# US 2013/0278170 A1 · Detection circuit for keyboard cable

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- Number: US 2013/0278170 A1
- Document ID: US20130278170A1
- Status: Published application
- Kind: A1
- Application number: 13/659,885
- Filed: 2012-10-24
- Published: 2013-10-24
- Earliest claimed: 2012-04-20
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Alejandro Lara ASCORRA; Brad Lee Patton; Shimon Elkayam
- Web page: https://patentgrep.com/patent/US20130278170A1

## CPC

- H05B 45/325: Pulse-width modulation [PWM]
- H05B 45/38: using boost topology
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

One embodiment of a display backlight driver integrated circuit can be configured for operation in at least two different ways. A first method transfers data from an EEPROM to hardware registers prior to regular operation. A second method also transfers data from an EEPROM to registers. However, hardware registers can be overwritten with data accepted from a control bus, prior to regular operation. A keyboard driver IC can detect the presence or absence of a cable to an LED. If the cable is absent, the driver IC will not supply power for the LED. One embodiment of a keyboard and display backlight control system can be configured to allow substantially independent operation.

## Claims

### Claim 1

A method for controlling output power state of a LED driver, the method comprising:
entering a configuration mode;
configuring a multimode pin to a first mode while in the configuration mode;
determining a logic state of the multimode pin;
configuring the output power state in accordance with the determined logic level of the multimode pin; and
configuring the multimode pin to a second mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein the entering of the configuration mode is in accordance with detecting a power on event.

### Claim 3 (depends on 2)

The method of claim 2, wherein the power on event is when the power for the LED driver transitions from zero volts to an operating voltage.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first mode of the multimode pin is an input mode.

### Claim 5 (depends on 1)

The method of claim 1, wherein the second mode of the multimode pin is an output mode.

### Claim 6 (depends on 1)

The method of claim 1, wherein the output power state of the LED driver is off when a first logic state of the multimode pin is determined.

### Claim 7 (depends on 6)

The method of claim 6, wherein the output power state of the LED driver is on then a second logic state of the multimode pin is determined.

### Claim 8 (depends on 1)

The method of claim 1, wherein the second mode is an output mode.

### Claim 10

An LED driver system, comprising:
a LED boost converter configured to provide an LED array voltage greater than an input voltage;
a current sink configured to conduct current from an LED array to ground;
an LED array port configured to couple the LED array voltage to the LED array and couple return current from the LED array to the current sink; and
a multimode configuration pin configured to control the LED array port.

### Claim 11 (depends on 10)

The LED driver system of claim 10, wherein when the multimode configuration pin is in a first mode after a power-on event.

### Claim 12 (depends on 11)

The LED driver system of claim 11, wherein the first mode is an input mode.

### Claim 13 (depends on 12)

The LED driver system of claim 12, wherein the LED array port is disabled when the multimode configuration pin is in a first logic state when the configuration pin is in the first mode.

### Claim 14 (depends on 13)

The LED driver system of claim 13, further comprising a flex cable connector coupled to the LED array port.

### Claim 15 (depends on 14)

The LED driver system of claim 14, wherein attaching a flex cable to the flex cable connector configures a second logic state.

### Claim 16 (depends on 14)

The LED driver system of claim 14, wherein attaching a flex cable biases a multimode configuration pin.

### Claim 17 (depends on 16)

The LED driver system of claim 16, wherein the multimode configuration pin is biased to a logical ‘0’.

### Claim 18 (depends on 16)

The LED driver system of claim 16, wherein the multimode configuration pin is biased to a logical ‘1’.

### Claim 19 (depends on 15)

The LED driver system of claim 15, wherein the second logic state enables the LED array port.

### Claim 20 (depends on 16)

The LED driver system of claim 16, further comprising an LED array coupled to the flex cable.