Differential signaling system and flat panel display with the same
A differential signaling system and a flat panel display using the system, where a first wiring and a second wiring are connected between a sending end and a receiving end as a differential signal line. A termination resistor is connected between the first wiring and the second wiring in the receiving end side. A programmable compensation circuit is connected to the termination resistor in parallel. The programmable compensation circuits includes: n switches M 1 , M 2 , M 3 , . . . , Mn connected between a first power line and a second power line; first n resistors R 11 , R 12 , R 13 , . . . , R 1 n connected between a source electrode of each of the switches and the first wiring; and second n resistors R 21 , R 22 , R 23 , . . . , R 2 n connected between a drain electrode of each of the switches and the second wiring.
1. A differential signaling system comprising:
a first wiring and a second wiring connected between a sending end and a receiving end as a differential signal line;
a termination resistor connected between the first wiring and the second wiring in the receiving end side; and
a programmable compensation circuit connected to the termination resistor in parallel,
the programmable compensation circuits includes:
n switches M 1 , M 2 , M 3 , . . . , Mn connected between a first power line and a second power line;
first n resistors R 11 , R 12 , R 13 , . . . , R 1 n connected between a source electrode of each of the switches and a first wiring;
second n resistors R 21 , R 22 , R 23 , . . . , R 2 n connected between a drain electrode of each of the switches and a second wiring;
third n resistors Rd 1 , Rd 2 , . . . , Rdn connected between the first power line and a source electrode of each of the switches; and
fourth n resistors Rs 1 , Rs 2 , . . . , Rsn connected between the second power line and a drain electrode of each of the switches.
2. The differential signaling system as claimed in claim 1 , wherein the third n resistors and the fourth n resistors have a resistance value of several kΩ.
3. The differential signaling system as claimed in claim 1 , wherein the number of the switches is a number of digital bits of a control signal to control the programmable compensation circuit.
4. The differential signaling system as claimed in claim 1 , wherein each of the switches is a transistor having a distributed gate resistance.
5. The differential signaling system as claimed in claim 1 , wherein resistances of the first n resistors R 11 , R 12 , R 13 , . . . , R 1 n and the second n resistors R 21 , R 22 , R 23 , . . . , R 2 n are the same value, which is (N/M)R b , wherein the R b refers to a resistance value of a resistor included in the programmable compensation circuit, the N is a digital control signal bit number inputted to the programmable compensation circuit, and the M is a logic high bit number of the input digital control signal.
6. A flat panel display comprising:
a display panel in which a plurality of data wirings and gate wirings are arranged to intersect each other;
a controller to receive an image signal and generate a control signal, and to output the image signal and the control signal through first and second wirings as a differential signal line;
a gate driver to receive the control signal from the controller and apply a scan signal to the gate wirings; and
a plurality of data driving circuits including a programmable compensation circuit connected to a terminal resistor in parallel installed between the first and second wirings, to automatically control an impedance value of the data driving circuit corresponding to a differential impedance value of the differential signal line, each of the data driving circuits including a data driver to receive the image signal and/or the control signal from the controller through the first and second wirings and apply the image signal to the data wirings, wherein
the programmable compensation circuits includes:
n switches M 1 , M 2 , M 3 , . . . , Mn connected between a first power line and a second power line,
first n resistors R 11 , R 12 , R 13 , . . . , R 1 n connected between a source electrode of each of the switches and the first wiring,
second n resistors R 21 , R 22 , R 23 , . . . , R 2 n connected between a drain electrode of each of the switches and the second wiring;
third n resistors Rd 1 , Rd 2 , . . . , Rdn connected between the first power line and a source electrode of each of the switches; and
fourth n resistors Rs 1 , Rs 2 , . . . , Rsn connected between the second power line and a drain electrode of each of the switches.
7. The flat panel display as claimed in claim 6 , wherein the third n resistors and the fourth n resistors have a resistance value of several kΩ.
8. The flat panel display as claimed in claim 6 , wherein the number of the switches is a number of digital bits of a control signal to control the programmable compensation circuit.
9. The flat panel display as claimed in claim 6 , wherein each of the switches is a transistor having a distributed gate resistance.
10. The flat panel display as claimed in claim 6 , wherein resistances of the first n resistors R 11 , R 12 , R 13 , . . . , R 1 n and the second n resistors R 21 , R 22 , R 23 , . . . , R 2 n are the same value, which is (N/M)Rb, wherein the R b represents a resistance value of a resistor included in the programmable compensation circuit, the N is a digital control signal bit number inputted to the programmable compensation circuit, and the M is a logic high bit number of the input digital control signal.
11. A data driving circuit to receive and output a differential signal in a flat panel display device, comprising:
a first power line and a second power line;
first and second wirings having impedance values; and
an impedance compensation circuit configured to selectively match the impedance values of the first and second wirings, the impedance compensation circuit including a plurality of individually selectable switches connected in parallel between the first and second wirings, wherein the impedance compensation circuit further includes a first plurality of resistors respectively corresponding to the switches and connected between the switches and the first and second power lines, wherein the selection of one or more of the switches varies an impedance value of the impedance compensation circuit to match the impedance values of the first and second wirings.
12. The data driving circuit of claim 11 , wherein the impedance compensation circuit further includes a second plurality of resistors respectively corresponding to the switches and connected between the switches and the first wiring and between the switches and the second wiring.
13. The data driving circuit of claim 11 , wherein the switches have a small resistance of less than a few Ω and the first plurality of the resistors have a large resistance of several kΩ.
14. The data driving circuit of claim 11 , further comprising a termination resistor connected in parallel with the impedance compensation circuit.
15. The data driving circuit of claim 14 , wherein the impedance value of the impedance compensation circuit matches the impedance values of the first and second wirings when a reflection coefficient is zero, and the reflection coefficient is expressed as
Γ
=
Z
diff
_
-
Z
TN
Z
diff
_
+
Z
TN
,
where, Z diff is a predetermined impedance, Z TN is a composite impedance of the impedance compensation circuit and the termination resistor connected in parallel.
16. The data driving circuit of claim 15 , wherein the Z TN is expressed by
Z
TN
=
R
t
//
Z
PCC
=
R
t
//
N
M
R
b
=
R
t
1
+
M
N
(
R
t
R
b
)
,
where, R t represents a terminal resistance of the terminal resistor, Z PCC represents a total composite resistance of the impedance compensation circuit, R b represents a resistance value of one or more resistors included in the impedance compensation circuit, N represents a bit number of a digital control signal inputted to the impedance compensation circuit, and M represents a logic high bit number of the input digital control signal.
17. A data driver comprising:
a plurality of the data driving circuit of claim 11 ; and
a termination resistor for each data driving circuit, wherein the impedance compensation circuit is connected to the termination resistor.
18. A flat panel display comprising:
the data driving circuit of claim 11 ;
a display panel connected to the data driving circuit to receive image signals.