M38027E8SP Datasheet, PDF (27/51 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3802 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
D-A Converter
The 3802 group has two internal D-A converters (DA1 and DA2)
with 8-bit resolutions.
The D-A converter is performed by setting the value in the D-A
conversion register. The result of D-A converter is output from the
DA1 or DA2 pin by setting the DA output enable bit to “1”.
When using the D-A converter, the corresponding port direction
register bit (P30/DA1 or P31/DA2) should be set to “0” (input sta-
tus).
The output analog voltage V is determined by the value n (base
10) in the D-A conversion register as follows:
V = VREF ! n/256 (n = 0 to 255)
Where VREF is the reference voltage.
At reset, the D-A conversion registers are cleared to “0016”, the DA
output enable bits are cleared to “0”, and the P30/DA1 and P31/
DA2 pins are set to input (high impedance).
The D-A output is not buffered, so connect an external buffer when
driving a low-impedance load.
Set VCC to 3.0 V or more when using the D-A converter.
D-A1 conversion register (8)
DA1 output enable bit
R-2R resistor ladder
P30/DA1
D-A2 conversion register (8)
DA2 output enable bit
R-2R resistor ladder
P31/DA2
Fig. 24 Block diagram of D-A converter
"0" DA1 output enable bit
R
R
R
R
R
R
P30/DA1
"1"
2R
2R
2R
2R
2R
2R
D-A1 conversion
register
MSB
"0" "1"
AVSS
VREF
Fig. 25 Equivalent connection circuit of D-A converter
R
2R
2R
2R
LSB
27