5-23

HV-2405E

R2 = 2.7

Ω, C2 = 330µF)

FIGURE 13. OUTPUT CURRENT vs TEMPERATURE (R1 = 150

Ω,

R2 = 2.7

Ω, C2 = 330µF)

≤30mA)

Fuse

Opens the connection to the power line should the system fail.

Recommended value: 1/4AG

R1 Source Resistor

R1 limits the input current into the HV-2405E. Needs to be

large enough to limit inrush current when C2 is discharged

fully. The maximum inrush current needs to be limited to less

than 2A (Vpeak / R1 < 2A). The equation for power dissipa-

tion in R1 is:

Wirewound resistors are recommended due to their superior

temperature characteristics.

R1 = 150

R2 Series Resistor

R2 limits the input current by boosting the voltage on pin 2

sooner in the cycle.

R2 = 2.7

Ω (5%), 1/4W

C1 Snubber Capacitor

C1 and R1 form a low pass filter that limits the voltage rate of

rise across SA1 (the main current carrying SCR of the HV-

2405E) and therefore its power dissipation.

C1 = 0.1

C2 Pre-Regulator Capacitor

C2 is charged once each line cycle. The post regulator sec-

tion of the HV-2405E is powered by C2 for most of the line

cycle. If the application requires a smaller input voltage, the

value of C2 can be reduced from that shown in Figure 7 or

Figure 8 (see section on “Optimizing Design” for details.

Note; capacitors with high ESR may not store enough

Pd = 2.8

25

20

15

10

5

0

0

102030405060708090

100

OUTPUT CURRENT (mA)

30

IMBEDDED SUPPLY

charge to maintain full load current. The voltage rating of C2

Recommended value = 330

otherwise specified.

C3 Inhibit Capacitor

C3 keeps the HV-2405E from turning on during large input

voltage transients.

C3 = 150pF (10%)

C4 Output Filter Capacitor

C4 is required to maintain the stability of the output stage.

Larger values may help in supplying short momentary

current peaks to the load and improves output ripple during

start-up.

C4 = 10

Z1 Output Voltage Adjust

Z1 is used to set the output voltage above the 5V reference

on pin 5 (see section titled “Setting The Output Voltage” for

more details).

Note, the wattage rating is different when configured as a

dual supply (see dual supply section for on how to determine

wattage).

An ideal application, taking advantage of the low voltage

operation, would be thermostat controls were 28Vrms is sup-

plied via a transformer. In this application the HV-2405E

could deliver a regulated 5V at 40mA with a power dissipa-

tion in R1 (R1= 20

components, in Figure 1, are not required at this low input

voltage level. See Figure 23 and Figure 24 for output vs tem-

perature.

FIGURE 14. LOW INPUT VOLTAGE SUPPLY

HV-2405E

C2

330

µF

C3

150pF

C4

10

µF

C1

0.1

µF

+

-

R1

20

Ω

COMPONENT LIST

FUSE = 1/ 4A, OPTIONAL

R1 = 20

Ω, 1W

C1 = 0.05

µF, AC RATED

C2 = 330

µF, 15V + V

Z1

AC

HIGH

AC

RETURN

28Vrms

FUSE

C3 = 150pF, CERAMIC

C4 = 10

µF, V