KIT33771TPLEVB evaluation board,
Rev. 2.0
NXP Semiconductors
15
Getting to know the hardware
3.13 Bus terminal communication
The transformers isolate communication between the MC33771 and the pack controller and between each MC33771. They are protected
against ESD (Z1, Z2, Z3, Z4). There are significant advantages to using transformers for isolation and communication:
•
High degree of voltage isolation
•
Communication rates of 2.0 MHz with very low radiated emissions
•
Ability to force the secondary signals to be true differential reducing radiated emissions
•
Ability to loop the network back to the pack controller
Figure 11. Bus terminal communication
Some component values may be placed and adjusted for EMC purpose: C91 (default 22 pf), C92 (default 22 pF), R107, R108, C68, C69,
and the pi filter made of R105, R106 and C93. By default, all other components (except C91 and C92) are not populated.
TP3
TP4
1
2
1
2
Z3
Z4
TPD1E10B09DPYT
C97
22 pF
C98
22 pF
ESMIT-4180
2
1
3
4
COMM_OUT
COMM_OUT
Pri
Sec
MC33771
RDTX_OUT
RDTX_OUT
RDTX_OUT
RDTX_OUT
RDTX_IN
RDTX_IN