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bq24170, bq24172
SLUSAD2C – NOVEMBER 2010 – REVISED APRIL 2015
bq2417x 1.6-MHz Synchronous Switched-Mode Li-Ion and Li-Polymer Stand-Alone Battery
Charger With Integrated MOSFETs and Power Path Selector
1 Features
•
1
•
•
•
•
•
•
– ±4% Input Current Regulation
VAVCC (SLEEP), TJ =
0°C to 85°C
15
BTST, SW, SRP, SRN, VAVCC > VUVLO, VAVCC
> VSRN, ISET < 40 mV, VBAT=12.6 V, Charge
disabled
25
BTST, SW, SRP, SRN, VAVCC > VUVLO, VAVCC
> VSRN, ISET > 120 mV, VBAT=12.6 V, Charge
done
25
µA
VAVCC > VUVLO, VAVCC > VSRN, ISET < 40 mV,
VBAT=12.6 V, Charge disabled
1.2
1.5
VAVCC > VUVLO, VAVCC > VSRN, ISET > 120
mV, Charge enabled, no switching
2.5
5
VAVCC > VUVLO, VAVCC > VSRN, ISET > 120
mV, Charge enabled, switching
15 (1)
CELL to AGND, 1 cell, measured on SRN
4.2
V
CELL floating, 2 cells, measured on SRN
8.4
V
CELL to VREF, 3 cells, measured on SRN
12.6
V
mA
CHARGE VOLTAGE REGULATION
VBAT_REG
VFB_REG
SRN regulation voltage (bq24170)
Feddback regulation voltage (bq24172)
Charge voltage regulation accuracy
IFB
Leakage current into FB pin (bq24172)
Measured on FB
2.1
V
TJ = 0°C to 85°C
–0.5%
0.5%
TJ = –40°C to 125°C
–0.7%
0.7%
VFB = 2.1 V
100
nA
0.8
V
CURRENT REGULATION – FAST CHARGE
VISET
ISET Voltage Range
RSENSE = 10 mΩ
KISET
Charge Current Set Factor (Amps of Charge
Current per Volt on ISET pin)
RSENSE = 10 mΩ
Charge Current Regulation Accuracy
(with Schottky diode on SW)
0.12
5
A/V
VSRP-SRN = 40 mV
–4%
VSRP-SRN = 20 mV
–7%
7%
VSRP-SRN = 5 mV
–25%
25%
VISET_CD
Charge Disable Threshold
ISET falling
VISET_CE
Charge Enable Threshold
ISET rising
IISET
Leakage Current into ISET
VISET = 2 V
40
4%
50
100
mV
120
mV
100
nA
INPUT CURRENT REGULATION
KDPM
Input DPM Current Set Factor (Amps of Input
Current per Volt on ACSET)
Input DPM Current Regulation Accuracy
(with Schottky diode on SW)
IACSET
Leakage Current into ACSET pin
RSENSE = 10mΩ
5
A/V
VACP-ACN = 80 mV
–4%
VACP-ACN = 40 mV
–9%
4%
9%
VACP-ACN = 20 mV
–15%
15%
VACP-ACN = 5 mV
–20%
20%
VACP-ACN = 2.5 mV
-40%
40%
VACSET = 2V
100
nA
CURRENT REGULATION – PRECHARGE
KIPRECHG
Precharge current set factor
10% (2)
Percentage of fast charge current
Precharge current regulation accuracy
VSRP-SRN = 4 mV
–25%
25%
VSRP-SRN = 2 mV
–40%
40%
CHARGE TERMINATION
KTERM
(1)
(2)
Termination current set factor
Percentage of fast charge current
10% (2)
Specified by design.
The minimum current is 120 mA on 10-mΩ sense resistor.
