TI BQ24105-Q1 Synchronous switchmode, li-ion and li-polymer charge-management ic with integrated power fets ( bqswitcherâ ¢) Datasheet

bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT
IC WITH INTEGRATED POWER FETs ( bqSWITCHER™)
The bqSWITCHER™ series are highly integrated
Li-ion
and
Li-polymer
switch-mode
charge
management devices targeted at a wide range of
portable applications. The bqSWITCHER™ series
offers integrated synchronous PWM controller and
power FETs, high-accuracy current and voltage
regulation, charge preconditioning, charge status, and
charge termination, in a small, thermally enhanced
QFN package.
The bqSWITCHER charges the battery in three
phases: conditioning, constant current, and constant
voltage.
Charge
is
terminated
based
on
user-selectable
minimum
current
level.
A
programmable charge timer provides a safety backup
for
charge
termination.
The
bqSWITCHER
automatically restarts the charge cycle if the battery
voltage falls below an internal threshold. The
bqSWITCHER automatically enters sleep mode when
VCC supply is removed.
2
1
20 19
3
18
4
17
5
16
6
15
7
14
8
13
9 10
11 12
STAT2
PGND
PGND
CE
SNS
BAT
FB
TS
VTSB
STAT1
IN
IN
PG
VCC
TTC
ISET1
ISET2
OUT
RHL PACKAGE
(TOP VIEW)
OUT
• Qualified for Automotive Applications
• Ideal For Highly Efficient Charger Designs For
Single-, Two-, or Three-Cell Li-Ion and
Li-Polymer Battery Packs
• Also for LiFePO4 Battery (see Using bq24105
to Charge LiFePO4 Battery)
• Integrated Synchronous Fixed-Frequency
PWM Controller Operating at 1.1 MHz
With 0% to 100% Duty Cycle
• Integrated Power FETs For Up To 2-A Charge
Rate
• High-Accuracy Voltage and Current Regulation
• Stand-Alone (Built-In Charge Management and
Control) Version
• Status Outputs For LED or Host Processor
Interface Indicates Charge-In-Progress, Charge
Completion, Fault, and AC-Adapter Present
Conditions
• 20-V Maximum Voltage Rating on IN and OUT
Pins
• High-Side Battery Current Sensing
• Battery Temperature Monitoring
• Automatic Sleep Mode for Low Power
Consumption
• Reverse Leakage Protection Prevents Battery
Drainage
• Thermal Shutdown and Protection
• Built-In Battery Detection
• Available in 20-Pin, 3.5 mm × 4.5 mm, QFN
Package
23
DESCRIPTION
VSS
FEATURES
1
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
bqSWITCHER, PowerPAD are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009, Texas Instruments Incorporated
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ORDERING INFORMATION (1)
PACKAGE (2)
TA
–40°C to 85°C
(1)
(2)
QFN – RHL
ORDERABLE PART NUMBER
Reel of 3000
BQ24105IRHLRQ1
TOP-SIDE MARKING
BQ24105
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
Package drawings, thermal data, and symbolization are available at www.ti.com/packaging.
ABSOLUTE MAXIMUM RATINGS (1)
over operating free-air temperature range (unless otherwise noted)
Supply voltage range (with respect to VSS)
IN, VCC
Input voltage range (with respect to VSS and PGND)
20 V
STAT1, STAT2, PG, CE, SNS, BAT
–0.3 V to 20 V
OUT
–0.7 V to 20 V
TS, TTC
7V
VTSB
3.6 V
ISET1, ISET2
3.3 V
Voltage difference between SNS and BAT inputs (VSNS – VBAT)
Output sink
STAT1, STAT2, PG
Output current (average)
OUT
±1 V
10 mA
2.2 A
TA
Operating free-air temperature range
–40°C to 85°C
TJ
Junction temperature range
–40°C to 125°C
Tstg
Storage temperature
–65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds
(1)
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 under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
PACKAGE DISSIPATION RATINGS
(1)
PACKAGE
θJA
θJC
TA < 40°C
POWER RATING
DERATING FACTOR
ABOVE TA = 40°C
RHL (1)
46.87°C/W
2.5°C/W
1.81 W
0.021 W/°C
This data is based on using the JEDEC High-K board, and the exposed die pad is connected to a copper pad on the board. This is
connected to the ground plane by a 2x3 via matrix.
RECOMMENDED OPERATING CONDITIONS
MIN
MAX
UNIT
Supply voltage, VCC and IN (Tie together)
4.35 (1)
16 (2)
V
Operating junction temperature range, TJ
–40
125
°C
(1)
(2)
The IC continues to operate below Vmin, to 3.5 V, but the specifications are not tested and not specified.
The inherent switching noise voltage spikes should not exceed the absolute maximum rating on either the IN or OUT pins. A tight layout
minimizes switching noise.
ELECTRICAL CHARACTERISTICS
TJ = 0°C to 125°C and recommended supply voltage range (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Input Currents
2
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
ELECTRICAL CHARACTERISTICS (continued)
TJ = 0°C to 125°C and recommended supply voltage range (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
VCC > VCC(min), PWM switching
I(VCC)
I(SLP)
VCC supply current
Battery discharge sleep current, (SNS,
BAT, OUT, FB pins)
TYP
MAX
UNIT
10
VCC > VCC(min), PWM NOT switching
mA
5
VCC > VCC(min), CE = HIGH
315
0°C ≤ TJ ≤ 65°C, VI(BAT) = 4.2 V,
VCC < V(SLP) or VCC > V(SLP) but not in charge
3.5
0°C ≤ TJ ≤ 65°C, VI(BAT) = 8.4 V,
VCC < V(SLP) or VCC > V(SLP) but not in charge
5.5
0°C ≤ TJ ≤ 65°C, VI(BAT) = 12.6 V,
VCC < V(SLP) or VCC > V(SLP) but not in charge
7.7
µA
µA
Voltage Regulation
VIBAT
Feedback regulation REF for bq24105
(W/FB)
Voltage regulation accuracy
IIBAT = 25 nA typical into pin
2.1
TA = 25°C
V
–0.5%
0.5%
–1%
1%
150
2000
–10%
10%
Current Regulation - Fast Charge
IOCHARGE
Output current range of converter
VLOWV ≤ VI(BAT) < VOREG,
V(VCC) - VI(BAT) > V(DO-MAX)
mA
100 mV ≤ VIREG≤ 200 mV,
V
IREG
+
1V
RSET1
1000,
VIREG
Voltage regulated across R(SNS) Accuracy
V(ISET1)
Output current set voltage
V(LOWV) ≤ VI(BAT) ≤ VO(REG),
V(VCC) ≤ VI(BAT) × V(DO-MAX)
1
K(ISET1)
