MAX1647EAP规格书,MAX1647EAU技术资料,MAX1648ESE,datasheet,PDF

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

19-1158; Rev 0; 12/96

Chemistry-Independent

Battery Chargers

_______________General Description

____________________________Features

The MAX1647/MAX1648 provide the power control neces-sary to charge batteries of any chemistry. In the MAX1647,oCharges Any Battery Chemistry: all charging functions are controlled via the Intel SystemLi-Ion, NiCd, NiMH, Lead Acid, etc.

Management Bus (SMBus ) interface. The SMBus 2-wireoIntel SMBus 2-Wire Serial Interface (MAX1647)serial interface sets the charge voltage and current, andprovides thermal status information. The MAX1647 func-oIntel/Duracell Level 2 Smart Battery Complianttions as a level 2 charger, compliant with the Duracell/Intel(MAX1647)Smart Battery Charger Specification. The MAX1648 omitso4A, 2A, or 1A Maximum Battery-Charge Currentthe SMBus serial interface, and instead sets the chargevoltage and current proportional to the voltage applied too11-Bit Control of Charge Currentexternal control pins.

oUp to 18V Battery VoltageIn addition to the feature set required for a level 2 charger,the MAX1647 generates interrupts to signal the host wheno10-Bit Control of Voltage

power is applied to the charger or a battery is installed oro±0.75% Voltage Accuracy with External ±0.1%removed. Additional status bits allow the host to checkReferencewhether the charger has enough input voltage, andwhether the voltage on or current into the battery is beingoUp to 28V Input Voltage

regulated. This allows the host to determine when lithium-oBattery Thermistor Fail-Safe Protection

ion batteries have completed charge without interrogatingthe battery.

The MAX1647 is available in a 20-pin SSOP with a 2mmprofile height. The MAX1648 is available in a 16-pin SOpackage.

______________Ordering Information

________________________Applications

Notebook ComputersPersonal Digital AssistantsCharger Base StationsPhones

__________________________________________________________Pin Configurations

SMBus is a trademark of Intel Corp.

________________________________________________________________Maxim Integrated Products

1

For free samples & the latest literature: , or phone 1-800-998-8800

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

ABSOLUTE MAXIMUM RATINGS

DCIN to AGND..........................................................-0.3V to 30VDCIN to IOUT...........................................................-0.3V to 7.5VBST to AGND............................................................-0.3V to 36VBST, DHI to LX............................................................-0.3V to 6VLX to AGND..............................................................-0.3V to 30VTHM, CCI, CCV, DACV, REF,

DLO to AGND................................................-0.3V to (VL + 0.3V)VL, SEL, INT, SDA, SCL to AGND (MAX1647)...........-0.3V to 6VSETV, SETI to AGND (MAX1648)................................-0.3V to 6VBATT, CS+ to AGND.................................................-0.3V to 20V

PGND to AGND.....................................................-0.3V to +0.3VSDA, INTCurrent................................................................50mAVL Current...........................................................................50mAContinuous Power Dissipation (TA= +70°C)

16-Pin SO (derate 8.7mW/°C above +70°C).................696mW20-Pin SSOP (derate 8mW/°C above +70°C)...............640mWOperating Temperature Range

MAX1647EAP, MAX1648ESE...........................-40°C to +85°CStorage Temperature.........................................-60°C to +150°CLead Temperature (soldering, 10sec).............................+300°C

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

(VDCIN= 18V, VREF= 4.096V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

2_______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

ELECTRICAL CHARACTERISTICS (continued)

(VDCIN= 18V, VREF= 4.096V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

Note 1:When DCIN is less than 4V, VL is less than 3.2V, causing the battery current to be typically 2µA (CS plus BATT input

current).

_______________________________________________________________________________________

3

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

ELECTRICAL CHARACTERISTICS

(VDCIN= 18V, VREF= 4.096V, TA= -40°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted. Limits over this temperature range are guaranteed by design.)

4

_______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

TIMING CHARACTERISTICS—MAX1647

(TA= 0°C to +85°C, unless otherwise noted.)

TIMING CHARACTERISTICS—MAX1647

(TA= -40°C to +85°C, unless otherwise noted. Limits over this temperature range are guaranteed by design.)

