Reference Voltage Generation Circuit - Epson LQ-1050 Technical Manual

2.3.5.1 Reference Voltage Generation Circuit

Figure 2-41 shows the generation circuit for reference voltage VDC) used in the A/D converter
in the CPU. This circuit employs a programmable shunt regulator TL43 1 (CY 1 ) for the reference voltage
supply.
+5
+12
A vcC
o
u
.
Fig. 2-41. Reference Voltage Genwation Circuit
Reference voltage VAREF depends on the combination of resistors R95 and R94 connected in parallel
TL431 .
to
' Iref = 2
Using the above formula, Varef is stabilized at about 4.75 V.
2-41