Output current set factor
VLOWV ≤ VI(BAT) < VO(REG),
V(VCC) ≤ VI(BAT) + V(DO-MAX)
1000
Programmed Where
5 kΩ ≤ RSET1 ≤ 10 kΩ, Select RSET1 to
program VIREG,
VIREG(measured) = IOCHARGE + RSNS
(–10% to 10% excludes errors due to RSET1
and R(SNS) tolerances)
V
V/A
Precharge and Short-Circuit Current Regulation
VLOWV
Precharge to fast-charge transition voltage
threshold, BAT,
bq24100/03/03A/04/05/08/09 ICs only
t
Deglitch time for precharge to fast charge
transition,
IOPRECHG
V(ISET2)
K(ISET2)
Precharge current set factor
68
71.4
75
%VO(REG)
Rising voltage;
tRISE, tFALL = 100 ns, 2-mV overdrive
20
30
40
ms
Precharge range
VI(BAT) < VLOWV, t < tPRECHG
15
200
mA
Precharge set voltage, ISET2
VI(BAT) < VLOWV, t < tPRECHG
100
mV
1000
V/A
100 mV ≤ VIREG-PRE ≤ 100 mV,
V
VIREG-PRE
Voltage regulated across RSNS-Accuracy
IREG*PRE
+ 0.1V
RSET2
1000,
(PGM) Where
1.2 kΩ ≤ RSET2 ≤ 10 kΩ, Select RSET1
to program VIREG-PRE,
VIREG-PRE (Measured) = IOPRE-CHG × RSNS
(–20% to 20% excludes errors due to RSET1
and RSNS tolerances)
–20%
20%
15
200
Charge Termination (Current Taper) Detection
ITERM
Charge current termination detection range
VI(BAT) > VRCH
VTERM
Charge termination detection set voltage,
ISET2
VI(BAT) > VRCH
K(ISET2)
Termination current set factor
tdg-TERM
100
mV
1000
Charger termination accuracy
VI(BAT) > VRCH
Deglitch time for charge termination
Both rising and falling,
2-mV overdrive tRISE, tFALL = 100 ns
–20%
20
V/A
20%
30
40
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
mA
ms
3
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
TJ = 0°C to 125°C and recommended supply voltage range (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Temperature Comparator and VTSB Bias Regulator
%LTF
Cold temperature threshold, TS, % of bias
VLTF = VO(VTSB) × % LTF/100
72.8%
73.5%
74.2%
%HTF
Hot temperature threshold, TS, % of bias
VHTF = VO(VTSB) × % HTF/100
33.7%
34.4%
35.1%
%TCO
Cutoff temperature threshold, TS, % of
bias
VTCO = VO(VTSB) × % TCO/100
28.7%
29.3%
29.9%
0.5%
1%
1.5%
20
30
40
LTF hysteresis
tdg-TS
Deglitch time for temperature fault, TS
Both rising and falling,
2-mV overdrive tRISE, tFALL = 100 ns
VO(VTSB)
TS bias output voltage
VCC > VIN(min),
I(VTSB) = 10 mA 0.1 µF ≤ CO(VTSB) ≤ 1 µF
VO(VTSB)
TS bias voltage regulation accuracy
VCC > IN(min),
I(VTSB) = 10 mA 0.1 µF ≤ CO(VTSB) ≤ 1 µF
3.15
–10%
ms
V
10%
Battery Recharge Threshold
VRCH
tdg-RCH
Recharge threshold voltage
Below VOREG
75
100
125
mV/cell
Deglitch time
VI(BAT) < decreasing below threshold,
tFALL = 100 ns 10-mV overdrive
20
30
40
ms
Stat1, Stat2, and PG Outputs
VOL(STATx)
Low-level output saturation voltage, STATx
IO = 5 mA
0.5
VOL(PG)
Low-level output saturation voltage, PG
IO = 10 mA
0.1
VIL
Low-level input voltage
IIL = 5 µA
VIH
High-level input voltage
IIH = 20 µA
V
CE Input
0
0.4
1.3
VCC
V
TTC Input
tPRECHG
Precharge timer
tCHARGE
Programmable charge timer range
t(CHG) = C(TTC) × K(TTC)
Charge timer accuracy
0.01 µF ≤ C(TTC) ≤ 0.18 µF
KTTC
Timer multiplier
CTTC
Charge time capacitor range
VTTC_EN
TTC enable threshold voltage
4
1440
1800
25
-10%
2160
s
572
minutes
10%
2.6
0.01
V(TTC) rising
Submit Documentation Feedback
min/nF
0.22
200
µF
mV
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
ELECTRICAL CHARACTERISTICS (continued)
TJ = 0°C to 125°C and recommended supply voltage range (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Sleep Comparator
VSLP-ENT
Sleep-mode entry threshold
VSLP-EXIT
Sleep-mode exit hysteresis,
tdg-SLP
Deglitch time for sleep mode
2.3 V ≤ VI(OUT) ≤ VOREG, for 1 or 2 cells
VCC ≤ VIBAT
+5 mV
VCC ≤ VIBAT
+75 mV
VI(OUT) = 12.6 V, RIN = 1 kΩ
bq24105/15 (1)
VCC ≤ VIBAT
-4 mV
VCC ≤ VIBAT
+73 mV
40
160
2.3 V ≤ VI(OUT)≤ VOREG
VCC decreasing below threshold,
tFALL = 100 ns, 10-mV overdrive,
PMOS turns off
VCC decreasing below threshold,
tFALL = 100 ns, 10-mV overdrive,
STATx pins turn off
V
mV
µs
5
20
30
40
3.50
ms
UVLO
VUVLO-ON
IC active threshold voltage
VCC rising
3.15
3.30
IC active hysteresis
VCC falling
120
150
V
mV
PWM
Internal P-channel MOSFET on-resistance
Internal N-channel MOSFET on-resistance
fOSC
7 V ≤ VCC ≤ VCC(max)
400
4.5 V ≤ VCC ≤ 7 V
500
7 V ≤ VCC ≤ VCC(max)
130
4.5 V ≤ VCC ≤ 7 V
mΩ
150
Oscillator frequency
1.1
Frequency accuracy
–9%
MHz
9%
DMAX
Maximum duty cycle
DMIN
Minimum duty cycle
100%
tTOD
Switching delay time (turn on)
20
ns
tsyncmin
Minimum synchronous FET on time
60
ns
0%
Synchronous FET minimum current-off
threshold (2)
50
400
mA
Battery Detection
IDETECT
Battery detection current during time-out
fault
VI(BAT) < VOREG – VRCH
IDISCHRG1
Discharge current
tDISCHRG1
Discharge time
IWAKE
tWAKE
2
mA
VSHORT < VI(BAT) < VOREG – VRCH
400
µA
VSHORT < VI(BAT) < VOREG – VRCH
1
s
Wake current
VSHORT < VI(BAT) < VOREG – VRCH
2
mA
Wake time
VSHORT < VI(BAT) < VOREG – VRCH
0.5
s
IDISCHRG2
Termination discharge current
Begins after termination detected,
VI(BAT) ≤ VOREG
400
µA
tDISCHRG2
Termination time
262
ms
Output Capacitor
COUT
Required output ceramic capacitor range
from SNS to PGND, between inductor and
RSNS
CSNS
Required SNS capacitor (ceramic) at SNS
pin
4.7
10
µF
47
µF
0.1
Protection
Threshold over VOREG to turn off P-channel
MOSFET, STAT1, and STAT2 during charge
or termination states
110
117
2.6
3.6
4.5
A
Short-circuit voltage threshold, BAT
VI(BAT) falling
1.95
2
2.05
V/cell
ISHORT
Short-circuit current
VI(BAT) ≤ VSHORT
TSHTDWN
Thermal trip
VOVP
OVP threshold voltage
ILIMIT
Cycle-by-cycle current limit
VSHORT
Thermal hysteresis
(1)
(2)
35
121
%VO(REG)
65
mA
165
°C
10
°C
For bq24105 and bq24115 only. RIN is connected between IN and PGND pins and needed to ensure sleep entry.
