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MAX1645BEEIN/a236avaiAdvanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
MAX1645BEEIMAXIMN/a246avaiAdvanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
MAX1645BEEIMAXN/a779avaiAdvanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting


MAX1645BEEI ,Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current LimitingELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = +3.3V, V = +16.8V, V = +18V, T = 0°C to +85°C, ..
MAX1645BEEI ,Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current LimitingApplications 3A (max) Battery Charge CurrentNotebook Computers 6-Bit Charge-Current Setting Point ..
MAX1645BEEI+ ,Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current LimitingApplications♦ 3A (max) Battery Charge CurrentNotebook Computers♦ 6-Bit Charge-Current Setting Point ..
MAX1645BEEI-T ,Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current LimitingELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = +3.3V, V = +16.8V, V = +18V, T = 0°C to +85°C, ..
MAX1645EEI ,Advanced Chemistry-Independent / Level 2 Battery Chargers with Input Current LimitingELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = +3.3V, V = +16.8V, V = +18V, T = 0°C to +85°C, ..
MAX1647EAP ,Chemistry-Independent Battery ChargersApplicationsMAX1647EAP -40°C to +85°C 20 SSOPNotebook ComputersMAX1648ESE -40°C to +85°C 16 Narrow ..
MAX4399CTK ,Audio/Video Switch for Three SCART ConnectorsApplicationsCVBS RGBSTBENCODERSatellite ReceiversTV SCARTR/L AUDIO R/L AUDIO CONNECTORSatellite Set ..
MAX4399CTK+ ,Audio/Video Switch for Three SCART ConnectorsApplicationsRGBCVBSSTBENCODERSatellite ReceiversTV SCARTR/L AUDIOR/L AUDIO CONNECTORSatellite Set-T ..
MAX4400AUK+T ,Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op Amps with Shutdownapplications.● 1.4mA of Sink and Source Load CurrentThe MAX4400 single amplifier is available in ul ..
MAX4400AUK-T ,Single/Dual/Quad / Low-Cost / Single-Supply / Rail-to-Rail Op Amps with ShutdownELECTRICAL CHARACTERISTICS (continued)(V = +5V, V = 0, V = 0, V = V /2, R = ∞ connected to V /2, SH ..
MAX4400AXK+T ,Single/Dual/Quad, Low-Cost, Single-Supply, Rail-to-Rail Op Amps with ShutdownElectrical Characteristics (continued)(V = +5V, V = 0V, V = 0V, V = V /2, R = ∞ connected to V /2, ..
MAX4400AXK-T ,Single/Dual/Quad / Low-Cost / Single-Supply / Rail-to-Rail Op Amps with ShutdownELECTRICAL CHARACTERISTICS(V = +5V, V = 0, V = 0, V = V /2, R = ∞ connected to V /2, SHDN = V (MAX4 ..


MAX1645BEEI
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
General Description
The MAX1645B is a high-efficiency battery charger
capable of charging batteries of any chemistry type. It
uses the Intel System Management Bus (SMBus) to
control voltage and current-charge outputs.
When charging lithium-ion (Li+) batteries, the MAX1645B
automatically transitions from regulating current to regu-
lating voltage. The MAX1645B can also limit line input
current so as not to exceed a predetermined current
drawn from the DC source. A 175s charge safety timer
prevents “runaway charging” should the MAX1645B stop
receiving charging voltage/current commands.
The MAX1645B employs a next-generation synchro-
nous buck control circuitry that lowers the minimum
input-to-output voltage drop by allowing the duty cycle
to exceed 99%. The MAX1645B can easily charge one
to four series Li+ cells.
Applications

Notebook Computers
Point-of-Sale Terminals
Personal Digital Assistants
Features
Input Current Limiting175s Charge Safety Timeout128mA Wake-Up ChargeCharges Any Chemistry Battery: Li+, NiCd,
NiMH, Lead Acid, etc.
Intel SMBus 2-Wire Serial InterfaceCompliant with Level 2 Smart Battery Charger
Spec Rev 1.0
+8V to +28V Input Voltage RangeUp to 18.4V Battery Voltage11-Bit Battery Voltage Setting±0.8% Output Voltage Accuracy with Internal
Reference
3A (max) Battery Charge Current6-Bit Charge-Current Setting 99.99% (max) Duty Cycle for Low-Dropout
Operation
Load/Source Switchover Drivers>97% Efficiency
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

