TLC5540 Datasheet, PDF (13/18 Pages) Texas Instruments – 8-BIT HIGH-SPEED ANALOG-TO-DIGITAL CONVERTER

TLC5540
www.ti.com
SLAS105D − JANUARY 1995 − REVISED APRIL 2004
PRINCIPLES OF OPERATION
internal reference voltage conversion
Three internal resistors allow the device to generate an internal reference voltage. These resistors are brought
out on terminals V_DDA, REFTS, REFT, REFB, REFBS, and AGND. Two different bias voltages are possible
without the use of external resistors.
Internal resistors are provided to develop REFT = 2.6 V and REFB = 0.6 V (bias option one) with only two
external connections. This is developed with a 3-resistor network connected to V_DDA. When using this feature,
connect REFT to REFTS and connect REFB to REFBS. For applications where the variance associated with
V_DDA is acceptable, this internal voltage reference saves space and cost (see Figure 14).
A second internal bias option (bias two option) is shown in Figure 15. Using this scheme REFB = AGND and
REFT = 2.28 V nominal. These bias voltage options can be used to provide the values listed in the following
table.
Table 1. Bias Voltage Options
BIAS OPTION
1
2
VRB
0.61
AGND
BIAS VOLTAGE
VRT
2.63
VRT − VRB
2.02
2.28
2.28
To use the internally-generated reference voltage, terminal connections should be made as shown in
Figure 14 or Figure 15. The connections in Figure 14 provide the standard video 2-V reference.
VDDA
18
5 V (Analog)
0.1 µF
0.1 µF
REFTS ₁₆
17
REFT
REFB ₂₃
22
REFBS
AGND 21
TLC5540
R1
320 Ω NOM
2.63 V dc
Rref
270 Ω NOM
0.61 V dc
R2
80 Ω NOM
Figure 14. External Connections Using the Internal Bias One Option
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