TLC876M_07 Datasheet, PDF (15/22 Pages) Texas Instruments – 10-BIT 20 MSPS PARALLEL OUTPUT CMOS ANALOG-TO-DIGITAL CONVERTERS

TLC876M, TLC876I, TLC876C
10-BIT 20 MSPS PARALLEL OUTPUT CMOS
ANALOG-TO-DIGITAL CONVERTERS
SLAS140E – JULY 1997 – REVISED OCTOBER 2000
PRINCIPLES OF OPERATION
driving the analog input (continued)
RL = 4.99 kΩ
VCC _{0.1 µF}
0 V dc
2V(PP)
REFBF
RIN = 4.99 kΩ
3 kΩ
14.7 kΩ
NC
7
2–
A†
1
6
3+
5
4
NC
TLC876
AIN
† _{Amplifier A can be an AD817 or AD818 with terminal numbers as shown. The AD817 and AD818}
are wide bandwidth single supply op-amps.
Figure 16. Bipolar Level Shift
driving the reference terminals
dc considerations
The TLC876 requires an external reference on terminals REFTF and REFBF and a resistor array, nominally
500 Ω, is connected between terminals REFTF and REFBF. A Kelvin connection, using the TLC876 reference
sense terminals REFTS and REFBS, minimizes voltage drops caused by external and internal wiring
resistance.
Figure 17 shows the equivalent input structure for the reference terminals. There is approximately 5 Ω of
resistance between both REFTF and REFBF terminals and the reference ladder. If the force-sense connections
are not used, the voltage drop across the 5-Ω resistors results in a reduced voltage appearing across the ladder
resistance. This reduces the input span of the converter. Applying a slightly larger span between the REFTF
and REFBF terminals compensates for this error. Note that the temperature coefficients of the 5-Ω resistors are
1350 ppm. The effects of temperature should be considered when a force-sense reference configuration is not
used.
REFTF
REFTS
REFBS
REFBF
5Ω
10 Ω
5Ω
5Ω
DAC
10 Ω
5Ω
5Ω
5Ω
TLC876
5Ω
CLK
RARRAY
500 Ω
CLK
5Ω
C (Equivalent)
Figure 17. TLC876 Equivalent Reference Structure
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