R1173 Datasheet, PDF (9/26 Pages) RICOH electronics devices division – Super low on resistance/Low voltage LDO

R1173x
Technical Notes on Output Voltage Setting of Adjustable Output type
(R1173x001x)
VOUT
ADJ
RIC
GND
R2
I2
IIC
VOUT
R3
I3
1.0V
The Output Voltage may be adjustable for any output voltage between its 1.0V reference and its VDD setting
level. An external pair of resistors is required, as shown above.
The complete equation for the output voltage is described step by step as follows;
I2=IIC+I3..................................................................................................................................... (1)
I3=1.0/R3 .................................................................................................................................. (2)
Thus,
I2=IIC+1.0/R3 ............................................................................................................................. (3)
Therefore,
VOUT=1.0+R2×I2 ........................................................................................................................ (4)
Put Equation (3) into Equation (4), then
VOUT =1.0+R2(IIC+1.0/R3)
=1.0(1+R2/R3)+R2×IIC ....................................................................................................... (5)
In 2nd term, or R2×IIC will produce an error in VOUT.
In Equation (5),
IIC=1.0/RIC .................................................................................................................................. (6)
R2×IIC =R2×1.0/RIC
=1.0×R2/RIC..................................................................................................................... (7)
For better accuracy, choosing R2 (<<RIC) reduces this error.
R1173x001x
2.0
1.8
1.6
1.4
1.2
1.0
∗) The graph is a typical
0.8
-50 -25 0 25 50 75 100
characteristic , please
evaluate the circuit with
Temperature Topt (°C)
an actual condition.
9