_______________________________________________________________________________________5

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

__________________________________________Typical Operating Characteristics

(Circuit of Figure 3, TA = +25°C, unless otherwise noted.)

MAX1647

BATT LOAD TRANSIENT

MAX1647/48-01

VCCI2.4V VCCV200mV/div12V

VBATT1V/div

12V

MAX1647

BATT LOAD TRANSIENT

MAX1647/48-02

VCCV2.3V VCCI100mV/div

VBATT5V/div

1ms/div

ChargingVoltage( ) = 0x2EE0 = 12000mV ChargingCurrent( ) = 0xFFFF = MAX VALUE ACDCIN = 18.0V, SEL = OPEN, R1 = 0.1 R2 = 10k , C1 = 68µF, C2 = 0.1µF, C3 = 47nF L1 = 22µH, VREF = 4.096V

2ms/div

ChargingVoltage( ) = 0x2EE0 = 12000mV ChargingCurrent( ) = 0x03E8 = 1000mA ACDCIN = 18.0V, SEL = OPEN, C1 = 68µF, C2 = 0.1µF, C3 = 47nF, R1 = 0.1 R2 = 10k , L1 = 22µH, VREF = 4.096V

VL VOLTAGE vs. LOAD CURRENT

5.55.0

4.5VL (V)

3.863.843.82VREF (V)3.803.783.763.74

10

20

30

40

50

LOAD CURRENT (mA)

3.723.70

INTERNAL REFERENCE VOLTAGE

MAX1647/48-04

4.0

3.5

0.51.01.52.0

LOAD CURRENT (mA)

INPUT AND OUTPUT POWER

DROP IN BATT OUTPUT VOLTAGE (%)

3530POWER (W)

2520151050

500

2000

CURRENT INTO BATT (mA)

1000

1500

2500

MAX1647

OUTPUT V-I CHARACTERISTIC

OUTPUT VOLTAGE ERROR

400.001

0.010.1

0.8OUTPUT VOLTAGE ERROR (%)

0.6

0.40.20

-0.2-0.4

1

10

500

1000

1500

2000

2500

100

LOAD CURRENT (mA)

4500850012,50016,500

PROGRAMMED VOLTAGE CODE IN DECIMAL

6_______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

______________________________________________________________Pin Description

_______________________________________________________________________________________7

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Figure 1. SMBus Serial Interface Timing—Address

Figure 2. SMBus Serial Interface Timing—Acknowledge8

_______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Figure 3. MAX1647 Typical Application Circuit

_______________________________________________________________________________________

9

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Table 1a. Component Selection for Figure 3 Circuit (Also Use for Figure 4)

10

______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Table 1b. Component Suppliers

_______________Detailed Description

Output Characteristics

The MAX1647/MAX1648 contain both a voltage-regulation loop and a current-regulation loop. Bothloops operate independently of each other. The volt-age-regulation loop monitors BATT to ensure that itsvoltage never exceeds the voltage set point (V0). Thecurrent-regulation loop monitors current delivered toBATT to ensure that it never exceeds the current-limitset point (I0). The current-regulation loop is in controlas long as BATT voltage is below V0. When BATT volt-age reaches V0, the current loop no longer regulates,and the voltage-regulation loop takes over. Figure 5shows the V-I characteristic at the BATT pin.

Figure 4. MAX1648 Typical Operating Circuit

______________________________________________________________________________________

11

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Whether the MAX1647 is controlling the voltage or cur-rent at any time depends on the battery’s state. If thebattery has been discharged, the MAX1647’s outputreaches the current-regulation limit before the voltagelimit, causing the system to regulate current. As the bat-tery charges, the voltage rises until the voltage limit isreached, and the charger switches to regulating voltage.The transition from current to voltage regulation is doneby the charger, and need not be controlled by the host.

Voltage Control

The internal GMV amplifier controls the MAX1647’s out-put voltage. The voltage at the amplifier’s noninvertinginput amplifier is set by a 10-bit DAC, which is controlledby a ChargingVoltage( ) command on the SMBus (seethe MAX1647 Logicsection for more information). Thebattery voltage is fed to the GMV amplifier through a 4:1resistive voltage divider. With an external 4.096V refer-ence, the set voltage ranges between 0 and 16.38V with16mV resolution.

