904 ieee journal of solid-state circuits, vol. 46, no. 4

904 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 46, NO. 4, APRIL 2011

Interleaving Energy-Conservation Mode (IECM)Control in Single-Inductor Dual-Output (SIDO)

Step-Down Converters With 91% Peak EfficiencyYu-Huei Lee, Student Member, IEEE, Yao-Yi Yang, Student Member, IEEE,

Shih-Jung Wang, Student Member, IEEE, Ke-Horng Chen, Senior Member, IEEE, Ying-Hsi Lin,Yi-Kuang Chen, and Chen-Chih Huang

Abstract—The proposed single-inductor dual-output (SIDO)converter with interleaving energy-conservation mode (IECM)control is designed using 65 nm technology to power the ultra-wideband (UWB) system. The energy-conservation mode (ECM) con-trol generates four different energy delivery paths for dual buckoutputs with only one inductor. In addition, the superpositiontechnique is used to achieve a minimized inductor current level.The average inductor current is equal to the summation of twooutput loads. Moreover, the IECM control activates the inter-leaving operation through the current interleaving mechanism toprovide large driving capability as well as to reduce the outputvoltage ripple. As a result, 91% peak efficiency is derived andthe output voltage ripple appears notably minimized by 50%using current interleaving at heavy load. The test chip occupies1.44 mm� in 65 nm CMOS and integrates with a three-dimensional(3-D) architecture for inductor integration.

Index Terms—Current interleaving, DC-DC converter, energydelivery path, output voltage ripple, power conversion efficiency,single-inductor dual-output (SIDO) converter, ultra-wide band(UWB) system.

I. INTRODUCTION

I N battery-powered mobile systems, a power IC should si-multaneously have high efficiency, satisfactory regulation,

small volume, and robustness. These characteristics are essen-tial in ultra-wide band (UWB) applications, such as the wirelessuniversal serial bus (USB) that has the advantage of speed overother wireless technologies. The single-inductor dual-output(SIDO) converter [1]–[10] has the capability to provide twohigh-quality output voltages for different function blocks byusing a single inductor. It can reduce the print-circuit-board(PCB) area compared to the single-inductor single-output(SISO) converter [11]–[15] when multi-output supply voltage

Manuscript received August 20, 2010; revised November 15, 2010; acceptedDecember 18, 2010. Date of publication March 03, 2011; date of current versionMarch 25, 2011. This paper was approved by Guest Editor Makoto Nagata. Thiswork was supported by the National Science Council, Taiwan, under Grant NSC97-2221-E-009-172 and Grant NSC 97-2220-E-009-027.

Y.-H. Lee, Y.-Y. Yang, S.-J. Wang, and K.-H. Chen are with the Instituteof Electrical Control Engineering, National Chiao Tung University, Hsinchu30010, Taiwan (e-mail: [email protected]).

Y.-H. Lin, Y.-K. Chen, and C.-C. Huang are with the Realtek SemiconductorCorporation, Hsinchu, Taiwan.

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/JSSC.2011.2108850

is requested in power management. The comparator-controlledtechnique with a simple control scheme for power distributioncan minimize power consumption to improve efficiency [1],[2], but it sacrifices regulation performance and needs to beredeemed by a post-regulator. The discontinuous conductionmode (DCM) [3] control can distribute the energy into the twooutputs of SIDO converter to minimize the cross regulation.However, at heavy loads, an increase in inductor peak currentcauses a large output voltage ripple. The tri-state control [15]utilizes the freewheel stage to reset the inductor current to adefault value at the beginning of every switching cycle. Thepseudo-continuous conduction mode (PCCM) [4] combines theadvantages of continuous conduction mode (CCM) and DCM,but results in large power loss due to high inductor currentlevel. In addition, to improve efficiency, the energy deliverypaths must be well arranged [5]–[7]. Thus, the number of powerswitches can be decreased [8], but the flexibility is reducedbecause the outputs must include at least one step-up regulationto release the inductor current for system stability. The energydistribution method in [9] leads to cross talk effect since theinductor charging scheme is controlled by the load conditionfrom one specific output. Fortunately, the CCM operation in[10] solves transient cross regulation and voltage spike by usinga flying capacitor. However, the bulk capacitor increases thecost in a real system application.

