Linear Technology DC1680B, Руководство пользователя

Страница: 5 / 28

5
dc1843bfa
DEMO MANUAL DC1843B
DEMONSTRATION CIRCUIT 1842B OPERATION
Board Layout
Proper board layout is crucial for proper LTC4290B/
LTC4271 chipset operation, robustness, and accuracy.
When laying out, pay attention to parts placement, Kelvin
sensing, power paths, and copper fill. It is imperative to
follow the LTC4290B/LTC4271 Layout Guide document
when laying out the board. Contact Linear Technology
Corporation for this document.
Figure 6. DC1842B Digital and Analog Isolation
Isolation and Power Supplies
The LTC4290B/LTC4271 chipset provides communication
across an isolation barrier through a data transformer
(Figure 6). This eliminates the need for expensive opto-
couplers. All digital pins reside on the digital ground refer-
ence and are isolated from the analog PoE supply. A 3.3V
supply for V
DD
and an isolated V
EE
supply are connected
to the DC1842B through the 30-pin connector.
V
DD33
V
DD33
T1
DND
CPD
CND
DPD
AGND
V
EE
DNA
V
EE
V
EE
ISOLATION
WÜRTH 7490100143
CPA
30-PIN
CONNECTOR
DC1842A SIDE DC1680B SIDE
V
DD33
SUPPLY
V
EE
SUPPLY
CNA
DPA
TX
+
RX
–
CT(4)
CT(2)
RX
+
TX
–
TD
+
RD
–
CT(3)
CT
RD
+
TD
–
U1
LTC4271
U2
LTC4290
C23
1µF
C21
0.1µF
R13
100Ω
DC1843A F06
DGND
C19
1µF
100V
D1
SMAJ58A
R14
100Ω
C22
1µF
R15
100Ω
R16
100Ω
R21
100Ω
R35
10Ω
R22
100Ω
R23
100Ω
R24
100Ω
C24, 2nF
2kV
TVS
BULK
C
BULK
+–
+–
+