# US 2013/0278175 A1 · Keyboard backlight driver ic

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- Number: US 2013/0278175 A1
- Document ID: US20130278175A1
- Status: Published application
- Kind: A1
- Application number: 13/659,890
- Filed: 2012-10-24
- Published: 2013-10-24
- Earliest claimed: 2012-04-20
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Alejandro Lara Ascorra; Eric G. Smith; Steven J. Sfarzo
- Web page: https://patentgrep.com/patent/US20130278175A1

## 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 LED driver device, the device comprising:
a voltage boost circuit configured to provide a boost voltage greater than a supply voltage received by the device;
a current sink circuit configured to couple a return current to ground;
a serial bus interface configured to receive control signals;
an enable input configured to enable the current sink circuit; and
a brightness input configured to control the current sink.

### Claim 2 (depends on 1)

The device of claim 1, wherein the brightness input is configured to receive a PWM signal.

### Claim 3 (depends on 2)

The device of claim 2, wherein the current sink can be configured with control signals received through the serial bus interface.

### Claim 4 (depends on 1)

The device of claim 1, wherein the voltage boost circuit is further configured to provide a voltage to a LED array.

### Claim 5 (depends on 4)

The device of claim 4, wherein the current sink circuit is further configured to receive a return current from the LED array.

### Claim 6 (depends on 1)

The device of claim 1, wherein the current sink is further configured to be enabled in accordance with the enable input and the brightness input.

### Claim 7

A keyboard LED controlling system comprising:
a LED array configured to backlight a keyboard of a computing device; and
a LED array controller, comprising:
a voltage boost circuit configured to provide a supply voltage to the LED array,
a current sinking circuit configured to sink current from the LED array, and
a configuration port configured to control, at least in part, the LED array controller;

### Claim 8 (depends on 7)

The system of claim 7, wherein the LED array controller further comprises an enable pin configured to turn on the LED array by allowing the current sinking circuit to couple return current from the LED array to ground.

### Claim 9 (depends on 7)

The system of claim 7, wherein the LED array controller further comprises a pulse width modulation (PWM) input configured to control the brightness of the LED array.

### Claim 10 (depends on 9)

The system of claim 9, wherein current sinking circuit operates in accordance with the PWM input.

### Claim 11 (depends on 10)

The system of claim 10, wherein the PWM input is provided by a state machine.

### Claim 12 (depends on 10)

The system of claim 10, wherein the PWM input is provided by a microcontroller.

### Claim 13 (depends on 10)

The system of claim 10, wherein the PWM input and the enable input are provided by a graphics processing unit.

### Claim 14 (depends on 7)

The system of claim 7, wherein the voltage boost circuit provides a supply voltage for a second LED array.

### Claim 15

A LED controller system for a portable computing device, the system comprising:
a first LED array configured to provide light for a keyboard of the portable computing device;
a second LED array configured to provide light for a backlight of the portable computing device; and
a LED array controller comprising:
a voltage boost circuit configured to supply a voltage to the first and the second LED arrays,
a current sink circuit configured to couple a return current to ground, and
a brightness input configured to control an operation of the current sink circuit.

### Claim 16 (depends on 15)

The system of claim 15, wherein the brightness input is further configured to receive a pulse width modulated signal to control the current sink circuit.

### Claim 17 (depends on 15)

The system of claim 15, wherein the LED array controller further comprises an enable input to control the current sink circuit.

### Claim 18 (depends on 15)

The system of claim 15, wherein the first LED array is coupled to the voltage boost circuit and the current sink circuit.

### Claim 19 (depends on 15)

The system of claim 15, further comprising a state machine configured to provide a PWM signal to the brightness input.

### Claim 20 (depends on 15)

The system of claim 15, further comprising a microcontroller configured to provide a PWM signal to the brightness input.