IJSOO7701173B2
`
`(12) United States Patent
`(10) Patent No.:
`US 7,701,173 B2
`
`Veselic
`(45) Date of Patent:
`Apr. 20, 2010
`
`(54) CHARGINGAND POWER SUPPLY FOR
`MOBILE DEVICES
`
`2006/0022640 A1*
`
`2/2006 Frith et a1.
`
`.................. 320/125
`
`(75)
`
`Inventor: Dusan Veselic, Oakville (CA)
`
`FOREIGN PATENT DOCUMENTS
`
`(73) Assignee: Research In Motion Limited, Waterloo,
`Ontario (CA)
`
`*
`
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`u Jectto any isc aimer,t e term 0 t
`patent is extended or adjusted under 35
`U.S.C. 15403) by 933 days.
`
`EP
`
`EP
`JP
`
`WO
`
`0623985 A
`
`11/1994
`
`0752748 A
`2003-32910 A
`
`1/1997
`“2003
`
`2004075371 A
`
`9/2004
`
`(21) Appl.No.: 11/299,701
`
`(22)
`
`Filed:
`
`Dec. 13, 2005
`
`(65)
`
`Prior Publication Data
`
`US 2007/0132427 A1
`
`Jun. 14, 2007
`
`(51)
`
`Int. Cl.
`(2006.01)
`H02] 7/00
`(52) US. Cl.
`........................ 320/128; 320/112; 320/114
`(58) Field of Classification Search ................. 320/106,
`320/1124114, 128
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`“19% NOT
`5,179,335 A *
`7/1995 Chiang ....................... 320/136
`5,432,427 A
`5,694,022 A * 12/1997 Ranta et al.
`................. 320/142
`6 031 359 A
`2/2000 Michelsen et a1
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`8/2000 Oglesbee et 31 '
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`6,188,199 B1 *
`2/2001 Beutler et al.
`............... 320/125
`
`6,222,347 B 1 *
`4/2001 Gong ............... 3 20/ 137
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`10/2001 Shum
`6,741,066 Bl *
`5/2004 DenSham et ah ~~~~~~~~~~~~ 320/ 145
`7,208,892 B2 *
`4/2007 Tondra et al.
`................. 318/53
`ese 10 e a .
`...............
`3882;812:38; :1 *
`$388: $553110 e: 31'
`320“”
`2004/0239294 A1
`12/2004 Veselic et a1.
`2004/0251878 A1
`12/2004 Veselic et al.
`
`OTHER PUBLICATIONS
`
`International Search Report issued on Mar. 21, 2007 in respect of
`PCT/CA2006/002025.
`
`(Continued)
`
`Primary ExamineriEdward Tso
`Assistant Examinerisamuel Berhanu
`(74) Attorney, Agent, or FirmiRidout & Maybee LLP
`
`(57)
`
`ABSTRACT
`
`Charging and power supply for mobile devices is disclosed. A
`USB-compliant charging and power supply circuit includes
`switch-mode battery charging circuitry for receiving power
`from an external power source and for supplying output
`.
`power through an output node to an electronic system of an
`electronic communication device and a battery. Battery iso-
`lation circuitry includes a semiconductor switch connecting
`the output node to the battery The battery isolation circuitry
`senses voltage at the output node and variably restricts current
`to the battery when the voltage is below a minimum voltage
`value by operationally controlling the semiconductor switch
`as current passes through it. During variable current restric-
`~
`~
`-
`~
`~
`~
`tion the electronic system is supplied required power with
`said battery being supplied any additional available power.
`
`2005/0046391 A1
`
`3/2005 Veselic et a1.
