Gate driver multi-chip module
A multi-chip module (MCM) provides power circuitry on a computer motherboard in a package of reduced size without sacrificing performance. The MCM co-packages essential power circuit components on a ball grid array (BGA) substrate. Two power MOSFETs disposed on the BGA substrate are connected in a half-bridge arrangement between an input voltage and ground. A MOSFET gate driver is electrically connected to respective gate inputs of the two power MOSFETs for alternately switching the power MOSFETs to generate an alternating output voltage at a common output node between the power MOSFETs. At least one Schottky diode is disposed on the BGA substrate and connected between the common output node and ground to minimize losses during deadtime conduction periods. The input capacitor of the circuit is contained within the MCM housing and is located close to the MOSFETs, reducing stray inductance in the circuit. The MCM package is thin and has dimensions of about 1 cm by 1 cm or less.
Latest International Rectifier Corporation Patents:
This is a continuation of U.S. patent application Ser. No. 09/813,011, filed Mar. 21, 2001 abandoned, which is based upon and claims priority of U.S. Provisional Application Ser. No. 60/191,125, filed Mar. 22, 2000.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a multi-chip module (MCM). More specifically, the present invention relates to an MCM power circuit for a computer motherboard.
2. Description of the Related Art
Power supply circuitry typically occupies a substantial area on a computer motherboard. It would be desirable to reduce the size of the power circuitry on a computer motherboard without sacrificing performance.
SUMMARY OF THE INVENTIONThe present invention provides an MCM which includes a MOSFET gate driver, two power MOSFETs, and associated passive elements including an input capacitor all mounted on a ball grid array (BGA) substrate and packaged in a single chip.
The power MOSFETs of the MCM of the present invention are connected in a half-bridge arrangement between an input voltage and ground. The MOSFET gate driver is connected to respective gate inputs of the two power MOSFETs, and alternately switches the power MOSFETs to generate an alternating output voltage at a common output node between the power MOSFETs. At least one Schottky diode is disposed on the BGA substrate and connected between a common output node and ground to minimize losses during deadtime conduction periods.
The passive circuit components include an input capacitor connected between the input voltage and ground which provides input capacitance for the converter. Advantageously, the input capacitor is physically close to all other components. Additional components provide appropriate biasing for the gate driver. All components are encased in a molding compound to form the MCM package.
By mounting the input capacitor very close to other components and within the very small package, a number of advantages are realized, as follows:
First, there is a very low stray inductance between the input capacitor and the MOSFETs which reduces the “ring” that would be caused in the circuit including the MOSFET parasitic capacitance COSS and the stray inductance L. Reducing the inductance reduces the circuit ring.
Second, the location of the input capacitor within the MCM package provides layout independence for the mother board, which no longer needs to contain that capacitor (at a distance from the MOSFETs in the MCM package).
Third, the capacitor acts as a bypass to conduction of unintended current (with a high di/dt) through the body diode of one of the MOSFETs in the package and acts to help clamp the QRR (reverse recovery charge) of the MOSFET.
The module preferably is enclosed in a package that has side dimensions of about 11 mm×11 mm (i.e., about 1 cm×1 cm) or less. Accordingly, the input capacitor is located less than 1 cm from the MOSFET.
The MCM of the present invention advantageously results in a 50% reduction in size with no performance trade off and is printed circuit board (PCB) independent. The package advantageously provides a performance increase over the discrete solution.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
Referring to
Die 8 and 10 are power MOSFETs, preferably IRFC7811A and IRFC7809A power MOSFETs, respectively, mounted in a half-bridge configuration. Die 12 is a MOSFET gate driver, preferably a Semtech SC1405 High Speed Synchronous Power MOSFET Smart Driver. Die 14, 16, and 18 are Schottky diodes, preferably SKM863 diodes, connected as shown in the circuit schematic of
The passive components shown in
Referring to
Referring to
Schottky diodes 16 and 18 are connected between common output node SW NODE and ground to minimize losses during dead time conduction periods. An input capacitor C4 is connected between the input voltage VIN and ground PGND. The use of two parallel diodes 16 and 18 helps in keeping a symmetrical layout of components. An output inductor 30 generally will be connected to the SW NODE and to the output voltage terminal VOUT. An output capacitor COUT is also in the output circuit.
A supply voltage VDD is provided to MOSFET gate driver 12 on pin VCC. A bootstrap circuit, consisting of Schottky diode 14, and resistor R1/capacitor C2 connected between the bootstrap pin BST and the DRN pin, is provided to develop a floating bootstrap voltage for high-side MOSFET 8.
A TTL-level input signal is provided on line DRV_IN to MOSFET driver pin CO. Operation of the device is enabled by providing a minimum of 2.0 volts on enable pin EN of MOSFET driver 12. Status pin PRDY indicates the status of the +5V supply voltage. When the supply voltage is less than 4.4V, this output is driven low. When the supply voltage is greater than 4.4V, this output is driven high. This output has a 10 mA source and 10 μA capability. When PRDY is low, undervoltage circuitry built into driver 12 guarantees that both driver outputs TG and BG are low.
