LTC1759
Smart Battery Charger
FEATURES
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DESCRIPTIO
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Single Chip Smart Battery Charger Controller
100% Compliant (Rev 1.0) SMBus Support
Allows for Operation with or without Host
SMBus Accelerator Improves SMBus Timing
Hardware Interrupt and SMBAlert Response
Eliminate Interrupt Polling
High Efficiency Synchronous Buck Charger
0.5V Dropout Voltage; Maximum Duty Cycle > 99.5%
AC Adapter Current Limit Maximizes Charge Rate*
1% Voltage Accuracy; 5% Current Accuracy
Up to 8A Charging Current Capability
Dual 10-Bit DACs for Charger Voltage and Current
Programming
User-Selectable Overvoltage and Overcurrent Limits
High Noise Immunity Thermistor Sensor
Small 36-Lead Narrow (0.209") SSOP Package
The LTC
®
1759 Smart Battery Charger is a single chip
charging solution that dramatically simplifies construc-
tion of an SBS compliant system. The LTC1759 imple-
ments a Level 2 charger function whereby the charger can
be programmed by the battery or by the host. A thermistor
on the battery being charged is monitored for tempera-
ture, connectivity and battery type information. The SMBus
interface remains alive when the AC power adapter is
removed and responds to all SMBus activity directed to it,
including thermistor status (via the ChargerStatus com-
mand). The charger also provides an interrupt to the host
whenever a status change is detected (e.g., battery
removal, AC adapter connection).
Charging current and voltage are restricted to chemistry
specific limits for improved system safety and reliability.
Limits are programmable by two external resistors. Addi-
tionally, the maximum average current from the AC adapter
is programmable to avoid overloading the adapter when
simultaneously supplying load current and charging cur-
rent. When supplying system load current, charging cur-
rent is automatically reduced to prevent adapter overload.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
Portable Computers
Portable Instruments
Docking Stations
*US Patent Number 5,723,970
TYPICAL APPLICATIO
AC
ADAPTER
INPUT
0.1µF
15.8k
1k
0.033Ω
+
10µF
35V V
DD
Al
0.1µF
7
16
4
5
12
33k
33k
25
24
18
3.83k
17
28
27
11
6
20
19
UV
V
DD
LTC1759
DCIN
DCDIV
INFET
V
CC
CLP
CLN
TGATE
BOOSTC
GBIAS
BOOST
SW
BGATE
SPIN
SENSE
BAT1
BAT2
V
SET
PGND
22
21
8
32
9
10
2
33
34
1
3
35
30
29
31
23
26
36
2.2µF
0.1µF
0.47µF
499Ω
SYSTEM
POWER
1µF
22µF
SYNC
SDB
CHGEN
V
LIMIT
I
LIMIT
DGND
I
SET
PROG
V
C
COMP1
AGND
RNR
THERM
SDA
SCL
INTB
0.68µF
1µF
0.33µF
0.68µF
1.5k
1k
V
DD
475k
10k
1k
14
15
13
Figure 1. 4A SMBus Smart Battery Charger
U
15µH
0.025Ω
U
U
+
22µF
SMART
BATTERY
200Ω
200Ω
68Ω
0.047µF 0.015µF
INTB
SCL
SDA
SMBus
TO
HOST
1759 F01
1
LTC1759
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
BOOST
TGATE
SW
SYNC
SDB
AGND
UV
INFET
CLP
1
2
3
4
5
6
7
8
9
36 PGND
35 BGATE
34 GBIAS
33 BOOSTC
32 V
CC
31 BAT1
30 SPIN
29 SENSE
28 PROG
27 V
C
26 V
SET
25 V
LIMIT
24 I
LIMIT
23 BAT2
22 DCIN
21 DCDIV
20 RNR
19 THERM
G PACKAGE
36-LEAD PLASTIC SSOP
Voltage at V
CC
, UV, BAT1, CLP,CLN, SPIN,
SENSE with respect to AGND ....................– 0.3V to 27V
Voltage at DCIN, BAT2 with Respect
to DGND ....................................................– 0.3V to 27V
Voltage at INTB, SDA, SCL, DCDIV with Respect
to DGND ..................................................... – 0.3V to 7V
BOOST, BOOSTC Voltage with Respect to V
CC
........ 10V
Voltage at V
DD
with Respect to DGND ........ – 0.3V to 7V
SW Voltage with Respect to AGND .............. – 2V to V
CC
GBIAS, SYNC ............................................ – 0.3V to 10V
V
C
, PROG, V
SET
Voltage with Respect
to AGND ......................................................– 0.3V to 7V
TGATE, BGATE Current Continuous ..................