`
`12 Claims, 4 Drawing Sheets
`
`{—112
`
`_________________________
`
`Switch-mode Power
`Supply Circuitry
`
`
`
`_____________________________________
`
`116
`_ VI—-¢.2v
`
`1
`
`APPLE 1038
`
`APPLE 1038
`
`1
`
`

`

`US 7,701,173 132
`
`Page 2
`
`OTHER PUBLICATIONS
`
`Digitally Programmable 1A Switch-Mode USB/AC Li-Ion Charger
`IC Sets Records for Charge Time, Power Dissipation and Size, pub-
`lished Feb. 21, 2006, http://Www.summitmicro.com/compiinfo/
`press/022106/pr022106.htm.
`Charging Batteries from USB, published Aug. 25, 2006, http://WWW.
`maxim-ic.com/appnotes.cfm/appnoteinumber/3607.
`Extended European Search Report issued in respect of EP Patent
`Application No. 051120665.
`
`Texas Instruments, “Synchronous Switchmode, Li-Ion and Li-Pol
`Charge Management
`IC
`with
`Integrated
`Powerfets
`(quWITCHER)”, Nov. 2004.
`Texas Instruments, Single-Chip, Li-Ion and Li-Pol Charger IC with
`Autonomous USB-Port and AC-Adapter Supply Management
`(quINYiII), Aug. 2004.
`Texas Instruments, “High-Efficiency Step-Down Low Power DC-DC
`Converter”, Sep. 2003.
`
`* cited by examiner
`
`2
`
`

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`US. Patent
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`Apr. 20, 2010
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`Sheet 1 of 4
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`US. Patent
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`Apr. 20, 2010
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`US. Patent
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`Apr. 20, 2010
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`US 7,701,173 B2
`
`1
`CHARGING AND POWER SUPPLY FOR
`MOBILE DEVICES
`
`FIELD
`
`Charging and power supply circuits for mobile devices.
`
`BACKGROUND
`
`As will be appreciated by those skilled in the art, there are
`various reasons for choosing a Universal Serial Bus (USB)
`port to supply charging power to a mobile device, rather than
`using a separate alternating current (AC) charger. Unfortu-
`nately, USB ports can only provide limited power.
`Power rails of mobile devices often require a very clean
`supply voltage. Thus, Low Drop-Out (linear mode) circuits
`have been used to meet this requirement. A problem with
`these circuits is that they can be quite inefficient power con-
`verters.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Reference will now be made, by way of example, to the
`accompanying drawings which show example embodiments;
`and in which:
`
`FIG. 1 shows, in diagrammatic form, a computer system
`connected to a mobile device via a USB port;
`FIG. 2 is a circuit schematic representation of a charging
`and power supply circuit architecture according to an
`example embodiment;
`FIG. 3 is a circuit schematic representation illustrating
`additional circuitry connected to the circuit depicted in FIG.
`2, the additional circuitry permitting variable VSYS output
`voltage; and
`FIG. 4 is a circuit schematic representation of a charging
`and power supply circuit architecture similar to the architec-
`ture of FIG. 2, but with most of the circuitry contained within
`a single integrated circuit chip.
`Similar reference numerals may have been used in differ-
`ent figures to denote similar components.
`
`DESCRIPTION OF EXAMPLE EMBODIMENTS
`
`According to one example embodiment, there is a USB-
`compliant charging and power supply circuit
`including
`switch-mode battery charging circuitry for receiving power
`from an external power source and for supplying output
`power through an output node to an electronic system of an
`electronic communication device and a battery. Battery iso-
`lation circuitry includes a semiconductor switch connecting
`the output node to the battery. The battery isolation circuitry
`senses voltage at the output node and variably restricts current
`to the battery when the voltage is below a minimum voltage
`value by operationally controlling the semiconductor switch
`as current passes through it. During variable current restric-
`tion the electronic system is supplied required power with the
`battery being supplied any additional available power.
`According to another example embodiment, there is an
`electronic communication device electrically connectable to
`an external power source. The device includes a device hous-
`ing and a rechargeable battery contained within the housing.
