R1130 Datasheet, PDF (20/22 Pages) RICOH electronics devices division – 300mA LDO REGULATOR

R1130x
APPENDIX
* Technical Notes on Output Voltage Setting of C type
Figure 1. Adjustable Regulator (C type)
The Output Voltage of Regulator in R1130xxxxC may be adjustable for any output voltage between its 1.8V
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;
I2=IIC+I3 ································································································· (1)
I3=1.8/R3 ······························································································· (2)
Thus,
I2=IIC+1.8/R3 ··························································································· (3)
Therefore,
VOUT=1.8+R2×I2 ····················································································· (4)
Put Equation (3) into Equation (4), then
VOUT=1.8+R2×(IIC+1.8/R3)
=1.8×(1+R2/R3)+R2×IIC ···································································· (5)
In 2nd term, or R2×IIC will produce an error in VOUT.
In Equation (5),
IIC=1.8/RIC ······························································································· (6)
R2×IIC=R2×1.8/RIC
=1.8×R2/RIC ·················································································· (7)
For better accuracy, choosing R2 (<<RIC) reduces this error.
* Adjustable Resistor Dependence of Output Voltage
R1130x001C
R1130x001C
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