This poses a challenge for charging four lithium-ioncells in series: because the lithium-ion battery’s typicalper-cell voltage is 4.2V maximum, 16.8V is required. A larger reference voltage can be used to circumventthis. Under this condition, the maximum battery voltageno longer matches the programmed voltage. The solu-tion is to use a 4.2V reference and host software.Contact Maxim’s applications department for moreinformation.

The GMV amplifier’s output is connected to the CCVpin, which compensates the voltage-regulation loop.Typically, a series-resistor/capacitor combination canbe used to form a pole-zero couplet. The pole intro-duced rolls off the gain starting at low frequencies. Thezero of the couplet provides sufficient AC gain at mid-frequencies. The output capacitor then rolls off the mid-frequency gain to below 1, to guarantee stability beforeencountering the zero introduced by the output capaci-tor’s equivalent series resistance (ESR). The GMVamplifier’s output is internally clamped to between one-fourth and three-fourths of the voltage at REF.

Figure 5. Output V-I Characteristic

Setting V0 and I0 (MAX1647)

Set the MAX1647’s voltage and current-limit set pointsvia the Intel System Management Bus (SMBus ) 2-wireserial interface. The MAX1647’s logic interprets the serial-data stream from the SMBus interface to set inter-nal digital-to-analog converters (DACs) appropriately.See the MAX1647 Logic

section for more information.

Setting V0 and I0 (MAX1648)

Set the MAX1648’s voltage- and current-limit set points(V0 and I0, respectively) using external resistive dividers.Figure 6b is the MAX1648 block diagram. V0 equals fourtimes the voltage on the SETV pin. I0 equals the voltageon SETI divided by 5.5, divided by R1 (Figure 4).

_____________________Analog Section

The MAX1647/MAX1648 analog section consists of acurrent-mode PWM controller and two transconduc-tance error amplifiers: one for regulating current andthe other for regulating voltage. The MAX1647 usesDACs to set the current and voltage level, which arecontrolled via the SMBus interface. The MAX1648 elimi-nates the DACs and controls the error amplifiers direct-ly from SETI (for current) and SETV (for voltage). Sinceseparate amplifiers are used for voltage and currentcontrol, both control loops can be compensated sepa-rately for optimum stability and response in each state.The following discussion relates to the MAX1647; how-ever, MAX1648 operation can easily be inferred fromthe MAX1647.

Current Control

The internal GMI amplifier and an internal currentsource control the battery current while the charger isregulating current. Since the regulator current’s accura-cy is not adequate to ensure full 11-bit accuracy, aninternal linear current source is used in conjunction withthe PWM regulator to set the battery current. The cur-rent-control DAC’s five least significant bits set the

12______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Figure 6a. MAX1647 Block Diagram

______________________________________________________________________________________

13

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Figure 6b. MAX1648 Block Diagram

14

______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

internal current sources’ state, and the six most signifi-The PWM comparator compares the current-sensecant bits control the switching regulator’s current. Theamplifier’s output to the higher output voltage of eitherinternal current source supplies 1mA resolution to thethe GMV or the GMI amplifier (the error voltage). Thisbattery to comply with the smart-battery specification.current-mode feedback corrects the duty ratio of theWhen the current is set to a number greater than 32,switched voltage, regulating the peak battery currentthe internal current source remains at 31mA. This guar-and keeping it proportional to the error voltage. Sinceantees that battery-current setting is monotonic regard-the average battery current is nearly the same as theless of current-sense resistor choice and current-sensepeak current, the controller acts as a transconductanceamplifier offset.

amplifier, reducing the effect of the inductor on the out-The GMI amplifier’s noninverting input is driven by a 4:1put filter LC formed by the output inductor and the bat-resistive voltage divider, which is driven by the 6-bittery’s parasitic capacitance. This makes stabilizing theDAC. If an external 4.096V reference is used, this inputcircuit easy, since the output filter changes from a com-is approximately 1.0V at full scale, and the resolution isplex second-order RLC to a first-order RC. To preserve16mV. The current-sense amplifier drives the invertingthe inner current-control loop’s stability, slope compen-input to the GMI amplifier. It measures the voltagesation is also fed into the comparator. This damps outacross the current-sense resistor (RSEN) (which isperturbations in the pulse width at duty ratios greaterbetween the CS and BATT pins), amplifies it by approx-than 50%.

