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PDF MAX1645 Data sheet ( Hoja de datos )
| Número de pieza | MAX1645 | |
| Descripción | Advanced Chemistry-Independent / Level 2 Battery Chargers with Input Current Limiting | |
| Fabricantes | Maxim Integrated | |
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19-1566; Rev 2; 1/01
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
General Description
The MAX1645 are high-efficiency battery chargers capa-
ble of charging batteries of any chemistry type. It uses the
Intel System Management Bus (SMBus) to control volt-
age and current charge outputs.
When charging lithium-ion (Li+) batteries, the MAX1645
automatically transition from regulating current to regu-
lating voltage. The MAX1645 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 MAX1645 stop
receiving charging voltage/ current commands.
The MAX1645 employs a next-generation synchronous
buck control circuity 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 175s 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
TOP VIEW
Pin Configuration
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
MAX1645A
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
MAX1645AEEI
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
28 QSOP
Typical Operating Circuit appears at end of data sheet.
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Advanced Chemistry-Independent, Level 2
Battery Chargers 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
CONDITIONS
MIN TYP MAX UNITS
SDA Output Data Valid from SCL
Maximum Charge Period
Without a ChargingVoltage() or
Charging Current() Loaded
tDV
tWDT
1
140 175 210
µs
s
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
GENERAL SPECIFICATIONS
DCIN Typical Operating Range
DCIN Supply Current
SYMBOL
CONDITIONS
VDCIN
IDCIN
8V < VDCIN < 28V
MIN MAX UNITS
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
V
5.65 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 Chargers with Input Current Limiting
Detailed Description
The MAX1645/MAX1645A consist 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 volt-
age and the current set by the SMBus interface. The
MAX1645/MAX1645A feature 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 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 cur-
rent limit.
Setting Output Voltage
The MAX1645/MAX1645A voltage DACs have a 16mV
LSB and an 18.432V full scale. The SMBus specifica-
tion allows for a 16-bit ChargingVoltage() command
that translates to a 1mV LSB and a 65.535V full-scale
voltage; therefore, the ChargingVoltage() value corre-
sponds to the output voltage in millivolts. The
MAX1645/MAX1645A ignore the first four LSBs and use
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/MAX1645A current DACs have 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 cur-
rent; the ChargingCurrent() value corresponds to the
charging voltage in milliamps. The MAX1645/
MAX1645A drop the first six LSBs and use 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 current 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/cur-
rent scaling.
Input Current Limiting
The MAX1645/MAX1645A limit the current drawn by the
charger when the load current becomes high. The
devices limit 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. 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
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. See also the MOSFET Drivers sec-
tion. 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/MAX1645A active while the supply to DCIN is
removed, connect an external supply to VDD.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX1645.PDF ] | |
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