`An electronic system is contained within the housing. Switch-
`mode battery charging circuitry receives power from an exter-
`nal power source and supplies output power through an out-
`put node to the electronic system and the battery. Battery
`isolation circuitry includes a semiconductor switch connect-
`ing the output node to the battery. The battery isolation cir-
`
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`cuitry senses voltage at the output node and variably restricts
`current to the battery when the voltage is below a minimum
`voltage value by operationally controlling the semiconductor
`switch as current passes through it. During variable current
`restriction the electronic system is supplied required power
`with the battery being supplied any additional available
`power.
`According to yet another example embodiment, there is a
`power management method for allocating power between a
`rechargeable battery and an electronic system having a power
`input and a number of modes of operation. The power is
`supplied to the battery and the electronic system from a req-
`uisite power source. The method includes generating the req-
`uisite power source and determining a minimum voltage
`needed at a node directly connected to the power input with
`reference to which of the modes of operation the electronic
`system is currently in. The method also includes monitoring
`voltage at the node and increasing power allocation to the
`electronic system by variably restricting current from the
`requisite power source to the battery when the voltage is
`below the minimum voltage. The method also includes sup-
`plying at least sufficient power to the electronic system for it
`to properly function.
`FIG. 1 is a diagram of a computer system 100 connected to
`a mobile device 102 via a computer data bus port 104 that in
`one embodiment is a USB port. The computer system 100
`could be a personal computer, a laptop, an entertainment
`system connected to a television, or one of a variety of other
`types of computer systems. In some example embodiments,
`the portable device 102 is a handheld device such as a per-
`sonal digital assistant (PDA), a cellular telephone, or a hand-
`held computer; however at least some example embodiments
`are not limited to these types of mobile devices.
`The portable device 102 includes a portable device housing
`108, a charging and power supply circuit 112, an electronic
`system 114, a rechargeable battery 116 and a number of other
`modules/components which are not illustrated because they
`do not further an understanding of what is herein being
`described. The device housing 108 will vary in shape and size
`depending upon the particular portable device 102.
`The rechargeable battery 116 is one of the components
`illustrated within the device housing 108. In one embodi-
`ment, the rechargeable battery 116 is a Li-ion battery. Nickel
`metal hydride and nickel-cadmium are other well known
`types ofrechargeable batteries, but practically speaking these
`types of rechargeable batteries have to a large degree been
`succeeded in mobile devices by Li-ion batteries. It will be
`understood that the rechargeable battery 116 need not neces-
`sarily be a single battery, but could instead be multiple bat-
`teries sourcing power in series, parallel or a combination of
`these. In one embodiment, the rechargeable battery 116 is a
`battery pack.
`In the illustrated embodiment, the portable device 102
`connects to the USB port 104 of computer system 100
`through a docking cradle 128 that is adapted to receive the
`portable device 102. It will be understood that the portable
`device 102 could alternatively be connectable to the bus port
`104 by just using a direct cable connectionto make the attach-
`ment; however having a docking, cradle can be practical. For
`example, the portable device 102 need only be set down in the
`docking cradle 128 to make an electronic connection to the
`computer system 100. In at least one alternative embodiment,
`at least a portion ofthe charging and power supply circuit 112
`is contained in the docking cradle 128.
`If the bus port 104 has sufficient power, it can be used to
`supply charging power to charge the battery 116. FIG. 2
`illustrates an architecture of the charging and power supply
`
`7
`
`

`

`US 7,701,173 B2
`
`3
`circuit 112 in accordance with an example embodiment. The
`circuit architecture includes switch-mode battery charging
`circuitry 200, that receives power from the external power
`source, system power supply circuitry 204 and battery isola-
`tion (and current split) circuitry 208. The circuit 112 is elec-
`trically connected at one of its output terminals (VBAT) to the
`rechargeable battery 116, and at another of its output termi-
`nals (VSYS) to a power source input of the electronic system
`114. External power (i.e. power originating from outside of
`the portable device 102, for example at USB port 104) is
`sourced through an input terminal (VCHARGE) of the circuit
`112.
