Rev. E 11/21

3

CAP300DG

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PCB Layout and External Resistor Selection

Figure 6 shows a typical PCB layout configuration for CAP300DG. The

external resistors in this case are divided into two separate surface

mount resistors to distribute loss under fault conditions – for example

where a short-circuit exists between CAP300DG terminals D1 and D2.

Resistors R1 and R2 should also be rated for 50% of the system input

voltage again to allow for the short-circuitry of CAP300DG D1 to D2

pins during single point fault testing.

If lower dissipation or lower voltage across each resistor is required

during fault tests, the total external resistance can be divided into

more discrete resistors, however the total resistance must be equal to

or greater than 54 kW.

Safety

CAP300DG meets safety requirements even if placed before the

system input fuse. If a short-circuit is placed between D1 and D2

terminals of CAP300DG, the system is identical to existing systems

where CAP300DG is not used.

With regard to open circuit tests, it is not possible to create a fault

condition through a single pin fault (for example lifted pin test) since

there are two pins connected to each of D1 and D2. If several pins

are lifted to create an open circuit, the condition is identical to an

open circuit X capacitor discharge resistor in existing systems where

CAP300DG is not used. If redundancy against open circuit faults is

required, two CAP300DG and R1 / R2 configurations can be placed in

parallel.

Discharge Operation

To meet the safety regulations of appliances, when the AC supply is

disconnected, CAP300DG will discharge the X capacitor to <34 V

levels according to the above functional description.

Figure 6. Typical PCB Layout.

PI-5610-020515

R1

X Capacitor

R2

≥4 mm