# Patent

## Title
Power quad flat no-lead (PQFN) package having bootstrap diodes on a common integrated circuit (IC)

## Abstract

According to an exemplary implementation, a power quad flat no-lead (PQFN) package includes a multi-phase inverter situated on a leadframe. The PQFN package further includes drivers situated on the leadframe and configured to drive the multi-phase inverter. The PQFN package also includes bootstrap diodes respectively coupled to the drivers. The bootstrap diodes are in a common integrated circuit (IC) that is situated on the leadframe. The common IC can include the drivers. The drivers can be high side drivers that are coupled to high side power switches of the multi-phase inverter. Also, the bootstrap diodes can be coupled to a supply voltage terminal of the PQFN package. Furthermore, the PQFN package can include wirebonds coupling the common IC to bootstrap supply voltage terminals of the PQFN package.

## Background
The present application claims the benefit of and priority to provisional application Ser. No. 61/774,541, filed on Mar. 7, 2013, and entitled “Power Quad Flat No-Lead (PQFN) Package Having Bootstrap Diodes on a Common Integrated Circuit (IC).” The present application is also a continuation-in-part of application Ser. No. 13/662,244 filed on Oct. 26, 2012, and entitled “Compact Wirebonded Power Quad Flat No-Lead (PQFN) Package,” which in turn claims priority to application Ser. No. 13/034,519 filed on Feb. 24, 2011, and entitled “Multi-Chip Module (MCM) Power Quad Flat No-Lead (PQFN) Semiconductor Package Utilizing a Leadframe for Electrical Interconnections,” which in turn claims priority to provisional application Ser. No. 61/459,527 filed on Dec. 13, 2010, and entitled “Low Cost Leadframe Based High Power Density Full Bridge Power Device.” The present application claims the benefit of and priority to all of the above-identified applications. Moreover, the disclosure and contents of all of the above-identified applications are hereby incorporated fully by reference into the present application.


BACKGROUND
I. Definition
As used herein, the phrase “group III-V” refers to a compound semiconductor including at least one group III element and at least one group V element. By way of example, a group III-V semiconductor may take the form of a III-Nitride semiconductor. “III-Nitride”, or “III-N”, refers to a compound semiconductor that includes nitrogen and at least one group III element such as aluminum (Al), gallium (Ga), indium (In), and boron (B), and including but not limited to any of its alloys, such as aluminum gallium nitride (AlxGa(1-x)N), indium gallium nitride (InyGa(1-y)N), aluminum indium gallium nitride (AlxInyGa(1-x-y)N), gallium arsenide phosphide nitride (GaAsaPbN(1-a-b), aluminum indium gallium arsenide phosphide nitride (AlxInyGa(1-x-y)AsaPbN(1-a-b)), for example. III-Nitride also refers generally to any polarity including but not limited to Ga-polar, N-polar, semi-polar, or non-polar crystal orientations. A III-Nitride material may also include either the Wurtzitic, Zincblende, or mixed polytypes, and may include single-crystal, monocrystalline, polycrystalline, or amorphous structures. Gallium nitride or GaN, as used herein, refers to a III-Nitride compound semiconductor wherein the group III element or elements include some or a substantial amount of gallium, but may also include other group III elements in addition to gallium. A group III-V or a GaN transistor may also refer to a composite high voltage enhancement mode transistor that is formed by connecting the group III-V or the GaN transistor in cascode with a lower voltage group IV transistor.
In addition, as used herein, the phrase “group IV” refers to a semiconductor that includes at least one group IV element such as silicon (Si), germanium (Ge), and carbon (C), and may also include compound semiconductors such as silicon germanium (SiGe) and silicon carbide (SiC), for example. Group IV also refers to semiconductor materials which include more than one layer of group IV elements, or doping of group IV elements to produce strained group IV materials, and may also include group IV based composite substrates such as silicon on insulator (SOI), separation by implantation of oxygen (SIMOX) process substrates, and silicon on sapphire (SOS), for example.
II. Background Art
Packages combining several semiconductor devices can simplify circuit design, reduce costs, and provide greater efficiency and improved performance by keeping related and dependent circuit components in close proximity. Furthermore, these packages can facilitate application integration and greater electrical and thermal performance compared to using separate packaging for components.
Quad flat no-dead (QFN) packages are leadless packages for electrical components, such as power semiconductor devices. The QFN packages can utilize a leadframe and wirebonds for connection to the electrical components housed therein. The QFN packages often have limited complexity and electrical routing can be challenging, particularly for more complex configurations. Thus, QFN packages often have simple configurations and house a small number of electrical components.
SUMMARY
A power quad flat no-lead (PQFN) package having bootstrap diodes on a common integrated circuit (IC), substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A illustrates a schematic diagram of an exemplary circuit of a power quad flat no-lead (PQFN) package.
FIG. 1B illustrates a schematic diagram of a PQFN package in an exemplary multi-phase inverter circuit.
FIG. 2A illustrates a top-plan view of a leadframe of an exemplary PQFN package.
FIG. 2B illustrates a top-plan view of an exemplary PQFN package with wirebonds.
FIG. 2C illustrates a bottom-plan view of an exemplary PQFN package.
FIG. 2D illustrates a cross sectional view of a portion of an exemplary PQFN package.



