 A.
It is recommended to add a small capacitor, CILIM, across RILIM. The value of this capacitor should be less than
that calculated in Equation 41.
This equation yields a maximum CILIM of 44 pF. A value half this is chosen, 22 pF.
26
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| TPS40074RHLR | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| TPS40074RHLRG4 | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| TPS40074RHLT | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| TPS40074RHLTG4 | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| TPS40075 | 制造商:TI 制造商全称:Texas Instruments 功能描述:4.5V TO 18V INPUT 10 PIN SYNCHRONOUS BUCK CONTROLLER WITH POWER GOOD |
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