`
`The circuitry 200 and the circuitry 204 are switch-mode
`circuitries.As will be appreciated by those skilled in the art, at
`least some examples of switch-mode circuitries are charac-
`terized by a high-pass power FET and a low-pass power FET
`(the two FETs are collectively referred to as a half-bridge)
`that are connected at a terminal of an inductor (in the present
`example, inductor 216) that is employed to build up current.
`The difference between switch-mode circuitry and linear
`mode circuitry will also be appreciated by those skilled in the
`art. Switch-mode circuitry is capable of providing a greater
`output current than the input current. For example, say
`VCHARGE is 8.4 Volts and the input current to the switch-mode
`battery circuitry 200 is 100 mA. Now if the voltage at the
`output of the circuitry 200 is to be less than the VCHARGE, the
`output current can theoretically be greater than 100 mA
`(Vin’X‘Iin is i Vom’X‘Iout). SO for example, if the voltage at the
`output of the circuitry 200 were to be 4.2 V, the output current
`from the circuitry 200 could be, for example, 150 mA or
`greater.
`By contrast, linear mode circuitry is not capable of provid-
`ing a greater output current than the input current. So again
`with reference to the above mentioned example, if the input
`voltage to linear mode circuitry was 8.4 V, and the output
`voltage from the linear mode circuitry were to be 4.2 Volts,
`there would be only 50% efficiency. In other words, 50% of
`the input power to the linear mode circuitry in this example
`would be dissipated as heat. An effect of lower efiiciency
`within a circuit similar to the example circuit 112 is that less
`power is available to the electronic system (and also the
`battery in the case of charging). One skilled in the art will
`appreciate that certain electronic systems (for example cer-
`tain handheld systems) increasingly need more power to
`function.
`
`In the illustrated example embodiment, the switch-mode
`battery charging circuitry 200 includes a Li-ion and Li-poly-
`mer switch-mode charge management integrated circuit (IC)
`212 such as part number bq24105 or bq241 15 available from
`Texas Instruments. As will be appreciated by one skilled in
`the art, the IC 212 is used in applications such as Li-ion
`battery (e. g. battery pack) charging. The IC 212 has a typical
`switching frequency of 1.1 MHZ and also the IC 212 charges
`the battery in three phases: conditioning, constant current and
`constant voltage. The first phase, the conditioning phase,
`applies if the voltage value of the battery 116 is below a
`certain threshold (for example, if the battery voltage is below
`between 68% and 75% of the fully charged voltage of the
`battery 116 depending upon the operating conditions of the
`IC 212). During this phase a precharge current is applied to
`the battery 116 to revive it if it has been deeply discharged.
`Otherwise, charging begins in the constant current phase
`during which the current sourced from the IC 212 is substan-
`tially a constant value. This phase continues until the IC 212
`detects that the battery 116 has been brought to its fully
`charged voltage value. (Battery voltage can be monitored
`indirectly through a BAT pin (not shown) ofthe IC 212). More
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`specifically, one skilled in the art will appreciate that, in some
`examples, the electronic system 114 is able to monitor the
`value of VBAT. Based 011 monitored values, the system 114
`generates appropriate signals that are transmitted through
`processor control lines to the IC 212).
`When the battery 116 has been brought to its fully charged
`voltage value, charging enters the final phase, the constant
`voltage phase. During the constant voltage phase, the battery
`116 is substantially maintained at the fully charged battery
`voltage value, with sourced current tapering off during this
`phase. Charge is terminated based on a user-selectable mini-
`mum current level. This current level is selected by the value
`of a programming resistor connected to the 15512 pin (not
`shown) of the IC 212.
