# US 8,148,817 B2 · Multi-die DC-DC buck power converter with efficient packaging

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- Number: US 8,148,817 B2
- Document ID: US8148817B2
- Status: Granted
- Kind: B2
- Application number: 12/889,673
- Filed: 2010-09-24
- Published: 2011-01-20
- Granted: 2012-04-03
- Earliest claimed: 2007-07-31
- Assignees: Alpha and Omega Semiconductor Incorporated
- Inventors: François Hébert; Allen Chang
- Web page: https://patentgrep.com/patent/US8148817B2

## CPC

- H10W 70/481: {for devices being provided for in groups H10D8/00 - H10D48/00}
- H10W 90/811: {Multiple chips on leadframes}
- H10W 72/5363: {the connected ends being wedge-shaped}
- H10W 72/5449: {not being orthogonal to a side surface of the chip, e.g. fan-out arrangements}
- H10W 72/5475: {multiple bond wires connected to common bond pads at both ends of the wires}
- H10W 72/879: {Bump connectors and bond wires}
- H10W 72/884: {Die-attach connectors and bond wires}
- H10W 74/00: Encapsulations, e.g. protective coatings
- H10W 90/00: Package configurations
- H10W 90/726: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10W 90/732: {between stacked chips}
- H10W 90/736: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10W 90/754: {between a chip and a stacked insulating package substrate, interposer or RDL}
- H10W 90/756: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A DC-DC buck converter in multi-die package is proposed having an output inductor, a low-side Schottky diode and a high-side vertical MOSFET controlled by a power regulating controller (PRC). The multi-die package includes a first die pad with the Schottky diode placed there on side by side with the vertical MOSFET. The PRC die is attached atop the first die pad via an insulating die bond. Alternatively, the first die pad is grounded. The vertical MOSFET is a top drain N-channel FET, the substrate of Schottky diode die is its anode. The Schottky diode and the vertical MOSFET are stacked atop the first die pad. The PRC is attached atop the first die pad via a conductive die bond. The Schottky diode die can be supplied in a flip-chip configuration with cathode being its substrate. Alternatively, the Schottky diode is supplied with anode being its substrate without the flip-chip configuration.

## Claims

### Claim 1

An efficiently packaged multi-die semiconductor package for DC-DC buck converter application where the buck converter down converts an unregulated DC input into a regulated DC output, the multi-die semiconductor package comprises:
a lead-frame having a first die pad thereon; a vertical MOSFET placed atop said first die pad; and
a Schottky diode with its cathode connected to the source of the vertical MOSFET, wherein the Schottky diode is placed on the first die pad side by side with the vertical MOSFET with the cathode of the Schottky diode being electrically connected to the source of the vertical MOSFET via the first die pad.

### Claim 2 (depends on 1)

The multi-die semiconductor package of claim 1 wherein the substrate of the Schottky diode die is its cathode and the top of the Schottky diode die is its anode and, correspondingly, the bottom of the vertical MOSFET die is its source and the top of the vertical MOSFET die has its gate and drain.

### Claim 3

An efficiently packaged multi-die semiconductor package for DC-DC buck converter application where the buck converter down converts an unregulated DC input into a regulated DC output, the multi-die semiconductor package comprises:
a lead-frame having a first die pad thereon; a vertical MOSFET placed atop said first die pad;
a Schottky diode with its cathode connected to the source of the vertical MOSFET; and
a power regulating controller (PRC) for controlling the gate of the vertical MOSFET, wherein the PRC die is further attached to the first die pad via an insulating die bonding material to achieve a further reduced footprint of the first die pad with the vertical MOSFET, the Schottky diode and the PRC co-packaged atop the first die pad.

### Claim 4

An efficiently packaged multi-die semiconductor package for DC-DC buck converter application where the buck converter down converts an unregulated DC input into a regulated DC output, the multi-die semiconductor package comprises:
a lead-frame having a first die pad thereon; a vertical MOSFET placed atop said first die pad;
a Schottky diode with its cathode connected to the source of the vertical MOSFET; and
a power regulating controller (PRC) for controlling the gate of the vertical MOSFET, wherein both the unregulated DC input and the regulated DC output are negative voltages hence the vertical MOSFET is a vertical P-channel FET, the bottom of the Schottky diode die is its anode, the bottom of the vertical MOSFET is its source and the top of the vertical MOSFET has its gate and drain whereby the Schottky diode die and the vertical MOSFET die are co-packaged side by side atop the first die pad.

### Claim 5 (depends on 4)

The multi-die semiconductor package of claim 4 wherein the substrate of the Schottky diode die is its cathode with the Schottky diode die being packaged in a flip-chip configuration.

### Claim 6 (depends on 4)

The multi-die semiconductor package of claim 4 wherein the substrate of the Schottky diode die is its anode with the Schottky diode die being packaged with its substrate connected to the first die pad.

### Claim 7 (depends on 4)

The multi-die semiconductor package of claim 4 wherein the PRC die is further attached to the first die pad via an insulating die bonding material to achieve a further reduced footprint of the first die pad with the Schottky diode, the vertical MOSFET and the PRC co-packaged atop the first die pad.

### Claim 8 (depends on 4)

The multi-die semiconductor package of claim 4 wherein said lead-frame further having a second die pad thereon and the PRC die is attached to the second die pad via a conductive die bonding material.