±200mA
TGATE, BGATE Output Energy (per Cycle) ................ 2µJ
PGND, DGND with Respect to AGND ....................
±0.3V
Current into Any Pin .........................................
±100mA
Operating Ambient Temperature Range ...... 0°C to 70°C
Operating Junction
Temperature Range .............................. – 40°C to 125°C
Storage Temperature ........................... – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1759CG
CLN 10
COMP1 11
CHGEN 12
INTB 13
SDA 14
SCL 15
V
DD
16
I
SET
17
DGND 18
T
JMAX
= 125°C,
θ
JA
= 85°C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range (T
J
= 0°C to 100°C), otherwise specifications are
T
A
= 25°C. V
CC
= DCIN = 18V, V
BAT1, 2
= 12.6V, V
DD
= 3.3V unless otherwise specified.
PARAMETER
Supply and Reference
DCIN, V
CC
Operating Voltage
V
CC
Operating Current
DCIN Operating Current
UV Lockout Threshold
UV Pin Input Current
Battery Discharge Current
V
DD
Operating Voltage
V
DD
Operating Current
V
DD
Undervoltage Lockout
Switching Regulator
Charging Voltage Accuracy (Notes 3, 5)
Charging Current Accuracy (Note 3)
2.465V
≤
V
BAT2
≤
V
MAX
R
SET
Tolerance = 1%
q
q
CONDITIONS
MIN
11
TYP
MAX
24
UNITS
V
mA
µA
V
µA
µA
V
mA
µA
V
%
%
V
CC
≤
24V
V
DCIN
= 24V
Voltage on UV Pin Rising
0V
≤
V
UV
≤
8V
V
UV
≤
0.4V, All Connected Pins
q
q
q
q
12
85
6.3
–1
40
3.0
1.35
80
6.7
20
150
7.25
5
80
5.5
2
150
2.9
1
5
q
Charging, V
DD
= 5.5V, Shorted Thermistor
Not Charging, V
DD
= 5.5V
q
1.6
–1
–5
2.2
2
U
W
U
U
W W
W
LTC1759
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range (T
J
= 0°C to 100°C), otherwise specifications are
T
A
= 25°C. V
CC
= DCIN = 18V, V
BAT1, 2
= 12.6V, V
DD
= 3.3V unless otherwise specified.
PARAMETER
BOOST Pin Current
CONDITIONS
V
BOOST
= V
SW
+ 8V, 0V
≤
V
SW
≤
20V
TGATE High
TGATE Low
Measured at (V
BOOST
– V
SW
)
Low to High
Hysteresis
V
BOOSTC
= V
CC
+ 8V
11V
≤
V
CC
≤
24V, 0V
≤
V
BAT
≤
20V
R
SET
= 4.93k
R
SET
= 49.3k
V
SDB
= High
V
SDB
= Low (Shutdown)
V
SDB
= High, V
SPIN
= 12.6V
V
SDB
= Low
0.5mA Output Current
Output Current from 50µA to 500µA
0.5mA Output Current
0.5mA Output Current
V
C
= 1V, I
VC
=
±1µA
Ouput Current from 50µA to 500µA
V
CC
≥
11V, I
GBIAS
≤
15mA, V
SDB
= High
I
TGATE
≤
20mA
I
BGATE
≤
20mA
I
TGATE
≤
50mA
I
BGATE
≤
50mA
V
INFET
= V
CC
– 6V
V
CC
Not Connected, I
INFET
< – 2µA
V
CC
= 12.4V, (V
CC
– V
INFET
)
≥
2V
V
SDB
= Low, I
TGATE
= I
BGATE
= 10µA
V
DCDIV
Rising from 0.8V to 1.2V
V
DCDIV
= 1V
AC_PRESENT = 1, V
DCIN
= 6V
AC_PRESENT = 1, V
DCIN
= 6V
0.9
V
SYNC
= 0V
V
SYNC
= 2V
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
TYP
2
2
MAX
3
3
7.6
UNITS
mA
mA
V
V
mA
V
BOOST
Threshold to Turn T
GATE
Off
(Note 6)
BOOSTC Pin Current
Sense Amplifier CA1 Gain and Input Offset Voltage
(With R
S2
= R
S3
= 200Ω)
(Measured Across R
S1
) (Note 4)
CA1 Bias Current (SENSE, BAT1)
CA1 Input Common Mode Range
SPIN Input Current
CL1 Turn-On Threshold
CL1 Transconductance
CLP Input Current
CLN Input Current
CA2 Transconductance
V
A
Transconductance (Note 5)
Gate Drivers
V
GBIAS
V
TGATE
High (V
TGAGE
– V
SW
)
V
BGATE
High
V
TGATE
Low (V
TGATE
– V
SW
)
V
BGATE
Low
