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參數資料
| 型號： | TPS40074RHLT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | 2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC20 |
| 封裝： | GREEN, PLASTIC, QFN-20 |
| 文件頁數： | 17/41頁 |
| 文件大小： | 765K |
| 代理商： | TPS40074RHLT |
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P
QSW + PQSW(CON) ) PQSW(SW) ) PQSW(GATE)
(27)
P
QSW(CON) + RDS(on)
I
D
2
+ RDS(on)
V
O
V
IN
I
LOAD
2
) D
I2
12
(28)
P
QSW(SW) + VIN
f
SW
I
LOAD )
DI
2
Q
gs1 ) Qgd
Ig
)
Q
OSS(SW) ) QOSS(SR)
2
(29)
P
QSW(GATE) + Qg(TOT)
Vg
F
SW
(30)
SLUS617B – APRIL 2005 – REVISED OCTOBER 2006
Equation 27 through Equation 30 can be used to calculate the power loss, P
QSW, in the switching MOSFET
where
P
QSW(CON) = conduction losses
P
QSW(SW) = switching losses
P
QSW(GATE) = gate drive losses
Q
gd = drain source charge or miller charge
Q
gs1 = gate source post threshold charge
I
g = gate drive current
Q
OSS(SW) = switching MOSFET output charge
Q
OSS(SR) = synchronous MOSFET output charge
Qg
(TOT) = total gate charge from zero volts to the gate voltage
Vg = gate voltage
If the total estimated loss is split evenly between conduction and switching losses, Equation 27 and Equation 28
yields preliminary values for RDS(on) and (Qgs1 + Qgd). Note output losses due to QOSS and gate losses have been
ignored here. Once a MOSFET is selected these parameters can be added.
The switching MOSFET for this design should have an RDS(on) of less than 9 m. The sum of Qgd and Qgs
should be approximately 4 nC.
It is not always possible to get a MOSFET which meets both these criteria so a comprise may have to be made.
Also by selecting different MOSFETs close to this criteria and calculating power loss the final selection can be
made. It was found that the PH6325L MOSFET from Philips semiconductor gave reasonable results. This device
has an RDS(on) of 6.3 m and a (Qgs1+Qgd) of 5.9 nC. The estimated conduction losses are 0.178 W and the
switching losses are 0.270 W. This gives a total estimated power loss of 0.448 W versus 0.5 W for our initial
boundary condition. Note this does not include gate losses of approximately 10 mW and output losses of less
than 1 mW.
3.1.5 Rectifier MOSFET, QSR
Similar criteria can be used for the rectifier MOSFET. There is one significant difference. Due to the body diode
conducting, the rectifier MOSFET switches with near zero voltage across its drain and source so effectively with
near zero switching losses. However, there are some losses in the body diode. These are minimized by
reducing the delay time between the transition from the switching MOSFET turn off to rectifier MOSFET turn on
and vice versa. The TPS40074 incorporates TI's proprietary predictive gate drive which helps reduce this delay
to between 10 ns and 20 ns.
24
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| TPS40074RHLTG4 | 功能描述:DC/DC 開關控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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| TPS40075RHLR | 功能描述:DC/DC 開關控制器 Wide Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| TPS40075RHLRG4 | 功能描述:DC/DC 開關控制器 Wide Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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