`The switch-mode battery charging circuitry 200 also
`includes a capacitor 214, an inductor 216, and a capacitor
`218, which in an example embodiment can have the values
`4.7 HF, 4.7 pH and 10 HF respectively (other values can also be
`used). It will be understood that with a supply voltage being
`supplied to the input (IN) pin of the IC 212 through terminal
`VCHARGE, the capacitor 214 filters the supply voltage (the
`capacitor 214 reduces interference). The inductor 216 has one
`of its terminals connected to the output (OUT) pin of the IC
`212, and its other terminal is connected to terminals of other
`components including the feedback (FB) pin of the IC 212
`and a terminal of the capacitor 218. The IC 212 is manufac-
`tured with the FB pin in order to provide for output voltage
`analog feedback adjustment. In the illustrated embodiment,
`the FB pin connection is such that the output node of the
`circuitry 200 (the VSYS node) is also the node of the FB pin,
`and the connection establishes a feedback means of the
`
`switch-mode battery charging circuitry 200 for adjusting a
`voltage value output to the electronic system 114 (FIG. 1).
`With reference now to the illustrated system power supply
`circuitry 204, this circuitry includes switch-mode power sup-
`ply (SMPS) circuitry. This SMPS circuitry includes a low
`power, switch-mode DC—DC converter IC 220. A suitable IC
`220 is the TPS62000 (TPS6200x) IC available from Texas
`Instruments. The TPS62000 IC is a current-mode pulse-width
`modulation (PWM) converter and is suitable for systems such
`as those powered by a one—cell Li—ion battery. The IC 220 is
`manufactured with an FB pin in order to provide for output
`voltage analog feedback adjustment. This FB pin operates in
`a manner similar to the FB pin of the IC 212. The IC 220
`typically operates down to an input voltage of 1.8 Volts, and it
`enters a power-saving pulse-frequency modulation (PFM)
`mode at light load currents. The IC 220 has a typical switch-
`ing frequency of 750 KHZ, permitting the use ofthe relatively
`small inductor 216.
`
`Like the IC 212, the IC 220 can run at a high efficiency
`because they are both switch-mode. Thus the IC 220 also
`contains a half-bridge, and the half-bridge is directly c011-
`nected to the inductor 216 (employed to build up current).
`Like the switch-mode battery charging circuitry 200, the sys-
`tem power supply circuitry 204 is capable of providing a
`greater output current than the input current.
`Li-ion battery 116 is connected to the input (IN) pin of the
`IC 220 because the IC 220 receives power from it. In one
`embodiment, the battery 116 provides an input voltage of
`about 4.2 Volts when the battery is fully charged. It will be
`understood however that the embodiments disclosed in this
`
`application are not limited just to portable devices that use
`batteries whose voltages are roughly 4.2 Volts.
`A capacitor 226 has one terminal connected to the IN pin of
`the IC 220. This capacitor filters the input voltage and reduces
`interference. In one embodiment, the capacitor 226 can be
`about 1 HF.
`
`8
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`

`

`US 7,701,173 B2
`
`5
`Like the IC 212, the output (OUT) pin of the IC 220 is
`connected to a terminal of the inductor 216 (in the illustrated
`embodiment the inductor 216 is within both the switch-mode
`
`battery charging circuitry 200 and the system power supply
`circuitry 204). The IC 220 supplies converted power to the
`electronic system 114 (FIG. 1) by way ofthe inductor 216 and
`then through the output node of the circuitry 200.
`A terminal of the inductor 216 (the terminal opposite the
`terminal connected to the OUT pins of ICs 212 and 220) is
`connected to a capacitor 228 and a resistor 230 that are in
`parallel. As will be understood by those skilled in the art, the
`capacitor 228 permits a much faster feedback response when
`transient spikes occur. Illustrated below the resistor 230 is a
`resistor 232 in parallel with the series combination of a resis-
`tor 234 and an n-channel enhancement field effect transistor
`
`(FET) 236.
