Datasheet

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SLAS105D − JANUARY 1995 − REVISED APRIL 2004
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13
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
BIAS VOLTAGE
BIAS OPTION
V
RB
V
RT
V
RT
− V
RB
1 0.61 2.63 2.02
2 AGND 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.
R1
320 Ω NOM
R
ref
270 Ω NOM
R2
80 Ω NOM
V
DDA
5 V (Analog)
REFTS
REFT
REFB
REFBS
AGND
TLC5540
16
17
22
21
23
18
0.1 µF
0.1 µF
2.63 V dc
0.61 V dc
Figure 14. External Connections Using the Internal Bias One Option