UCD3138064RGCT datasheet(81/104 Pages) TI

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12.1.4.7.1 RESET Pin

The RESET pin must have one at least 2.2 µF low ESL capacitor locally decoupled with SGND plane. As

shown in RESET Pin Connection, this capacitor must be placed very close to the device RESET pin. TI highly

recommends using a small resistance (such as 2.2 kΩ) to connect the RESET pin (pin 11 for UCD3138RGC)

with V33DIO (pin 9 for UCD3138RGC). The resistor must be placed close to the RESET pin, as well. The

grounding point of the capacitor must be tied to SGND plane locally by a ground via, which is generally larger

than a signal via.

Figure 12-6. RESET Pin Connection

12.1.4 UART Communication Port

UART is used for communicating between the primary side and secondary side with isolation boundary.

Normally, the communication wires are long. These wires can easily be interfered by EMI and pick up noise

of switching power supplies. First, the wires must be routed without directly exposing the traces to the

switching noise source, and then a termination is needed at the end of the trace, as shown in Termination

for Communication Port (UART). For example, R = 50 Ω, C = 47 pF if they don’t significantly slow down the slew

rate of the signals. When the pins are not used, tie them to the single ground plane SGND.

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UCD3138064

SLUSB72D – MARCH 2013 – REVISED APRIL 2021

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