In conclusion, the essential design issues of the SIDO con-verter are low output voltage ripple, minimized cross regula-tion, and high power conversion efficiency. To meet the powerrequirements of UWB system, the proposed SIDO converteradopts the buck operation that steps down the battery power todual low voltages. The interleaving energy-conservation mode(IECM) control can achieve the power management functionthrough the demand of four power switches. These four powerswitches in one SIDO converter constitute the proper energy de-livery paths for dual step-down outputs. In addition, a minimuminductor current level is maintained in the proposed control toimprove efficiency and provide low ripple, minimized cross reg-ulation, and step-down outputs with a compact 3-D package atthe same time.

Fig. 1 shows the proposed SIDO modules constituting thepower management function to supply the UWB system withdifferent operation modes. The integration of the two SIDOmodules can supply four distinct output voltages, namely, ,

0018-9200/$26.00 © 2011 IEEE

LEE et al.: INTERLEAVING ENERGY-CONSERVATION MODE (IECM) CONTROL IN SIDO STEP-DOWN CONVERTERS WITH 91% PEAK EFFICIENCY 905

Fig. 1. The proposed SIDO modules form the power management function to supply the UWB system with different operation modes for enhancing the totalsystem efficiency containing power management and UWB.

, , and . The two-bit signal is used to indi-cate the supply function of the two SIDO modules. The single-phase operation of the two SIDO modules is achieved by theenergy-conservation mode (ECM) control, whereas the inter-leaving-ECM (IECM) control is activated in the data transmis-sion period enabled by the signal generated from the UWBsystem. The IECM control also provides large supply power andminimizes output voltage ripple through the current interleavingmechanism.

Power management can vary the supply voltages to meet thedistinct power requests in the UWB system with different oper-ation modes according to the throughput constraint. During thesilent mode, there are no data in the vacant transmission timeslot. Thus, the power request is low, and only the slave SIDOmodule operates in order to reduce power dissipation as wellas shutdown the master SIDO module to extend battery life.The voltages and generated from the slave moduleare set to 1.5 V and 1 V, respectively, to supply the awaitingcircuit in the UWB system. The master module is activated inthe upcoming period of data transmission. The output voltages,

and , are raised to 1.8 V and 1.2 V to supply theradio frequency (RF) circuits and digital circuits, respectively.The voltages, and , yielded from the slave modulecan be raised up to 1.8 V and 1.2 V, respectively, to form aninterleaving operation for large driving capability. The currentbalance mechanism can guarantee the current matching to en-sure the equivalent power delivery ability of the two SIDO mod-ules. Aside from this, a green-mode operation is implementedto decrease power dissipation of UWB. According to the UWBprotocol for supporting multiple low-power modes, the standbyand hibernate modes can be used during data transmissions.Thus, the slave SIDO module can scale down the output volt-ages, and , back to 1.5 V and 1 V, respectively, forsome low-power blocks. In the proposed power management de-sign, green-mode would be activated if the interval between twodata transmission period in UWB is shorter than 1 ms since the

re-startup procedure of the proposed SIDO module needs the re-sponse time about 0.1 ms. Moreover, it can enhance the systemefficiency containing the power management and UWB owingto the reduction of the power consumption.

The brief comparison of the power management implemen-tation is listed in Table I. The proposed SIDO module with thesingle phase ECM control and the interleaving operation derivedfrom IECM is a suitable solution to supply the UWB systemunder the different operation modes. In this paper, the structureof a SIDO converter is described in Section II. The ECM con-trolled single-phase and interleaving operations with the IECMcontrol are illustrated in Section III. Detailed circuit implemen-tations of the SIDO converter are discussed in Section IV. Ex-perimental results and the 3-D inductor integration are presentedin Section V. Finally, the conclusion is given in Section VI.

II. PROPOSED SIDO CONVERTER STRUCTURE

The structure of the proposed SIDO converter is shown inFig. 2. The control circuits in the proposed SIDO converter areall implemented using 65 nm deep-submicron devices with a1.2 V voltage supply [16], . Thus, low power consumptionand small silicon area are achieved.

