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.
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
Features
MAX1645
Applications
Notebook Computers
Point-of-Sale Terminals
Personal Digital Assistants
Pin Configuration
TOP VIEW
DCIN 1
LDO 2
CLS 3
REF 4
CCS 5
CCI 6
CCV 7
GND 8
BATT 9
DAC 10
V
DD
11
THM 12
SCL 13
SDA 14
28 CVS
27 PDS
26 CSSP
25 CSSN
24 BST
Ordering Information
PART
MAX1645EEI
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
MAX1645
23 DHI
22 LX
21 DLOV
20 DLO
19 PGND
18 CSIP
17 CSIN
16 PDL
15 INT
Typical Operating Circuit appears at end of data sheet.
QSOP
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.
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
MAX1645
ABSOLUTE MAXIMUM RATINGS
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 (V
CSSP
+ 0.3V)
BST to LX..................................................................-0.3V to +6V
DHI to LX ...................................................-0.3V to (V
BST
+ 0.3V)
CSIP, CSIN, BATT to GND .....................................-0.3V to +22V
LDO to GND .....................-0.3V to (lower of 6V or V
DCIN
+ 0.3V)
DLO to GND ...........................................-0.3V to (V
DLOV
+ 0.3V)
REF, DAC, CCV, CCI, CCS, CLS to GND.....-0.3V to (V
LDO
+ 0.3V)
V
DD
, SCL, SDA, INT, DLOV to GND.........................-0.3V to +6V
THM to GND ...............................................-0.3V to (V
DD
+ 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
LDO Continuous Current.....................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C).......860mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature.........................................-60°C to +150°C
Lead 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 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.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
DD
= +3.3V, V
BATT
= +16.8V, V
DCIN
= +18V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
GENERAL SPECIFICATIONS
DCIN Typical Operating Range
DCIN Supply Current
DCIN Supply Current Charging
Inhibited
DCIN Undervoltage Threshold
LDO Output Voltage
V
DD
Input Voltage Range
(Note 1)
V
DD
Undervoltage Threshold
V
DD
Quiescent Current
REF Output Voltage
BATT Undervoltage Threshold
(Note 2)
PDS Charging Source Switch
Turn-Off Threshold
PDS Charging Source Switch
Threshold Hysteresis
PDS Output Low Voltage, PDS
Below CSSP
PDS Turn-On Current
PDS Turn-Off Current
PDL Load Switch Turn-Off
Threshold
V
PDL-OFF
V
PDS-OFF
V
PDS-HYS
I
DD
V
REF
V
LDO
V
DCIN
I
DCIN
8V < V
DCIN
< 28V
8V < V
DCIN
< 28V
When AC_PRESENT
switches
DCIN rising
DCIN falling
7
5.15
2.8
V
DD
rising
V
DD
falling
2.1
2.55
2.5
80
4.066
2.4
50
100
8
100
10
-150
100
200
10
150
50
-100
-50
4.096
150
4.126
2.8
150
300
12
300
8
1.7
0.7
7.5
7.4
5.4
5.65
5.65
2.8
28
6
2
7.85
V
mA
mA
V
V
V
V
µA
V
V
mV
mV
V
µA
mA
mV
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
8V < V
DCIN
< 28V, 0 < I
LDO
< 15mA
8V < V
DCIN
< 28V
When the SMB res-
ponds to commands
0 < V
DCIN
< 6V, V
DD
= 5V, V
SCL
= 5V,
V
SDA
= 5V
0 < I
REF
< 200µA
When I
CHARGE
drops to 128mA
V
CVS
referred to V
BATT
, V
CVS
falling
V
CVS
referred to V
BATT
I
PDS
