OUT
16
14
OUT
V
R
R
5.875 V
V
æ
ö
=
´
ç
÷
ç
÷
-
è
ø
IN
1
OUT
2
3
NR
4
EN
5
6
GND
U2
TPS73733DCQ
EN
1
VCON
2
FB
3
SGND
4
VOUT
5
PGND
6
VIN
7
VREF
8
PAD
9
U3
LMZ10501SIL
V5_dc
GND
GND
GND
GND
1µF
C16
OUT
1
NC
2
EN
3
BIAS
4
GND
5
IN
6
PAD
7
U5
TPS72011DRV
GND
GND
GND
V25phy
V11phy
Vddio
Vddio
Vaux2
V5_dc
0
R9
0
R15
0
R8
0
R12
150k
R14
0.1µF
C24
0.1µF
C22
0.1µF
C15
470pF
C21
10µF
C17
10µF
C18
2.2µF
C23
110k
R16
0
R8
System Overview
29
JAJU324B – March 2015 – Revised July 2017
翻訳版
—
最新の英語版資料
http://www-s.ti.com/sc/techlit/TIDU832
Copyright © 2015–2017, Texas Instruments Incorporated
EMI/EMC
規格準拠、産業用温度範囲のデュアルポート・ギガビット・イーサネットの
リファレンス・デザイン
(1)
Estimated power dissipation and max current at 85°C using junction-to-ambient thermal resistance.
表
表
15. 3.3-V and 1.1-V LDO Power Dissipation per Package
DEVICE
INPUT
VOLTAGE
OUTPUT
VOLTAGE
VOLTAGE
DROP
MAX POWER
DISSIPATION
AT 85°C
AMBIENT
TEMPERATURE
R
ɵ
JA
MAX CURRENT
AT 85°C
TPS72011DRV
2.5 V
1.1 V
1.4 V
615 mW
65 K/W
439.29 mA
TPS73733DCQ
5 V
3.3 V
1.7 V
790 mW
(1)
53.1 K/W
464.71 mA
(1)
The 2.5-V rail at LMZ10501 was chosen due to the fact that an LDO with the current needed would be a
very expensive device and would dissipate a significant amount of power. When two PHYs are powered
approximately 526 mA is required, with margin the 1-A LMZ10501 was chosen.
図
図
15. Schematic of Power Supply for Two DP83867IR Gigabit Ethernet PHYs
Use
to calculate the output voltage for the LMZ10501.
(13)
R
14
needs to between 80 and 300 k
Ω
and R
16
can be calculated. R
14
has to be minimum 80 k
Ω
to ensure
that the V
REF
output current loading is not greater than 30
μ
A and the reference voltage is maintained. This
design needed a 2.5-V output voltage and the R
14
was decided to be 150 k
Ω
and the R
16
is now calculated
to 111.1 k
Ω
. A 110-k
Ω
resistor was chosen. A small filter capacitor of 470 pF with a voltage rating of 6.3 V
or 10 V is connected in parallel to R
16
. The input and output capacitors are recommended to be X5R or
X7R.