
Rev.1.00
Oct 27, 2008
REJ03B0266-0100
3804 Group (Spec.L)
D/A CONVERTER
The 3804 group (Spec.L) has two internal D/A converters (DA1
and DA2) with 8-bit resolution.
The D/A conversion is performed by setting the value in each
DA conversion register. The result of D/A conversion 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) must be set to “0” (input
status).
The output analog voltage V is determined by the value n
(decimal notation) in the DA conversion register as follows:
V = VREF × n/256 (n = 0 to 255)
Where VREF is the reference voltage.
At reset, the DA conversion registers are cleared to “0016”, and
the DA output enable bits are cleared to “0”, and the P30/DA1
and P31/DA2 pins become high impedance.
The DA output does not have buffers. Accordingly, connect an
external buffer when driving a low-impedance load.
Fig. 56 Block diagram of D/A converter
Fig. 57 Equivalent connection circuit of D/A converter (DA1)
DA1 conversion register (8)
DA1 output enable bit
P30/DA1
Da
ta
bu
s
R-2R resistor ladder
DA2 conversion register (8)
DA2 output enable bit
P31/DA2
R-2R resistor ladder
DA1 output enable bit
AVSS
VREF
R
2R
R
2R
LSB
“1”
“0”
MSB
DA1 conversion register
P30/DA1
“0”
“1”