N-channel always turns on for ~60 ns and then turns off if current is too low.
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
5
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
TERMINAL FUNCTIONS
TERMINAL
NAME
NO.
I/O
DESCRIPTION
BAT
14
I
Battery voltage sense input. Bypass it with a 0.1 µF capacitor to PGND if there are long inductive leads
to battery.
CE
16
I
Charger enable input. This active low input, if set high, suspends charge and places the device in the
low-power sleep mode. Do not pull up this input to VTSB.
FB
13
I
Output voltage analog feedback adjustment. Connect the output of a resistive voltage divider powered
from the battery terminals to this node to adjust the output battery voltage regulation.
IN
3, 4
I
Charger input voltage.
ISET1
8
I/O
Charger current set point 1 (fast charge). Use a resistor to ground to set this value.
ISET2
9
I/O
Charge current set point 2 (precharge and termination), set by a resistor connected to ground.
1, 20
O
Charge current output inductor connection. Connect a zener TVS diode between OUT pin and PGND
pin to clamp the voltage spike to protect the power MOSFETs during abnormal conditions.
5
O
Power-good status output (open drain). The transistor turns on when a valid VCC is detected. It is turned
off in the sleep mode. PG can be used to drive a LED or communicate with a host processor.
OUT
PG
PGND
17,18
Power ground input
SNS
15
I
Charge current-sense input. Battery current is sensed via the voltage drop developed on this pin by an
external sense resistor in series with the battery pack. A 0.1-µF capacitor to PGND is required.
STAT1
2
O
Charge status 1 (open-drain output). When the transistor turns on indicates charge in process. When it
is off and with the condition of STAT2 indicates various charger conditions (see Table 1).
STAT2
19
O
Charge status 2 (open-drain output). When the transistor turns on indicates charge is done. When it is
off and with the condition of STAT1 indicates various charger conditions (see Table 1).
TS
12
I
Temperature sense input. This input monitors its voltage against an internal threshold to determine if
charging is allowed. Use an NTC thermistor and a voltage divider powered from VTSB to develop this
voltage (see Figure 6).
TTC
7
I
Timer and termination control. Connect a capacitor from this node to GND to set the bqSWITCHER
timer. When this input is low, the timer and termination detection are disabled.
VCC
6
I
Analog device input. A 0.1-µF capacitor to VSS is required.
VSS
10
VTSB
11
Exposed
Thermal Pad
6
Pad
Analog ground input
O
TS internal bias regulator voltage. Connect capacitor (with a value between a 0.1-µF and 1-µF) between
this output and VSS.
There is an internal electrical connection between the exposed thermal pad and VSS. The exposed
thermal pad must be connected to the same potential as the VSS pin on the printed circuit board. The
power pad can be used as a star ground connection between VSS and PGND. A common ground plane
may be used. VSS pin must be connected to ground at all times.
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
TYPICAL APPLICATION CIRCUIT
LOUT
BQ24105
VIN
CIN
1.5 KW
10 mF
1.5 KW
Adapter
Present
1.5 KW
Done
Charge
3
IN
OUT 1
4
IN
OUT 20
6
VCC
RSNS
10 mH
COUT
D1
0.1W
10 mF
Battery
Pack
Pack+
Pack-
MMBZ18VALT1
PGND 17
103AT
2
STAT1 PGND 18
19 STAT2
5
PG
7
TTC
SNS 15
BAT 14
ISET1 8
7.5 KW RISET1
VTSB
7.5 KW
CTTC
16 CE
ISET2 9
0.1 mF
10 VSS
0.1 mF
13 FB
9.31 KW
RT1
442 KW
RT2
RISET2
TS 12
VTSB 11
0.1 mF
0.1 mF
301 KW
100 KW
Figure 1. Stand-Alone 2-Cell Application
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
7
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
TYPICAL OPERATING PERFORMANCE
EFFICIENCY
vs
CHARGE CURRENT
100
90
Efficiency - %
VI = 5 V
80
VI = 16 V
70
V(BAT) = 4.2 V
1-Cell
60
50
0
0.5
1
1.5
2
I(BAT) - Charge Current - A
Figure 2.
EFFICIENCY
vs
CHARGE CURRENT
100
VI = 9 V
90
Efficiency - %
VI = 16 V
80
70
V(BAT) = 8.4 V
2-Cell
60
50
0
0.5
1
1.5
2
I(BAT) - Charge Current - A
Figure 3.
8
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
VCC
Term &
Timer
Disable
VCC
VTSB
VCC
VSS
TTC
STAT2
STAT1
CE
PG
VTSB
VCC
IN
IN
0.5V
1V
CE
CHARGE
50 mV
BAT
TERM
OVP
Charge
Submit Documentation Feedback
(STATE
MACHINE)
TIMER
FF CHAIN
PRE-CHG
TIMEOUT
TIMER CLK
*Patent Pending #36889
TG
CONTROL
LOGIC
DSABL_TERM
PRE-CHARGE
WAKE
DISCHARGE
0.75V
bq2410x
VCC
V(3.6A)
Icntrl
Sense FET
VCC-6V
Poff VCC PG
2.1V
0.25V
SLEEP
VCC-6V
bqSWITCHER
VCC
VTSB
Voltage
Reference
Vuvlo UVLO/POR
POR
CHARGE
SLEEP
+
-
VIN
Protection PMOS FET is OFF when not charging
or in SLEEP to prevent discharge of battery
when IN < BAT
OVP
MOD
FAST CHG
TIMEOUT
RESET
SLEEP
SYNCH
VSHORT
LowV 30ms
Dgltch
BAT_PRS_dischg
Vrch 30ms
Dgltch
Vovp
Q R
Q S
I
2.1V
BAT
VCC
+
-
SNS+
1V
TS
SPIN
SUSPEND
FASTCHG
Disable
BAT
20uA
VCC
Ibat Reg
+
-
+
-
+
-
TCO
HTF
LTF
30ms
dgltch
PRE-CHG
Disable
0.1V
FASTCHG
Disable
TEMP
SUSPEND
0.1V
SNS
+
1k
-
TERM
SLEEP
SUSPEND
1V
Vbat Reg
+
2.1V
20uA
VCC
VCC
RAMP
(Vpp=VCC/10)
VCC
RAMP
OSC
VCC/10
*
COMPENSATION
Discharge
Charge
PkILim
+
BG
Wake
Vreg
BAT
CLAMP
Synch
Gate
Drive
TG
VSHORT
BAT_PRS_
disch
LowV
Term_Det
Vrch
UVLO/
POR
SUSPEND
6V
VCC-6V
VCC
V(150 mA)
Isynch
PkILim or OVP
TIMEOUT FAULT
SUSPEND
TERM
UVLO/POR
MOD
OVP
SYNCH
TIMEOUT
PkILim
BG
Sense FET
1C
2C
FB
SPIN
BAT
1k
Term_Det
VTSB
+
-
10
Co
10 F
H
Lo
Rsns
TS
ISET2
ISET1
VTSB
RSET2
RSET1
FB
CELLS (bq24103/04/13)
FB (bq24105/15)
N/C (bq24100)
VTSB
BAT
SNS
PGND
PGND
OUT
OUT
to FB
FB
SPIN
ONLY
+
Pack+
Temp
Pack-
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
FUNCTIONAL BLOCK DIAGRAM
9
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
OPERATIONAL FLOW CHART
POR
Check for Battery
Presence
Battery
Detect?