imately 5.45, and level shifts it to ground. The full-scaleAt heavy loads, the PWM controller switches at a fixedcurrent is approximately 0.2V / RSEN, and the resolutionfrequency and modulates the duty cycle to control theis 3.2mV / RSEN.

battery voltage or current. At light loads, the DC currentThe current-regulation-loop is compensated by addingthrough the inductor is not sufficient to prevent the cur-a capacitor to the CCI pin. This capacitor sets the cur-rent from going negative through the synchronous recti-rent-feedback loop’s dominant pole. The GMI amplifier’sfier (Figure 3, M2). The controller monitors the currentoutput is clamped to between approximately one-fourththrough the sense resistor RSEN; when it drops to zero,and three-fourths of the REF voltage. While the current isthe synchronous rectifier turns off to prevent negativein regulation, the CCV voltage is clamped to withincurrent flow.

80mV of the CCI voltage. This prevents the battery volt-age from overshooting when the DAC voltage setting isMOSFET Drivers

updated. The converse is true when the voltage is inThe MAX1647 drives external N-channel MOSFETs toregulation and the current is not at the current DAC set-regulate battery voltage or current. Since the high-sideting. Since the linear range of CCI or CCV is about 1.5VN-channel MOSFET’s gate must be driven to a voltageto 3.5V or about 2V, the 80mV clamp results in a rela-higher than the input source voltage, a charge pump istively negligible overshoot when the loop switches fromused to generate such a voltage. The capacitor C7voltage to current regulation or vice versa.

(Figure 3) charges to approximately 5V through D2when the synchronous rectifier turns on. Since one sidePWM Controller

of C7 is connected to the LX pin (the source of M1), theThe battery voltage or current is controlled by the cur-high-side driver (DHI) can drive the gate up to the volt-rent-mode, pulse-width-modulated (PWM), DC-DC con-age at BST, which is greater than the input voltage,verter controller. This controller drives two externalwhen the high-side MOSFET turns on.

N-channel MOSFETs, which switch the voltage from theThe synchronous rectifier behaves like a diode, but withinput source. This switched voltage feeds an inductor,a smaller voltage drop to improve efficiency. A smallwhich filters the switched rectangular wave. The con-dead time is added between the time that the high-sidetroller sets the pulse width of the switched voltage so thatMOSFET turns off and the synchronous rectifier turnsit supplies the desired voltage or current to the battery.on, and vice versa. This prevents crowbar currents (cur-The heart of the PWM controller is the multi-input com-rents that flow through both MOSFETS during the briefparator. This comparator sums three input signals totime that one is turning on and the other is turning off).determine the pulse width of the switched signal, set-Connect a Schottky rectifier from ground to LX (acrossting the battery voltage or current. The three signals arethe source and drain of M2) to prevent the synchronousthe current-sense amplifier’s output, the GMV or GMIrectifier’s body diode from conducting. The body diodeerror amplifier’s output, and a slope-compensation sig-typically has slower switching-recovery times, so allow-nal, which ensures that the controller’s internal current-ing it to conduct would degrade efficiency.

control loop is stable.

______________________________________________________________________________________15

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

The synchronous rectifier may not be completelyreplaced by a diode because the BST capacitorcharges while the synchronous rectifier is turned on.Without the synchronous rectifier, the BST capacitormay not fully charge, leaving the high-side MOSFETwith insufficient gate drive to turn on. However, the syn-chronous rectifier may be replaced with a small MOS-FET, such as a 2N7002, to guarantee that the BSTcapacitor is allowed to charge. In this case, most of thecurrent at high currents is carried by the diode and notby the synchronous rectifier.

