參數(shù)資料
型號(hào)： TPS40022PWPR
廠商： TEXAS INSTRUMENTS INC
元件分類： 穩(wěn)壓器
英文描述： 0.01 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
封裝： POWERPAD, PLASTIC, HTSSOP-16
文件頁(yè)數(shù)： 8/29頁(yè)
文件大?。?/td> 337K
代理商： TPS40022PWPR
TPS40020
TPS40021
TPS40022
SLUS535 – MARCH 2003
www.ti.com
16
REFERENCE DESIGN
This design used the TPS40020 PWM controller to facilitate a step-down application from 3.3-V to 1.5 V. (see
Figure 6) Design specifications include:
D Input voltage: 2.5 V ≤ VIN ≤ 5.0 V
D Nominal voltage: 3.3 V
D Output voltage VOUT: 1.5 V
D Output current IOUT: 20 A
D Switching frequency: 300 kHz
DESIGN PROCEDURE
Setting the Frequency
Choosing the optimum switching frequency is complicated. The higher the frequency, the smaller the
inductance and capacitance needed, so the smaller the size, but then the the switching losses are higher, the
efficiency is poorer. For this evaluation module, 300 kHz is chosen for reasonable efficiency and size.
A resistor R4, which is connected from pin 7 to ground, programs the oscillator frequency. The approximate
operating frequency is calculated in equation (3)
f
OSC (MHz) +
35.4
R4 (k
W) [
118 k
W
Therefore, a 118-k
resistor is chosen for 300 kHz operation.
Inductance Value
The inductance value can be calculated by equation (2).
L
(min) +
V
OUT
f
I
RIPPLE
1
*
V
OUT
V
IN(max)
where IRIPPLE is the ripple current flowing through the inductor, which affects the output voltage ripple and core
losses.
Based on 20% ripple current and 300 kHz, the inductance value is calculated to 0.76
H and a 0.75-H inductor
(part number is CDEP149–0R7) is chosen. The ESR of this inductor is 1.1 m
and the loss is 440 mW, which
is approximately 1.5% of output power.
C
OUT(min) +
I
RIPPLE
8
f
V
RIPPLE
ESR
OUT +
V
RIPPLE
I
RIPPLE
With 1% output voltage ripple, the needed capacitance is at least 114
F and its ESR should be less than 3.7
m
. Three 2-V, 470-F, POSCAP capacitors from Sanyo are used. The ESR is 10 m each.
The required input capacitance is calculated in equation (5). The calculated value is approximately 348
F.
Three 6.0-V, 330-
F POSCAP capacitors with 10 m ESR are used to handle 10 A of RMS input current.
Additionally, two ceramic capacitors are used to reduce the switching ripple current.
C
IN(min) + IOUT(max)
D
(max)
T
S
V
RIPPLE
(3)
(4)
(5)
(6)
(7)
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TPS40040DRBRG4 功能描述:DC/DC 開關(guān)控制器 Lo Vin Synch Buck DC/DC Cntrlr RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
TPS40040DRBT 功能描述:DC/DC 開關(guān)控制器 Low Vin Synch Buck DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
TPS40040DRBT 制造商:Texas Instruments 功能描述:Peak Reflow Compatible (260 C):Yes
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