Rev. C 11/18

3

CAP200DG

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If the measured peak Drain voltage exceeds 950 V, an external 1 kV

ceramic capacitor of value up to 47 pF can also be placed between

D1 and D2 terminals to attenuate the voltage applied between the

CAP200DG terminals during surge. This optional external capacitor

placement is shown as C

EXT in Figure 4. It should be noted that use

of an external capacitor in this way will increase power consumption

slightly due to the C

EXT charge/discharge currents flowing in R1 and

R2 while AC is connected. A C

EXT value of 33 pF will add approximately

0.5 mW at 230 VAC, 50 Hz.

PCB Layout and External Resistor Selection

Figure 5 shows a typical PCB layout configuration for CAP200DG. 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 CAP200DG terminals D1 and D2.

R1 and R2 values are selected according to Table 1.

Under a fault condition where CAP200DG terminals D1 and D2 are

shorted together, each resistor will dissipate a power that can be

calculated from the applied AC voltage and the R1 and R2 values.

For example, in an application with R1=R2=75 kW. If CAP200DG is

shorted out at 265 VAC then R1 and R2 will each dissipate 234 mW.

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

voltage again to allow for the short-circuitry of CAP200DG 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 150 kW.

Safety

CAP200DG meets safety requirements even if placed before the

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

terminals of CAP200DG, the system is identical to existing systems

where CAP200DG 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

Figure 5. Typical PCB Layout.

PI-5610-020515

R1

X Capacitor

R2

≥4 mm

CAP200DG is not used. If redundancy against open circuit faults is

required, two CAP200DG and R1 / R2 configurations can be placed in

parallel.

Discharge Operation

To meet the safety regulations, when the AC supply is disconnected,

CAP200DG will discharge the X capacitor to the safety extra low

voltage (SELV) levels according to the above functional description.

Although there are no specific safety requirements below SELV,

CAP200DG still continues the discharge until the X capacitor is fully

discharged. As such CAP200DG can be safely used at low input

voltages such as the common industrial 18 VAC and 24 VAC supply

rails while retaining X capacitor discharge when the AC source is

disconnected.