TCM4300IPZ datasheet(45/69 Pages) TI1

45 / 69 page

4–10

4.9

Auxiliary DACs, LCD Contrast Converter

Auxiliary DACs generate AFC, AGC and power control signals for the RF system. These three D/A

converters are updated when the corresponding data is received from the DSP. In fewer than 5

µs after the

corresponding registers are written to, the output has settled to within 1 LSB of its new value (see

Table 4–10).

Table 4–10. Auxiliary D/A Converters

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

AVDD > 3 V†,

AUXFS [1:0] = 00

0.2

2.5

Output range

AVDD > 4.5 V†,

AUXFS [1:0] = 10

0.2

AVDD > 5 V†,

AUXFS [1:0] = 11

0.2

4.5

Resolution AGC, AFC, PWRCONT

DACs

bits

Resolution LCDCONTR DAC

bits

Gain + offset error (full scale) AGC,

AFC, PWRCONT DAC

±3%

Gain + offset error (full scale)

LCDCONTR DAC

±7%

Differential nonlinearity

±0.75

±1

LSB

Integral nonlinearity

±0.75

±1

LSB

† Range settings depends only on AUXFS [1:0]. The supply voltage is not detected.

The LCDCONTR output is used by the microcontroller to adjust the contrast of the LCD. This converter is

a separate 4-bit DAC.

The auxiliary DACs can be powered down. The AGC and AFC DACs have dedicated bits in the MIntCtrl

LCDCONTR DAC is enabled when the LCDEN bit of the LCD D/A register clears to 0, the four data bits being

left justified. The AFC, AGC, and PWRCONT DACs are disabled after powerup or after a reset of the

TCM4300. After power up or reset, the default AUXFS[1:0] is 00. When the DACs are powered down, their

output terminals go to a high-impedance state and can tolerate any voltage present on the terminal that falls

within the supply range.

The slope and the corresponding output values for the auxiliary DACs are listed in Table 4–11 and

Table 4–12.

Table 4–11. Auxiliary D /A Converters Slope (AGC, AFC, PWRCONT)

AUXFS[1:0]

SETTING

SLOPE

NOMINAL LSB

VALUE

(V)

NOMINAL OUTPUT VOLTAGE

FOR DIGITAL CODE = 128

(MIDRANGE)

(V)

NOMINAL OUTPUT VOLTAGE

FOR DIGITAL CODE = 256†

(MAX VALUE)

(V)

2.5/256

0.0098

1.25

2.5

Do not

use

Do not use

4/256

0.0156

4.5/256

0.0176

2.25

4.5

† The maximum input code is 255. The value shown for 256 is extrapolated.

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