No
Indicate BATTERY
ABSENT
Yes
Suspend Charge
TS Pin
in LTF to HTF
Range?
No
Indicate CHARGE
SUSPEND
Yes
VBAT <VLOWV
Yes
Regulate
IPRECHG
Reset and Start
T30min timer
Indicate ChargeIn-Progress
No
Suspend Charge
Reset and Start
FSTCHG timer
TS pin
in LTF to TCO
range?
Regulate
Current or Voltage
Yes
No
Indicate CHARGE
SUSPEND
No
TS pin
in LTF to HTF
range?
Indicate ChargeIn-Progress
No
VBAT <VLOWV
Suspend Charge
TS Pin
in LTF to TCO
Range?
Yes
Yes
No
Indicate CHARGE
SUSPEND
Yes
No
T30min
Expired?
No
TS pin
in LTF to HTF
range?
FSTCHG Timer
Expired?
No
Yes
Yes
Yes
VBAT <VLOWV
Yes
No
- Fault Condition
- Enable I DETECT
No
ITERM detection?
Indicate Fault
No
Yes
Battery
Replaced?
(Vbat < Vrch?)
- Turn Off Charge
- Enable I DISCHG for
tDISCHG2
Indicate ChargeIn-Progress
*NOTE: If the TTC pin is
pulled low, the safety timer
and termination are
disabled; the charger
continues to regulate, and
the STAT pins indicate
charge in progress.
If the TTC pin is pulled high
(VTSB), only the safety
timer is disabled
(termination is normal).
Yes
Charge Complete
VBAT < VRCH ?
No
Indicate DONE
*
Battery Removed
Yes
Indicate BATTERY
ABSENT
Figure 4. Stand-Alone Version Operational Flow Chart
10
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
DETAILED DESCRIPTION
The bqSWITCHER™ supports a precision Li-ion or Li-polymer charging system for one-, two-, or three-cell
applications. See Figure 4 for a typical charge profile.
Precharge
Phase
Voltage Regulation and
Charge Termination Phase
Current Regulation Phase
Regulation Voltage
Regulation Current
Charge Voltage
VLOW
VSHORT
Charge Current
Precharge
and Termination
ISHORT
UDG-04037
Precharge
Timer
Programmable
Safety Timer
Figure 5. Typical Charging Profile
PWM Controller
The bq24105 provides an integrated fixed 1MHz frequency voltage-mode controller with Feed-Forward function
to regulate charge current or voltage. This type of controller is used to help improve line transient response,
thereby simplifying the compensation network used for both continuous and discontinuous current conduction
operation. The voltage and current loops are internally compensated using a Type-III compensation scheme that
provides enough phase boost for stable operation, allowing the use of small ceramic capacitors with very low
ESR. There is a 0.5-V offset on the bottom of the PWM ramp to allow the device to operate between 0% to 100%
duty cycle.
The internal PWM gate drive can directly control the internal PMOS and NMOS power MOSFETs. The high-side
gate voltage swings from VCC (when off), to VCC – 6 (when on and VCC is greater than 6 V) to help reduce the
conduction losses of the converter by enhancing the gate an extra volt beyond the standard 5V. The low-side
gate voltage swings from 6 V, to turn on the NMOS, down to PGND to turn it off. The bq24105 has two back to
back common-drain P-MOSFETs on the high side. An input P-MOSFET prevents battery discharge when IN is
lower than BAT. The second P-MOSFET behaves as the switching control FET, eliminating the need of a
bootstrap capacitor.
Cycle-by-cycle current limit is sensed through the internal high-side sense FET. The threshold is set to a nominal
3.6A peak current. The low-side FET also has a current limit that decides if the PWM Controller will operate in
synchronous or non-synchronous mode. This threshold is set to 100mA and it turns off the low-side NMOS
before the current reverses, preventing the battery from discharging. Synchronous operation is used when the
current of the low-side FET is greater than 100mA to minimize power losses.
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
11
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
Temperature Qualification
The bqSWITCHER continuously monitors battery temperature by measuring the voltage between the TS pin and
VSS pin. A negative temperature coefficient thermistor (NTC) and an external voltage divider typically develop
this voltage. The bqSWITCHER compares this voltage against its internal thresholds to determine if charging is
allowed. To initiate a charge cycle, the battery temperature must be within the V(LTF)-to-V(HTF) thresholds. If
battery temperature is outside of this range, the bqSWITCHER suspends charge and waits until the battery
temperature is within the V(LTF)-to-V(HTF) range. During the charge cycle (both precharge and fast charge), the
battery temperature must be within the V(LTF)-to-V(TCO) thresholds. If battery temperature is outside of this range,
the bqSWITCHER suspends charge and waits until the battery temperature is within the V(LTF)-to-V(HTF) range.
The bqSWITCHER suspends charge by turning off the PWM and holding the timer value (i.e., timers are not
reset during a suspend condition). Note that the bias for the external resistor divider is provided from the VTSB
output. Applying a constant voltage between the V(LTF)-to-V(HTF) thresholds to the TS pin disables the
temperature-sensing feature.
VO(VTSB) ´ RTHCOLD ´ RTHHOT ´
1 - 1
VLTF
VHTF
RT2 =
RTHHOT ´
(
VO(VTSB)
-1
VHTF
VO(VTSB)
-1
VLTF
)
- RTHCOLD ´
(
VO(VTSB)
-1
VLTF
)
Where:
VLTF = VO(VTSB) ´ % LTF¸100 / 100
VHTF = VO(VTSB) ´ % HTF¸100 / 100
RT1 =
1 +
1
RT2 RTHCOLD
(1)
VCC
Charge Suspend
Charge Suspend
V(LTF)
Temperature Range
to Initiate Charge
V(HTF)
V(TCO)
Charge Suspend
Temperature Range
During Charge Cycle
Charge Suspend
VSS
Figure 6. TS Pin Thresholds
Battery Preconditioning (Precharge)
On power up, if the battery voltage is below the VLOWV threshold, the bqSWITCHER applies a precharge current,
IPRECHG, to the battery. This feature revives deeply discharged cells. The bqSWITCHER activates a safety timer,
tPRECHG, during the conditioning phase. If the VLOWV threshold is not reached within the timer period, the
bqSWITCHER turns off the charger and enunciates FAULT on the STATx pins. In the case of a FAULT
condition, the bqSWITCHER reduces the current to IDETECT. IDETECT is used to detect a battery replacement
condition. Fault condition is cleared by POR or battery replacement.