Internal Regulator and Reference

The MAX1647 uses an internal low-dropout linear regula-tor to create a 5.4V power supply (VL), which powers itsinternal circuitry. VL can supply up to 20mA. A portion ofthis current powers the internal circuitry, but the remain-ing current can power the external circuitry. The currentused to drive the MOSFETs comes from this supply,which must be considered when calculating how muchpower can be drawn. To estimate the current required todrive the MOSFETs, multiply the total gate charge ofeach MOSFET by the switching frequency (typically250kHz). The internal circuitry requires as much as 6mAfrom the VL supply. To ensure VL stability, bypass the VLpin with a 1µF or greater capacitor.

The MAX1647 has an internal ±2% accurate 3.9V refer-ence voltage. An external reference can be used toincrease the charger’s accuracy. Use a 4.096V reference,such as the MAX874, for compliance with the Intel/Duracell smart-battery specification. Voltage-settingaccuracy is ±0.65%, so the total voltage accuracy is theaccuracy added to the reference accuracy. For 1% totalvoltage accuracy, use a reference with ±0.35% or greateraccuracy. If the internal reference is used, bypass it witha 0.1µF or greater capacitor.

MAX1647 Logic

The MAX1647 uses serial data to control its operation. Theserial interface complies with the SMBus specification (seeSystem Management Bus Specification, from IntelArchitecture Labs; /IAL/power-mgm.html; Intel Architecture Labs: 800-253-3696).Charger functionality complies with the Intel/DuracellSmart Charger Specification for a level 2 charger.

The MAX1647 uses the SMBus Read-Word and Write-Word protocols to communicate with the battery it ischarging, as well as with any host system that monitorsthe battery to charger communications. The MAX1647never initiates communication on the bus; it onlyreceives commands and responds to queries for statusinformation. Figure 7 shows examples of the SMBusWrite-Word and Read-Word protocols.

16

Figure 7. Write-Word and Read-Word Examples

______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Each communication with the MAX1647 begins with aChargingVoltage( )

start condition that is defined as a falling edge on SDAThe ChargingVoltage( ) command uses Write-Wordwith SCL high. The device address follows the startprotocol. The command code for ChargingVoltage( ) iscondition. The MAX1647 device address is 0b00010010x15; thus, the CMD7–CMD0 bits in Write-Word proto-(0bindicates a binary number), which may also becol should be 0b00010101. The 16-bit binary numberdenoted as 0x12 (0xindicates a hexadecimal number)formed by D15–D0 represents the voltage set pointfor Write-Word commands, or 0x13 in hexadecimal for(V0) in millivolts; however, since the MAX1647 has onlyRead-Word commands (note that the address is only16mV resolution in setting V0, the D0, D1, D2, and D3seven bits, and the hexadecimal representation usesbits are ignored. For D15 = D14 = 0:

R/Was its least significant bit).

ChargerMode( )

The ChargerMode( ) command uses Write-Word proto-col. The command code for ChargerMode( ) is 0x12;thus the CMD7–CMD0 bits in Write-Word protocolIn equation 1, VDAC is the decimal equivalent of theshould be 0b00010010. Table 2 describes the functionsbinary number represented by bits D13, D12, D11,of the 16 different data bits (D0–D15). Bit 0 refers to theD10, D9, D8, D7, D6, D5, and D4 programmed with theD0 bit in the Write-Word protocol (Figure 7).

ChargingVoltage( ) command. For example, if D4–D13Whenever the BATTERY_PRESENT status bit is clear,are all set, VDAC is the decimal equivalent ofthe HOT_STOP bit is set, regardless of any previous0b1111111111 (1023). If either D15 or D14, or bothChargerMode( ) command. To charge a battery thatD15 and D14, are set, all the bits in the voltage DAChas a thermistor impedance in the HOT range (i.e.,(Figure 6a) are set, regardless of D13–D0, and the THERMISTOR_HOT = 1 and THERMISTOR_UR = 0),status register’s VOLTAGE_OR bit is set. For D15 = 1the host must use the ChargerMode( ) command toand/or D14 = 1:

clear HOT_STOP afterthe battery is inserted. TheHOT_STOP bit returns to its default power-up condition(‘1’) whenever the battery is removed.

Table 2. ChargerMode( ) Bit Functions

*Bit position in the D15–D0 data.**Power-on reset value.

N/A = Not available.

