MOS Integrated Circuit Data Sheet

234
µ PD17062
19.2 D/A CONVERTER CONFIGURATION
The D/A converter used in the A/D converter of the
µ PD17062 is a resistor string D/A converter consisting
of 16 resistors connected in series between the V
DD and GND pins in which a voltage at each resistor connection
point is selected. The configuration of the D/A converter is shown in Fig. 19-2.
Fig. 19-2 D/A Converter Configuration
With the configuration shown above, the D/A converter outputs a ground level when the ADCR is set with
value 0000B. It also outputs 1/32 × V
DD when the ADCR is set with 0001B. The following expression represents
the reference voltage V
REF that the D/A converter outputs when the ADCR is set with value n (decimal).
V
REF = VDD ×
2n – 1
(where 15 ≥ n ≥ 1)
32
Table 19-1 D/A Converter Reference Voltage
ADCR 4
01 2 131415
Selector
1/2R R R R R R 3/2R
V
DD
D/A output
(reference voltage)
Set data (ADCR) Reference voltage (VREF)
Hexadecimal Binary × VDD VDD = 5 V
0 0000 0 0 [V]
1 0001 1/32 0.15625
2 0010 3/32 0.46875
3 0011 5/32 0.78125
4 0100 7/32 1.09375
5 0101 9/32 1.40625
6 0110 11/32 1.71875
7 0111 13/32 2.03125
8 1000 15/32 2.34375
9 1001 17/32 2.65625
A 1010 19/32 2.96875
B 1011 21/32 3.28125
C 1100 23/32 3.59375
D 1101 25/32 3.90625
E 1110 27/32 4.21875
F 1111 29/32 4.53125