12
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
The magnitude of the precharge current, IO(PRECHG), is determined by the value of programming resistor, R(ISET2),
connected to the ISET2 pin.
K (ISET2) V (ISET2)
I O(PRECHG) +
ǒR(ISET2) R(SNS)Ǔ
(2)
where
RSNS is the external current-sense resistor
V(ISET2) is the output voltage of the ISET2 pin
K(ISET2) is the V/A gain factor
V(ISET2) and K(ISET2) are specified in the Electrical Characteristics table.
Battery Charge Current
The battery charge current, IO(CHARGE), is established by setting the external sense resistor, R(SNS), and the
resistor, R(ISET1), connected to the ISET1 pin.
In order to set the current, first choose R(SNS) based on the regulation threshold VIREG across this resistor. The
best accuracy is achieved when the VIREG is between 100 mV and 200 mV.
V IREG
R (SNS) +
I OCHARGE
(3)
If the results is not a standard sense resistor value, choose the next larger value. Using the selected standard
value, solve for VIREG. Once the sense resistor is selected, the ISET1 resistor can be calculated using the
following equation:
K
V ISET1
R ISET1 + ISET1
RSNS I CHARGE
(4)
Battery Voltage Regulation
The voltage regulation feedback occurs through the BAT pin. This input is tied directly to the positive side of the
battery pack. The bqSWITCHER monitors the battery-pack voltage between the BAT and VSS pins.
Output regulation voltage is specified as:
(R1 + R2)
VOREG =
R2 x VIBAT
(5)
where R1 and R2 are resistor divider from BAT to FB and FB to VSS, respectively.
Recharge threshold voltage is specified as:
(R1 + R2)
VRCH =
R2 x 50 mV
(6)
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
13
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
Charge Termination and Recharge
The bqSWITCHER monitors the charging current during the voltage regulation phase. Once the termination
threshold, ITERM, is detected, the bqSWITCHER terminates charge. The termination current level is selected by
the value of programming resistor, R(ISET2), connected to the ISET2 pin.
K (ISET2) V TERM
I TERM +
ǒR(ISET2) R(SNS)Ǔ
(7)
where
R(SNS) is the external current-sense resistor
VTERM is the output of the ISET2 pin
K(ISET2) is the A/V gain factor
VTERM and K(ISET2) are specified in the Electrical Characteristics table
As a safety backup, the bqSWITCHER also provides a programmable charge timer. The charge time is
programmed by the value of a capacitor connected between the TTC pin and GND by the following formula:
t CHARGE + C(TTC) K(TTC)
(8)
where
C(TTC) is the capacitor connected to the TTC pin
K(TTC) is the multiplier
A
•
•
•
•
new charge cycle is initiated when one of the following conditions is detected:
The battery voltage falls below the VRCH threshold.
Power-on reset (POR), if battery voltage is below the VRCH threshold
CE toggle
TTC pin, described as follows.
In order to disable the charge termination and safety timer, the user can pull the TTC input below the VTTC_EN
threshold. Going above this threshold enables the termination and safety timer features and also resets the timer.
Tying TTC high disables the safety timer only.
14
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
Sleep Mode
The bqSWITCHER enters the low-power sleep mode if the VCC pin is removed from the circuit. This feature
prevents draining the battery during the absence of VCC.
Charge Status Outputs
The open-drain STAT1 and STAT2 outputs indicate various charger operations as shown in Table 1. These
status pins can be used to drive LEDs or communicate to the host processor. Note that OFF indicates that the
open-drain transistor is turned off.
Table 1. Status Pins Summary
STAT1
STAT2
Charge-in-progress
Charge State
ON
OFF
Charge complete
OFF
ON
Charge suspend, timer fault, overvoltage, sleep mode, battery absent
OFF
OFF
Table 2. Status Pins Summary
Charge State
STAT1
STAT2
OFF
OFF
Charge-in-progress
ON
OFF
Charge complete
OFF
ON
Battery over discharge, VI(BAT) < V(SC)
ON/OFF (0.5 Hz)
OFF
Charge suspend (due to TS pin and internal thermal protection)
ON/OFF (0.5 Hz)
OFF
Precharge timer fault
ON/OFF (0.5 Hz)
OFF
Fast charge timer fault
ON/OFF (0.5 Hz)
OFF
OFF
OFF
Battery absent
Sleep mode
PG Output
The open-drain PG (power good) indicates when the AC-to-DC adapter (i.e., VCC) is present. The output turns on
when sleep-mode exit threshold, VSLP-EXIT, is detected. This output is turned off in the sleep mode. The PG pin
can be used to drive an LED or communicate to the host processor.
CE Input (Charge Enable)
The CE digital input is used to disable or enable the charge process. A low-level signal on this pin enables the
charge and a high-level VCC signal disables the charge. A high-to-low transition on this pin also resets all timers
and fault conditions. Note that the CE pin cannot be pulled up to VTSB voltage. This may create power-up
issues.
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
15
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
Timer Fault Recovery
As shown in Figure 6, bqSWITCHER provides a recovery method to deal with timer fault conditions. The
following summarizes this method.
Condition 1 VI(BAT) above recharge threshold (VOREG - VRCH) and timeout fault occurs.
Recovery method: bqSWITCHER waits for the battery voltage to fall below the recharge threshold. This could
happen as a result of a load on the battery, self-discharge or battery removal. Once the battery falls below the
recharge threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or
CE toggle also clears the fault.
Condition 2 Charge voltage below recharge threshold (VOREG – VRCH) and timeout fault occurs
Recovery method: Under this scenario, the bqSWITCHER applies the IDETECT current. This small current is used
to detect a battery removal condition and remains on as long as the battery voltage stays below the recharge
threshold. If the battery voltage goes above the recharge threshold, then the bqSWITCHER disables the IDETECT
current and executes the recovery method described in Condition 1. Once the battery falls below the recharge
threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or CE toggle
also clears the fault.
Output Overvoltage Protection
The bqSWITCHER provides a built-in overvoltage protection to protect the device and other components against
damages if the battery voltage gets too high, as when the battery is suddenly removed. When an overvoltage
condition is detected, this feature turns off the PWM and STATx pins. The fault is cleared once VIBAT drops to the
recharge threshold (VOREG – VRCH).
Inductor, Capacitor, and Sense Resistor Selection Guidelines
The bqSWITCHER provides internal loop compensation. With this scheme, best stability occurs when LC
resonant frequency, fo is approximately 16 kHz (8 kHz to 32 kHz). Equation 9 can be used to calculate the value
of the output inductor and capacitor. Table 3 provides a summary of typical component values for various charge
rates.
