Integrated half-bridge power circuit
View Patent ↗A down converter includes an integrated circuit, which includes a control FET (CF) and a synchronous rectifier FET (SF). The control FET is a lateral double-diffused (LDMOS) FET, and the conductivity-type of the LDMOS FET and the conductivity-type of the substrate are of the same type.
1. A down converter, comprising:
an integrated circuit having a control Field Effect Transistor (FET) (CF) disposed in a first well having a first polarity; and
a synchronous rectifier FET (SF) having a source region and a channel region both disposed in a second well having a second polarity opposite the first polarity,
wherein the control FET is a Lateral Double-Diffused Metal Oxide Semiconductor (LDMOS) type and the SF is a vertical Metal Oxide Semiconductor type; the first and second wells are formed in contact with a heavily doped region of a substrate; and a conductivity- type of the LDMOS FET and a conductivity-type of the heavily doped region of the substrate are of the same type;
wherein at least a portion of the heavily doped region forms a drain region for the SF; and a source contact of the CF is connected to drain region of the SF via a conductive plug in the substrate.
2. A down converter as recited in claim 1 , wherein the synchronous rectifier FET is a Vertical Double-Diffused Metal Oxide Semiconductor (VDMOS) FET.
3. A down converter as recited in claim 1 , wherein the synchronous rectifier FET is a vertical trench DMOS FET.
4. A down converter as recited in claim 1 , wherein the integrated circuit does not include isolation regions between the CF and the SF.
5. A down converter as recited in claim 1 , wherein the conductivity type of the heavily doped region is n-type.
6. A down converter as recited in claim 1 , wherein the integrated circuit further includes one or more additional FETs configured to control gate switching of the control FET and the synchronous rectifier FET.
7. A down converter as recited in claim 1 further comprising an inductor, wherein the source contact of the control FET and a drain contact of the synchronous rectifier FET are connected to the inductor of the down converter.
8. A down converter as recited in claim 1 further comprising an inductor, wherein the source contact of the control FET and a drain contact of the synchronous rectifier FET are connected to the inductor of the down converter, the conductive plug forms a low-ohmic connection to mitigate resistive and inductive parasitics of the integrated circuit.
9. A down converter as recited in claim 8 , wherein the integrated circuit has a parasitic inductance on the order of 1 nH or less.
10. A down converter as recited in claim 1 further including a voltage input, wherein the control FET has a drain contact connected to the voltage input of the down converter.
11. A down converter as recited in claim 10 , wherein the source contact of the control FET is connected to the drain contact of the synchronous rectifier FET via the conductive plug and a portion of the heavily doped region in the substrate.
12. A down converter as recited in claim 1 wherein the control FET includes a gate driven by a control block supplied by an external capacitor.