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參數資料
| 型號： | TPS40042DRCTG4 |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | 3 X 3 MM, GREEN, PLASTIC, SON-10 |
| 文件頁數： | 14/35頁 |
| 文件大小： | 746K |
| 代理商： | TPS40042DRCTG4 |
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R
DS(on_Q2) +
P
CON_Q2
I
L(rms)
2
1 *
V
OUT
V
IN
(18)
Bootstrap Capacitor (C7)
C
BOOST +
20
Q
GS_Q1
V
IN(min)
(19)
VDD Bypass Capacitor (C6)
VDD Filter Resistor (R7)
R
VDD t
V
RVDD(max)
I
DD
+
25 mV
2 mA ) QG_Q1 ) QG_Q2 FSW
(20)
Short Circuit Protection (R2)
V
CS + IL(peak)
R
DS(on_Q1)
(21)
REFIN Divider Resistors
SLUS777 – NOVEMBER 2007
Estimating 50% of total MOSFET losses are in the SR as conduction losses, repeat equation 14. Then calculate
the maximum RDS(on) of the SR by the equation:
For this design IL_RMS = 6 A at 5.5 V to 0.9 V RDS(on_Q2) < 15.9 m. The table below summarizes the MOSFET
requirements.
MOSFET Requirements
PARAMETER
SYMBOL
VALUE
UNITS
High-side FET RDS(on)
RDS(on_Q1)
39
m
High-side FET turn-on charge
QGS2_Q1 +QGD_Q1
10.8
nC
Low-side FET RDS(on)
RDS(on_Q2)
15.9
m
IRF7910 has an RDSON(max) of 15 m at 4.5-V gate drive,QGD of 6.2 nC, and QGS2 of 2 nC.
To ensure proper charging of the upper switch MOSFET gate, limit the ripple voltage on the bootstrap capacitor
to < 5% of the minimum gate drive voltage of 3.0 V.
Based on the IRF7910 MOSFET with a maximum total gate charge of 26 nC, calculate a minimum of 116 nF of
capacitance. The next higher standard value of 220 nF is selected.
Select a 1.0-
F ceramic bypass capacitor for VDD.
An optional resistor in series with VDD helps filter switching noise from the device. Driving the two IRF7910
MOSFETs, with a typical total QG of 17 nC each, we calculate a maximum IDD current of 22 mA. The result of
equation 19, leads to selecting a 1-
resistor, and limits the voltage drop across this resistor to less than 25 mV.
The TPS40042 use the forward drop across the upper switch MOSFET during the ON time to measure the
inductor current. The voltage drop across the high-side MOSFET is given by:
When VIN = 4.5 V to 5.5 V, IL_PEAK = 7.2A. Using the IRF7910 MOSFET, we calculate the peak voltage drop to
be 108 mV. The TPS40042’s internal 3100-ppm temperature coefficient helps compensate for the MOSFET’s
RDS(on) temperature coefficient. For this design, select the short circuit protection voltage threshold of 180 mV by
selecting R2 = OPEN.
In DDR2 applications, VTT=1/2 VDDQ. A 2:1 resistor divider with R11=R12 =100-k
provides VREFIN. If a buffer
is to be used to provide VTT_REF, the output of the buffer should be tied to VREFIN on the TPS40042 to minimize
offset from VTT_REF to VTT.
Copyright 2007, Texas Instruments Incorporated
21
Product Folder Link(s): TPS40042
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| TPS40050 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:WIDE-INPUT SYNCHRONOUS BUCK CONTROLLER |
| TPS40050PWP | 功能描述:DC/DC 開關控制器 Wide Input Vltg Synch Buck Cntrlr 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 |
| TPS40050PWPG4 | 功能描述:DC/DC 開關控制器 Wide Input Vltg Synch Buck Cntrlr 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 |
| TPS40050PWPR | 功能描述:DC/DC 開關控制器 Wide Input Vltg Synch Buck Cntrlr 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 |
| TPS40050PWPRG4 | 功能描述:DC/DC 開關控制器 Wide Input Vltg Synch Buck Cntrlr 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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