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PDF MAX1645EEI Data sheet ( Hoja de datos )
| Número de pieza | MAX1645EEI | |
| Descripción | Advanced Chemistry-Independent / Level 2 Battery Chargers with Input Current Limiting | |
| Fabricantes | Maxim Integrated | |
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19-1566; Rev 0a; 10/99
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
General Description
The MAX1645 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 MAX1645
automatically transitions from regulating current to reg-
ulating voltage. The MAX1645 can also limit line input
current so as not to exceed a predetermined current
drawn from the DC source. A 175sec charge safety
timer prevents “runaway charging” should the
MAX1645 stop receiving charging voltage/current com-
mands.
The MAX1645 employs a next-generation synchronous
buck control circuitry that lowers the minimum input-to-
output voltage drop by allowing the duty cycle to
exceed 99%. The MAX1645 can easily charge one to
four series Li+ cells.
Applications
Notebook Computers
Point-of-Sale Terminals
Personal Digital Assistants
Features
o Input Current Limiting
o 175sec Charge Safety Timeout
o 128mA Wake-Up Charge
o Charges Any Chemistry Battery:
Li+, NiCd, NiMH, Lead Acid, etc.
o Intel SMBus 2-Wire Serial Interface
o Compliant with Level 2 Smart Battery Charger
Spec. Rev. 1.0
o +8V to +28V Input Voltage Range
o Up to 18.4V Battery Voltage
o 11-Bit Battery Voltage Setting
o ±0.8% Output Voltage Accuracy with Internal
Reference
o 3A max Battery Charge Current
o 6-Bit Charge Current Setting
o 99.99% max Duty Cycle for Low-Dropout Operation
o Load/Source Switchover Drivers
o >97% Efficiency
Pin Configuration
TOP VIEW
DCIN 1
LDO 2
CLS 3
REF 4
CCS 5
CCI 6
CCV 7
GND 8
BATT 9
DAC 10
VDD 11
THM 12
SCL 13
SDA 14
MAX1645
QSOP
28 CVS
27 PDS
26 CSSP
25 CSSN
24 BST
23 DHI
22 LX
21 DLOV
20 DLO
19 PGND
18 CSIP
17 CSIN
16 PDL
15 INT
PART
MAX1645EEI
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
Typical Operating Circuit appears at end of data sheet.
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
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
TA = +25°C.)
PARAMETER
SYMBOL
SDA Output Data Valid from SCL tDV
Maximum Charge Period
Without a ChargingVoltage() or
Charging Current() Loaded
tWDT
CONDITIONS
MIN TYP MAX UNITS
1 µs
140 175 210 sec
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40°C to +85°C, unless otherwise noted. Guaranteed by design.)
PARAMETER
SYMBOL
CONDITIONS
MIN MAX UNITS
GENERAL SPECIFICATIONS
DCIN Typical Operating Range
DCIN Supply Current
VDCIN
IDCIN
8V < VDCIN < 28V
8 28 V
6 mA
DCIN Supply Current Charging
Inhibited
8V < VDCIN < 28V
2 mA
DCIN Undervoltage Threshold
LDO Output Voltage
VLDO
When AC_PRESENT
switches
DCIN rising
DCIN falling
8V < VDCIN < 28V, 0 < ILDO < 15mA
7
5.15
7.85
5.65
V
V
VDD Input Voltage Range
(Note 1)
8V < VDCIN < 28V
2.8
5.65
V
VDD Undervoltage Threshold
When the SMB res- VDD rising
ponds to commands VDD falling
2.1
2.8
V
VDD Quiescent Current
IDD
0 < VDCIN < 6V, VDD = 5V, VSCL = 5V,
VSDA = 5V
150 µA
REF Output Voltage
VREF 0 < IREF < 200µA
4.035
4.157
V
BATT Undervoltage Threshold
(Note 2)
When ICHARGE drops to 128mA
2.4 2.8 V
PDS Charging Source Switch
Turn-Off Threshold
VPDS-OFF VCVS referred to VBATT, VCVS falling
50
150 mV
PDS Charging Source Switch
Threshold Hysteresis
VPDS-HYS VCVS referred to VBATT
100 300 mV
PDS Output Low Voltage, PDS
Below CSSP
PDS Turn-On Current
PDS Turn-Off Current
PDL Load Switch Turn-Off
Threshold
IPDS = 0
PDS = CSSP
VPDS = VCSSP - 2V, VDCIN = 16V
VPDL-OFF VCVS referred to VBATT, VCVS rising
8
100
10
-150
12 V
300 µA
mA
-50 mV
PDL Load Switch Threshold
Hysteresis
PDL Turn-Off Current
VPDL-HYS VCVS referred to VBATT
VCSSN - VPDL = 1V
100 300 mV
6 mA
_______________________________________________________________________________________ 5
5 Page 
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
Detailed Description
The MAX1645 consists of current-sense amplifiers, an
SMBus interface, transconductance amplifiers, refer-
ence 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 cur-
rent set by the SMBus interface. The MAX1645 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 current-regulation loop monitors cur-
rent delivered to BATT to ensure that it never exceeds
the current-limit set point (I0). The battery current-regu-
lation 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 bat-
tery-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 MAX1645’s 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 MAX1645 ignores the first four
LSBs and uses the next 11 LSBs to control the voltage
DAC. All codes greater than or equal to 0b0100 1000
0000 0000 (18432mV) result in a voltage overrange,
limiting the charger voltage to 18.432V. All codes below
0b0000 0100 0000 0000 (1024mV) terminate charging.
Setting Output Current
The MAX1645’s current DAC has a 64mA LSB and a
3.008A full scale. The SMBus specification allows for a
16-bit ChargingCurrent() command that translates to a
1mA LSB and a 65.535A full-scale current; the
ChargingCurrent() value corresponds to the charging
voltage in milliamps. The MAX1645 drops the first six
LSBs and uses the next six LSBs to control the current
DAC. All codes above 0b00 1011 1100 0000 (3008mA)
result in a current overrange, limiting the charger cur-
rent to 3.008A. All codes below 0b0000 0000 1000
0000 (128mA) turn the charging current off. A 50mΩ
sense resistor (R2 in Figure 1) is required to achieve
the correct CODE/current scaling.
Input Current Limiting
The MAX1645 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 compares the volt-
age between CSSP and CSSN to the voltage at CLS/20.
VCLS is 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
actual source current required is determined as follows:
ISOURCE = ILOAD + [(ICHARGE · VBATT) / (VIN · η)]
where η is the efficiency of the DC-DC converter (typi-
cally 85% to 95%).
VCLS determines 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 - VCSSN to 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
The LDO provides a +5.4V supply derived from DCIN
and 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 actually powered by
DLOV and BST, which must be connected to LDO
through a lowpass filter and a diode as shown in Figure
1. See also the MOSFET Drivers section. The LDO also
supplies the 4.096V reference and most of the control
circuitry. Bypass LDO with a 1µF capacitor.
VDD Supply
This input provides power to the SMBus interface and
the thermistor comparators. Typically connect VDD to
LDO or, to keep the SMBus interface of the MAX1645
active while the supply to DCIN is removed, connect an
external supply to VDD.
______________________________________________________________________________________ 11
11 Page | ||
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| PDF Descargar | [ Datasheet MAX1645EEI.PDF ] | |
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