DETAILED DESCRIPTION
The following description contains specific information pertaining to implementations in the present disclosure. The drawings in the present application and their accompanying detailed description are directed to merely exemplary implementations. Unless noted otherwise, like or corresponding elements among the figures may be indicated by like or corresponding reference numerals. Moreover, the drawings and illustrations in the present application are generally not to scale, and are not intended to correspond to actual relative dimensions.
FIG. 1A illustrates a schematic diagram of an exemplary circuit of power quad flat no-lead (PQFN) package 100. FIG. 1B illustrates a schematic diagram of PQFN package 100 in multi-phase inverter circuit 150.
Referring to FIGS. 1A and 1B, PQFN package 100 includes driver integrated circuit (IC) 102 and multi-phase inverter 180. Multi-phase inverter 180 includes U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b. Driver IC 102 includes input logic 162, level shifter 164, level shifter 166, undervoltage protection circuit 168, comparator 170, latch 172, drivers 174a (e.g. high side drivers), drivers 174b (e.g. low side drivers), capacitor CR, and bootstrap diodes 176. Drivers 174a include drivers 142c, 142b, and 142a. Bootstrap diodes 176 include U-phase bootstrap diode D1, V-phase bootstrap diode D2, and W-phase bootstrap diode D3 (also referred to as “bootstrap diodes D1, D2, and D3”). Bootstrap capacitors 178 in FIG. 1B include U-phase bootstrap capacitor CB1, V-phase bootstrap capacitor CB2, and W-phase bootstrap capacitor CB3 (also referred to as “bootstrap capacitors CB1, CB2, and CB3”).
In multi-phase inverter circuit 150 of FIG. 1B, PQFN package 100 is connected to bus voltage source 114, supply voltage source 116, microcontroller 124, motor 126, bootstrap capacitors 178, resistor R1, capacitor C1, and shunt RS, as one example. Any of PQFN package 100, microcontroller 124, motor 126, resistor R1, capacitor C1, bootstrap capacitors 178, and shunt RS can be mounted on a printed circuit board (PCB). Furthermore, PQFN package 100 can be connected to any of bus voltage source 114, supply voltage source 116, microcontroller 124, motor 126, resistor R1, capacitor C1, bootstrap capacitors 178, and shunt RS through conductive leads on the PCB.
PQFN package 100 also includes VBUS terminal 112a, VCC terminal 112b, HIN1 terminal 112c, HIN2 terminal 112d, HIN3 terminal 112e, LINT terminal 112f, LIN2 terminal 112g, LIN3 terminal 112h, EN terminal 112i, FAULT terminal 112j, RCIN terminal 112k, IM terminal 112l, VSS terminal 112m, VCOM terminal 112n, SW1 terminal 112o, SW2 terminal 112p, SW3 terminal 112q, VB1 terminal 112r, VB2 terminal 112s, and VB3 terminal 112t, which are collectively referred to as I/O terminals 112.
In PQFN package 100, VBUS terminal 112a receives VBUS (e.g. a bus voltage) as input from bus voltage source 114. VCC terminal 112b receives supply voltage VCC as input to driver IC 102 from supply voltage source 116 and can also be referred to as supply voltage terminal 112b of PQFN package 100. HIN1 terminal 112c, HIN2 terminal 112d, and HIN3 terminal 112e receive HIN1, HIN2, and HIN3 respectively as inputs to driver IC 102 from microcontroller 124. LINT terminal 112f, LIN2 terminal 112g, and LIN3 terminal 112h receive LINT, LIN2, and LIN3 respectively as inputs to driver IC 102 from microcontroller 124.
Also in PQFN package 100, EN terminal 112i receives EN as input to driver IC 102 from microcontroller 124. FAULT terminal 112j receives FAULT as output from driver IC 102 to microcontroller 124. RCIN terminal 112k receives RCIN as input to driver IC 102 from resistor R1 and capacitor C1. IM terminal 112l receives ITRIP as input to driver IC 102 and microcontroller 124 from U-phase power switch 104b, V-phase power switch 106b, and W-phase power switch 108b. 
Further in PQFN package 100, VSS terminal 112m receives VSS as input to driver IC 102 from logic ground GVSS. VCOM terminal 112n receives VCOM as input to driver IC 102, U-phase power switch 104b, V-phase power switch 106b, and W-phase power switch 108b from power stage ground GCOM. SW1 terminal 112o receives SW1 from U-phase output node 110a as output to motor 126. Driver IC 102 also receives SW1 as input from U-phase output node 110a. SW2 terminal 112p receives SW2 from V-phase output node 110b as output to motor 126. Driver IC 102 also receives SW2 as input from V-phase output node 110b. SW3 terminal 112q receives SW3 from W-phase output node 110c as output to motor 126. Driver IC 102 also receives SW3 as input from W-phase output node 110c. 
Additionally, in PQF package 100, VB1 terminal 112r receives bootstrap supply voltage VB1 as input to driver IC 102 from bootstrap capacitor CB1 and can also be referred to as bootstrap supply voltage terminal 112r. VB2 terminal 112s receives bootstrap supply voltage VB2 as input to driver IC 102 from bootstrap capacitor CB2 and can also be referred to as bootstrap supply voltage terminal 112s. VB3 terminal 112t receives bootstrap supply voltage VB3 as input to driver IC 102 from bootstrap capacitor CB3 and can also be referred to as bootstrap supply voltage terminal 112t. 
It will be appreciated that in various implementations, the number, quantity, and location of I/O terminals 112 are different than what is shown. For example, in various implementations, a driver IC that is different than driver IC 102 can be utilized, which can have different capabilities and/or I/O requirements than driver IC 102. This may be reflected in I/O terminals 112 as well as other connections of PQFN package 100. As one specific example, in one implementation, driver IC 102 is instead a functionally integrated IC that incorporates at least some of the functionality of driver IC 102 and microcontroller 124. Thus, additional I/O terminals 112 may be included for certain functionality, while certain I/O terminals 112, such as FAULT terminal 112j may not be required.
