SW
1
SW
2
CBOOT
3
VCC
4
BIAS
5
SYNC
6
RT
7
PGOOD
8
FB
9
AGND
10
SS/TRK
11
EN
12
VIN
13
VIN
14
PGND
15
PGND
16
PAD
17
U1
LM46002PWP
GND
GND
GND
GND
GND
GND
GND
4.7µF
C13
GND
GND
8.2pF
C14
L2
MSS1260-153MLB
GND
453k
R2
1.00M
R6
249k
R7
100k
R4
0.022µF
C12
DNP
0402 footprint
10µF
C1
10µF
C2
10µF
C3
1µF
C10
10µF
C11
0.47µF
C4
80.6k
R5
DC/DC
5 V: LM46002
Host processor
Vrtc: TPS71718
PMIC: TPS65910A3
Gigabit
PHY rails
2v5: LMZ10501
1v1: TPS72011
DDR3 termination
regulator
TPS51200
5 V
Enable
signal
Gigabit
PHY I/O rail
3v3: TPS73733
24-V input
Enable
signal
Stage 1
Stage 2
Stage 3
System Overview
22
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
2.3.1.3
Power Supplies
The power supplies are realized in three stages. The first stage is a 24-V to 5-V DC/DC to provide an
intermediate 5-V rail to the other two stages. The second stage is a PMIC supplying the host processor,
and the last stage is supplying the two Gigabit PHYs.
図
図
12. TIDA-00204 Power Supply Stages
2.3.1.3.1
24-V to 5-V DC/DC Buck Converter
For this stage, the LM46002 SIMPLE SWITCHER® regulator was chosen. It is an easy-to-use
synchronous step-down DC-DC converter capable of driving up to 2 A of load current from an input
voltage ranging from 3.5 to 60 V. The LM46002 provides exceptional efficiency, output accuracy, and
drop-out voltage in a very small solution size. The family requires few external components. Pin
arrangement allows for a simple, optimum PCB layout.
An extended family is available in various load current options with pin-to-pin compatible packages,
including LM46001.
The schematic of the LM46002 is shown in
.
図
図
13. Schematic of 24-V to 5-V DC/DC Buck Converter With LM46002