= 0
PDS = CSSP
V
PDS
= V
CSSP
- 2V, V
DCIN
= 16V
V
CVS
referred to V
BATT
, V
CVS
rising
2
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
DD
= +3.3V, V
BATT
= +16.8V, V
DCIN
= +18V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
PDL Load Switch Threshold
Hysteresis
PDL Turn-Off Current
PDL Turn-On Resistance
CVS Input Bias Current
SYMBOL
V
PDL-HYS
CONDITIONS
V
CVS
referred to V
BATT
V
CSSN
- V
PDL
= 1V
PDL to GND
V
CVS
= 28V
ChargingVoltage() = 0x41A0
BATT Full-Charge Voltage
V0
ChargingVoltage() = 0x3130
ChargingVoltage() = 0x20D0
Charging Voltage() = 0x1060
ChargingCurrent() =
0x0BC0
BATT Charge Current (Note 3)
I0
R
CS
= 50mΩ
ChargingCurrent() =
0x0080
V
CLS
= 4.096V
V
CLS
= 2.048V
16.666
12.492
8.333
4.150
2.798
61.6
4.714
2.282
20
0
Total of I
BATT
, I
CSIP,
and I
CSIN
;
V
BATT
= 0 to 20V
Total of I
BATT
, I
CSIP,
and I
CSIN
;
V
BATT
= 0 to 20V, charge inhibited
Total of I
BATT
, I
CSIP,
and I
CSIN
;
V
BATT
= 0 to 20V, V
DCIN
= 0
V
CSSP
= V
CSSN
= V
DCIN
= 0 to 28V
V
CSSP
= C
CSSN
= V
DCIN
= 0 to 28V
V
CSSP
= V
CSSN
= 28V, V
DCIN
= 0
From BATT to CCV
V
CLS
= V
REF
/2 to V
REF
From BATT to CCV, ChargingVoltage() =
0x41A0, V
BATT
= 16.8V
From CSIP/SCIN to CCI, ChargingCurrent() =
0x0BC0, V
CSIP
- V
CSIN
= 150.4mV
From CSSP/CSSN to CCS, V
CLS
= 2.048V,
V
CSSP
- V
CSSN
= 102.4mV
V
CCV
= V
CCI
= V
CCS
= 0.25V to 2V
-700
-100
-5
-100
-100
-1
200
-1
0.111
0.5
0.5
150
500
0.05
0.222
1
1
300
1
0.444
2
2
600
540
35
MIN
100
6
50
TYP
200
12
100
6
16.8
12.592
8.4
4.192
3.008
128
5.12
2.56
128
150
20
16.934
12.692
8.467
4.234
3.218
194.4
5.526
2.838
200
20
700
100
5
1000
100
1
A
mA
A
mA
V
µA
µA
µA
µA
mA
µA
V/V
µA
µA/mV
µA/mV
µA/mV
mV
V
MAX
300
UNITS
mV
mA
kΩ
µA
MAX1645
DCIN Source Current Limit
(Note 3)
BATT Undervoltage Charge
Current
BATT/CSIP/CSIN Input Voltage
Range
Total BATT Input Bias Current
Total BATT Quiescent Current
Total BATT Standby Current
CSSP Input Bias Current
CSSN Input Bias Current
CSSP/CSSN Quiescent Current
Battery Voltage-Error Amp DC
Gain
CLS Input Bias Current
Battery Voltage-Error Amp
Transconductance
Battery Current-Error Amp
Transconductance
Input Current-Error Amp
Transconductance
CCV/CCI/CCS Clamp Voltage
(Note 4)
R
CSS
= 40mΩ
V
BATT
= 1V, R
CSI
= 50mΩ
_______________________________________________________________________________________
3
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
MAX1645
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
DD
= +3.3V, V
BATT
= +16.8V, V
DCIN
= +18V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
Minimum Off-Time
Maximum On-Time
Maximum Duty Cycle
LX Input Bias Current
LX Input Quiescent Current
BST Supply Current
DLOV Supply Current
Inductor Peak Current Limit
DHI Output Resistance
DLO Output Resistance
V
DCIN
= 28V, V
BATT
= V
LX
= 20V
V
DCIN
= 0, V
BATT
= V
LX
= 20V
DHI high
V
DLOV
= V
LDO
, DLO low
R
CSI
= 50mΩ
DHI high or low, V
BST
- V
LX
= 4.5V
DLO high or low, V
DLOV
= 4.5V
V
THM
= 4% of V
DD
to 96% of V
DD
,
V
DD
= 2.8V to 5.65V
V
DD
= 2.8V to 5.65V, V
THM
falling
V
DD
= 2.8V to 5.65V, V
THM
falling
V
DD
= 2.8V to 5.65V, V
THM
falling
V
DD
= 2.8V to 5.65V, V
THM
falling
All 4 comparators, V
DD
= 2.8V to 5.65V