In PQFN package 100, driver IC 102 can be a high voltage IC (HVIC) for driving U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b of multi-phase inverter 180. Examples of driver IC 102 include “5th generation” HVICs available from International Rectifier Corporation®. In the present implementation, U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b are vertical conduction power devices, for example, group IV semiconductor power metal-oxide-semiconductor field effect transistors (power MOSFETs) such as fast-reverse epitaxial diode field effect transistors (FREDFETs), or group IV semiconductor insulated-gate bipolar transistors (IGBTs). In other implementations group III-V semiconductor FETs, HEMTs (high electron mobility transistors) and, in particular, GaN FETs and/or HEMTs can be used as power devices in U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b. As defined above, Gallium nitride or GaN, as used herein, refers to a III-Nitride compound semiconductor wherein the group III element or elements include some or a substantial amount of gallium, but may also include other group III elements in addition to gallium. As previously stated, a group III-V or a GaN transistor may also refer to a composite high voltage enhancement mode transistor that is formed by connecting the group III-V or the GaN transistor in cascode with a lower voltage group IV transistor. While PQFN package 100 provides a full bridge power device, alternative implementations can provide other package configurations as required by the particular application.
In PQFN package 100, HIN1, HIN2, and HIN3 are control signals for U-phase power switch 104a, V-phase power switch 106a, and W-phase power switch 108a, which are high side power switches. Input logic 162 receives HIN1, HIN2, and HIN3, which are respectively provided to level shifter 164. In the present implementation, level shifter 164 is a high-voltage level shifter having termination that can sustain, for example, approximately 600 volts. Level shifted versions of HIN1, HIN2, and HIN3 are received by drivers 174a to provide high side gate signals H1, H2, and H3 to U-phase power switch 104a, V-phase power switch 106a, and W-phase power switch 108a, as shown in FIG. 1A. Drivers 174a generate high side gate signals H1, H2, and H3 from HIN1, HIN2, and HIN3 respectively. Drivers 174a further receive SW1, SW2, and SW3 from U-phase output node 110a, V-phase output node 110b, and W-phase output node 110c respectively. Thus, drivers 174a are high side drivers and are coupled to high side power switches of multi-phase inverter 180.
Similarly, LIN1, LIN2, and LIN3 are control signals for U-phase power switch 104b, V-phase power switch 106b, and W-phase power switch 108b, which are low side power switches. Input logic 162 receives LIN1, LIN2, and LIN3, which are respectively provided to level shifter 166. In the present implementation, level shifter 166 is a low-voltage level shifter, which compensates for differences between logic ground GVSS and power stage ground GCOM. This can be, for example, approximately one to approximately two volts. Level shifted versions of LIN1, LIN2, and LIN3 are respectively provided to drivers 174b to provide low side gate signals L1, L2, and L3 to U-phase power switch 104b, V-phase power switch 106b, and W-phase power switch 108b, as shown in FIG. 1A. Drivers 174b generate low side gate signals L1, L2, and L3 from LIN1, LIN2, and LIN3 respectively. Thus, drivers 174b are low side drivers and are coupled to low side power switches of multi-phase inverter 180.
Driver IC 102 can thereby drive switching of U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b using drivers 174a and 174b to power motor 126 (as one example), which generates motor current IM (i.e. load current). In the present implementation, drivers 174a and 174b are impedance matched to respective ones of U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b. Drivers 174a and 174b can thereby drive U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b without gate resistors which allows PQFN package 100 to be smaller and less complex.
VBUS is a bus voltage from bus voltage source 114, which is coupled to respective drains of U-phase power switch 104a, V-phase power switch 106a, and W-phase power switch 108a. As one example, bus voltage source 114 can be an AC to DC rectifier. The AC can be, as one example, an outlet voltage, such as 230 volts. The DC voltage can be, for example, approximately 300 volts to approximately 400 volts for VBUS.
VSS is a logic ground of a support logic circuit of driver IC 102 from logic ground GVSS. As one example, FIG. 1A shows VSS as a logic ground for capacitor CR. VSS is also a logic ground for other components of the support logic circuit, which includes input logic 162, level shifter 164, undervoltage protection circuit 168, comparator 170, latch 172, and capacitor CR, but can include different components. VCOM is a power stage ground of U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b from power stage ground GCOM. FIG. 1A shows VCOM connected to sources of U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b within PQFN package 100. VCOM can also be for driver IC 102. As shown in FIG. 1A, VCOM coupled to drivers 174b of driver IC 102.
A logic ground separate from a power stage ground is provided for in multi-phase inverter circuit 150 using shunt RS. Shunt RS is coupled across VSS terminal 112m and VCOM terminal 112n. Shunt RS is also coupled to sources of each of U-phase power switch 104b, V-phase power switch 106b, and W-phase power switch 108b through VCOM terminal 112n. Thus, motor current IM from motor 126, shown in FIG. 1A, is combined phase current from U-phase leg 182a, V-phase 182b, and W-phase leg 182c of multi-phase inverter 180. Motor current IM is provided to, for example, microcontroller 124 through IM terminal 112l. Microcontroller 124 utilizes motor current IM to reconstruct individual phase currents (U, V, and W) to control pulse-width modulation (PWM) by controlling HIN1, HIN2, HIN3, LIN1, LIN2, and LIN3.
Thus, in the present implementation, PQFN package 100 has a logic ground separate from a power stage ground. During switching of U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b, a voltage can develop across shunt RS. By having a logic ground separate from a power stage ground, supply voltage VCC for the support logic circuit can be made with respect to ground instead of the voltage across shunt RS. Thus, by using separate grounds, PQFN package 100 is protected from latch up and noise malfunction, which otherwise can be caused by excess switching voltages from U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b. 
In other implementations, PQFN package 100 instead has a single ground for logic and power. For example, VSS terminal 112m and VCOM terminal 112n can be combined into a single terminal or can be are shorted to one another. In one such implementation, PQFN package 100 is an open source/emitter PQFN package, in which motor current from at least two of U-phase leg 182a, V-phase leg 182b, and W-phase leg 182c of multi-phase inverter 180 are provided as respective outputs terminals of PQFN package 100. Thus, for example, microcontroller 124 and/or another device or devices can utilize those motor currents to control pulse-width modulation (PWM) by controlling HIN1, HIN2, HIN3, LIN1, LIN2, and LIN3.
