Output current reference circuit and method

A control system operable to supply a plurality of output currents to a plurality of peripheral devices, comprising:

• a control circuit operable to generate and transmit control data;
• a control register circuit operable to receive and store said control data and generate a plurality of control signals responsive to said control data;
• a central current reference circuit operable to generate a reference current having temperature coefficient substantially equal to zero;
• and
• said central current reference circuit including:
• first and second bipolar transistors having different sizes, collector currents of said bipolar transistors being substantially equal such that the base emitter voltages associated with said transistors exhibit a voltage differential having a first temperature coefficient and
• a resistance coupled between the bases of said first and second bipolar transistors, said resistance having a second temperature coefficient substantially equal to said first temperature coefficient, and
• a central output mirror circuit coupled to said central current reference circuit and said control register circuit, said central output mirror circuit operable to receive said reference current and to generate currents proportional to said reference current responsive to said plurality of control signals,
• an output driver circuit coupled to said central output mirror circuit and operable to receive one of said proportional currents and to generate one of the plurality of output currents responsive to said one of said proportional currents, said one of said plurality of output currents having a temperature coefficient substantially equal to zero.

A method of providing an output current to a peripheral device, comprising the steps of:

• generating a reference current in a central current reference circuit having a temperature coefficient substantially equal to zero;
• and
• generating collector currents from first and second bipolar transistors of said central current reference current, said first and second bipolar transistors being of different sizes;
• and
• generating base emitter voltages of said first and second bipolar transistors to form a voltage differential having a final temperature coefficient;
• and
• forming a second temperature coefficient substantially equal to first temperature coefficient based on a resistance coupled between bases of said first and second bipolar transistors;
• and
• generating currents proportional to the reference current in a central output mirror circuit coupled to the central current reference circuit;
• receiving one of the proportional currents in an output driver circuit coupled to the central output mirror circuit;
• and
• generating one of the plurality of output currents responsive to the received one of the proportional currents, the received one of the plurality of output current having a temperature coefficient substantially equal to zero.