M38040F5HKP datasheet(57/116 Pages) RENESAS

57 / 116 page

Rev.1.01

Jan 25, 2005

page 57 of 114

REJ03B0131-0101Z

3804 Group (Spec. H)

D/A CONVERTER

The 3804 group (Spec. H) 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

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 ex-

ternal buffer when driving a low-impedance load.

Fig. 52 Block diagram of D/A converter

Fig. 53 Equivalent connection circuit of D/A converter (DA1)

P30/DA1

DA1 conversion register (8)

R-2R resistor ladder

DA1 output enable bit

P31/DA2

DA2 conversion register (8)

R-2R resistor ladder

DA2 output enable bit

AVSS

VREF

“0”

“1”

MSB

“0”

“1”

2R2R

LSB

P30/DA1

DA1 conversion register

DA1 output enable bit

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