______________________________________________________________________________________17

MAX1647/MAX1648

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Figure 8 shows the mapping between V0 (the voltage-regulation-loop set point) and the ChargingVoltage( )data.

The power-on reset value for the ChargingVoltage( )register is 0xFFF0; thus, the first time a MAX1647 ispowered on, the BATT voltage regulates to 16.368Vwith VREF= 4.096V. Any time the BATTERY_PRESENTstatus bit is clear, the ChargingVoltage( ) registerreturns to its power-on reset state.

ChargingCurrent( )

The ChargingCurrent( ) command uses Write-Wordprotocol. The command code for ChargingCurrent( ) is0x14; thus, the CMD7–CMD0 bits in Write-Word proto-col should be 0b00010100. The 16-bit binary numberformed by D15–D0 represents the current-limit set point(I0) in milliamps. Tying SEL to AGND selects a 1.023Amaximum setting for I0. Leaving SEL open selects a2.047A maximum setting for I0. Tying SEL to VL selectsa 4.095A maximum setting for I0.

16.368

VREF = 4.096V

12.592

VOLTAGE SET POINT (V0)

8.400

4.192

0b000000000000xxxx

0x000x

0b000100000110xxxx

0x106x

0b001000001101xxxx

0x20Dx

0b001100010011xxxx

0x313x

0b001111111111xxxx

0x3FFx

0b111111111111xxxx

0xFFFx

ChargingVoltage( ) D15–D0 DATA

Figure 8. ChargingVoltage( ) Data to Voltage Mapping18

______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Two sources of current in the MAX1647 charge the bat-tery: a binary-weighted linear current source sourcesfrom IOUT, and a switching regulator controls the currentflowing through the current-sense resistor (R1). IOUTprovides a small maintenance charge current to com-pensate for battery self-discharge, while the switchingregulator provides large currents for fast charging.IOUT sources from 1mA to 31mA. Table 3 shows therelationship between the value programmed with the

ChargingCurrent( ) command and IOUT source current. The CCV_LOW comparator checks to see if the outputvoltage is too high by comparing CCV to REF / 4. IfCCV_LOW = 1 (when CCV < REF / 4), IOUT shuts off,preventing the output voltage from exceeding the voltageset point specified by the ChargingVoltage( ) register.VOLTAGE_NOTREG = 1 whenever the internal clamppulls down on CCV. (The internal clamp pulls down onCCV to keep its voltage close to CCI’s voltage.)

MAX1647/MAX1648

Table 3. Relationship Between IOUT Source Current and ChargingCurrent( ) Value

Note 1:Logical AND of THERMISTOR_HOT, HOT_STOP, NOT(THERMISTOR_UR).

185

SEL = OPEN OR SEL = VL

)

EVGAm(T LNOOIVT TATLAUBG -E SR94

CT ENEGRARREUVC ANI2.94

0b000001

0b100000

0b111111

CURRENT DAC CODE, DA5–DA0 BITS

Figure 9. Average Voltage Between CS and BATT vs. Current DAC Code

______________________________________________________________________________________

19

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent Battery ChargersMAX1647/MAX1648

Table 4. Relationship Between Current DAC Code and the ChargingCurrent( ) Value

Note 1:Logical AND of THERMISTOR_HOT, HOT_STOP, NOT(THERMISTOR_UR).Note 2:Value of CURRENT_OR bit in the ChargerStatus( ) register.N/C = No change

Table 5. Effect of SEL Pin-Strapping on the ChargingCurrent( ) Data Bits

*When SEL = VL, D5 = 1 forces DA0 to be 1 regardless of the D6 bit value.

With the switching regulator on, the current through R1(Figure 3) is regulated by sensing the average voltagebetween CS and BATT. A 6-bit current DAC controlsthe current-limit set point. DA5–DA0 denote the bits inthe current DAC code. Figure 9 shows the relationshipbetween the current DAC code and the average volt-age between CS and BATT.

20

When the switching regulator is off, DHI is forced to LX and DLO is forced to ground. This prevents currentfrom flowing through inductor L1. Table 4 shows therelationship between the ChargingCurrent( ) registervalue and the switching regulator current DAC code.

______________________________________________________________________________________

Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

With SEL = AGND, R1 should be as close as possible to0.185 / 1.023 = 181m to ensure that the actual outputcurrent matches the data value programmed with theChargingCurrent( ) command. With SEL = open, R1should be as close as possible to 90m . With SEL = VL,R1 should be as close as possible to 45m . Table 5 sum-marizes how SEL affects the R1 value and the meaning ofprotocol returns D15–D0 (Figure 7). Table 7 describesthe meaning of the individual bits. The latched bits,THERMISTOR_HOT and ALARM_INHIBITED, arecleared whenever BATTERY_PRESENT = 0 orChargerMode( ) is written with POR_RESET = 1.

Interrupts and the Alert-Response

data bits D15–D0 in the ChargingCurrent( ) command.Address

DA5–DA0 denote the current DAC code bits, and I4–I0An interrupt is triggered (INTgoes low) whenever powerdenote the IOUT linear-current source binary weightingis applied to DCIN, the BATTERY_PRESENT bit changes,bits. Note that whenever any current DAC bits are set, theor the POWER_FAIL bit changes. BATTERY_PRESENTlinear-current source is set to full scale (31mA).

and POWER_FAIL have interrupt masks that can be setThe power-on reset value for the ChargingCurrent( )or cleared via the ChargerMode( ) command. INTstaysregister is 0x000C. Irrespective of the SEL pin setting,low until the interrupt is cleared. There are two methodsthe MAX1647 powers on with I0 set to 12mA (i.e.,for clearing the interrupt: issuing a ChargerStatus( ) com-DA5–DA0, I1, and I0 all equal to zero, and only I3 andmand, and using the Receive Byte protocol with a 0x19I2 set). Anytime the BATTERY_PRESENT status bit isAlert-Response address. The MAX1647 responds to theclear (battery removed), the ChargingCurrent( ) registerAlert-Response address with the 0x89 byte.

returns to its power-on reset state. This ensures thatupon insertion of a battery, the initial charging current is__________Applications Information

12mA.

Using the MAX1647

AlarmWarning( )

with Duracell Smart Batteries

The AlarmWarning( ) command uses Write-Word protocol.The following pseudo-code describes an interrupt rou-The command code for AlarmWarning( ) is 0x16; thus thetine that is triggered by the MAX1647 INToutput goingCMD7–CMD0 in Write-Word protocol should below. This interrupt routine keeps the host informed of0b00010110. The AlarmWarning( ) command sets theany changes in battery-charger status, such as DCINALARM_INHIBITED status bit in the MAX1647 if D15, D14,power detection, or battery removal and insertion.or D12 of the Write-Word protocol data equals 1. Table 6DOMAX1647:

summarizes the AlarmWarning( ) command’s function. { This is the beginning of the routine that handlesThe ALARM_INHIBITED status bit remains set until MAX1647 interrupts. }

BATTERY_PRESENT = 0 (battery removed) or a{ Check the status of the MAX1647. }

ChargerMode() command is written with the POR_RESETTEMPWORD = ReadWord( SMBADDR = 0b00010011bit set. As long as ALARM_INHIBITED = 1, the MAX1647= 0x13, COMMAND = 0x13 )

switching regulator and IOUT current source remain off.{ Check for the normal power-up case without a batteryinstalled. THERMISTOR_OR = 1, BATTERY_PRESENT =ChargerStatus( )

0. Use 0b1011111011111111 = 0xBEFF as the mask. }The ChargerStatus( ) command uses Read-Word proto-IF (TEMPWORD OR 0xBEFF) = 0xBFFF THEN GOTOcol. The command code for ChargerStatus( ) is 0x13;NOBATT:

thus, the CMD7–CMD0 bits in Write-Word protocol{ Check to see if the battery is installed. BATTERY_should be 0b00010011. The ChargerStatus( ) com-PRESENT = 1. Use 0b1011111111111111 = 0xBFFF asmand returns information about thermistor impedancethe mask. }

and the MAX1647’s internal state. The Read-Word

Table 6. Effect of the AlarmWarning( ) Command

______________________________________________________________________________________21

MAX1647/MAX1648

本文来源：https://www.bwwdw.com/article/dv4j.html