The power stage is composed of four power switches,– , for the dual step-down outputs. These power

switches are implemented by the I/O devices in 65 nm processfor high voltage tolerance. It has four different energy deliverypaths to transfer energy from the battery, , to the dual out-puts with only one inductor used. Sensor gains are decided bytwo voltage dividers that contain , , , and forthe feedback of output voltage information to the two cascadeerror amplifiers [16], which yields high DC voltage gain underthe low voltage operation. The two error current signals,and , generated by voltage-to-current ( -to- ) convertersat the output of two EAs, are sent to the ECM controller todecide the duty ratio of the dual outputs. The current ,which is the summation of and , indicates the peak


TABLE IBRIEF COMPARISON OF THE POWER MANAGEMENT IMPLEMENTATIONS FOR UWB SYSTEM

Fig. 2. Structure of the proposed SIDO converter with the IECM control.

inductor current as well as the required energy in one switchingcycle through the ECM control. Therefore, by using the ECMcontroller, the average inductor current is lowered to equal thesummation of the two output load currents. In addition,is adjusted by the current adjusting signal to ensure thecurrent matching in the IECM control with the interleavingoperation. is generated from the current adjusting circuit inthe current balance controller. It can adjust the inductor currentlevels of each SIDO module in the interleaving operation.

The current sensing signal, , generated from the currentsensing circuit is added to a slope compensation signal, ,to avoid sub-harmonic oscillation [17]. Hence, the currents,

, , and are used to determine the four-bit signal,, in the path decision circuit. Additionally, the current

sensing signal , which is derived from the current sensingof the other SIDO module, and are used to achieve thecurrent balance when the IECM control is activated. Moreover,

is generated from the sawtooth circuit, and isderived from the other SIDO converter. Thus, the phase shiftcircuit can generate system clock to accomplish the inter-leaving operation. The level-shift and deadtime driver circuitproduces the control signals, - , from the four-bit signal

to drive the power switches due to the use of low-voltagecontroller. The level-shift circuit can enhance the driving ability

of power switches by increasing the gate driving voltages. Thedeadtime circuit can prohibit the simultaneous on-state to avoidthe shoot-through current between power switches and

.

III. IECM OPERATION

For high efficiency operation in the UWB system, single-phase and interleaving operations are included in the proposedSIDO converter. Thus, the integration of the two SIDO con-verters can provide either four different output voltages in thegreen-mode period or two distinct output voltages with highdriving capability in the data transmission period.

A. Single-Phase Operation – ECM Control

Fig. 3 shows the energy delivery paths of the SIDO converter.The four energy delivery paths, path-I to path-IV, constitute dis-tinct inductor current slopes. Path-I and path-III indicate the in-ductor charging path and deliver energy from the input to theoutputs and , respectively. Path-II and path-IV indi-cate the inductor discharging path and deliver energy from theinductor to the outputs and , respectively. The pro-posed ECM control, which uses one of the combinations ofthese possible energy delivery paths, can achieve the CCM dualbuck operations with a minimum average inductor current level.


Fig. 3. Energy delivery paths in the power stage of the SIDO converter.

Fig. 4. The time diagram of the proposed ECM control.

Fig. 4 shows the time diagram of the ECM control with the orderof path-I, path-III, path-IV, and path-II. This ordered sequencecirculates by the triggering of the system clock, . ,which is decided by the summation of the two error signals,and , indicates the peak inductor current. The error signal

determines the transitions from path-I to path-III and frompath-IV to path-II. That is, the Path-I and Path-II are decidedby and for the output . Similarly, the Path-IIIand Path-IV are decided by and , which is the dif-ference between and . The ECM control can achievethe separated dual step-down operations with the superpositionscheme. Thus, each output can receive battery power in onePWM switching period through the ECM control. Besides, eachpower switch, to , would switch twice in the periodof one switching cycle time with the ordered energy deliverypaths.

