Curvature compensated band-gap design trimmable at a single temperature
AssigneeSanDisk Technologies LLC
InventorBehdad Youssefi
Life of this patent
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Abstract
A band-gap reference circuit is compensated for temperature dependent curvature in its output. A voltage across a diode with a fixed current is subtracted from a voltage across a diode with a proportional to absolute temperature (PTAT) current. The resultant voltage is then magnified and added to a PTAT voltage and a diode's voltage that has a complementary-to-absolute temperature (CTAT) characteristic, resulting in a curvature corrected hand-gap voltage. This allows for the band-gap reference circuit to be trimmed at a single temperature. This allows the circuit to be made with only a single trimmable parameter, which, in the exemplary circuits, is a resistance value.
Claims10
A trimmable reference voltage circuit, comprising:
- a first diode connected between a proportional to absolute temperature current source and ground;
- a first resistance connected between the first diode and the proportional to absolute temperature current source;
- a first op-amp having a first input connected to a node between the first resistance and the first diode, an output connected to the gate of a first transistor connected between a high voltage level and ground, wherein the first transistor is connected to ground though a second resistance and the second input of the first op-amp is connected to a node between the first transistor and the second resistance;
- a second diode connected between ground and the high voltage level, wherein the second diode is connected to the voltage level by a first and a second leg, wherein:
- the first leg includes a second transistor whose gate is connected to receive the output of the first op-amp;
- and
- the second leg includes a third transistor connected in series with a resistive voltage divider, where the resistive voltage divider is connected between the second diode and the third transistor and includes a trimmable element, the trimmable element of the resistive voltage divider being the only trimmable element of the reference voltage circuit;
- and
- a second op-amp having an output connected to the gate of the third transistor, a first input connected to a node between the proportional to absolute temperature current source and the first resistance, and a second input connected to a node of the resistive voltage divider,
- wherein the reference voltage is provided from a node between the third transistor and the resistive voltage divider.
Dependencies are inferred from the claim text.