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| 型号： | TPS40021PWP |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 0.01 A SWITCHING CONTROLLER, 1100 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | GREEN, PLASTIC, HTSSOP-16 |
| 文件页数： | 16/36页 |
| 文件大小： | 724K |
| 代理商： | TPS40021PWP |
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TPS40020
TPS40021
SLUS535D MARCH 2003 REVISED JULY 2007
www.ti.com
23
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 29) Design specifications include:
D Input voltage: 2.5 V ≤ VIN ≤ 5.0 V
D Nominal output 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)
R
T (kW) +
37.736
103
f
OSC
(kHz)
* 5.09 (kW)
Using equation (2), RT is calculated to be 120 k and 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 24% ripple current and 300 kHz, the inductance value is calculated to 0.71
H and a 0.75-H inductor
(part number is CDEP1490R7) is chosen. The DCR 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 1.2% output voltage ripple, the needed capacitance is at least 109
F and its ESR should be less than
3.75 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 390
F for
a 100-mV input ripple. 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)
1
f
OSC
V
IN(ripple)
(4)
(5)
(6)
(7)
(8)
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| TPS40021PWPG4 | 功能描述:DC/DC 开关控制器 Low Input Sync Buck Cntrlr source/sink 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 |
| TPS40021PWPR | 功能描述:DC/DC 开关控制器 Low Input Sync Buck Cntrlr source/sink 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 |
| TPS40021PWPRG4 | 功能描述:DC/DC 开关控制器 Low Input Sync Buck Cntrlr source/sink 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 |
| TPS40022PWP | 制造商:Texas Instruments 功能描述: |
| TPS40040 | 制造商:TI 制造商全称:Texas Instruments 功能描述:LOW PIN COUNT, LOW VIN (2.5 V TO 5.5 V) SYNCHRONOUS BUCK DC-TO-DC CONTROLLER WITH ENABLE |
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