Fig. 5 illustrates the inductor current waveform under dif-ferent load conditions with the ECM control. The combina-tion of the two separated step-down operations in ECM con-trol results in the average inductor current, , to beequal to the summation of the two output loads. The value of

is lower than that of derived fromthe PCCM control, which needs a freewheel stage to regulatethe inductor current. As such, the ECM control can yield a lowaverage inductor current level to reduce conduction loss and en-hance efficiency by removing the freewheel stage. Moreover, theduty cycle of each regulated output voltage varies depending onthe loading in the ECM control. For example, if the load cur-rent of the output voltage increases and the load cur-rent of the output voltage is fixed, there would bean increase in total output power. Thus, the average inductorcurrent of the ECM control arises to reflect the

heavy load condition. The total energy for in Fig. 5must keep constant at both light load and heavy load conditionssince would not change. On the other hand, the total en-ergy for should be increased to provide a sufficientpower owing to the increase of . As a result, the periods ofpath-I and path-II are reduced, but the periods of path-III andpath-IV are extended because of the increase in .Moreover, the effect from PVT condition to the proposed ECMcontrol can be minimized since the high gain error amplifiers[16] are used to compensate these variations. They modulatethe error signals properly to ensure the correct function of ECMcontrol. Consequently, adequate energy is delivered to the out-puts to satisfy the output loads. In other words, the low value of

greatly enhances the power conversion efficiencyin ECM control owing to the use of superposition technique.Furthermore, the derivation of the minimum average inductorcurrent level helps reduce the output voltage ripple to better thesupply quality of the proposed SIDO converter.

B. Interleaving Operation – Interleaving ECM (IECM)Control

The increase in load current can cause a large output voltageripple due to the discontinuous inductor current derived at theoutput nodes of the SIDO converter. Thus, to better enhance theperformance at heavy loads, the IECM control is utilized for apower management function to the UWB system. That is, the in-terleaving operation focuses on providing a large power supplyduring the data transmission period. The interleaving schemefor the UWB system is depicted in Fig. 1. When the interleavingoperation is enabled during the data transmission period,is paralleled to to provide a large supply power to the RFPA and Mixer circuit in the UWB system. Similarly, isparalleled to to simultaneously deliver energy to the dig-ital circuit in the UWB system. The power management (PM)master in the UWB processor activates the interleaving opera-tion of the two SIDO modules and decides the power manage-ment functions according to the demand with different UWBoperation modes.

The interconnection of the control signals between the twoSIDO modules is also shown in Fig. 1. To achieve currentmatching and output voltage ripple minimization, some controlsignals between the two SIDO modules should be adequately


Fig. 5. The inductor current waveform under different load conditions with different control methods.

Fig. 6. The current interleaving mechanism in the proposed IECM control during the interleaving operation.

linked together to achieve the interleaving operation. Two sig-nals of and generated from different current sensingcircuits are used to achieve the current balance. In each SIDOmodule, the signal indicates the current sensing signal ofthe SIDO module itself, whereas the signal represents thecurrent sensing signal generated from the other SIDO module.Similarly, the signal, obtained from the SIDO moduleitself and obtained from the other SIDO module, areutilized to adjust the phase difference between the two SIDOmodules.

The detailed current interleaving mechanism in the in-terleaving operation is shown in Fig. 6. is the inductorcurrent of the master module, whereas is the inductorcurrent of the salve module. The single-phase SIDO converterhas to provide energy for two output nodes, which results in adiscontinuous inductor current at each output nodes. Throughthe interleaving operation of the two proposed SIDO modules,the two separated inductor currents interleave with each otherso that the output current appears to be a continuous function.That is, with the current interleaving mechanism, derivesenergy from and through the different phase opera-

tions. It helps inductor current be continuous at the node .Furthermore, the existence of the parasitic equivalent seriesresistance (ESR) in the output capacitor also causes a largeoutput voltage ripple due to the discontinuous inductor currentin the single-phase operation. Nevertheless, the interleavingoperation can produce the continuous inductor current bycurrent interleaving to minimize the output voltage ripple. Theglitches carried out by the ESR can also be cancelled naturally.Additionally, if the load increases during the interleavingoperation, the error signals and the peak signalsin each SIDO modules are also increased. Thus, both of theaverage inductor current in each SIDO module is raised tosupply the output load simultaneously. Moreover, the currentadjusting circuit in the current balance controller shown inFig. 2 ensures the current matching in the interleaving op-eration. The current adjusting signal is used to slightlyadjust the inductor current level of the two SIDO modules forguaranteeing the current matching. As a result, the interleavingoperation is a way of suppressing the output voltage ripple aswell as of providing high power driving capability to supplythe UWB system.