In PQFN package 100, supply voltage VCC is a supply voltage for driver IC 102 from supply voltage source 116, which can be, for example, approximately 15 volts. In some implementations, supply voltage source 116 generates supply voltage VCC from VBUS. Drivers 174b are powered by supply voltage VCC whereas drivers 174a are powered by bootstrap supply voltages VB1, VB2, and VB3.
Bootstrap supply voltages VB1, VB2, and VB3 are generated using bootstrap capacitors 178, bootstrap diodes 176, and supply voltage VCC. As shown in FIG. 1A, bootstrap diodes 176 are coupled to supply voltage terminal 112b of PQFN package 100 and are respectively coupled to drivers 174a. Bootstrap diodes 176 and drivers 174a are each respectively coupled to bootstrap supply voltage terminals 112r, 112s, and 112t. As shown in FIG. 1B, bootstrap capacitors 178 are respectively coupled to SW1 terminal 112o, SW2 terminal 112p, and SW3 terminal 112q and bootstrap supply voltage terminals 112r, 112s, and 112t. Thus, in the present implementation, bootstrap diodes 176 are configured for connection to respective bootstrap capacitors 178 and can thereby be configured to charge bootstrap supply voltages VB1, VB2, and VB3.
Typical QFN packages have limited functionality with simple configurations and a small number of electrical components. As functionality increases it becomes difficult to rout wires for connections while avoiding wire crossing and wire shorting. Moreover, long lengths of wiring adversely affect electrical and thermal performance. However, PQFN packages, in accordance with various implementations of the present disclosure, can have high levels of functionality while avoiding wire crossing and wire shorting and achieving high electrical and thermal performance.
In the implementation shown, PQFN package 100 accommodates multi-phase inverter 180 situated on a leadframe. PQFN package 100 further accommodates drivers 174a and 174b situated on the leadframe and configured to drive multi-phase inverter 180. Furthermore, PQFN package 100 accommodates bootstrap diodes 176 respectively coupled to drivers 174a. These features can be accommodated with PQFN package 100 having a footprint of, for example, approximately 12 mm by approximately 12 mm with high electrical and thermal performance. In other implementations, PQFN package 100 can have a footprint of greater than 12 mm by 12 mm. In still other implementations, PQFN package 100 can have a footprint of less than 12 mm by 12 mm.
Bootstrap diodes are typically external to semiconductor packages and for multi-phase inverters in particular. However, including bootstrap diodes 176 in PQFN package 100 simplifies circuit design, reduces costs, and provides greater efficiency and improved performance at least by keeping related and dependent circuit components in close proximity. Furthermore, PQFN package 100 facilitates application integration and greater electrical and thermal performance. As can be seen in FIG. 1A, bootstrap diodes D1, D2, and D2 add significant complexity to the circuit of PQFN package 100. However, by including bootstrap diodes D1, D2, and D3 on a common IC, for example, driver IC 102, this circuit complexity has a reduced impact on the configuration PQFN package 100. Also, in implementations where the common IC includes drivers 174a and/or 174b, such as in PQFN package 100, the impact can be further reduced.
Bootstrap diodes D1, D2, and D3 would consume significant package space if included as discrete components. For example, in the present implementation, PQFN package 100 is for high power applications. Thus, bootstrap diodes D1, D2, and D3 have high breakdown voltages, such as, for example approximately 200 volts to approximately 600 volts. As such, bootstrap diodes D1, D2, and D3 would be exceedingly large as discrete components. However, by including bootstrap diodes D1, D2, and D3 on a common IC, for example, driver IC 102, the size of bootstrap diodes D1, D2, and D3 has a reduced impact on the configuration of PQFN package 100. This may allow PQFN package 100 to internalize such functionality as being enabled/disabled responsive to input, providing fault indications, having undervoltage protection, having overcurrent protection, and/or having separate logic and power grounds.
In the implementation shown, supply voltage VCC is coupled to undervoltage protection circuit 168. Undervoltage protection circuit 168 detects an undervoltage condition when supply voltage VCC falls below a threshold voltage, such as approximately 9 volts. Supply voltage VCC notifies input logic 162 of the undervoltage condition to thereby disable switching in driver IC 102. Switching in driver IC 102 can also be altered using EN. EN can be used by, for example, microcontroller 124, to enable/disable switching of driver IC 102. More particularly, driver IC 102 is configured to enable/disable switching of H1, H2, H3, L1, L2, and L3 responsive to EN.
FIG. 1A shows motor current IM provided to driver IC 102 as ITRIP. Driver IC 102 utilizes ITRIP for overcurrent protection. For example, FIG. 1A shows comparator 170 comparing ITRIP to a reference voltage that is generated by capacitor CR. If ITRIP exceeds the reference voltage, comparator 170 triggers latch 172, which indicates an overcurrent condition to microcontroller 124 by providing FAULT to FAULT terminal 112j. Input logic 162 also receives FAULT to disable switching of driver IC 102. Driver IC 102 utilizes RCIN to automatically reset latch 172 from the overcurrent protection. As shown in FIG. 1B, resistor R1 is coupled between VCC terminal 112b and RCIN terminal 112k to charge capacitor C1. Capacitor C1 is coupled between RCIN terminal 112k and VSS terminal 112m. Resistor R1 and capacitor C1 can be changed to alter timing of automatic reset for the overcurrent protection.
Turning to FIGS. 2A, 2B, and 2C, FIG. 2A illustrates a top-plan view of a leadframe of PQFN package 200 of FIGS. 2B and 2C. FIG. 2B illustrates a top-plan view of PQFN package 200. FIG. 2C illustrates a bottom-plan view of PQFN package 200. In the present implementation, PQFN package 200 is a multi-chip module (MCM) PQFN package, which can have a footprint of approximately 12 mm by approximately 12 mm. In other implementations, PQFN package 200 can have a footprint of greater than 12 mm by 12 mm. In still other implementations, PQFN package 200 can have a footprint of less than 12 mm by 12 mm.
