Granted Patent B1

US 7,511,651 · App. 11/852,471 · Granted Mar 31, 2009

Abstract

Claims (42)

1. A switching interface for a first receiver, a second receiver, and a resistor ladder, comprising:

a first terminal coupled to a first resistor of the resistor ladder;

a second terminal coupled to the first resistor;

a third terminal coupled to a reference voltage;

a switch having a first state coupling the first terminal to the third terminal and a second state coupling the second terminal to the third terminal;

a first analog-to-digital (A/D) converter coupled to the resistor ladder and the first receiver, the first A/D configured to compare a first voltage with a second voltage to determine if the switch is positioned in the first state or the second state; and

a second analog-to-digital (A/D) converter coupled to the resistor ladder and the second receiver, the second A/D configured to compare the first voltage with the second voltage to determine if the switch is positioned in the first state or the second state.

2. The switching interface of claim 1 , further including a fourth terminal coupled to the first resistor giving the switch a third state coupling the fourth terminal to the third terminal, the first and second A/D converters determining if the switch is positioned in the first, second, or third states.

3. The switching interface of claim 1 , further including a second switch coupled in parallel with the first switch.

4. The switching interface of claim 3 , further including a first diode coupled to the first terminal to isolate the first receiver from the second receiver.

5. The switching interface of claim 4 , further including a second diode coupled to the second terminal to isolate the second receiver from the first receiver.

6. The switching interface of claim 5 , wherein the first resistor is coupled in series with the first diode.

7. The switching interface of claim 6 , further including a second resistor coupled in series with the second diode.

8. The switching interface of claim 7 , further including a third resistor connected across the first and second terminals.

9. The switching interface of claim 8 , wherein the third resistor is in electrical communication between the first receiver and the third terminal, or alternatively, in electrical communication between the second receiver and the third terminal depending upon whether the switch is in the first or the second state.

10. A switching interface for a first receiver, a second receiver, and a resistor ladder, comprising:

means for coupling a first terminal to a first resistor of the resistor ladder;

means for coupling a second terminal to the first resistor;

means for coupling a third terminal to a reference voltage;

means for coupling a fourth terminal to the first resistor;

means for switching to a first state connecting the first terminal to the third terminal, a second state connecting the second terminal to the third terminal, and a third state connecting the fourth terminal to the third terminal;

first means for converting analog-to-digital (A/D) coupled to the resistor ladder and the first receiver, the first means for converting A/D configured to compare a first voltage with a second voltage to determine if the switch is positioned in the first state, the second state, or the third state; and

second means for converting analog-to-digital (A/D) coupled to the resistor ladder and the second receiver, the second means for converting A/D configured to compare the first voltage with the second voltage to determine if the switch is positioned in the first state, the second state, or the third state.

11. The switching interface of claim 10 , further including means for coupling a first diode to the first terminal to isolate the first receiver from the second receiver.

12. The switching interface of claim 11 , further including means for coupling a second diode to the second terminal to isolate the second receiver from the first receiver.

13. An automotive switching interface for a first receiver, a second receiver, and a resistor ladder, comprising:

a first terminal coupled to a first resistor of the resistor ladder;

a second terminal coupled to a second resistor of the resistor ladder;

a third terminal coupled to a reference voltage;

a third resistor connected across the first and second terminals;

a switch having a first state coupling the first terminal to the third terminal and a second state coupling the second terminal to the third terminal;

a first diode coupled to the first resistor;

a second diode coupled to the second resistor;

a first analog-to-digital (A/D) converter coupled to the resistor ladder and the first receiver, the first A/D configured to compare a first voltage with a second voltage to determine if the switch is positioned in the first state or the second state; and

a second analog-to-digital (A/D) converter coupled to the resistor ladder and the second receiver, the second A/D configured to compare the first voltage with the second voltage to determine if the switch is positioned in the first state or the second state.

14. The switching interface of claim 13 , wherein the first voltage is a five volt (5V) voltage supply.

15. The switch apparatus of claim 14 , wherein the resistance of the first resistor is about 1100 ohms, and the resistance of the second and third resistors is about 160 ohms.

16. The switch apparatus of claim 14 , wherein the resistance of the switch is about 100 ohms.

17. The switch apparatus of claim 13 , wherein the first voltage is a 12 volt (12V) variable voltage supply.

18. The switch apparatus of claim 17 , wherein the resistance of the first resistor is about 3900 ohms, and the resistance of the second and third resistors is about 890 ohms.

19. The switch apparatus of claim 17 , wherein the resistance of the switch is about 20 ohms or less.

20. The switch apparatus of claim 13 , wherein the reference voltage is associated with a supply voltage reference or a ground reference.

Assignments (12)