Fig. 7. The current balance controller circuit. (a) Full-range current sensing circuit. (b) Current adjusting circuit.

IV. CIRCUIT IMPLEMENTATION

A. Current Balance Controller

Fig. 7 shows the current balance controller containing thefull-range current sensing circuit and the current adjusting cir-cuit. The inductor current information is necessary for ECM orIECM control owing to the current-mode operation. The full-range current sensing is utilized to achieve the four different en-ergy delivery paths with the superposition technique in the pro-posed SIDO converter.

Fig. 7(a) shows the schematic of the full-range currentsensing circuit. is the current flowing through the inductorand is the sensing factor of both to and to

. These four transistors are all implemented by I/O devicesfor high voltage tolerance. The transistor produces thesensing current during the turn-on period of the high-side powerswitch . The source-to-drain voltages of andare approximately equal because of the closed-loop generatedby the operational amplifier . Accordingly, the current

flowing through the transistors becomes proportionalto the current flowing through the , thus achieving thehigh-side current sensing. Identically, the transistor pro-duces the inductor current information during the low-sideturn-on period. The closed-loop generated by the operationalamplifier carries out a sensing current flowing throughthe transistor and the sensing transistor . Therefore,the full-range current sensing signal , which is the voltageacross the sensing resistor , is generated through the summa-

tion of the two sensing currents, and . The descriptionis shown in (1).

(1)

Current balance mechanism between the two SIDO modulesis implemented to ensure equivalent driven capability when theIECM control is activated for interleaving operation. As shownin Fig. 7(b), the current adjusting circuit, which is composedof the low-pass filter (LPF) and the current amplifier (I-AMP),is adopted to adjust the inductor current level of the two inter-leaved SIDO modules. The full-range current sensing signalis buffered for transmission to the other SIDO module throughthe signal, . Similarly, the sensing signal is generatedfrom the other SIDO module. The buffer stage eliminates theload effect and also filters out the switching noise. Hence, thesetwo full-range current sensing signals are filtered by the LPFto obtain the average inductor current of each SIDO modulein the interleaving operation. Additionally, the capacitors,to , in the LPF are implemented by the capacitor multipliertechnique to achieve the fully on-chip integration [11]. The av-erage inductor current information of the two SIDO modules,

and , are sent to the I-AMP circuit to generatean adjusting current to achieve the current balance whenthe IECM control is activated. An auxiliary resistor in theI-AMP circuit can strengthen the linearity of . The illustra-tion of the absolute value of is shown in (2).

(2)


Fig. 8. The path decision circuit. (a) Current comparator. (b) Path decisionlogic.

B. ECM Controller

As shown in Fig. 8, the path decision circuit in the ECM con-troller, which contains the current comparator and the path deci-sion logic, generates duty cycles to the two outputs in one SIDOmodule. The current comparator shown in Fig. 8(a) operateswith , and . The values of and used toindicate the transition of energy delivery paths are decided bythe intersection of with and , respectively.

The path decision logic depicted in Fig. 8(b) generates thefour-bit signal to achieve the energy delivery paths. Thehysteresis buffer enhances the noise immunity of the currentcomparator to get a robust ECM control. As the illustrationof timing diagram shows in Fig. 9, triggers the PWMswitching as well as energy delivery path-I. is set tohigh when intersects during the inductor chargingperiod. Thus, the energy delivery path is changed from path-Ito path-III. In addition, is triggered to realize the pathtransition from path-III to path-IV when reaches .Moreover, path-II is carried out when intersectsagain. The energy delivery path is swapped from path-IV topath-II with a negative edge voltage trigger provided by .Finally, path-II appears until the occurrence of the next ,thus initialing the next PWM switching. The stages of thecurrent comparator are minimized by using D-flip-flops due tothe path decision logic. Furthermore, and indicate theenergy delivery paths with binary code, which can be decodedthrough the decoder to generate a four-bit signal toachieve the ECM control.

C. Phase Shift Circuit

The IECM control interconnects the two SIDO modules toprovide a large power supply and minimize the output voltageripple simultaneously. Thus, the system clocks in the two SIDO

Fig. 9. Timing diagram of the path decision circuit.

modules must be out of phase to achieve the current interleavingmechanism effectively. The proposed phase shift circuit shownin Fig. 10 produces the system clock , which is relative tothe interconnected signals, and , generated from thetwo distinct SIDO modules. In addition, once activates theinterleaving operation, from the PM master in the UWBsystem will indicate either the master or slave function to eachSIDO modules.