PQFN package 200 corresponds to PQFN package 100 in FIGS. 1A and 1B. For example, PQFN package 200 includes driver IC 202, U-phase power switches 204a and 204b, V-phase power switches 206a and 206b, and W-phase power switches 208a and 208b corresponding respectively to driver IC 102, U-phase power switches 104a and 104b, V-phase power switches 106a and 106b, and W-phase power switches 108a and 108b in FIG. 1A.
Furthermore, PQFN package 200 includes VBUS terminal 212a, VCC terminal 212b, HIN1 terminal 212c, HIN2 terminal 212d, HIN3 terminal 212e, LIN1 terminal 212f, LIN2 terminal 212g, LIN3 terminal 212h, EN terminal 212i, FAULT terminal 212j, RCIN terminal 212k, IM terminal 212l, VSS terminal 212m (also referred to as “logic ground terminal 112m”), VCOM terminal 212n (also referred to as “power stage ground terminal 112n”), SW1 terminal 212o (also referred to as “U-phase output terminal 212o”), SW2 terminal 212p (also referred to as “V-phase output terminal 212p”), SW3 terminal 212q (also referred to as “W-phase output terminal 212q”), VB1 terminal 212r, VB2 terminal 212s, and VB3 terminal 212t (also referred to as “I/O terminals 212”) corresponding respectively to VBUS terminal 112a, VCC terminal 112b, HIN1 terminal 112c, HIN2 terminal 112d, HIN3 terminal 112e, LIN1 terminal 112f, LIN2 terminal 112g, LIN3 terminal 112h, EN terminal 112i, FAULT terminal 112j, RCIN terminal 112k, IM terminal 112l, VSS terminal 112m, VCOM terminal 112n, SW1 terminal 112o, SW2 terminal 112p, SW3 terminal 112q, VB1 terminal 112r, VB2 terminal 112s, and VB3 terminal 112t in PQFN package 100.
FIG. 2A shows leadframe 260 including driver IC die pad 220, W-phase die pad 222a, V-phase die pad 222b, U-phase die pad 222c, and common die pad 228. Leadframe island 233 is electrically and mechanically connected (e.g. integrally connected) to driver IC die pad 220. Leadframe 260 further includes leadframe strips 230 and 232 and I/O terminals 212. Leadframe island 234 is on leadframe strip 230 of leadframe 260 and leadframe strip 230 is electrically and mechanically connected (e.g. integrally connected) to V-phase die pad 222b of leadframe 260. Leadframe island 236 is on leadframe strip 232 of leadframe 260 and leadframe strip 232 is electrically and mechanically connected (e.g. integrally connected) to U-phase die pad 222c of leadframe 260. As shown in FIG. 2B, leadframe strips 230 and 232 can optionally extend to edge 242c of PQFN package 200. In doing so, any of leadframe strips 230 and 232 can provide, for example, additional I/O terminals for PQFN package 200. For example, leadframe strip 232 is shown as providing an additional SW1 terminal 212o at edge 242c of PQFN package 200.
Leadframe 260 can comprise a material with high thermal and electrical conductivity such as copper (Cu) alloy C194 available from Olin Brass®. Top-side 240a of leadframe 260 can be selectively plated with materials for enhanced adhesion to device dies and wires. The plating can comprise silver (Ag) plating that is selectively applied to leadframe 260, which is available from companies such as QPL Limited.
FIGS. 2A and 2B show that leadframe 260 is an etched leadframe, such as a half-etched leadframe. Portions of leadframe 260, which are unetched (e.g. not half-etched) are indicated in FIGS. 2A and 2B using dashed lines. Leadframe islands 233, 234, and 236 are examples of such unetched portions. For example, FIG. 2C shows bottom-side 240b of leadframe 260 (which also corresponds to a bottom-side of PQFN package 200). FIG. 2C further shows mold compound 265 of PQFN package 200, which covers etched portions of leadframe 260. Mold compound 265 can be a plastic that has a low flexural modulus, such as CEL9220ZHF10 (v79) available from Hitachi® Chemical. To provide resilience against package cracking, the height (or thickness) of PQFN package 200 as defined by mold compound 265 may be kept thin, such as 0.9 mm or less.
I/O terminals 212, leadframe island 233, leadframe island 234, and leadframe island 236 are unetched and are exposed through mold compound 265 on bottom-side 240b of leadframe 260 (which also corresponds to a bottom-side of PQFN package 200). As such, I/O terminals 212, leadframe island 233, leadframe island 234 and leadframe island 236 are exposed on bottom-side 240b of leadframe 260 for high electrical conductivity and/or thermal dissipation. By providing a (PCB) with matching lands, this feature can optionally be exploited. The exposed areas of leadframe 260 can be plated, for example, with Tin (Sn).
Driver IC 202 is situated on leadframe 260 and is configured to drive U-phase power switches 204a and 204b, V-phase power switches 206a and 206b, and W-phase power switches 208a and 208b, which correspond to multi-phase inverter 180 in FIG. 1A. More particularly, driver IC 202 is situated on driver IC die pad 220 of leadframe 260. Driver IC die pad 220 is larger than driver IC 202 and can therefore accommodate different, larger driver ICs, which may have different features than driver IC 202. Driver IC 202, U-phase power switches 204a and 204b, V-phase power switches 206a and 206b, and W-phase power switches 208a and 208b are interconnected utilizing wirebonds and leadframe 260.
FIG. 2B also shows that wirebonds, such as wirebond 244a electrically and mechanically connect driver IC 202 to VCC terminal 212b, HIN1 terminal 212c, HIN2 terminal 212d, HIN3 terminal 212e, LIN1 terminal 212f, LIN2 terminal 212g, LIN3 terminal 212h, EN terminal 212i, FAULT terminal 212j, RCIN terminal 212k, IM terminal 212l, VSS terminal 212m, VB1 terminal 212r, VB2 terminal 212s, VB3 terminal 212t, and to respective gates of U-phase power switches 204a and 204b, V-phase power switches 206a and 206b, and W-phase power switches 208a and 208b. 
Wirebond 244a and similarly depicted wirebonds in FIG. 2B can include, for example, 1.3 mil diameter G1 type Gold (Au) wires. Thicker wires can be utilized for power connections, such as wirebonds 246a, 246b, 246c, 246d, 246e, and 246f (also referred to as “wirebonds 246”). Wirebonds 246 can be, for example, 2.0 mil diameter copper (Cu) wires, such as Maxsoft® LD wires available from Kulicke & Soffa®. Wirebonds 246 can be bonded using bond stitch on ball (BSOB) bonding. As shown in FIG. 2B, multiple wirebonds, such as two wirebonds, can be in parallel with wirebonds 246 to for additional current handling.