`In the illustrated battery isolation circuitry 208, a resistor
`240, a resistor 242, and a capacitor 244 having example
`values of 76.8 k9, 681 kg and l nF respectively, each have a
`terminal connected to the non-inverting terminal of an opera-
`tional amplifier (op-amp) 248. The output of the op-amp 248
`is connected to the gate of a p-channel enhancement FET 252.
`The capacitor 244 filters out the output voltage ripple. The
`resistors 240 and 242 act as a voltage divider of the example
`2.5V voltage source so that the voltage at the non-inverting
`terminal of the op-amp 248 is 2.25V. As will be appreciated
`by those skilled in the art, varying the voltage at the non-
`inverting terminal will impact the behavior of the op-amp
`248. For example, the output of the op-amp 248 will move
`within the range of ground and its VCC in order to keep the
`inverted and non-inverted inputs at the same voltage poten-
`tial.
`
`It will be understood that when the FET 236 is off, the
`voltage at the VSYS node is calculated as some adjustable
`value (which is dependent upon the voltage at the non-invert-
`ing input terminal ofthe op-amp 248) multiplied by 1 plus the
`value of the resistor 230 divided by the value of the resistor
`232. It will also be understood that the formula is different
`
`when the FET 236 is in saturation: the voltage at the VSYS
`node will go up in the adjusted formula because the resistor
`234 and the resistor 232 in parallel form a lower resistance
`than the resistor 232 by itself.
`In the illustrated example embodiment, the relationship
`between IBATTER Y (the current passing through node VBAT),
`ICHARGE (the current passing through node VCHARGE), and
`ISYS (the current passing through node ISYS)
`is IBATTER Y
`:ICHARGE —ISYS. Based on this relationship and assuming a
`fixed ICHARGE,
`it will be understood that
`ISYS must be
`decreased for IBATTER Yto increase. It will also be understood
`that ICHARGE could be limited in the case where the current is
`being supplied from a computer bus port such as a USB port.
`Therefore in the case where the battery 116 is substantially
`discharged (e.g. at say 2.3 Volts) and the battery 116 is to be
`charged by bus port charging, it will be understood that the
`system could be starved if current to the substantially dis-
`charged battery is not regulated.
`At the interface between the switch-mode battery charging
`circuitry 200 and the battery 116, the FET 252 provides this
`regulation. The FET 252 functions as a semiconductor switch
`between nodes VSYS and VBAT. As one skilled in the art will
`appreciate, the FET 252 can be made to act in a manner
`somewhat similar to a variable resistor when the voltages on
`its terminals correspond to operation in the triode region of
`the FET. In FIG. 2, the behavior of the FET 252 is controlled
`in part by the op-amp 248, the output of which is in turn
`determined in part by the resistors 230 and 232.
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`The circuitry 208 works against VSYS falling below a cer-
`tain voltage. The battery isolation circuitry 208 does this by
`operationally controlling the FET 252. In particular, at times
`when the voltage ofthe battery 11 6 is low enough to urge V5Y5,
`below the minimum voltage, the configuration of the battery
`isolation circuitry 208 causes the FET 252 to present a vari-
`able resistance to limit IBATTERYas will be apparent to those
`skilled in the art. Thus, it will be understood that the circuitry
`208 monitors VSYS in order that the FET 252 can limit IBA].
`TERYtO keep VSYS from falling too low. For the circuit archi-
`tecture of the illustrated example, the minimum VSYS during
`charging is the voltage at the non-inverting input terminal of
`the op-amp 248 divided by the value of (resistor 232+(resistor
`232+resistor 230)).
`It will be understood that an effect of the circuitry 208
`working against VSm falling below a minimum value is to
`make the example circuit 112 USB-compliant. Those skilled
`in the art will appreciate that in at least some examples ofUSB
`at least the following lines exist: D+, D', VBUS, GND. Refer-
`ring to FIG. 1, during setup between the computer system 100
`and the electronic system 114, the system 114, in at least some
`examples, has to make D+ go from low to high at 100 ms.