19-2593; Rev 0; 10/02
Pin ConfigurationOrdering Information
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DCIN, CVS, CSSP, CSSN, LX to GND....................-0.3V to +30V
CSSP to CSSN, CSIP to CSIN...............................-0.3V to +0.3V
PDS, PDL to GND...................................-0.3V to (VCSSP+ 0.3V)
BST to LX..................................................................-0.3V to +6V
DHI to LX...................................................-0.3V to (VBST+ 0.3V)
CSIP, CSIN, BATT to GND.....................................-0.3V to +22V
LDO to GND.....................-0.3V to (lower of 6V or VDCIN+ 0.3V)
DLO to GND...........................................-0.3V to (VDLOV+ 0.3V)
REF, DAC, CCV, CCI, CCS, CLS to GND.....-0.3V to (VLDO+ 0.3V)
VDD, SCL, SDA, INT, DLOV to GND.........................-0.3V to +6V
THM to GND...............................................-0.3V to (VDD+ 0.3V)
PGND to GND.......................................................-0.3V to +0.3V
LDO Continuous Current.....................................................50mA
Continuous Power Dissipation (TA= +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C).........860mW
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at= +25°C.)
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at= +25°C.)
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at
ELECTRICAL CHARACTERISTICS
MAX1645B
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
Typical Operating Characteristics

(Circuit of Figure 1, VDCIN= 20V, TA = +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VDD= +3.3V, VBATT= +16.8V, VDCIN= +18V, TA= -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
Note 1:
Guaranteed by meeting the SMB timing specs.
Note 2:
The charger reverts to a trickle-charge mode of ICHARGE= 128mA below this threshold.
Note 3:
Voltage difference between CCV and CCI or CCS when one of these three pins is held low and the others try to pull high.
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

EFFICIENCY vs. BATTERY CURRENT
(VOLTAGE-CONTROL LOOP)

MAX1645B toc07
BATTERY CURRENT (mA)
EFFICIENCY (%)
EFFICIENCY vs. BATTERY CURRENT
(CURRENT-CONTROL LOOP)
MAX1645B toc08
ChargingCurrent() (CODE)
EFFICIENCY (%)
OUTPUT VI CHARACTERISTICS
MAX1645B toc09
LOAD CURRENT (mA)
DROP IN BATT OUTPUT VOLTAGE (%)150020005001000250030003500
0.38000400012,00016,00020,000
BATT VOLTAGE ERROR
vs. ChargingVoltage() CODE

MAX1645B toc10
ChargingVoltage() (CODE)
BATT VOLTAGE ERROR (%)10005001500200025003000
CURRENT-SETTING ERROR
vs. ChargingCurrent() CODE

MAX1645B toc11
ChargingCurrent() (CODE)
BATT CURRENT ERROR (%)
SOURCE/BATT CURRENT vs. LOAD CURRENT
WITH SOURCE CURRENT LIMIT
MAX1645B toc12
LOAD CURRENT (A)
SOURCE/BATT CURRENT (A)
SOURCE/BATT CURRENT vs. VBATT
WITH SOURCE CURRENT LIMIT
MAX1645B toc13
VBATT (V)
SOURCE/BATT CURRENT (A)
Typical Operating Characteristics (continued)

(Circuit of Figure 1, VDCIN= 20V, TA = +25°C, unless otherwise noted.)
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
Pin Description
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
Detailed Description

The MAX1645B consists of current-sense amplifiers, an
SMBus interface, transconductance amplifiers, reference
circuitry, and a DC-DC converter (Figure 2). The DC-DC
converter generates the control signals for the external
MOSFETs to maintain the voltage and the current set by
the SMBus interface. The MAX1645B features a voltage-
regulation loop and two current-regulation loops. The
loops operate independently of each other. The voltage-
regulation loop monitors BATT to ensure that its voltage
never exceeds the voltage set point (V0). The battery cur-
rent-regulation loop monitors current delivered to BATT to
ensure that it never exceeds the current-limit set point
(I0). The battery current-regulation loop is in control as
long as BATT voltage is below V0. When BATT voltage
reaches V0, the current loop no longer regulates. A third
loop reduces the battery-charging current when the sum
of the system (the main load) and the battery charger
input current exceeds the charging source current limit.
Setting Output Voltage

