TLC7225 Datasheet, PDF (14/22 Pages) Texas Instruments – QUADRUPLE 8-BIT DIGITAL-TO-ANALOG CONVERTERS

TLC7225C, TLC7225I
QUADRUPLE 8-BIT DIGITAL-TO-ANALOG CONVERTERS
SLAS109B – OCTOBER 1996 – REVISED FEBRUARY 2001
APPLICATION INFORMATION
AGND bias for positive output offset
The TLC7225 AGND terminal can be biased above or below the system ground terminal, DGND, to provide an
offset-zero analog-output voltage level. Figure 10 shows a circuit configuration to achieve this for channel A of
+ ) ǒ Ǔ the TLC7225. The output voltage, VO at OUTA, can be expressed as:
VO Vbias DA VI
where D_A is a fractional representation of the digital input word (0 ≤ D ≤ 255/256).
VI
AGND
6
Vbias
5 ^Vref
TLC7225^†
22 ^VDD
_
DAC A
+
2
VO(OUTA)
3
VSS
7
DGND
† _{Digital inputs omitted for clarity.}
Figure 10. AGND Bias Circuit
Increasing AGND above system ground reduces the output range. V_DD – V_ref must be at least 4 V to ensure
specified operation. Since the AGND terminal is common to all four DACs, this method biases up the output
voltages of all the DACs in the TLC7225. Supply voltages V_DD and V_SS for the TLC7225 should be referenced
to DGND.
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