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Renesas Electronics Europe - Knowledgebase

What is VREF in uPC1093 data sheet, and how's VOUT calculated with VREF?

Latest Updated:11/01/2007


What is VREF (standard connection) listed in the uPC1093 data sheet, and how is VOUT calculated with VREF?


VREF is the input voltage of the REF pin, and is the reference voltage. The output voltage is led by VREF and two external resistors.

The following relationships exist as a result.

VOUT = VREF + Voltage dropped by R1
VOUT =VREF (1 + R1/R2) + IREF × R1

Here, IREF being a current of the µA order, it is possible to posit the following equation by omitting IREF × R1:

VOUT ≈ VREF (1 + R1/R2)

This can also be easily visualized using law of dividing voltage.

VOUT:VREF = (R1 + R2):R2
VOUT × R2 = VREF × (R1 + R2)
VOUT = VREF × (R1 + R2)/R2 = VREF × (1 + R1/R2)

VREF becomes constant at 2.495 V (typ.), so that the output voltage (VOUT) can be changed (recommended operation condition: Min. VREF to Max. 36 V) depending on the ratio of R1 and R2.

When using the uPC1093 as a 2.5 V constant power supply, the following connection with R1 = 0, R2 = ∞ (open) is used.

Suitable Products
Shunt Regulators