The MAX1645B voltage DAC has a 16mV LSB and an
18.432V full scale. The SMBus specification allows for a
16-bit ChargingVoltage() command that translates to a
1mV LSB and a 65.535V full-scale voltage; therefore,
the ChargingVoltage() value corresponds to the output
voltage in millivolts. The MAX1645B ignores the first 4
LSBs and uses the next 11 LSBs to control the voltage
DAC. All codes greater than or equal to 0x4800
(18432mV) result in a voltage overrange, limiting the
charger voltage to 18.432V. All codes below 0x0400
(1024mV) terminate charging.
Setting the Charge Current

The MAX1645B charge-current DAC has a 3.2mV to
150.4mV range. The SMBus specification allows for a
16-bit ChargingCurrent() command that translates to a
0.05mV LSB and a 3.376V full-scale current-sense volt-
age. The MAX1645B drops the first 6 LSBs and uses
the remaining 6 MSBs to control the charge-current
DAC. All codes above 0x0BC0 result in an overrange
condition, limiting the charge current-sense voltage to
150.4mV. All codes below 0x0080 turn off the charging
current. Therefore, the charging current (ICHARGE) is
determined by:
ICHARGE= VDACI/ RCSI
where VDACIis the current-sense voltage set by
ChargingCurrent(), and RCSIis the battery current-
sense resistor (R2 in Figure 1). When using a 50mΩ
current-sense resistor, the ChargingCurrent() value cor-
responds directly to the charging current in milliamps
(0x0400 = 1024mA = 52.2mV/50mΩ).
Input Current Limiting

The MAX1645B limits the current drawn by the charger
when the load current becomes high. The device limits
the charging current so the AC adapter voltage is not
loaded down. An internal amplifier, CSS, compares the
voltage between CSSP and CSSN to the voltage at
CLS/20. VCLSis set by a resistor-divider between REF
and GND.
The input source current is the sum of the device cur-
rent, the charge input current, and the load current. The
device current is minimal (6mA max) in comparison to
the charge and load currents. The charger input cur-
rent is generated by the DC-DC converter; therefore, the
actualsource current required is determined as follows:
ISOURCE= ILOAD+ [(ICHARGE✕VBATT)/ (VIN✕η)]
where ηis the efficiency of the DC-DC converter (typi-
cally 85% to 95%).
VCLSdetermines the threshold voltage of the CSS com-
parator. R3 and R4 (Figure 1) set the voltage at CLS.
Sense resistor R1 sets the maximum allowable source
current. Calculate the maximum current as follows:
IMAX= VCLS/ (20 ✕R1)
(Limit VCSSP - VCSSNto between 102.4mV and
204.8mV.)
The configuration in Figure 1 provides an input current
limit of:
IMAX= (2.048V / 20) / 0.04Ω= 2.56A
LDO Regulator

An integrated LDO regulator provides a +5.4V supply
derived from DCIN, which can deliver up to 15mA of
current. The LDO sets the gate-drive level of the NMOS
switches in the DC-DC converter. The drivers are actu-
ally powered by DLOV and BST, which must be con-
nected to LDO through a lowpass filter and a diode as
shown in Figure 1. Also see the MOSFET Driverssec-
tion. The LDO also supplies the 4.096V reference and
most of the control circuitry. Bypass LDO with a 1µF
capacitor.
VDDSupply

This input provides power to the SMBus interface and
the thermistor comparators. Typically connect VDDto
LDO or, to keep the SMBus interface of the MAX1645B
active while the supply to DCIN is removed, connect an
external supply to VDD.
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

Figure 1. Typical Application Circuit
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

Figure 2. Functional Diagram
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
Operating Conditions