Fig. 11 shows the timing diagram of the phase shift circuit.In a single-phase operation, is set to low, and is de-rived from through the selection of a multiplexer. isalso directly obtained from when one SIDO converter isutilized as the power management master in the interleaving op-eration. The signal is set to high to indicate the masterpower management module. However, the SIDO module is pro-nounced a slave module if the is set to low. is gener-ated from the two shift-cells in order to obtain an out-of-phaseoperation to reduce the output voltage ripple. That is, islinked to the system clock of the master module through theinterconnections and generates the signals and by thefrequency divider. and trigger the shift-cells and ac-quire the sawtooth waveforms, and . When the signal

is set to high, the switch in the circuit ison in order to charge the capacitor with a fixed current .On the contrary, is discharged with the current , until the

reverts to the value of . The amplitude of the sawtoothwaveform is . This operation is illustrated in (3).

(3)

The D-flip-flop detects when the discharge period is over. isset to high at the half period location with . Similarly,is produced through the identical operation mechanism in the

circuit triggered by . By the equations shownin (3), and are equal to , which is used to assure the in-terleaving operation. Finally, is carried out by the OR oper-ation from and in the slave SIDO module to achieve theinterleaving operation. Moreover, the bottom plates of capacitor

in each shift-cell are fixed to a constant voltage decidedby the buffer stage, which is composed of the operational ampli-fier and the transistor . This design helps avoid the voltagenonlinear phenomenon in the charging and discharging periodsowing to the MOSFET as a capacitor. The interleaving opera-tion with IECM control is shown in Fig. 12 that demonstrate the


Fig. 10. The phase shift circuit for interleaving operation.

Fig. 11. Timing diagram of the phase shift circuit.

Fig. 12. The interleaving operation with the IECM control in the proposedSIDO modules.

current matching in load transient response and the operation ofthe phase shift circuit.

V. EXPERIMENTAL RESULTS

This proposed SIDO converter with the IECM control wasfabricated by 65 nm CMOS technology. The measured wave-forms of the single-phase operation are shown in Figs. 13–15.Fig. 13 demonstrates the single-phase operation in steady-statewith of 1.8 V and of 1.2 V. The energy delivery paths

Fig. 13. Measured single-phase operation of ECM control with � �

�� mA and � � �� mA.

in the ECM control are verified through the occurrence of path-I,path-III, path-IV, and path-II in sequence. With a load current of100 mA at each output, the average inductor current is continu-ously maintained at 200 mA, which is equal to the summation ofthe two output loads. The output voltage ripple is about 20 mVat each output due to the discontinuous inductor current. Wheneach output has 200 mA load current, the measured single-phaseoperation with the ECM control is also achieved through theordered energy delivery paths shown in Fig. 14. Similarly, theaverage inductor current is equal to the summation of the twooutput load currents. The output voltage ripple is about 30 mV ateach output. Fig. 15 shows the measured load transient responsein single-phase operation. The largest output drop voltage isabout 80 mV, whereas the largest overshoot voltage is about60 mV. The voltage recovery time is derived within 30 s. Inaddition, good voltage regulation and fast transient response arealso achieved because of the high dc loop gain and bandwidth.The average inductor current is always equal to the summationof two output loads by the ECM control. Thus, the minimum in-ductor current level is achieved through the superposition tech-nique to enhance the power conversion efficiency and reduce theoutput voltage ripple.


Fig. 14. Measured single phase-operation of ECM control with � �

�� mA and � � �� mA.

Fig. 15. Measured single-phase operation in case of load transient response.

Fig. 16. Measured interleaving operation of the power managementintegration.

Fig. 16 shows the measured waveform of the power man-agement function. When the UWB system enters the datatransmission period, an increase in the power request activatedthe IECM control to provide a large driving capability simulta-neously from the two interleaving SIDO modules. Moreover,owing to the current interleaving mechanism, the output voltageripple is greatly reduced, and the voltage spike resulting fromthe ESR is nearly eliminated. The output voltage ripple isreduced to 15 mV at each output with 200 mA output loadcurrent.