Referring to
The supply voltage can range between 4.2 and 6.0 V. Input voltages of between 5 and 12 volts can be used, providing an output voltage range of 0.9-2.0 V. Output current is typically 15A. The device operates at frequencies from 300-1,000 kHz.
The operation of the circuit of
First, the removal of capacitor C4 from the mother board increases layout flexibility for the mother board.
Second, since the capacitor C4 is very close to MOSFETs 8 and 10, the stray inductance in the circuit is reduced in comparison to that which would be produced with C4 located outside the chip, on the mother board. This close location (about one centimeter or less) substantially reduces the “ring” in the circuit. More specifically, as shown in
A third benefit of capacitor C4 is that it clamps QRR (reverse recovery charge) of MOSFET 10 and keeps high di/dt from flowing out of module 2 and into the mother board. More specifically,
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.
Claims
1. A multi-chip module (MCM) for providing power circuitry on a computer motherboard, comprising:
- a ball grid array (BGA) substrate having a first surface and a second opposing surface;
- two power MOSFETs disposed on the first surface of the BGA substrate and connected in a half-bridge arrangement between an input voltage and ground;
- a MOSFET gate driver disposed on the first surface of the BGA substrate and electrically connected to respective gate inputs of the two power MOSFETs for alternatively switching the power MOSFETs to generate an alternating output voltage at a common output node between the power MOSFETs; and
- at least one diode disposed on the first surface of the BGA substrate and connected between the common output node and ground to minimize losses during deadtime connection periods; and
- an input capacitor disposed on the first surface of the BGA and connected between the input voltage and ground;
- wherein the input capacitor is located adjacent to, and spaced less than 1 cm from the first and second MOSFETs, and wherein the input capacitor and the first and second MOSFETs are positioned side-by-side.
2. The module of claim 1, further comprising another diode connected in parallel with the diode connected between the common output node and between the common output node and ground.
3. The module of claim 1, wherein the substrate has an area of about 1 cm by 1 cm or less.
4. The module of claim 1, which further includes an insulation housing enclosing the substrate, the MOSFETs, the gate driver and the at least one diode, the ball grid array being exposed through the bottom of the housing for mounting to a mother board.
5. A multichip module comprising:
- a substrate having a first surface and an opposing second surface;
- a power input connection;
- a ground connection;
- two power switching devices disposed on said first surface of said substrate and connected in series according to a half-bridge arrangement between said power input connection and said ground connection, a terminal of one of said two power switching devices directly connected to said power input connection and a terminal of another of said two power switching devices directly connected to said ground connection; and
- an input capacitor connected between said power input connection and said ground connection, wherein said input capacitor is disposed on said first surface of said substrate and spaced no more than one centimeter from said two either power switching devices device, and wherein said input capacitor and said power switching devices are positioned side-by-side.
6. A The multichip module according to claim 5, wherein said power switching devices are MOSFETs.
7. A The multichip module according to claim 5, wherein said substrate is a ball grid array.
8. A The multichip module according to claim 5, wherein said half-bridge connection includes an output node located between said two power switching devices, and further comprising at least one Schottky diode connected between said output node and said ground connection.
9. A The multichip module according to claim 8, further comprising another Schottky diode connected between said output node and said ground connection.
10. A The multichip module according to claim 5, further comprising a controller disposed on said substrate for selective control of the operation of said two power switching devices.
11. A The multichip module according to claim 5, wherein said multichip module is 1 cm by 1 cm or less.
12. A The multichip module according to claim 5, wherein said input capacitor reduces the stray inductance to reduce the ringing due to resonance in said at least one of said two power switching devices.
13. A The multichip module according to claim 5, wherein said input capacitor is disposed on said substrate and spaced no more than one centimeter from the low side power switching device in said half-bridge arrangement.
4967332 | October 30, 1990 | Claydon et al. |
5331253 | July 19, 1994 | Counts |
5384691 | January 24, 1995 | Neugebauer et al. |
5629563 | May 13, 1997 | Takiar et al. |
5642262 | June 24, 1997 | Terrill et al. |
5747982 | May 5, 1998 | Dromgoole et al. |
5818669 | October 6, 1998 | Mader |
6002213 | December 14, 1999 | Wood |
6031338 | February 29, 2000 | Yoon et al. |
6058012 | May 2, 2000 | Cooper et al. |
6137167 | October 24, 2000 | Ahn et al. |
7015561 | March 21, 2006 | Saxelby et al. |
20020163322 | November 7, 2002 | Saxelby et al. |
08-130282 | May 1996 | JP |
11-067947 | March 1999 | JP |
Type: Grant
Filed: Apr 12, 2007
Date of Patent: Aug 30, 2011
Assignee: International Rectifier Corporation (El Segundo, CA)
Inventor: David Jauregui (Downey, CA)
Primary Examiner: Hung S Bui
Attorney: Farjami & Farjami LLP
Application Number: 11/787,234
International Classification: H05K 7/00 (20060101);