PS10 datasheet(5/13 Pages) SUTEX

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PS10/PS11

A051204

UVOFF = VUVL = 1.12 = (VEEUV(off)) x (R2+R3)/(R1+R2+R3)

OVOFF = VOVL = 1.22 = (VEEOV(off)) x R3/(R1+R2+R3)

Where (VEEUV(off)) and (VEEOV(off)) relative to VEE are Under

and Over Voltage Shut Down Threshold points.

If we select a divider current of 100

µA at a nominal oper-

ating input voltage of 50 Volts, then

R1+R2+R3 = 50V/100

µA = 500kΩ

From the second equation, for an OV shut down threshold

of 65V, the value of R3 may be calculated.

OVOFF = 1.22 = (65xR3)/500k

R3 = (1.22x 500k)/65 = 9.38k

The closest 1% value is 9.31k

Ω.

From the first equation, for a UV shut down threshold of

35V, the value of R2 can be calculated.

UVOFF = 1.12 = 35 x (R2+R3)/ 500k

R2 = ((1.12 x 500k)/35) – 9.76k = 6.69k

6.65k

Ω is a standard 1% value

Then

R1 = 500k – R2 – R3 = 484.04k

Ω.

487k

Ω, is a standard 1% value.

From the calculated resistor values the OV and UV start

up threshold voltages can be calculated as follows:

UVON = VUVH = 1.22 = (VEEUV(on)) x (R2+R3)/(R1+R2+R3)

OVON = VOVL = 1.12 = (VEEOV(on)) x R3/(R1+R2+R3)

Where (VEEUV(on)) and (VEEOV(on)) are Under and Over Volt-

age Start Up Threshold points relative to VEE.

Then

(VEEUV(on)) = 1.22 x (R1+R2+R3)/(R2+R3)

(VEEUV(on)) = 1.22 x (487k+6.65k+9.31k)/(6.65k+9.31k )

= 38.45V

And

(VEEOV(on)) = 1.12 x (R1+R2+R3)/R3

(VEEOV(on) ) = 1.12 x (487k +6.65k +9.31k)/9.31k = 60.51V

Therefore, the circuit will start when the input supply volt-

age is in the range of 38.45V to 60.51V.

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