`In order for the electronic system 114 to do this, the elec-
`tronic system 114 needs to be able to talk over USB in less
`than 100 ms. The example circuit 112 can permit this even
`when the battery 116 has a voltage that is significantly lower
`than the minimum value forVSYS. This is because the circuitry
`208 ensures thatVSYS is (without significant delay) brought to
`a high enough value to permit the electronic system 114 to
`talk over USE. As a result, the example circuit 112 is USB-
`compliant.
`The FET 252 will variably restrict current to the battery
`116 to ensure that the electronic system has the requisite
`power source. As for the battery 116, it is supplied any addi-
`tional available power (i.e. the leftover portion of the output
`power from the switch-mode battery charging circuitry 200).
`However, ifVSYS is not urged by the battery 116 to fall below
`the minimum voltage because VBAT is sufficiently high, the
`FET 252 will be in full saturation if the battery 116 is being
`charged. The FET 252 can be turned off ifthe CH_EN signal,
`which is also fed to the CEnot pin ofthe IC 212 and the EN pin
`of the IC 220, is set to high, which causes the FET 236 to
`saturate, thereby creating a positive output from the op-amp
`248 which shuts the FET 252 off. Thus, the charging and
`power supply circuit can include circuitry for turning the FET
`252 off when charging is disabled.
`Referring to FIG. 3, a circuit architecture similar to the one
`ofFIG. 2 is illustrated, except that the circuit ofthis schematic
`includes additional circuitry 260 permitting variable VSYS
`output voltage. In the circuitry 260, the terminal at VSYSl is
`connected to the VSYS node, and resistors 270 and 272 provide
`a voltage divider to scale down the voltage at the positive
`input terminal of op-amp 275 through resistor 276 from the
`VSYS voltage. The values of the resistors 270 and 272 will
`depend on the maximum voltage of the variable voltage
`source 274 as compared to the maximum VSYS. For example,
`if the voltage source 274 will provide up to a maximum
`voltage that is four times less than the maximum VSYS, then
`the resistor 270 should be three times larger than the resistor
`272. When the circuitry 260 is added. (and the terminal at
`VSYSl is connected to the VSYS node) VSYS is related to the
`voltage provided by the voltage source 274 by the following
`formula: VSYSfl/oltage source 274*(resistor 272+resistor
`270)/resistor 272. (In one example where the voltage source
`274 can be raised to the maximum VSYS, the voltage divider
`will be absent from the circuitry 260 and VSYS will be equal to
`the voltage source 274).
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`

`US 7,701,173 B2
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`7
`The voltage source 274 is, in some examples, provided by
`the electronic system 114 (as later explained in this descrip-
`tion). A resistor 271 and a capacitor 273 having example
`values of 301 K9 and 33 pF respectively are connected in
`series between an output terminal and a non-inverting input
`terminal ofthe op -amp 275. The resistor 271 and the capacitor
`273 provide positive feedback for the operation ofthe op-amp
`275.
`
`The illustrated configuration could, in some applications,
`allow for flexible and increased power gain. For example, a
`handheld device might need different values for VSYS during
`different periods of operation. During one period when a
`handheld device is in sleep mode the required VSYS could be
`significantly lower than during another period when the hand-
`held device needs to supply power to modules and sub-
`systems required for the processing of communications. Out-
`put from the op-amp 275 ofthe circuitry 260 (as controlled by
`the voltage source 274) effects feedback input provided to the
`ICs 212 and 220, and in this manner dynamic variation of the
`voltage value at the VSYS node is possible. For. example, in the
`circuit architecture of FIG. 2, when the SMPS circuitry is
`supplying the power (i.e. no charging) the voltage at the VSYS
`node is calculated as 0.45 V*(1 +(resistor 230/resistor 232|
`resistor 234)). (This formula is known to those familiar with
`the operation ofthe IC 220). In the circuit architecture of FIG.
`3, the output node of the additional circuitry 260 is directly
`connected to the node between the resistor 230 and the resis-
`
`tors 232 and 234 that are in parallel. In this manner the output
`ofthe circuitry 260 can be seen to override the resistor-value-
`based determination of the voltage at the VSYS node. In par-
`ticular, when the circuitry 260 is active, the resistors 230, 232
`and 234 become irrelevant in the determination of the VSYS
`node voltage, and the voltage at the VSYS node can be dictated
`by suitable increasing or decreasing of the voltage of the
`variable voltage source 274 in accordance with the formula
`VSYSq/oltage source 274*(resistor 272+resistor 270)/
`resistor 272.
`
`In some examples, the microprocessor of the device will
`change the voltage provided by the voltage source 274 when
`the device enters a mode corresponding to a different required
`VSYS. For example (as shown in FIG. 1) the portable device
`102 could include a voltage notification module 297 interact-
`ing with an operating system 299 stored on the device 102. In
`such examples, the operating system 299 might periodically
`provide the voltage notification module 297 with the current
`mode of operation of the-device 102 in order that the voltage
`notification module 297 might take action if required. Such
`action could include the generation of an appropriate voltage
`at a pin of the device’s microprocessor which would provide
`the voltage source 274 within the circuitry 260.
`In some examples, the microprocessor of the device 102
`would be configured to implement the voltage notification
`module 297. In other examples, some or part of the function-
`ality of the voltage notification module 297 would be imple-
`mented through firmware or hardware components instead of
`or in combination with computer software instructions
`executed by a processor of the device 102.
`In at
`least one example embodiment where there is
`dynamic variation of VSYS in relation to requirements of the
`electronic system 114, the value of variable VSYS is dictated
`by the highest power rail during a particular period (e.g.
`mode) of operation. The following example scenario illus-
`trates this concept. During sleep mode for an example device,
`the device’s microprocessor might only require a 1 .1 V power
`rail and the device’ s volatile memory might only require a 1.5
`V power rail. Hence the highest power rail required during
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`8
`sleep mode might only be 1 .5 V. Therefore during sleep mode,
`the minimum VSYS might only be 1.5 V plus possibly some
`value (e.g. 150 mV) to account for a voltage drop across
`transistor(s)
`inside a voltage regulating Low-Drop Out
`(LDO) regulator of the device. (Such an LDO would be at the
`interface of the VSYS node and VCC of one or more circuitries
`within the electronic system 114).
`On the other hand in a different mode of operation, the
`example device’s RF module might need to be powered. In
`this second mode of operation the device’s microprocessor
`might require a 1.7 V power rail, the volatile memory might
`still require a 1.5 V power rail, but the RF module might
`require a 2.8V power rail. Therefore assuming the RF module
`requires the highest power rail, the minimum VSYS during the
`second mode of operation might be 2.8 V plus the previously
`mentioned additional value to account for the transistor volt-
`
`age drop.
`It will be understood that the ICs ofthe illustrated example
`embodiments both have the characteristic of stepping down
`voltage. For this and other reasons understood by those
`skilled in the art, it would be practical, in a number of cir-
`cumstances, to combine the functionality of the IC 212 and
`the functionality of the IC 220 within a single IC, thereby
`reducing the number of needed ICs by one.
`FIG. 4 illustrates this possibility. Illustrated example IC
`290 would provide a solution similar to the solution provided
`by the example circuit 112, except although the entire battery
`isolation circuitry is implemented within the IC 290, certain
`components of the circuit 112 (in particular the capacitors
`214, 218, 226 and the inductor 216) are not contained in this
`particular IC. Also, a switch element 292 within the IC 290
`replaces the FET 236 and the resistor 234.
`In some examples of ICs similar to the IC 290, multiple
`OUT pins in ele