1
f0 +
Ǹ
2p
L OUT C OUT
(9)
Table 3. Output Components Summary
CHARGE CURRENT
0.5 A
1A
Output inductor, LOUT
22 µH
10 µH
4.7 µH
Output capacitor, COUT
4.7 µF
10 µF
22 µF (or 2 × 10 µF) ceramic
Sense resistor, R(SNS)
0.2 Ω
0.1 Ω
0.05 Ω
16
Submit Documentation Feedback
2A
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
Battery Detection
For applications with removable battery packs, bqSWITCHER provides a battery absent detection scheme to
reliably detect insertion and/or removal of battery packs.
POR or VRCH
Detection routine runs on power up
and if VBAT drops below refresh
threshold due to removing battery
or discharging battery.
Yes
Enable
I(DETECT)
for t(DETECT)
VI(BAT)<V(LOWV)
No
BATTERY
PRESENT,
Begin Charge
No
BATTERY
PRESENT,
Begin Charge
Yes
Apply I(WAKE)
for t(WAKE)
VI(BAT) >
VO(REG)
-VRCH
Yes
BATTERY
ABSENT
Figure 7. Battery Absent Detection
The voltage at the BAT pin is held above the battery recharge threshold, VOREG – VRCH, by the charged battery
following fast charging. When the voltage at the BAT pin falls to the recharge threshold, either by a load on the
battery or due to battery removal, the bqSWITCHER begins a battery absent detection test. This test involves
enabling a detection current, IDISCHARGE1, for a period of tDISCHARGE1 and checking to see if the battery voltage is
below the short circuit threshold, VSHORT. Following this, the wake current, IWAKE is applied for a period of tWAKE
and the battery voltage is checked again to ensure that it is above the recharge threshold. The purpose of this
current is to attempt to close an open battery pack protector, if one is connected to the bqSWITCHER.
Passing both of the discharge and charge tests indicates a battery absent fault at the STAT pins. Failure of either
test starts a new charge cycle. For the absent battery condition, typically the voltage on the BAT pin rises and
falls between 0V and VOVPthresholds indefinitely.
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
17
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
VBAT
Battery
Connected
VOREG
No
Battery
Detected
2V/cell
No
Battery
Detected
Yes
Battery
Detected
IWAKE
IBAT
- IDISCHRG1
t DISCHRG1
tWAKE
t DISCHRG1
Figure 8. Battery Detect Timing Diagram
Battery Detection Example
In order to detect a no battery condition during the discharge and wake tests, the maximum output capacitance
should not exceed the following:
a. Discharge (IDISCHRG1 = 400 µA, tDISCHRG1 = 1s, VSHORT = 2V)
I
t DISCHRG1
C MAX_DIS + DISCHRG1
V OREG * V SHORT
C MAX_DIS +
400 mA 1s
4.2 V * 2 V
C MAX_DIS + 182 mF
(10)
b. Wake (IWAKE = 2 mA, tWAKE = 0.5 s, VOREG – VRCH = 4.1V)
I WAKE t WAKE
C MAX_WAKE +
ǒVOREG * VRCHǓ * 0 V
C MAX_WAKE +
2 mA 0.5s
(4.2 V * 0.1 V) * 0V
C MAX_WAKE + 244 mF
(11)
Based on these calculations the recommended maximum output capacitance to ensure proper operation of the
battery detection scheme is 100 µF which will allow for process and temperature variations.
Figure 9 shows the battery detection scheme when a battery is inserted. Channel 3 is the output signal and
Channel 4 is the output current. The output signal switches between VOREG and GND until a battery is inserted.
Once the battery is detected, the output current increases from 0A to 1.3A, which is the programmed charge
current for this application.
18
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
Figure 9. Battery Detection Waveform When a Battery is Inserted
Figure 10 shows the battery detection scheme when a battery is removed. Channel 3 is the output signal and
Channel 4 is the output current. When the battery is removed, the output signal goes up due to the stored energy
in the inductor and it crosses the VOREG – VRCH threshold. At this point the output current goes to 0A and the IC
terminates the charge process and turns on the IDISCHG2 for tDISCHG2. This causes the output voltage to fall down
below the VOREG – VRCHG threshold triggering a Battery Absent condition and starting the battery detection
scheme.
Figure 10. Battery Detection Waveform When a Battery is Removed
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
19
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
Current Sense Amplifier
A current sense amplifier feature that translates the charge current into a DC voltage is offered. Figure 11 is a
block diagram of this feature.
OUT
ICHARGE
SNS
RSNS
+
KISET2
BAT
+
-
+
FASTCHG
Disable
ISET2
RISET2
Figure 11. Current Sense Amplifier
The voltage on the ISET2 pin can be used to calculate the charge current. Equation 12 shows the relationship
between the ISET2 voltage and the charge current:
VISET2 K(ISET2)
I CHARGE +
R SNS R ISET2
(12)
This feature can be used to monitor the charge current (Figure 12) during the current regulation phase
(Fastcharge only) and the voltage regulation phase. The schematic for the application circuit for this waveform is
shown in Figure 14
CH3 = Inductor Current
CH3
500 mA/div
CH1 = ISET2
CH3
0A
CH1
200 mV/div
CH2 = OUT
CH1
0V
CH2
16 V
CH2
10 V/div
t = Time = 200 ms/div
Figure 12. Current Sense Amplifier Charge Current Waveform
20
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
bqSWITCHER SYSTEM DESIGN EXAMPLE
The following section provides a detailed system design example for the bq24100.
System Design Specifications:
•
•
•
•
•
•
•
1.
VIN = 16V
VBAT = 4.2V (1-Cell)
ICHARGE = 1.33 A
IPRECHARGE = ITERM = 133 mA
Safety Timer = 5 hours
Inductor Ripple Current = 30% of Fast Charge Current
Initiate Charge Temperature = 0°C to 45°C
Determine the inductor value (LOUT) for the specified charge current ripple:
DI L + I CHARGE I CHARGERipple
L OUT +
L OUT +
ǒVINMAX * VBATǓ
VBAT
ƒ
V INMAX
DI L
4.2 (16 * 4.2)
(1.1 106) (1.33
16
0.3)
L OUT + 7.06 mH
(13)
Set the output inductor to standard 10 µH. Calculate the total ripple current with using the 10 µH inductor:
DI L +
DI L +
ǒVINMAX * VBATǓ
VBAT
V INMAX
16
ƒ
LOUT
4.2 (16 * 4.2)
(1.1 106) (10
10 *6)
DI L + 0.282 A
(14)
Calculate the maximum output current (peak current):
DI
I LPK + I OUT ) L
2
I LPK + 1.33 ) 0.282
2
I LPK + 1.471 A
(15)
Use standard 10 µH inductor with a saturation current higher than 1.471A. (i.e., Sumida CDRH74-100)
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
21
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
2. Determine the output capacitor value (OUT) using 16 kHz as the resonant frequency:
1
ƒo +
2p ǸLOUT COUT
1
C OUT +
4p 2
ƒo
C OUT +
4p 2
(16
2
L OUT
1
10 3)2
(10
10 *6)
C OUT + 9.89 mF
(16)
Use standard value 10 µF, 25V, X5R, ±20% ceramic capacitor (i.e., Panasonic 1206 ECJ-3YB1E106M
3. Determine the sense resistor using the following equation:
V
R SNS + RSNS
I CHARGE
(17)
In order to get better current regulation accuracy (±10%), let VRSNS be between 100 mV and 200 mV. Use
VRSNS = 100 mV and calculate the value for the sense resistor.