The measured power conversion efficiency of thesingle-phase operation is shown in Fig. 17. The conduc-

Fig. 17. Measured power conversion efficiency in the single-phase operationwith � � �� , � � �� , and � � �� .

Fig. 18. The comparison of the output voltage ripple by using different controlmethods with � � �� , � � �� , and � � �� .

tion loss of the power switches can be greatly reduced owing tothe proposed ECM control. Peak efficiency increases to 91%,where the 80% efficiency is achieved by today’s commercialproducts with four power switches. The comparison of theoutput voltage ripple with different loads is shown in Fig. 18.Output voltage ripple in the ECM control decreases by as muchas 36% compared with that in the PCCM control. Specifically,a 50% reduction in the output ripple is presented at heavy loadsbecause of the current interleaving with the IECM control.The design specifications of the proposed SIDO converter arelisted in Table II. Moreover, the comparisons of the prior SIDOmethodologies are shown in Table III.

Fig. 19 shows a chip micrograph and the illustration of a3-D package. The occupied silicon area of the single SIDOmodule is 1.44 mm . The inductor is placed on the top of thepower management ICs to shorten the distance of the boundingwire. The performance is enhanced through the alleviation of thebond wire effect since the length of the bonding wire is short-


TABLE IIDESIGN SPECIFICATIONS OF THE PROPOSED SIDO CONVERTER

TABLE IIICOMPARISON OF THE PREVIOUS SIDO (SIMO) METHODOLOGIES

Fig. 19. The chip micrograph and the illustration of inductor integration.

ened as well as the equivalent bond wire inductance. It mini-mizes the switching noise and voltage spike resulting from the

Fig. 20. The details of the inductor integration.

power stage. The details of the inductor integration are given inFig. 20. Chip function is affected by the magnetic flux gener-ated from the inductor. However, a magnetic flux produced byconductive coil cannot be blocked by insulating it from its sur-rounding materials [18]. Nevertheless, the magnetic field can bea short-circuited in place of the high permeability magnetic ma-terial, which provides an easy path with low reluctance for thereturn magnetic flux to form a closed magnetic circuit. There-fore, the magnetic flux would propagate along the high per-meability material, which is composed of the ferrite and fer-


rite-magnet (FM ) film and ferrite/resin composite, to largelydecrease the interference to the chip function. In addition, rel-ative to the ferrite and FM material, the permeability of air islow. Thus, the leakage flux and the magnetic field interferencefrom the inductor can be minimized. Consequently, the integra-tion of the inductor with the proposed SIDO converter achievesthe area-efficient power management module and enhances thecompetitiveness to the UWB system or other system-on-a-chipapplications.

VI. CONCLUSION

The proposed SIDO converter with IECM control wasfabricated by 65 nm CMOS technology. The ECM control isachieved through the ordered energy delivery paths to powerthe UWB system. Besides, the superposition technique helpsderive a minimum average inductor current, which is equal tothe summation of two output loads. In addition, ICEM controlis activated to realize the interleaving operation with currentinterleaving. Thus, a larger supply power can be providedduring the data transmission period, and the output voltageripple can be reduced owing to the current interleaving mech-anism. Experimental results demonstrate the single-phase andinterleaving operations of the proposed SIDO converter. Apeak efficiency of 91% is achieved and the output voltageripple appears notably minimized by over 50% through currentinterleaving at heavy load. The test chip occupies 1.44 mmand integrates with a 3-D architecture for inductor integration.

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Yu-Huei Lee (S’09) was born in Taipei, Taiwan.He received the B.S. and M.S. degrees from theDepartment of Electrical and Control Engineering,National Chiao Tung University, Hsinchu, Taiwan,in 2007 and 2009, respectively. He is currentlypursuing the Ph.D. degree in the Institute of Elec-trical Control Engineering, National Chiao TungUniversity, Hsinchu, Taiwan.

He is a Faculty Member at the Mixed Signal andPower Management IC Laboratory, Institute of Elec-trical Control Engineering, National Chiao Tung Uni-

versity, Hsinchu, Taiwan. His current research interests include the power man-agement integrated circuit design, light-emitting diode driver IC design, andanalog integrated circuits.