FIG. 2B shows that U-phase power switches 204a and 204b, V-phase power switches 206a and 206b, W-phase power switches 208a and 208b, and driver IC 202 are electrically and mechanically connected to leadframe 260. This can be accomplished utilizing solder or conductive adhesive, such as silver filled QMI 529HT available from Henkel Corporation.
As shown in FIG. 2B, U-phase power switch 204b, V-phase power switch 206b, and W-phase power switch 208b are situated on leadframe 260 along edge 242a of PQFN package 200. W-phase power switch 208b is situated on W-phase die pad 222a. More particularly, drain 236a of W-phase power switch 208b is situated on W-phase die pad 222a. Similarly, V-phase power switch 206b is situated on V-phase die pad 222b. More particularly, drain 236b of V-phase power switch 206b is situated on V-phase die pad 222b. Also, U-phase power switch 204b is situated on U-phase die pad 222c. More particularly, drain 236c of U-phase power switch 204b is situated on U-phase die pad 222c. Thus, U-phase power switch 204b, V-phase power switch 206b, and W-phase power switch 208b are individually coupled to respective die pads of leadframe 260. As such, W-phase die pad 222a can correspond to W-phase output terminal 212q of PQFN package 200, V-phase die pad 222b can correspond to V-phase output terminal 212p of PQFN package 200, and U-phase die pad 222c can correspond to U-phase output terminal 212o of PQFN package 200, as shown in FIG. 2B.
Also shown in FIG. 2B, U-phase power switch 204a, V-phase power switch 206a, and W-phase power switch 208a are situated on leadframe 260 along edge 242b of PQFN package 200, which intersects edge 242a. U-phase power switch 204a, V-phase power switch 206a, and W-phase power switch 208a are situated on common die pad 228 of leadframe 260. More particularly, drain 236d of U-phase power switch 204a, drain 236e of V-phase power switch 206a, and drain 236f of W-phase power switch 208a are situated on common die pad 228 of leadframe 260. Thus, common die pad 228 can correspond to VBUS terminal 212a (e.g. a bus voltage input terminal) of PQFN package 200, as shown in FIG. 2B.
An example of this configuration is shown in more detail in FIG. 2D. FIG. 2D illustrates a cross sectional view of a portion of PQFN package 200. The cross sectional view in FIG. 2D corresponds to cross section 2D-2D, of FIGS. 2B and 2C. FIG. 2D shows drain 236e of V-phase power switch 206a connected to common die pad 228 through conductive adhesive 254 and plating 248a of leadframe 260. Conductive adhesive 254 can include silver filled adhesive such as QMI 529HT. Other dies in PQFN package 200 can similarly be connected to leadframe 260.
U-phase power switch 204b, V-phase power switch 206b, and W-phase power switch 208b are coupled respectively to U-phase power switch 204a, V-phase power switch 206a, and W-phase power switch 208a through leadframe 260.
In FIG. 2B, wirebond 246a electrically and mechanically connects source 238d of U-phase power switch 204a to leadframe 260. More particularly, source 238d is connected via wirebond 246a to leadframe island 236 of leadframe strip 232. Thus, U-phase output node 110a of FIG. 1A is situated on leadframe strip 232 of leadframe 260, where leadframe strip 232 is connected to U-phase die pad 222c of leadframe 260. As such, PQFN package 200 has significant flexibility in arranging wirebond 246a, and other wirebonds, such as wirebond 244b, while avoiding wire shorts due to wire crossing and achieving high electrical and thermal performance.
Similarly, wirebond 246b electrically and mechanically connects source 238e of V-phase power switch 206a to leadframe 260. FIG. 2D illustrates one example of this connection. Source 238e is connected via wirebond 246b to leadframe island 234 of leadframe strip 230 through plating 248b of leadframe 260. Leadframe strip 230 then connects to drain 236b of V-phase power switch 206b through V-phase die pad 222b. A similar connection can be employed for connecting source 238d to drain 236c of U-phase power switch 204b. Wirebond 246b electrically and mechanically connects source 238e of V-phase power switch 206a to leadframe strip 230 at leadframe island 234. Thus, V-phase output node 110b of FIG. 1A is situated on leadframe strip 230 of leadframe 260, where leadframe strip 230 is connected to V-phase die pad 222b of leadframe 260. As such, PQFN package 200 has significant flexibility in arranging wirebond 246b, and other wirebonds, such as wirebond 244c, while avoiding wire shorts due to wire crossing and achieving high electrical and thermal performance.
It is noted that PQFN package 200 can include leadframe islands 234 and/or 236 without leadframe strip 230 and/or 232. For example, leadframe island 234 can be connected to V-phase die pad 222b through a trace on a PCB. It is further noted that PQFN package 200 can include leadframe strip 230 and/or 232 without leadframe islands 234 and/or 236. However, having leadframe strips 230 and 232 with leadframe islands 234 and 236 can offer significant flexibility in arranging wirebonds in PQFN package 200 while achieving high electrical and thermal performance.
In FIG. 2B, wirebond 246c is electrically and mechanically connecting source 238f of W-phase power switch 208a to leadframe 260. More particularly, wirebond 246b electrically and mechanically connects source 238f of W-phase power switch 208a to W-phase die pad 222a on leadframe 260. Thus, W-phase output node 110c of FIG. 1A is situated on W-phase die pad 222a of leadframe 260 with W-phase power switch 208b. As W-phase power switch 208b is adjacent to W-phase power switch 208a, source 238f of W-phase power switch 208a can be coupled to drain 236a of W-phase power switch 208b while easily avoiding wire shorts due to wire crossing and achieving high electrical and thermal performance. This can be accomplished without utilizing a leadframe strip and/or leadframe island.
Thus, PQFN package 200 can be made significantly smaller while avoiding arcing between U-phase output node 110a, V-phase output node 110b, and W-phase output node 110c. For example, an additional leadframe strip and/or leadframe island would require a larger PQFN package 200 to maintain sufficient spacing 252 between leadframe strips 230 and 232 so as to prevent arcing (e.g. at least 1 mm). Furthermore, this configuration does not significantly impact flexibility in arranging wirebonds in PQFN package 200. Also, as W-phase die pad 222a is exposed on bottom-side 240b of PQFN package 200 (shown in FIG. 2C), heat generated at W-phase output node 110c can be effectively dissipated from PQFN package 200.
PQFN package 200 includes a logic ground of leadframe 260 coupled to a support logic circuit of driver IC 202. The logic ground of leadframe 260 includes logic ground terminal 212m. At least wirebond 244g is electrically and mechanically connecting logic ground terminal 212m of leadframe 260 to driver IC 202 and more particularly, is connecting logic ground terminal 212m of leadframe 260 to the support logic of driver IC 202.
PQFN package 200 further includes a power stage ground of leadframe 260 coupled to sources 238c, 238b, and 238a of U-phase power switch 204b, V-phase power switch 206b, and W-phase power switch 208b. The power stage ground of leadframe 260 includes power stage ground terminal 212n, driver IC die pad 220, and leadframe island 233. In FIG. 2B, at least wirebond 246d is electrically and mechanically connecting power stage ground terminal 212n of the power stage ground of leadframe 260 to source 238a of W-phase power switch 208b. At least wirebond 246e is electrically and mechanically connecting source 238a of W-phase power switch 208b to source 238b of V-phase power switch 206b. Also, at least wirebond 246f is electrically and mechanically connecting source 238b of V-phase power switch 206b to source 238c of U-phase power switch 204b. Thus, sources 238a, 238b, and 238c are electrically connected to each other within PQFN package 200.
In other implementations, PQFN package 200 is an open source/emitter PQFN package (which may also be referred to as an open emitter PQFN package), in which sources 238a, 238b, and 238c are not electrically connected to each other within PQFN package 200. For example, wirebonds, such as wirebonds 246 can electrically and mechanically connect sources 238a, 238b, and 238c to respective current source terminals of PQFN package 200.
In the present implementation, the power stage ground of leadframe 260 is coupled to drivers (e.g. drivers 174b in FIG. 1) of driver IC 202. Wirebonds 244e and 244f are connecting source 238c of U-phase power switch 204b to drivers 174b of driver IC 202 through leadframe 260. Wirebond 244e is electrically and mechanically connecting source 238c of U-phase power switch 204b to leadframe island 233 of leadframe 260. Wirebond 244f is electrically and mechanically connecting leadframe island 233 of leadframe 260 to driver IC 202. Connecting source 238c of U-phase power switch 204b to driver IC 202 through leadframe 260, offers flexibility in connecting PQFN package 200. However, it is noted that leadframe island 233 is optional and a wirebond may directly connect source 238c of U-phase power switch 204b to driver IC 202. Furthermore, in some implementations, driver IC 202 optionally has ground 256, which is situated on driver IC die pad 220 of leadframe 260. Ground 256 can be the power stage ground and/or the logic ground. In the implementation shown, where ground 256 is the power stage ground, wirebond 244f may be excluded.
Thus, PQFN package 200 includes a multi-phase inverter (e.g. multi-phase inverter 180) situated on leadframe 260, drivers (e.g. drivers 174a) situated on leadframe 260 and configured to drive the multi-phase inverter. PQFN package 200 further includes bootstrap diodes (e.g. bootstrap diodes 176) respectively coupled to the drivers, where the bootstrap diodes are in a common integrated circuit (IC) (e.g. driver IC 202) that is situated on leadframe 260.
In the implementation shown, the common IC (e.g. driver IC 202) includes drivers 174a. Wirebond 244b electrically and mechanically connects driver IC 202 (e.g. U-phase driver 142a) and leadframe strip 232 of leadframe 260 at leadframe island 236. U-phase output node 110a of FIG. 1A is situated on leadframe island 236 of leadframe 260. Thus, U-phase driver 142a of FIG. 1A is coupled to U-phase output node 110a of multi-phase inverter 180, where U-phase output node 110a is situated on leadframe island 236 (and/or leadframe strip 232) of leadframe 260.
Similarly, wirebond 244b electrically and mechanically connects driver IC 202 (e.g. V-phase driver 142b) and leadframe strip 230 of leadframe 260 at leadframe island 234. V-phase output node 110B of FIG. 1A is situated on leadframe island 234 of leadframe 260. Thus, V-phase driver 142b of FIG. 1A is coupled to V-phase output node 110b of multi-phase inverter 180, where V-phase output node 110b is situated on leadframe island 234 (and/or leadframe strip 230) of leadframe 260.
Wirebond 244d electrically and mechanically connects driver IC 202 (e.g. W-phase driver 142c) and source 238f of w-phase power switch 208a. In the present implementation, wirebond 244d is a direct electrical connection between driver IC 202 and source 238f. W-phase driver 142c of FIG. 1A is thereby coupled to W-phase output node 110c of multi-phase inverter 180.
PQFN package 200 further includes wirebonds 244g, 244h, and 244i respectively coupling the common IC (e.g. driver IC 202) to bootstrap supply voltage terminals 212r, 212s, and 212t of PQFN package 200. As bootstrap diodes 176 are in the common IC, PQFN package 200 only requires a single supply voltage terminal, VCC terminal 212b, where wirebond 244a couples VCC terminal 212b to each of bootstrap diodes 176. Bootstrap capacitors 178 can be respectively coupled from bootstrap supply voltage terminals 212r, 212s, and 212t to U-phase output terminal 212o, V-phase output terminal 212p, and W-phase output terminal 212q so as to power drivers 174a. 
Thus, as described above with respect to FIGS. 1A, 1B, and 2A through 2D, in accordance with various implementations, PQFN packages can include bootstrap diodes in a common IC that is situated on a leadframe. In some implementations, the common IC includes drivers of a multi-phase inverter. In doing so, the PQFN packages can be substantially more complex than typical QFN packages while avoiding wire crossing and wire shorting and achieving high electrical and thermal performance.
From the above description it is manifest that various techniques can be used for implementing the concepts described in the present application without departing from the scope of those concepts. Moreover, while the concepts have been described with specific reference to certain implementations, a person of ordinary skill in the art would recognize that changes can be made in form and detail without departing from the scope of those concepts. As such, the described implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present application is not limited to the particular implementations described above, but many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

## Claims

1. A power quad flat no-lead (PQFN) package comprising:
a multi-phase inverter situated on a leadframe;
drivers situated on said leadframe and configured to drive said multi-phase inverter;
bootstrap diodes respectively coupled to said drivers, said bootstrap diodes being in a common integrated circuit (IC) that is situated on said leadframe;
wherein at least one of said drivers is coupled to a first leadframe strip, said first leadframe strip extending from a first die pad at a first edge of said PQFN package to a second edge on an opposite side of said PQFN package.

2. The PQFN package of claim 1, wherein said common IC includes said drivers.

3. The PQFN package of claim 1, wherein said drivers are high side drivers and are coupled to a high side power switch of said multi-phase inverter.

4. The PQFN package of claim 1, wherein said bootstrap diodes are coupled to a supply voltage terminal of said PQFN package.

5. The PQFN package of claim 1, comprising wirebonds coupling said common IC to bootstrap supply voltage terminals of said PQFN package.

6. The PQFN package of claim 1, wherein said at least one of said drivers is coupled to an output node of said multi-phase inverter, said output node being situated on said first leadframe strip of said leadframe.

7. The PQFN package of claim 1, wherein said at least one of said drivers is coupled to an output node of said multi-phase inverter, said output node being situated on a first leadframe island of said leadframe.

8. The PQFN package of claim 1, wherein said multi-phase inverter comprises high side power switches that are situated on a common die pad of said leadframe.

9. The PQFN package of claim 8, wherein said high side power switches comprise group III-V transistors.

10. The PQFN package of claim 1, wherein said PQFN package has a footprint of greater than 12 mm by 12 mm.

11. The PQFN package of claim 1, wherein said PQFN package has a footprint of less than 12 mm by 12 mm.

12. A power quad flat no-lead (PQFN) package comprising:
a multi-phase inverter situated on a leadframe;
a driver integrated circuit (IC) situated on said leadframe and configured to drive said multi-phase inverter;
a plurality of bootstrap diodes configured for connection to respective bootstrap capacitors, said plurality of bootstrap diodes being in said driver IC;
wherein said driver IC is coupled to a first leadframe strip, said first leadframe strip extending from a first die pad at a first edge of said PQFN package to a second edge on an opposite side of said PQFN package.

13. The PQFN package of claim 12, wherein said driver IC is configured to drive high side power switches of said multi-phase inverter.

14. The PQFN package of claim 12, wherein said bootstrap diodes are coupled to a supply voltage terminal of said PQFN package.

15. The PQFN package of claim 12, comprising wirebonds coupling said driver IC to bootstrap supply voltage terminals of said PQFN package.

16. The PQFN package of claim 12, wherein said driver IC is coupled to an output node of said multi-phase inverter, said output node being situated on said first leadframe strip of said leadframe.

17. The PQFN package of claim 12, wherein said driver IC is coupled to an output node of said multi-phase inverter, said output node being situated on a first leadframe island of said leadframe.

18. The PQFN package of claim 12, wherein said multi-phase inverter comprises high side power switches that are situated on a common die pad of said leadframe.

19. A power quad flat no-lead (PQFN) package comprising:
U-phase, V-phase, and W-phase power switches situated on a leadframe;
U-phase, V-phase, and W-phase drivers situated on said leadframe and respectively coupled to said U-phase, V-phase, and W-phase power switches;
U-phase, V-phase, and W-phase bootstrap diodes respectively coupled to said U-phase, V-phase, and W-phase drivers, said U-phase, V-phase, and W-phase bootstrap diodes being in a common integrated circuit (IC) that is situated on said leadframe;
wherein at least one of said U-phase, V-phase, and W-phase drivers is coupled to a first leadframe strip, said first leadframe strip extending from a first die pad at a first edge of said PQFN package to a second edge on an opposite side of said PQFN package.

20. The PQFN package of claim 19, wherein said common IC includes said U-phase, V-phase, and W-phase drivers.