System on a chip with backlight controller
A backlight control module includes a gain module, a variable voltage reference, a comparator, and a pulse width modulator. The gain module is coupled to amplify a representation of LED current to produce an amplified current sense signal. The variable voltage reference source is coupled to produce a reference voltage based on the backlight setting to produce a representation of the backlight setting. The comparator is coupled to compare the reference voltage with the amplified current sense signal to produce the comparison signal. The pulse width modulator is coupled to produce a pulse width modulated (PWM) signal as the brightness control signal based on the comparison signal, wherein the brightness control signal is provided to an off-chip variable supply voltage source that provides power to the off-chip LED.
1 . A system on a chip (SOC) comprises:
a bus structure;
a processing module coupled to the bus structure;
read only memory (ROM) coupled to the bus structure;
random access memory (RAM) coupled to the bus structure;
a display interface coupled to the bus structure;
an external memory interface coupled to the bus structure;
a digital to analog conversion (DAC) module coupled to the bus structure, wherein the digital to analog converter produces an analog audio signal;
an analog to digital conversion (ADC) module coupled to the bus structure;
a headphone amplifier circuit coupled to amplify the analog audio signal; and
a backlight control module coupled to:
sense current of an off-chip light emitting diode (LED) that provides backlighting of a display;
compare a representation of the current with a representation of a backlight setting to produce a comparison signal;
convert the comparison signal into a brightness control signal; and
provide the brightness control signal to an off-chip variable supply voltage source that provides power to the off-chip LED.
2 . The SOC of claim 1 , wherein the backlight control module comprises:
a gain module coupled to amplify the representation of the current to produce an amplified current sense signal, wherein the representation of the current is produced by an off-chip resistor in series with the off-chip LED;
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce the representation of the backlight setting;
a comparator coupled to compare the reference voltage with the amplified current sense signal to produce the comparison signal; and
a pulse width modulator coupled to produce a pulse width modulated (PWM) signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
3 . The SOC of claim 2 further comprises:
a current sense input integrated circuit (IC) pin for facilitating a connection between the off-chip LED and the gain module; and
a PWM IC pin for facilitating a connection between the DC-DC converter and the pulse width modulator.
4 . The SOC of claim 1 , wherein the backlight control module comprises:
a gain module coupled to amplify the representation of the current to produce an amplified current sense signal;
a multiplexer coupled to output the amplified current sense signal or the representation of the current based on a multiplexer control signal to produce a selected current sense signal;
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce the representation of the backlight setting;
a comparator coupled to compare the reference voltage with the selected current sense signal to produce the comparison signal; and
a pulse width modulator coupled to produce a pulse width modulated (PWM) signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
5 . The SOC of claim 1 , wherein the backlight control module comprises:
a representation module coupled to convert a voltage drop across the off-chip LED into the representation of the current, wherein the representation module is coupled to the off-chip LED;
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce the representation of the backlight setting;
a comparator coupled to compare the reference voltage with the representation of the current to produce the comparison signal; and
a pulse width modulator coupled to produce a pulse width modulated (PWM) signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
6 . The SOC of claim 1 , wherein the backlight control module further comprises:
an input to receive a representation of ambient light, wherein the backlight control module adjusts the representation of the backlight setting based on the representation of ambient light.
7 . A system on a chip (SOC) comprises:
a bus structure;
a processing module coupled to the bus structure;
read only memory (ROM) coupled to the bus structure;
random access memory (RAM) coupled to the bus structure;
a display interface coupled to the bus structure;
an external memory interface coupled to the bus structure;
a digital to analog conversion (DAC) module coupled to the bus structure, wherein the digital to analog converter produces an analog audio signal;
an analog to digital conversion (ADC) module coupled to the bus structure;
a headphone amplifier circuit coupled to amplify the analog audio signal; and
a backlight control module coupled to:
sense brightness of an off-chip light emitting diode (LED) that provides backlighting of a display;
compare a representation of the brightness with a representation of a backlight setting to produce a comparison signal;
convert the comparison signal into a brightness control signal; and
provide the brightness control signal off-chip to adjust brightness the off-chip LED in accordance with the backlight setting.
8 . The SOC of claim 7 , wherein the sensing of the brightness of the off-chip LED comprises:
receiving a representation of light emitted by the off-chip LED; and
converting the representation of the light into a voltage.
9 . The SOC of claim 8 , wherein the receiving the representation comprises at least one of:
receiving a voltage drop of an off-chip light receiving diode that is proximal to the off-chip LED; and
receiving, via an on-chip light receiving diode, the light emitted by the off-chip LED.
10 . The SOC of claim 7 further comprises:
the sensing of the brightness of the off-chip LED includes receiving a representation of current of the off-chip LED, wherein the backlight control module includes:
a gain module coupled to amplify the representation of the current to produce an amplified current sense signal, wherein the representation of the current is produced by an off-chip resistor in series with the off-chip LED;
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce the representation of the backlight setting;
a comparator coupled to compare the reference voltage with the amplified current sense signal to produce the comparison signal; and
a gating control circuit to gate and ungate a pulse width modulated (PWM) signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
11 . A system on a chip (SOC) comprises:
a processing module coupled to coordinate display of data;
a display interface coupled to provide the data to an off-chip display;
a backlight sense integrated circuit (IC) pin coupled to receive a representation of brightness of a light emitting diode (LED) backlight of the off-chip display;
a comparator coupled to compare the representation of brightness with a brightness setting to produce a comparison signal;
a control signal generating module coupled to convert the comparison signal into a brightness control signal; and
a brightness control signal IC pin coupled to provide the brightness control signal to an off-chip variable supply voltage source that provides power to the LED.
12 . The SOC of claim 11 further comprises:
a gain module coupled to amplify a representation of current of the LED to produce an amplified current sense signal, wherein the representation of the current corresponds to the representation of brightness; and
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce a representation of the backlight setting, wherein the comparator compares the reference voltage with the amplified current sense signal to produce the comparison signal, and wherein the control signal generating module produces a modulation signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
13 . The SOC of claim 11 further comprises:
a gain module coupled to amplify a representation of current of the LED to produce an amplified current sense signal, wherein the representation of the current corresponds to the representation of brightness;
a multiplexer coupled to output the amplified current sense signal or the representation of the current based on a multiplexer control signal to produce a selected current sense signal; and
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce a representation of the backlight setting, wherein the comparator compares the reference voltage with the selected current sense signal to produce the comparison signal, and wherein the control signal generating module produces a modulation signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
14 . The SOC of claim 11 further comprises:
a representation module coupled to convert a voltage drop across the LED into a representation of current, wherein the representation module is coupled to the off-chip LED and wherein the representation of the current corresponds to the representation of brightness; and
a variable voltage reference source coupled to produce a reference voltage based on the backlight setting to produce a representation of the backlight setting, wherein the comparator compares the reference voltage with the representation of current to produce the comparison signal, and wherein the control signal generating module produces a modulation signal as the brightness control signal based on the comparison signal, wherein the off-chip variable supply voltage source is a DC-DC converter.
15 . The SOC of claim 11 further comprises:
an input to receive a representation of ambient light, wherein the control signal generating module adjusts the backlight setting based on the representation of ambient light.