Yao-Yi Yang (S’09) was born in Changhua, Taiwan.He received the B.S. and M.S. degrees from ChungYuan Christian University and National TaipeiUniversity of Technology in 2004 and 2007, respec-tively. He is currently pursuing the Ph.D. degreein the Institute of Electrical Control Engineering,National Chiao Tung University, Hsinchu, Taiwan.

He is a member of the Mixed Signal and PowerManagement IC Laboratory at National Chiao TungUniversity. His research interests include the powermanagement IC design, LED driver IC design and,

the analog integrated circuits.

Shih-Jung Wang (S’09) was born in Taipei, Taiwan.He received the B.S. and M.S. degrees from the De-partment of Electrical and Control Engineering, Na-tional Chiao Tung University, Hsinchu, Taiwan, in2007 and 2009, respectively.

He is a member of the Mixed Signal and PowerManagement IC Laboratory at National Chiao TungUniversity. His research interests include the designof power management circuit, LED driver ICs, andthe analog integrated circuit designs.


Ke-Horng Chen (M’04–SM’09) received the B.S.,M.S., and Ph.D. degrees in electrical engineeringfrom National Taiwan University, Taipei, Taiwan, in1994, 1996, and 2003, respectively.

From 1996 to 1998, he was a part-time IC De-signer at Philips, Taipei. From 1998 to 2000, he wasan Application Engineer at Avanti, Ltd., Taiwan.From 2000 to 2003, he was a Project Manager atACARD, Ltd., where he was engaged in designingpower management ICs. He is currently an AssociateProfessor in the Department of Electrical Engi-

neering, National Chiao Tung University, Hsinchu, Taiwan, where he organizeda Mixed-Signal and Power Management IC Laboratory. He is the authoror coauthor of more than 80 papers published in journals and conferences,and also holds several patents. His current research interests include powermanagement ICs, mixed-signal circuit designs, display algorithm and driverdesigns of liquid crystal display (LCD) TV, red, green, and blue (RGB) colorsequential backlight designs for optically compensated bend (OCB) panels,and low-voltage circuit designs.

Ying-Hsi Lin received the B.S. degree from NationalChiao-Tung University, Hsinchu, Taiwan, in 1993,and the M.S. degree in electrical engineering fromNational Taiwan University in 1995.

He joined the Computer and CommunicationResearch Lab at ITRI as a researcher in 1995,and became project leader of CMOS RF and highspeed mixed-signal circuits design in 1998. Sincejoining ITRI CCL, he has been working on CMOSradio frequency integrated circuits and mixed-signalcircuits IC design for computer and communication

application. In October 1999, He joined Realtek Semiconductor Corp., as anRF manager, where he was responsible for several R&D CMOS RF projectsincluding Bluetooth, WLAN 802.11abg, 802.11n, WLAN CE and UWB, andalso involving CMOS RF IC mass production planning. In the circuits design,his activities ranged are RF synthesizer, LNA, Mixer, modulator, PA, filter,PGA, mixed-signal circuits, ESD circuits, RF device modeling, RF systemcalibration and communication system design. In 2010, he became the VicePresident of Realtek and led the Research and Design Center. He holds morethan 30 patents in the area of mixed-signal and RF IC design.

Yi-Kuang Chen received the B.S. and M.S. degreesfrom National Cheng Kung University, Tainan,Taiwan, in 2003 and 2005, respectively.

He joined Realtek Semiconductor Corporation inSeptember 2005 as a circuit designer. He is currentlyinvolved in analog and mixed-signal circuits design.His research interests include line drivers andswitching regulators for SoC.

Chen-Chih Huang received the B.S. degree fromNational Chiao-Tung University, Hsinchu, Taiwan,in 1990, and the M.S. degree in electrical engineeringfrom National Taiwan University, Taipei, Taiwan, in1992.

He joined Mosel Vitelic Inc., Hsinchu, as anengineer in 1994. In 1995, He joined Realtek Semi-conductor Corp., Hsinchu, as an analog circuit designengineer. During 1995–2010, he was responsiblefor several projects including fast Ethernet/GigabitEthernet network interface controller/ PHYceiver/

switch controller, Clock generator, USB, ADSL router, Gateway controller,etc. He is currently the Senior Manager of the Analog_CN design team of theR&D center.

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