R SNS + 100 mV
1.33 A
R SNS + 0.075 W
(18)
This value is not standard in resistors. If this happens, then choose the next larger value which in this case is
0.1Ω. Using the same equation (15) the actual VRSNS will be 133mV. Calculate the power dissipation on the
sense resistor:
P RSNS + I CHARGE
P RSNS + 1.332
2
R SNS
0.1
P RSNS + 176.9 mW
(19)
Select standard value 100 mΩ, 0.25W 0805, 1206 or 2010 size, high precision sensing resistor. (i.e., Vishay
CRCW1210-0R10F)
4. Determine ISET 1 resistor using the following equation:
K
V ISET1
R ISET1 + ISET1
RSNS I CHARGE
R ISET1 + 1000 1.0
0.1 1.33
R ISET1 + 7.5 kW
(20)
Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)
5. Determine ISET 2 resistor using the following equation:
KISET2 VISET2
R ISET2 +
RSNS I PRECHARGE
R ISET2 + 1000 0.1
0.1 0.133
R ISET2 + 7.5 kW
(21)
Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)
22
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
6. Determine TTC capacitor (TTC) for the 5.0 hours safety timer using the following equation:
t
C TTC + CHARGE
K TTC
C TTC + 300 m
2.6 mńnF
C TTC + 115.4 nF
(22)
Select standard value 100 nF, 16V, X7R, ±10% ceramic capacitor (i.e., Panasonic ECJ-1VB1C104K). Using
this capacitor the actual safety timer will be 4.3 hours.
7. Determine TS resistor network for an operating temperature range from 0°C to 45°C.
VTSB
RT1
TS
RTH
RT2
103AT
Figure 13. TS Resistor Network
Assuming a 103AT NTC Thermistor on the battery pack, determine the values for RT1 and RT2 using the
following equations:
VO(VTSB) ´ RTHCOLD ´ RTHHOT ´
1 - 1
VLTF
VHTF
RT2 =
RTHHOT ´
(
VO(VTSB)
-1
VHTF
VO(VTSB)
-1
VLTF
RT1 =
1 +
1
RT2 RTHCOLD
)
- RTHCOLD ´
(
VO(VTSB)
-1
VLTF
)
Where:
VLTF = VO(VTSB) ´ % LTF¸100 / 100
VHTF = VO(VTSB) ´ % HTF¸100 / 100
(23)
RTH COLD + 27.28 kW
RTH HOT + 4.912 kW
RT1 + 9.31 kW
RT2 + 442 kW
(24)
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
23
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
APPLICATION INFORMATION
Charging Battery and Powering System Without Affecting Battery Charge and Termination
RSYS
LOUT
BQ24100
VIN
CIN
1.5 KW
10 mF
1.5 KW
Adapter
Present
1.5 KW
Done
3
Charge
IN
OUT 1
4
IN
6
VCC
2
STAT1 PGND 18
10 mH
OUT 20
PGND 17
RSNS
D1
COUT
0.1W
10 mF
Battery
Pack
Pack+
Pack-
MMBZ18VALT1
103AT
19 STAT2
5
PG
7
TTC
SNS 15
BAT 14
7.5 KW
ISET1 8
VTSB
7.5 KW
CTTC
16 CE
9.31 KW
ISET2 9
0.1 mF
10 VSS
0.1 mF
13 NC
TS 12
VTSB 11
442 KW
0.1 mF
0.1 mF
Figure 14. Application Circuit for Charging a Battery and Powering a System Without Affecting
Termination
The bqSWITCHER was designed as a stand-alone battery charger but can be easily adapted to power a system
load, while considering a few minor issues.
Advantages:
1. The charger controller is based only on what current goes through the current-sense resistor (so precharge,
constant current, and termination all work well), and is not affected by the system load.
2. The input voltage has been converted to a usable system voltage with good efficiency from the input.
3. Extra external FETs are not needed to switch power source to the battery.
4. The TTC pin can be grounded to disable termination and keep the converter running and the battery fully
charged, or let the switcher terminate when the battery is full and then run off of the battery via the sense
resistor.
Other Issues:
1. If the system load current is large (≥ 1 A), the IR drop across the battery impedance causes the battery
voltage to drop below the refresh threshold and start a new charge. The charger would then terminate due to
low charge current. Therefore, the charger would cycle between charging and termination. If the load is
smaller, the battery would have to discharge down to the refresh threshold resulting in a much slower
cycling. Note that grounding the TTC pin keeps the converter on continuously.
2. If TTC is grounded, the battery is kept at 4.2 V (not much different than leaving a fully charged battery set
unloaded).
3. Efficiency declines 2-3% hit when discharging through the sense resistor to the system.
24
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
Using bq24105 to Charge LiFePO4 Battery
The LiFePO4 battery has many unique features such as a high thermal runaway temperature, discharge current
capability, and charge current. These special features make it attractive in many applications such as power
tools. The recommended charge voltage is 3.6 V and termination current is 50 mA. Figure 15 shows an
application circuit for charging one cell LiFePO4 using bq24105. The charge voltage is 3.6 V and recharge
voltage is 3.516 V. The fast charging current is set to 1.33 A while the termination current is 50 mA. This circuit
can be easily changed to support two or three cell applications. However, only 84 mV difference between
regulation set point and rechargeable threshold makes it frequently enter into recharge mode when small load
current is applied. This can be solved by lower down the recharge voltage threshold to 200 mV to discharge
more energy from the battery before it enters recharge mode again. See the application report, Using the
bq24105/25 to Charge LiFePO4 Battery (SLUA443), for additional details. The recharge threshold should be
selected according to real application conditions.
LOUT
BQ24105
VIN
CIN
1.5 KW
10 mF
1.5 KW
Adapter
Present
1.5 KW
Done
Charge
3
IN
OUT 1
4
IN
OUT 20
6
VCC
RSNS
10 mH
COUT
D1
0.1W
10 mF
Battery
Pack
Pack+
Pack-
MMBZ18VALT1
PGND 17
103AT
2
STAT1 PGND 18
19 STAT2
5
PG
7
TTC
SNS 15
BAT 14
ISET1 8
7.5 KW RISET1
VTSB
20 KW
CTTC
16 CE
ISET2 9
0.1 mF
10 VSS
0.1 mF
13 FB
9.31 KW
RT1
442 KW
RT2
RISET2
TS 12
VTSB 11
0.1 mF
0.1 mF
143 KW
200 KW
Figure 15. 1-Cell LiFePO4 Application
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
25
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
THERMAL CONSIDERATIONS
The SWITCHER is packaged in a thermally enhanced MLP package. The package includes a thermal pad to
provide an effective thermal contact between the IC and the printed circuit board (PCB). Full PCB design
guidelines for this package are provided in the application report entitled: QFN/SON PCB Attachment
(SLUA271).