The MAX1645B changes its operation depending on
the voltages at DCIN, BATT, VDD,and THM. Several
important operating states follow:AC Present.When DCIN is >7.5V, the battery is con-
sidered to be in an AC present state. In this condi-
tion, both the LDO and REF function properly and
battery charging is allowed. When AC is present, the
AC_PRESENT bit (bit 15) in the ChargerStatus() reg-
ister is set to 1.Power Fail.When DCIN is in the power-fail state, since the charger does not
have enough input voltage to charge the battery. In
power fail, the PDS input PMOS switch is turned off
and the POWER_FAIL bit (bit 13) in the
ChargerStatus() register is set to 1.Battery Present.When THM is <91% of VDD, the
battery is considered to be present. The MAX1645B
uses the THM pin to detect when a battery is con-
nected to the charger. When the battery is present,
the BATTERY_PRESENT bit (bit 14) in the
ChargerStatus() register is set to 1 and charging can
proceed. When the battery is not present, all of the
registers are reset. With no battery present, the
charger performs a “float” charge to minimize con-
tact arcing on battery connection. The “float” charge
still tries to regulate the BATT pin voltage at 18.32V
with 128mA of current compliance.Battery Undervoltage.When BATT <2.5V, the bat-
tery is in an undervoltage state. This causes the
charger to reduce its current compliance to 128mA.
The content of the ChargingCurrent() register is unaf-
fected and, when the BATT voltage exceeds 2.7V,
normal charging resumes. ChargingVoltage() is unaf-
fected and can be set as low as 1.024V.VDDUndervoltage.When VDD<2.5V, the VDDsup-
ply is in an undervoltage state, and the SMBus inter-
face does not respond to commands. Coming out of
the undervoltage condition, the part is in its Power-
On Reset state. No charging occurs when VDDis
under voltage.
SMBus Interface

The MAX1645B receives control inputs from the SMBus
interface. The serial interface complies with the SMBus
specification (refer to the System Management Bus
Specification from Intel Corporation). Charger function-
ality complies with the Intel/Duracell Smart Charger
Specification for a Level 2 charger.
The MAX1645B uses the SMBus read-word and write-
word protocols to communicate with the battery being
charged, as well as with any host system that monitors
the battery-to-charger communications as a Level 2
SMBus charger. The MAX1645B is an SMBus slave
device and does not initiate communication on the bus.
It receives commands and responds to queries for sta-
tus information. Figure 3 shows examples of the SMBus
write-word and read-word protocols, and Figures 4 and
5 show the SMBus serial-interface timing.
Each communication with this part begins with the
MASTER issuing a START condition that is defined as a
falling edge on SDA with SCL high and ends with a
STOP condition defined as a rising edge on SDA with
SCL high. Between the START and STOP conditions,
the device address, the command byte, and the data
bytes are sent. The MAX1645B’s device address is
0x12 and supports the charger commands as
described in Tables 1–6.
Battery Charger Commands
ChargerSpecInfo()

The ChargerSpecInfo() command uses the read-word
protocol (Figure 3b). The command code for
ChargerSpecInfo() is 0x11 (0b00010001). Table 1 lists
the functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the read-word protocol. The MAX1645B com-
plies with Level 2 Smart Battery Charger Specification
Revision 1.0; therefore, the ChargerSpecInfo() command
returns 0x09.
ChargerMode()

The ChargerMode() command uses the write-word
protocol (Figure 3a). The command code for
ChargerMode() is 0x12 (0b00010010). Table 2 lists the
functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the write-word protocol.
To charge a battery that has a thermistor impedance in
the HOT range (i.e., THERMISTOR_HOT = 1 and
THERMISTOR_UR = 0), the host must use the
ChargerMode() command to clear HOT_STOP after the
battery is inserted. The HOT_STOP bit returns to its
default power-up condition (1) whenever the battery is
removed.
ChargerStatus()

The ChargerStatus() command uses the read-word
protocol (Figure 3b). The command code for
ChargerStatus() is 0x13 (0b00010011). Table 3
describes the functions of the data bits (D0–D15). Bit 0
refers to the D0 bit in the read-word protocol.
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

The ChargerStatus() command returns information
about thermistor impedance and the MAX1645B’s inter-
nal state. The latched bits, THERMISTOR_HOT and
ALARM_INHIBITED, are cleared whenever BATTERY_
PRESENT = 0 or ChargerMode() is written with
POR_RESET = 1. The ALARM_INHIBITED status bit can
also be cleared by writing a new charging current OR
charging voltage.
MAX1645B
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting

Figure 4. SMBus Serial Interface Timing—Address
Figure 5. SMBus Serial Interface Timing—Acknowledgment
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