INFET “ON” Clamping Voltage (V
CC
– V
INFET
)
INFET “ON” Drive Current
INFET “OFF” Clamping Voltage
INFET “OFF” Drive Current
V
TGATE
, V
BGATE
at Shutdown
Trip Points
DCDIV Threshold
DCDIV Hysteresis
DCDIV Input Bias Current
Power-Fail Indicator (V
BAT2
≥
V
DCIN
) (Note 7)
Power-Fail Indicator Hysteresis (V
BAT2
≥
V
DCIN
)
SYNC Pin Threshold
SYNC Pin Input Current
6.8
7.3
0.25
1
92
7
100
10
– 50
108
13
–120
–10
V
CC
– 0.3
2
10
mV
mV
µA
µA
V
mA
µA
mV
mho
µA
mA
µmho
mho
V
V
V
– 0.25
87
0.5
92
1
1
0.8
97
3
3
2
300
1
9.6
150
0.21
8.4
5.6
6.2
200
0.6
9.1
6.6
7.2
0.8
0.8
6.5
8
7.8
20
1.4
–2.5
1
0.9
1.0
25
1.1
100
0.84
0.89
0.02
1.4
2.0
– 500
–30
0.97
9
V
V
V
mA
V
mA
V
V
mV
nA
V/V
V/V
V
µA
µA
q
q
q
3
LTC1759
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range (T
J
= 0°C to 100°C), otherwise specifications are
T
A
= 25°C. V
CC
= DCIN = 18V, V
BAT1, 2
= 12.6V, V
DD
= 3.3V unless otherwise specified.
PARAMETER
Thermistor Decoder (Note 11)
Combined Input Leakage on RNR and THERM
Thermistor Trip (COLD/OR)
Thermistor Trip (IDEAL/COLD)
Thermistor Trip (HOT/IDEAL)
Thermistor Trip (UR/HOT)
DACs
Charging Current Resolution
Charging Current Granularity
Guaranteed Monotonic Above I
MAX
/16
R
ILIMIT
= 0
R
ILIMIT
= 10k
±1
%
R
ILIMIT
= 33k
±1
%
R
ILIMIT
= Open (or Short to V
DD
)
R
ILIMIT
= 0
R
ILIMIT
= 10k
±1
%
R
ILIMIT
= 33k
±1
%
R
ILIMIT
= Open (or Short to V
DD
)
V
ISET
= 2.7V
Guaranteed Monotonic (2.5V
≤
V
BAT
≤
21V)
R
VLIMIT
= 0
R
VLIMIT
= 10k
±1
%
R
VLIMIT
= 33k
±1
%
R
VLIMIT
= 100k
±1
%
R
VLIMIT
= Open (or Short to V
DD
)
R
VLIMIT
= 0
R
VLIMIT
= 10k
±1
%
R
VLIMIT
= 33k
±1
%
R
VLIMIT
= 100k
±1
%
R
VLIMIT
= Open (or Short to V
DD
) (Note 2)
q
q
q
q
q
CONDITIONS
MIN
TYP
MAX
200
UNITS
nA
kΩ
kΩ
kΩ
Ω
bits
R
WEAK
= 475k
±1%
R
NR
= 10k
±1
%
R
NR
= 10k
±1
%
R
UR
= 1k
±1
%
q
q
q
q
80
26.4
2.64
440
10
100
30
3
500
120
33.6
3.36
560
1
2
4
8
80
1023
2046
4092
8184
25
1
10
16
16
32
32
32
8.33
12.50
16.67
20.82
8.432
12.64
16.864
21.056
32.736
8.485
12.72
16.97
21.18
mA
mA
mA
mA
mA
mA
mA
mA
mA
Ω
µA
bits
mV
mV
mV
mV
mV
V
V
V
V
V
V
V
0.4
1
1
0.4
V
µA
µA
V
µA
V
V
2
8
V
µA
µs
Wake-Up Charging Current (I
WAKE-UP
) (Note 8)
Charging Current Limit (I
MAX
)
I
SET
R
DS(ON)
I
SET
I
OFF
Charging Voltage Resolution
Charging Voltage Granularity
Charging Voltage Limit
Logic Levels (Note 12)
SCL/SDA Input Low Voltage (V
IL
)
SCL/SDA Input High Voltage (V
IH
)
SDA Output Low Voltage (V
OL
)
SCL/SDA Input Current (I
IL
)
SCL/SDA Input Current (I
IH
)
INTB Output Low Voltage (V
OL
)
INTB Output Pull-Up Current
CHGEN Output Low Voltage (V
OL
)
CHGEN Output High Voltage (V
OH
)
SDB Shutdown Threshold
SDB Pin Current
Power-On Reset Duration
0V
≤
V
SDB
≤
3V
V
DD
Ramp from 0V to > 3V in < 5µs
100
I
PULLUP
= 350µA
V
SDA
, V
SCL
= V
IL
V
SDA
, V
SCL
= V
IH
I
PULLUP
= 500µA
V
INTB
= V
OL
I
OL
= 200µA
I
OH
= – 200µA
q
q
q
q
q
q
q
q
q
V
DD
– 0.4
q
0.6
1.4
3.5
10
17.5
0.4
1
4
LTC1759
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range (T
J
= 0°C to 100°C), otherwise specifications are
T
A
= 25°C. V
CC
= DCIN = 18V, V
BAT1, 2
= 12.6V, V
DD
= 3.3V unless otherwise specified.
