Shanghai ZLAN Information Technology Co., Ltd Tel: +86-17321037177 http://www.zlmcu.com
27
lm1117-1.8 is better than ZLAN1003, the overall heat dissipation effect is better than
that of the internal voltage regulator. But this approach will increase the cost of
designing a 1.8V regulator. This method is recommended.
2) Slow operation: lower the speed of the chip by SPD0 and SPD1, and reduce the
total required current of VCC18. The effect of this method is not as effective as the
first method, because ZLAN1003 still use the regulating circuit of heating, but the
heat will decrease obviously. This approach eliminates the need for additional
design costs. However, it is important to note that if the user use the baud rate of
115200bps, the method cannot be used because the low-speed operation does not
support 115200bps.
3.6 PCB wiring
PCB wiring don
’t have high requirement. Please note the following points:
1) The crystal should be as close to the pin as possible. Do not let the network line RX-,
RX+, TX-, TX+ pass through the near of the crystal oscillator.
2) RX-, RX+ is a pair of difference lines, TX-, TX+ is a pair of difference lines, and a pair
of difference lines should be taken together to avoid the separated route.
3) When do PCB design for ZLAN1003 chip, if the condition allows it can add 5 large
guide holes at the bottom, this can increase the heat dissipation. Refer to PCB of
SNMP card.
Figure 17 ZLAN1003 Heat Dissipation Design
TXOP1
TXOM1
RXIP1
RXIM1
NET_RX-
NET_TX-
TXOM1
RXIM1
RXIP1
TXOP1
LINK
ACT
VCC33
VCC33
C13
0.1uF
R19
49.9 1%
R15
75
R12
49.9 1%
R14
75
R11
49.9 1%
R21
1K
R16
75
C18
0.1uF
C17
0.1uF
3
1
2
4
8
7
6
5
14
13
12
11
10
9
15
16
U5
PM44_11BG
R22
1K
R13
75
TXP
3
RXP
1
RXM
2
CM1
4
CM4
8
CM3
7
TXM
6
CM2
5
GRE-
9
GRE+
10
YE L+
11
YE L-
12
J5
RJ45
R17
49.9 1%
VCC33