TLC7226C_15 Datasheet, PDF (11/24 Pages) Texas Instruments – QUADRUPLE 8-BIT DIGITAL-TO-ANALOG CONVERTERS

ą
TLC7226C, TLC7226I, TLC7226M
QUADRUPLE 8ĆBIT DIGITALĆTOĆANALOG CONVERTERS
ą
SLAS060F − JANUARY 1995 − REVISED APRIL 2009
APPLICATION INFORMATION
bipolar output operation using external amplifier
Each of the DACs of the TLC7226 can also be individually configured to provide bipolar output operation, using
an external amplifier and two resistors per channel. Figure 9 shows a circuit used to implement offset binary
coding (bipolar operation) with DAC A of the TLC7226. In this case:
ǒ _VO
+
1
)
R2
R1
DA
Ǔ _Vref
*
R2
R1
ǒ_VrefǓ
(2)
with R1 + R2
VO + ^ǒ2DA * 1^Ǔ Vref
where DA is a fractional representation of the digital word in latch A.
Mismatch between R1 and R2 causes gain and offset errors. Therefore, these resistors must match and track
over temperature. The TLC7226 can be operated with a single power supply or from positive and negative
power supplies.
REF
R1†
R2†
4
TLC7226
_
DAC A
+
15 V
_
2
+
VO
−15 V
† _{R1 = R2 = 10 kΩ ±0.1%}
Figure 9. Bipolar Output Circuit
staircase window comparator
In many test systems, it is important to be able to determine whether some parameter lies within defined limits.
The staircase window comparator shown in Figure 10 is a circuit that can be used to measure the V_OH and V_OL
thresholds of a TTL device under test. Upper and lower limits on both V_OH and V_OL can be programmed using
the TLC7226. Each adjacent pair of comparators forms a window of programmable size (see Figure 11). When
the test voltage (V_test) is within a window, then the output for that window is higher. With a reference of 2.56 V
applied to the REF input, the minimum window size is 10 mV.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
11