The most common measure of package thermal performance is thermal impedance (θJA) measured (or modeled)
from the chip junction to the air surrounding the package surface (ambient). The mathematical expression for θJA
is:
T * TA
q (JA) + J
P
(25)
Where:
TJ = chip junction temperature
TA = ambient temperature
P = device power dissipation
Factors that can greatly influence the measurement and calculation of θJA include:
• Whether or not the device is board mounted
• Trace size, composition, thickness, and geometry
• Orientation of the device (horizontal or vertical)
• Volume of the ambient air surrounding the device under test and airflow
• Whether other surfaces are in close proximity to the device being tested
The device power dissipation, P, is a function of the charge rate and the voltage drop across the internal power
FET. It can be calculated from the following equation:
P = [Vin × lin - Vbat × Ibat]
Due to the charge profile of Li-xx batteries, the maximum power dissipation is typically seen at the beginning of
the charge cycle when the battery voltage is at its lowest. (See Figure 5.)
26
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
PCB LAYOUT CONSIDERATION
It is important to pay special attention to the PCB layout. The following provides some guidelines:
• To obtain optimal performance, the power input capacitors, connected from input to PGND, should be placed
as close as possible to the bqSWITCHER. The output inductor should be placed directly above the IC and the
output capacitor connected between the inductor and PGND of the IC. The intent is to minimize the current
path loop area from the OUT pin through the LC filter and back to the GND pin. The sense resistor should be
adjacent to the junction of the inductor and output capacitor. Route the sense leads connected across the
R(SNS) back to the IC, close to each other (minimize loop area) or on top of each other on adjacent layers (do
not route the sense leads through a high-current path). Use an optional capacitor downstream from the sense
resistor if long (inductive) battery leads are used.
• Place all small-signal components (CTTC, RSET1/2 and TS) close to their respective IC pin (do not place
components such that routing interrupts power stage currents). All small control signals should be routed
away from the high current paths.
• The PCB should have a ground plane (return) connected directly to the return of all components through vias
(three vias per capacitor for power-stage capacitors, three vias for the IC PGND, one via per capacitor for
small-signal components). A star ground design approach is typically used to keep circuit block currents
isolated (high-power/low-power small-signal) which reduces noise-coupling and ground-bounce issues. A
single ground plane for this design gives good results. With this small layout and a single ground plane, there
is not a ground-bounce issue, and having the components segregated minimizes coupling between signals.
• The high-current charge paths into IN and from the OUT pins must be sized appropriately for the maximum
charge current in order to avoid voltage drops in these traces. The PGND pins should be connected to the
ground plane to return current through the internal low-side FET. The thermal vias in the IC PowerPAD™
provide the return-path connection.
• The bqSWITCHER is packaged in a thermally enhanced MLP package. The package includes a thermal pad
to provide an effective thermal contact between the IC and the PCB. Full PCB design guidelines for this
package are provided in the application report entitled: QFN/SON PCB Attachment (SLUA271). Six 10-mil to
13-mil vias are a minimum number of recommended vias, placed in the IC's power pad, connecting it to a
ground thermal plane on the opposite side of the PWB. This plane must be at the same potential as VSS and
PGND of this IC.
• See user guide SLUU200 for an example of good layout.
WAVEFORMS: All waveforms are taken at Lout (IC Out pin). VIN = 7.6 V and the battery was set to 2.6 V, 3.5 V,
and 4.2 V for the three waveforms. When the top switch of the converter is on, the waveform is at ~7.5 V, and
when off, the waveform is near ground. Note that the ringing on the switching edges is small. This is due to a
tight layout (minimized loop areas), a shielded inductor (closed core), and using a low-inductive scope ground
lead (i.e., short with minimum loop) .
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
27
bq24105-Q1
SLUS953 – AUGUST 2009................................................................................................................................................................................................. www.ti.com
Precharge: The current is low in precharge; so, the bottom synchronous FET turns off after its minimum on-time
which explains the step between ≈0 V and -0.5 V. When the bottom FET and top FET are off, the current
conducts through the body diode of the bottom FET which results in a diode drop below the ground potential.
The initial negative spike is the delay turning on the bottom FET, which is to prevent shoot-through current as the
top FET is turning off.
Fast Charge: This is captured during the constant-current phase. The two negative spikes are the result of the
short delay when switching between the top and bottom FETs. The break-before-make action prevents current
shoot-through and results in a body diode drop below ground potential during the break time.
Charge during Voltage Regulation and Approaching Termination: Note that this waveform is similar to the
precharge waveform. The difference is that the battery voltage is higher so the duty cycle is slightly higher. The
bottom FET stays on longer because there is more of a current load than during precharge; it takes longer for the
inductor current to ramp down to the current threshold where the synchronous FET is disabled.
28
Submit Documentation Feedback
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24105-Q1
PACKAGE OPTION ADDENDUM
www.ti.com
22-Aug-2009
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
BQ24105IRHLRQ1
ACTIVE
QFN
RHL
Pins Package Eco Plan (2)
Qty
20
3000 Green (RoHS &
no Sb/Br)
Lead/Ball Finish
CU NIPDAU
MSL Peak Temp (3)
Level-3-260C-168 HR
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
OTHER QUALIFIED VERSIONS OF BQ24105-Q1 :
• Catalog: BQ24105
NOTE: Qualified Version Definitions:
• Catalog - TI's standard catalog product
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
22-Aug-2009
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
BQ24105IRHLRQ1
Package Package Pins
Type Drawing
QFN
RHL
20
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
3000
330.0
12.4
Pack Materials-Page 1
3.8
B0
(mm)
K0
(mm)
P1
(mm)
4.8
1.6
8.0
W
Pin1
(mm) Quadrant
12.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
22-Aug-2009
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
BQ24105IRHLRQ1
QFN
RHL
20
3000
346.0
346.0
29.0
Pack Materials-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Applications
Audio
www.ti.com/audio
Communications and Telecom www.ti.com/communications
Amplifiers
amplifier.ti.com
Computers and Peripherals
www.ti.com/computers
Data Converters
dataconverter.ti.com
Consumer Electronics
www.ti.com/consumer-apps
DLP® Products
www.dlp.com
Energy and Lighting
www.ti.com/energy
DSP
dsp.ti.com
Industrial
www.ti.com/industrial
Clocks and Timers
www.ti.com/clocks
Medical
www.ti.com/medical
Interface
interface.ti.com
Security
www.ti.com/security
Logic
logic.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Power Mgmt
power.ti.com
Transportation and Automotive www.ti.com/automotive
Microcontrollers
microcontroller.ti.com
Video and Imaging
RFID
www.ti-rfid.com
OMAP Mobile Processors
www.ti.com/omap
Wireless Connectivity
www.ti.com/wirelessconnectivity
TI E2E Community Home Page
www.ti.com/video
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated