MAX1773AEUP-T中文资料

19-1796; Rev 1; 1/03

Power Source Selector for

Dual-Battery Systems

General Description

Features

The MAX1773/MAX1773A highly integrated ICs serveas the control logic for a system with multiple poweroPatented 7-MOSFET Topology Offers Low-Costsources. They directly drive external P-channelSolutionMOSFETs to select from an AC adapter and dual bat-oAutomatically Detects and Responds to:

tery sources for charge and discharge. The selection isLow Battery Voltage Conditionmade based on the presence of the power sources andBattery Insertion and Removalthe state of the batteries. The MAX1773/MAX1773Adetect low battery conditions using integrated analogAC Adapter Presencecomparators and check for the presence of a batteryoDirect Drive of P-Channel MOSFETsby using battery thermistor outputs.

oSimplifies Power Management µP FirmwareThe MAX1773/MAX1773A are designed for use with abuck topology charger. They provide a simple and easilyoExtends Battery Life by Allowing Powercontrolled solution to a difficult analog power control prob-Management µP to Enter Standbylem. The MAX1773/MAX1773A provide most of the powero4.75V to 28V AC Adapter Input Voltage Rangesource monitoring and selection, freeing the system powermanagement microprocessor (µP) for other tasks. This notoIntegrated LDO with 1mA Drive Capabilityonly simplifies development of the power managementoSmall Footprint 20-Pin TSSOP Package

firmware for the µP but also allows the µP to enter standby,thereby reducing system power consumption.

Ordering Information

The MAX1773A is recommended for new designs.

________________________Applications

Notebook and Subnotebook Computers PDAs and Handy-TerminalsPin Configuration appears at end of data sheet.

Internet Tablets

Dual-Battery Portable Equipment

Covered by U.S. Patent number 5,764,032.

Typical Operating Circuit

________________________________________________________________Maxim Integrated Products1

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at http://.

MAX1773/MAX1773A

Power Source Selector for Dual-Battery SystemsMAX1773/MAX1773A

ABSOLUTE MAXIMUM RATINGS

VBATA, VBATBto GND............................................-0.3V to +20VVCOMAto GND........................................-0.3V to (VBATA+ 0.3V)VCOMBto GND........................................-0.3V to (VBATB+ 0.3V)VCHGA, VCHGB, VEXTLD, VACDETto GND..............-0.3V to +30VVPDS, VDISA, VDISBto GND...................-0.3V to (VEXTLD+ 0.3V)VDD, VBATSEL, VACPRES, VBATSTAT, VTCOMP,

VMINVto GND.......................................................-0.3V to +6VVTHMA, VTHMB (Note 1)............................................ -0.3V to +6V

Continuous Current out of THMA, THMB............................20mAIACPRES, IBATSTATSink Current..........................................30mAContinuous Power Dissipation (TA= +70°C)

20-Pin TSSOP (derate 7.0mW/°C above +70°C)........560mWOperating Temperature ......................................-40°C to +85°CStorage Temperature ........................................-65°C to +150°CLead Temperature (soldering, 10s).................................+300°C

Note 1:Signals on THMA and THMB below -0.3V are clamped by internal diodes limit forward diode current to maximum continuous current. When voltageon these pins is below -0.3V.

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V, VBATSEL= 0, CCOMA= CCOMB= CDISA= CDISB= CCHGA= CCHGB= CPDS= 5nF, TA= 0°C to +85°C,unless otherwise noted.)

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Power Source Selector for

Dual-Battery Systems

ELECTRICAL CHARACTERISTICS (continued)

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V,

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MAX1773/MAX1773A

Power Source Selector for Dual-Battery Systems

MAX1773/MAX1773A

ELECTRICAL CHARACTERISTICS (continued)

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V, VBATSEL= 0, CCOMA= CCOMB= CDISA= CDISB= CCHGA= CCHGB= CPDS= 5nF, TA= 0°C to +85°C,unless otherwise noted.)

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V,

Power Source Selector for

Dual-Battery Systems

ELECTRICAL CHARACTERISTICS (continued)

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V,VBATSEL= 0, CCOMA= CCOMB= CDISA= CDISB= CCHGA= CCHGB= CPDS= 5nF, TA= -40°C to +85°C,unless otherwise noted.)

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MAX1773/MAX1773A

Power Source Selector for Dual-Battery Systems

MAX1773/MAX1773A

ELECTRICAL CHARACTERISTICS (continued)

(VBATA= VBATB= 16.8V, CVDD= 3.3µF, VMINV= 0.93V, VEXTLD= VACDET= 28V, VTCOMP= 3V, VTHMA= VTHMB= 1.65V,VBATSEL= 0, CCOMA= CCOMB= CDISA= CDISB= CCHGA= CCHGB= CPDS= 5nF, TA= -40°C to +85°C,unless otherwise noted.)“absent” (VTHM_> VTCOMP).

Note 3:VACDETmust remain above 2.2V, except in power-up.

Note 4:COMA cannot sink current until VCOMB> VBATB- 2V. Likewise, COMB cannot sink current until VCOMA> VBATA- 2V.Note 5:DISA cannot sink current until VDISB> VEXTLD- 2V. Likewise, DISB cannot sink current until VDISA> VEXTLD- 2V.

Note 6:Battery Switchover Delay starts when either VCOM_or VDIS_of the connected battery begins to rise and ends when both

VCOM_and VDIS_of the other battery have fallen 3V below their sources (Figures 1 and 2).

Note 7:Battery Action Delay starts when the connected battery’s voltage falls below 5 VMINVand ends when both VCOM_and

VDIS_of the other battery have fallen 3V below their sources (Figures 1 and 2).

Note 8:Thermistor Action Delay begins when VTHM_of the connected battery rises above VTCOMPand ends when both VCOM_

and VDIS_of the other battery have fallen 3V below their sources (Figures 3 and 4).

Note 9:AC to Battery Switchover Delay begins when VACDETfalls below its threshold and ends when both VCOM_and VDIS_of the

battery being switched to have fallen 3V below their sources (Figure 5).

Note 10:Battery to AC Switchover Delay begins when VACDETrises above its threshold and ends when VDIS_of the battery being

switched from has begun to rise (Figure 6).

Note 11:CHG_ Turn-on Delay begins when VCHG_of the battery being switched from begins to rise and ends when VCHG_of the

battery being switched to begins to fall (Figures 7 and 8).

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Power Source Selector for

Dual-Battery Systems

MAX1773/MAX1773A

(TA = +25°C, unless otherwise noted.)

VDD ERROR vs. INPUT VOLTAGE

VDD ERROR vs. IDD

MAX1773-02

VDD ERROR vs. TEMPERATURE

0.0400.5

0VDD ERROR (%)

-0.5-1.0

-1.5-2.0

-1

ERROR (%)

-0.04

ERROR (%)

-2

-0.08

-0.12

5

10

15VIN (V)

20

25

30

-30.01

-2.5

0.1

IDD (mA)

1

10

-40

-15

10

35

60

85

TEMPERATURE (°C)

BATTERY CURRENT vs. BATTERY VOLTAGE

(VACDET = 20V)

TRANSITION FROM

BATTERY A TO BATTERY B (MINV)(IEXTLD = 1A, CEXTLD = 66µF)

MAX1773-05

TRANSITION FROM

BATTERY A TO BATTERY B (MINV)(IEXTLD = 1A, CEXTLD = 66µF)

15V

MAX1773-06

10IBATTERY_ (µA)TOTAL CURRENT FROM THE BATTERY

VBATB

5V15V

VEXTLD

5V

VBATA

12V5 VMINV

VDISBVDISAVCOMBVCOMA

5V010V010V05V 0

5µs/div

VBATA = 12VVBATB = 10.75V

8

6

4

2

00

4

8

12

16

20

VBATTERY_ (V)

100µs/div

VBATA = 12V, BATTERY A REMOVED AT 100µsVBATB = 10.75VVMINV = 1.4V

2V

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Power Source Selector for Dual-Battery SystemsMAX1773/MAX1773A

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

TRANSITION FROM

BATTERY A TO BATTERY B (TCOMP)(IEXTLD = 4A, CEXTLD = 66µF)

MAX1773-07

TRANSITION FROM

BATTERY A TO BATTERY B (TCOMP)(IEXTLD = 4A, CEXTLD = 66µF)

MAX1773-08

TRANSITION FROM

BATTERY A TO BATTERY B (BATSEL)(IEXTLD = 4A, CEXTLD = 66µF)

MAX1773-09

12V

VCOMA

10V0

11V

11V

VEXTLD

4V

VDISAVCOMB

10V010V0

VEXTLD

10V

VBATSEL

4V

VTHMA

10µs/div

VBATA = 10.5V AT 4AVBATB = 12V AT 4A

VDISB

5µs/div

VBATA = 10.5V AT 4AVBATB = 12V AT 4A

10V 0

50µs/div

VBATA = 9.4V AT 4AVBATB = 10.8V AT 4A

TRANSITION FROM AC ADAPTER TO BATTERY A(IEXTLD = 4A, CEXTLD = 66µF)

MAX1773-10

TRANSITION FROM

TRANSITION FROM BATTERY A TO AC ADAPTER

(IEXTLD = 4A, CEXTLD = 66µF)

20V

IBATA

(CURRENT FROM THE BATTERY)

VBATA

20V

MAX1773-11

10A0-10A12V10V

VACDETVBATA

10V

VEXTLDVDISA

10V

VDISAVCHGA

20µs/div

VBATA = 10.8V AT 4A

VACADAPTER = 17.5V AT 4A

100µs/div

VACADAPTER = 17.5A AT 4AVBATA = 10.5V AT 4A

VACADAPTER APPLIED AT 240µsCHARGER INPUT OPEN

10V010V0

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Power Source Selector for

Dual-Battery Systems

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MAX1773/MAX1773A

Power Source Selector for Dual-Battery SystemsMAX1773/MAX1773A

(VCOM_GS = COM_ turn-on clamp voltage, VDIS_GS = DIS_ turn-on clamp voltage, VCHARGER = system step-down charger output.)

Figure 1. Battery Delay (Battery A to Battery B)Figure 2. Battery Delay (Battery B to Battery A)

Figure 3. Thermistor Switchover Delay (Battery A to Battery B)Figure 4. Thermistor Switchover Delay (Battery B to Battery A)

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Power Source Selector for

Dual-Battery Systems

(VCOM_GS = COM_ turn-on clamp voltage, VDIS_GS = DIS_ turn-on clamp voltage, VCHARGER = system step-down charger output.)

Figure 5. AC to Battery Switchover DelayFigure 6. Battery to AC Switchover Delay

Figure 7. Charge Turn-On Delay (Battery A to Battery B)

Figure 8. Charge Turn-On Delay (Battery B to Battery A)

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MAX1773/MAX1773A

Power Source Selector for Dual-Battery SystemsMAX1773/MAX1773A

The MAX1773/MAX1773A provide the functions neces-sary to allow an external controller to manage thepower connections needed for two battery packs, anAC adapter input, a battery charger, and the systemload. The MAX1773/MAX1773A use seven PMOS FETsto provide all the switching necessary in systems usinga step-down charger powered by the AC adapter(Figures 9 and 10). The MAX1773/MAX1773A automati-cally adapt to many transient conditions—such as ACplug-in, battery hot swapping, and battery switchover—to provide constant power to the system without requir-ing real-time support from an external controller. TheMAX1773/MAX1773A draw their power from the highestvoltage supply present (Figure 11).

tery when no AC adapter is present. AC adapter Statesmode provides functionality when an AC Adapter is pre-sent. Standard Battery States mode provides functionalitywhen one or both batteries are present, the AC adapter isnot present, and EXTLD is above 2.2V. The StandardBattery States mode requires an external supply with anoutput voltage between 2.2V and 4.5V for ACDET, asshown in Figure 10. The external power supply must bepowered from EXTLD.

AC Adapter States

The MAX1773/MAX1773Acheck for the presence of anAC adapter by sensing the voltage at ACDET. WhenVACDETexceeds the batteries’ voltage and 4.75V, thenthe MAX1773/MAX1773Ause the AC adapter to powerthe load. In addition, if the selected battery is present,the MAX1773/MAX1773Aconnect the selected battery’scharge path. See Table 1 for a detailed listing of theMAX1773/MAX1773Astates for operation with an ACadapter detected.

Battery Detection

The MAX1773/MAX1773Amonitor the battery’s thermis-tor voltage to determine the presence of the battery.The devices compare the battery’s thermistor voltage(VTHM_) to the thermistor trip point (VTCOMP). If VTHM_< VTCOMP, then the MAX1773/MAX1773Aassume thatthe battery is present. However, if VTHM_> VTCOMP,the MAX1773/MAX1773Aassume that the battery isabsent and do not charge or discharge the battery.

Standard Battery States

When the AC adapter power supply is not present, theMAX1773/MAX1773Ause the batteries to supply theload. BATSEL allows an external controller to select abattery. Table 2 shows the simplified standard batterystates that normally control operation. However, theBattery Switchover Latch, the Low-Battery Latch, andthe Discharged Battery Latch are able to suspend thestate table and provide additional functionality.

Modes of Operation

The MAX1773/MAX1773Aprovide three modes of oper-ation. Start-up States mode provides functionality whenthe MAX1773/MAX1773A areinitially powered by a bat-12

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Power Source Selector for

Dual-Battery Systems

The Battery Switchover Latch stops the MAX1773/To prevent the MAX1773/MAX1773A from switching to aMAX1773Afrom oscillating when the device switchesdischarged battery, the Low-Battery Latch suspends thefrom the selected battery and then the selected bat-state table when the unconnected battery’s voltage istery’s voltage recovers. According to the state table,below 5 and the discharging battery’s voltagethe MAX1773/MAX1773Awould switch back to thedrops below 5 VMINV selected battery as soon as the battery’s voltageunconnected battery, the MAX1773/MAX1773A continueVMINV. Instead of switching to therecovered. The Battery Switchover Latch suspends theto power from the discharging battery. This latch isstate table as soon as the MAX1773/MAX1773Aswitchcleared when the unconnected battery is removedover to the nonselected battery. This causes the(VMAX1773/MAX1773Ato continue to power from theTHM_> VTCOMP), when in the Startup States mode,when in the AC Adapter States mode, and if the uncon-nonselected battery unless the latch is cleared. Thenected battery’s voltage rises above 5 VBattery Switchover Latch is cleared when BATSEL isMINV.

toggled (to select the other battery), when in theThe Discharged Battery Latch sets whenever theStartup States mode, in the AC Adapter States mode,MAX1773/MAX1773Aare in the Standard Battery Statesand when the selected battery is removed (Vmode, both batteries are present (VVTHM_>TCOMP).

< 5 THM_< VTCOMP),one of the batteries is low (VBAT_ V’s voltage is below VMINV), and theother batteryACDET. While the

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13

MAX1773/MAX1773A

Power Source Selector for Dual-Battery Systems

MAX1773/MAX1773A

Figure 10. Standard Application Circuit

Discharged Battery Latch is set, the state table is sus-pended, the MAX1773/MAX1773A arenot allowed toswitch batteries, and the Low Battery Latch is cleared.The Discharged Battery Latch is cleared when bothbatteries are above VACDET,in the AC Adapter Statesmode, and in the Startup States mode.

Startup States

When VACDETrises at startup, the MAX1773/MAX1773A use Startup States. See Table 3 for adetailed listing of the MAX1773/MAX1773A states inthis mode. Note that once ACDET rises above 2.2V, theMAX1773/MAX1773A are no longer in the Startup

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Power Source Selector for

Dual-Battery Systems

Figure 11. Functional Diagram

States mode and enters either the Standard BatteryIn the AC Adapter States mode, the BATSEL ActionStates mode or the AC Adapter States mode.

Delay (see Electrical Characteristics) allows the exter-Status and Configuration

nal controller to tell if both batteries are absent. WhenBATSTAT and ACPRESprovide information to an exter-both batteries are absent in the AC Adapter Statesnal controller. Table 4 shows the different states ofmode and BATSEL changes states, BATSTAT is imme-BATSTAT and ACPRES.

diately updated. However, changes to the connectionstates are delayed (see Table 1 for connection states).

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15

MAX1773/MAX1773A

Power Source Selector for Dual-Battery SystemsMAX1773/MAX1773A

If BATSEL is returned to its original state within theBATSEL Action Delay, then changes to the connectionstates are never made. Note that in the StandardBattery States mode and in the AC Adapter Statesmode when one or both batteries are present, bothBATSTAT and the connection states are delayed duringthe BATSEL Update Delay.

where VGS(MIN)is the minimum P7 gate-to-source voltage, IPDS(SINK)is the PDS sink current, and RPDS isR13.

The MAX1773/MAX1773A use open-collector drivers toopen the charge paths. Minimize the value of the pullupresistors on the charge paths (R12 and R14) to allowthe MAX1773/MAX1773A to quickly turn on the PMOSFETs; however, keep the value large enough to preventa lower VGSthan specified by the PMOS FET. The mini-mum VGSis:

VGS(MIN)= -ICHG_(SINK) RCHG_

where VGS(MIN)is the minimum P1 or P4 gate-to-sourcevoltage, ICHG_(SINK)is the CHG_ sink current (seeElectrical Characteristics), and RCHG_is R12 or R14.The MAX1773/MAX1773A feature an internal linear reg-ulator to provide power for itself and external circuitry.The linear regulator’s output is available at VDDand isnominally 3.3V. When the linear regulator is not used topower external circuitry, bypass it with a 0.33µF ceram-ic capacitor. To supply external loads up to 1mA,bypass the linear regulator with a 3.3µF tantalumcapacitor.

MOSFET Drivers

To minimize the time when no supply is connected tothe external load during switchover transients, theMAX1773/MAX1773A use active pullup drivers for thedischarge paths (DIS_) and the common paths(COM_). When the MAX1773/MAX1773A initially beginto pull up one of these pins, they use a large current(Initial COM_ Source Current and Initial DIS_ SourceCurrent; see Electrical Characteristics). Once theCOM_ voltage rises to within 2V of VBAT_or the DIS_voltage rises to within 2V of VEXTLD,then a weaker dri-ver is used to hold up the voltage (Final COM_ SourceCurrent and Final DIS_ Source Current; see ElectricalCharacteristics).

The MAX1773/MAX1773A are designed to preventshoot-through from one battery to the other when transi-tioning from discharging one battery to discharging theother battery. To accomplish this, the MAX1773/MAX1773A do not connect the second battery toEXTLD until it senses that the first battery is disconnect-ed from EXTLD. See Notes 4 and 5 of ElectricalCharacteristics.

To allow flexibility when choosing the higher voltagePDS PMOS FET (P7, Figure 10), the MAX1773/MAX1773A do not limit the gate-to-source voltageapplied to the PDS PMOSFET. The minimum VGSis setby the MAX1773/MAX1773A PDS sink current (seeElectrical Characteristics) and the external resistor fromPDS to EXTLD (R13):

VGS(MIN)= -IPDS(SINK) RPDS

VDDRegulator

Applications Information

Load Switchover Transients

When power switches from one power source to anoth-er, a transient is created on the load. This transient( VEXTLD) is minimized by the capacitance on the load(CEXTLD). The voltage transient can be approximatedas:

where tSWITCHOVERis the time where no supply is con-

nected to the EXTLD.

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