R1154 Datasheet, PDF (21/22 Pages) RICOH electronics devices division – 150mA Voltage Regulator (Wide Input Voltage Range)

R1154x
The Output Voltage of Regulator in R1154xxxxC may be adjustable for any output voltage between its
2.5V reference and its VDD setting level. An external pair of resistors is required, as shown in Figure 1.
The complete equation for the output voltage is described step by step as follows;
I1IICI2 ..................................................................................................................................... (1)
I22.5/R2 .................................................................................................................................. (2)
Thus,
I1IIC2.5/R2 ............................................................................................................................. (3)
Therefore,
VOUT2.5R1I1 ........................................................................................................................ (4)
Put Equation (3) into Equation (4), then
VOUT2.5R1(IIC2.5/R2)
2.5(1R1/R2)R1IIC........................................................................................................ (5)
In 2nd term, or R1IIC will produce an error in VOUT.
In Equation (5),
IIC2.5/RIC .................................................................................................................................. (6)
R1IICR12.5/RIC
2.5R1/RIC.................................................................................................................... (7)
For better accuracy, choosing R1 (<<RIC) reduces this error.
RIC of the R1154x001C is approximately Typ.17MΩ (Ta=25C, guaranteed by Design Engineering).
RIC could be affected by the temperature, therefore evaluate the circuit taking the actual conditions of use into
account when deciding the resistance values for R1 and R2.
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