5.0
6
5
6.0
6
6
SYMBOL
t
OFF
t
ON
CONDITIONS
MIN
1
5
99
TYP
1.25
10
99.99
200
500
1
15
10
7.0
14
14
MAX
1.5
15
UNITS
µs
ms
%
µA
µA
µA
µA
A
Ω
Ω
DC-TO-DC CONVERTER SPECIFICATIONS
THERMISTOR COMPARATOR SPECIFICATIONS
THM Input Bias Current
Thermistor Overrange Threshold
Thermistor Cold Threshold
Thermistor Hot Threshold
Thermistor Underrange
Threshold
Thermistor Comparator
Threshold Hysteresis
SDA/SCL Input Low Voltage
SDA/SCL Input High Voltage
SDA/SCL Input Hysteresis
SDA/SCL Input Bias Current
SDA Output Low Sink Current
INT
Output High Leakage
INT
Output Low Voltage
SCL High Period
SCL Low Period
Start Condition Setup Time
from SCL
Start Condition Hold Time
from SCL
SDA Setup Time from SCL
SDA Hold Time from SCL
t
HIGH
t
LOW
t
SU:STA
t
HD:STA
t
SU:DAT
t
HD:DAT
V
SDA
= 0.4V
V
INT
= 5.65V
I
INT
= 1mA
4
4.7
4.7
4
250
0
25
-1
6
1
200
1.4
220
1
-1
89.5
74
22
6
91
75.5
23.5
7.5
1
1
92.5
77
25
9
µA
% of V
DD
% of V
DD
% of V
DD
% of V
DD
% of V
DD
SMB INTERFACE LEVEL SPECIFICATIONS
(V
DD
= 2.8V to 5.65V)
0.6
V
V
mV
µA
mA
µA
mV
µs
µs
µs
µs
ns
ns
SMB INTERFACE TIMING SPECIFICATIONS
(V
DD
= 2.8V to 5.65V, Figures 4 and 5)
4
_______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
DD
= +3.3V, V
BATT
= +16.8V, V
DCIN
= +18V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
SDA Output Data Valid from SCL
Maximum Charge Period
Without a ChargingVoltage() or
Charging Current() Loaded
SYMBOL
t
DV
t
WDT
140
175
CONDITIONS
MIN
TYP
MAX
1
210
UNITS
µs
sec
MAX1645
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
DD
= +3.3V, V
BATT
= +16.8V, V
DCIN
= +18V,
T
A
= -40°C to +85°C,
unless otherwise noted. Guaranteed by design.)
PARAMETER
GENERAL SPECIFICATIONS
DCIN Typical Operating Range
DCIN Supply Current
DCIN Supply Current Charging
Inhibited
DCIN Undervoltage Threshold
LDO Output Voltage
V
DD
Input Voltage Range
(Note 1)
V
DD
Undervoltage Threshold
V
DD
Quiescent Current
REF Output Voltage
BATT Undervoltage Threshold
(Note 2)
PDS Charging Source Switch
Turn-Off Threshold
PDS Charging Source Switch
Threshold Hysteresis
PDS Output Low Voltage, PDS
Below CSSP
PDS Turn-On Current
PDS Turn-Off Current
PDL Load Switch Turn-Off
Threshold
PDL Load Switch Threshold
Hysteresis
PDL Turn-Off Current
V
PDL-OFF
V
PDL-HYS
V
PDS-OFF
V
PDS-HYS
I
DD
V
REF
V
LDO
V
DCIN
I
DCIN
8V < V
DCIN
< 28V
8V < V
DCIN
< 28V
When AC_PRESENT
switches
DCIN rising
DCIN falling
7
5.15
2.8
V
DD
rising
V
DD
falling
2.1
150
4.035
2.4
50
100
8
100
10
-150
100
6
-50
300
4.157
2.8
150
300
12
300
5.65
5.65
2.8
8
28
6
2
7.85
V
mA
mA
V
V
V
V
µA
V
V
mV
mV
V
µA
mA
mV
mV
mA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
8V < V
DCIN
< 28V, 0 < I
LDO
< 15mA
8V < V
DCIN
< 28V
When the SMB res-
ponds to commands
0 < V
DCIN
< 6V, V
DD
= 5V, V
SCL
= 5V,
V
SDA
= 5V
0 < I
REF
< 200µA
When I
CHARGE
drops to 128mA
V
CVS
referred to V
BATT
, V
CVS
falling
V
CVS
referred to V
BATT
I
PDS
= 0
PDS = CSSP
V
PDS
= V
CSSP
- 2V, V
DCIN
= 16V
V
CVS
referred to V
BATT
, V
CVS
rising
V
CVS
referred to V
BATT
V
CSSN
- V
PDL
= 1V
_______________________________________________________________________________________
5
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