PARAMETER
Charger Timing
V
TGATE
, V
BGATE
Rise/Fall Time
TGATE, BGATE Peak Drive Current
Regulator Switching Frequency
Synchronization Frequency
Maximum Duty Cycle in Start-Up Mode (Note 9)
t
TIMEOUT
for Wake-Up Charging a
Cold or Underrange Battery
SCL Serial Clock High Period (t
HIGH
)
SCL Serial Clock Low Period (t
LOW
)
SDA/SCL Rise Time (t
r
)
SDA/SCL Fall Time (t
f
)
SMBus Accelerator Boosted Pull-Up Current
Start Condition Setup Time (t
SU:STA
)
Start Condition Hold Time (t
HD:STA
)
SDA to SCL Rising-Edge Setup Time (t
SU:DAT
)
SDA to SCL Falling-Edge Hold Time,
Slave Clocking in Data (t
HD:DAT
)
t
TIMEOUT
Between Receiving Valid
ChargingCurrent() and ChargingVoltage()
Commands (Note 10)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
This limit is greater than the absolute maximum for the charger.
Therefore, there is no effective limitation on voltage when this option is
selected. If the charger is requested to charge with a higher voltage than
the nominal limit, the VOLTAGE_OR bit will be set.
Note 3:
Total system accuracy from SMBus request to output voltage or
output current.
Note 4:
Test Circuit #1.
Note 5:
Voltage accuracy is calculated using measured reference voltage,
obtained from V
SET
pin using Test Circuit #2, and VDAC resistor divider
ratio.
Note 6:
When supply and battery voltage differential is low, high oscillator
duty cycle is required. The LTC1759 has a unique design to achieve duty
cycle greater than 99% by skipping cycles. Only when V
BOOST
drops below
the comparator threshold, will TGATE be turned off. See Applications
Information section.
V
DD
= 3V
I
PULLUP
= 350µA, C
LOAD
= 150pF
I
PULLUP
= 350µA, C
LOAD
= 150pF
C
LOAD
= 150pF
1nF Load
10nF Load
q
q
q
q
CONDITIONS
MIN
TYP
25
1
MAX
UNITS
ns
A
170
240
85
140
200
90
175
230
280
210
kHz
kHz
%
sec
SMBus Timing (refer to System Management Bus Specification, Revision 1.0, section 2.1 for timing diagrams) (Note 12)
q
q
q
q
q
q
q
q
q
q
4
4.7
1000
30
1
4.7
4.0
250
300
140
175
210
2.5
300
µs
µs
ns
ns
mA
µs
µs
ns
ns
sec
Note 7:
Power failure bit is set when the battery voltage is above 89% of
the power adapter voltage (V
DCIN
).
Note 8:
The charger provides wake-up current when a battery is inserted
into the connector, prior to the battery requesting charging current and
voltage. See Smart Battery Charger Specification (Revision 1.0), section
6.1.3 and 6.1.8.
Note 9:
In system start-up, C6 (boost capacitor) has no charge stored in it.
The LTC1759 will keep TGATE off, and turn BGATE on for 0.2µs, thus
charging C6. A comparator senses V
BOOST
and switches to the normal
PWM mode when V
BOOST
is above its threshold.
Note 10:
Refer to Smart Battery Charge Specification (Revision 1.0),
section 6.1.2.
Note 11:
Maximum total external capacitance on RNR and THERM pins
is 75pF.
Note 12:
SMBus operation guaranteed by design from –40°C to 85°C.
5
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