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Electrical Characteristics (continued)
4.5 V ≤ V(PVCC, AVCC) ≤ 17 V, –40°C < TJ + 125°C, typical values are at TA = 25°C, with respect to AGND (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
Termination current regulation accuracy
–25%
VSRP-SRN = 2 mV
–40%
tTERM_DEG
Deglitch time for termination (both edges)
tQUAL
Termination qualification time
VSRN > VRECH and ICHG < ITERM
Termination qualification current
Discharge current once termination is
detected
IQUAL
MIN
VSRP-SRN = 4 mV
TYP
MAX
UNIT
25%
40%
100
ms
250
ms
2
mA
INPUT UNDERVOLTAGE LOCKOUT COMPARATOR (UVLO)
VUVLO
AC undervoltage rising threshold
Measure on AVCC
VUVLO_HYS
AC undervoltage hysteresis, falling
Measure on AVCC
3.4
3.6
3.8
300
V
mV
SLEEP COMPARATOR (REVERSE DISCHARGING PROTECTION)
VSLEEP
SLEEP mode threshold
VAVCC – VSRN falling
VSLEEP_HYS
SLEEP mode hysteresis
VAVCC – VSRN rising
50
200
90
150
mV
mV
tSLEEP_FALL_CD
SLEEP deglitch to disable charge
VAVCC – VSRN falling
1
ms
tSLEEP_FALL_FETOFF
SLEEP deglitch to turn off input FETs
VAVCC – VSRN falling
5
ms
tSLEEP_FALL
Deglitch to enter SLEEP mode, disable VREF
and enter low quiescent mode
VAVCC – VSRN falling
100
ms
tSLEEP_PWRUP
Deglitch to exit SLEEP mode, and enable VREF VAVCC – VSRN rising
30
ms
ACN-SRN COMPARATOR
VACN-SRN
Threshold to turn on BATFET
VACN-SRN falling
VACN-SRN_HYS
Hysteresis to turn off BATFET
VACN-SRN rising
150
220
100
300
mV
mV
tBATFETOFF_DEG
Deglitch to turn on BATFET
VACN-SRN falling
2
ms
tBATFETON_DEG
Deglitch to turn off BATFET
VACN-SRN rising
50
µs
BAT LOWV COMPARATOR
VLOWV
Precharge to fast charge transition
VLOWV_HYS
Fast charge to precharge hysteresis
bq24170, CELL to AGND, 1 cell, measure on
SRN
2.87
2.9
2.93
bq24170, CELL floating, 2 cells, measure on
SRN
5.74
5.8
5.86
bq24170, CELL to VREF, 3 cells, measure on
SRN
8.61
8.7
8.79
bq24172, measure on FB
1.43
1.45
1.47
bq24170, CELL to AGND, 1 cell, measure on
SRN
200
bq24170, CELL floating, 2 cells, measure on
SRN
400
bq24170, CELL to VREF, 3 cells, measure on
SRN
600
bq24172, measure on FB
100
V
mV
tpre2fas
VLOWV rising deglitch
Delay to start fast charge current
25
ms
tfast2pre
VLOWV falling deglitch
Delay to start precharge current
25
ms
RECHARGE COMPARATOR
Recharge Threshold, below regulation voltage
limit, VBAT_REG-VSRN (bq24170), or VFB_REG-VFB
(bq24172)
VRECHG
bq24170, CELL to AGND, 1 cell, measure on
SRN
70
100
130
bq24170, CELL floating, 2 cells, measure on
SRN
140
200
260
bq24170, CELL to VREF, 3 cells, measure on
SRN
210
300
390
35
50
65
bq24172, measure on FB
mV
tRECH_RISE_DEG
VRECHG rising deglitch
VFB decreasing below VRECHG
10
ms
tRECH_FALL_DEG
VRECHG falling deglitch
VFB increasing above VRECHG
10
ms
BAT OVERVOLTAGE COMPARATOR
VOV_RISE
8
Overvoltage rising threshold
As percentage of VBAT_REG (bq24170) or
VFB_REG (bq24172)
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104%
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SLUSAD2C – NOVEMBER 2010 – REVISED APRIL 2015
Electrical Characteristics (continued)
4.5 V ≤ V(PVCC, AVCC) ≤ 17 V, –40°C < TJ + 125°C, typical values are at TA = 25°C, with respect to AGND (unless
otherwise noted)
PARAMETER
VOV_FALL
TEST CONDITIONS
MIN
As percentage of VSRN (bq24170) or VFB_REG
(bq24172)
Overvoltage falling threshold
TYP
MAX
UNIT
1.63
V
102%
INPUT OVERVOLTAGE COMPARATOR (ACOV)
VACOV
AC Overvoltage Rising Threshold to turn off
ACFET
OVPSET rising
VACOV_HYS
AC overvoltage falling hysteresis
OVPSET falling
50
mV
tACOV_RISE_DEG
AC Overvoltage Rising Deglitch to turn off
ACFET and Disable Charge
OVPSET rising
1
µs
tACOV_FALL_DEG
AC Overvoltage Falling Deglitch to turn on
ACFET
OVPSET falling
30
ms
1.57
1.6
INPUT UNDERVOLTAGE COMPARATOR (ACUV)
VACUV
AC Undervoltage Falling Threshold to turn off
ACFET
OVPSET falling
VACUV_HYS
AC Undervoltage Rising Hysteresis
OVPSET rising
100
mV
tACOV_FALL_DEG
AC Undervoltage Falling Deglitch to turn off
ACFET and Disable Charge
OVPSET falling
1
µs
tACOV_RISE_DEG
AC Undervoltage Rising Deglitch to turn on
ACFET
OVPSET rising
30
ms
ISET > 120 mV, Charging
120
°C
0.487
0.497
0.507
V
THERMAL REGULATION
TJ_REG
Junction Temperature Regulation Accuracy
THERMAL SHUTDOWN COMPARATOR
TSHUT
Thermal shutdown rising temperature
Temperature rising
150
°C
TSHUT_HYS
Thermal shutdown hysteresis
Temperature falling
20
°C
tSHUT_RISE_DEG
Thermal shutdown rising deglitch
Temperature rising
100
µs
tSHUT_FALL_DEG
Thermal shutdown falling deglitch
Temperature falling
10
ms
THERMISTOR COMPARATOR
VLTF
Cold Temperature Threshold, TS pin Voltage
Rising Threshold
Charger suspends charge. As percentage to
VVREF
VLTF_HYS
Cold Temperature Hysteresis, TS pin Voltage
Falling
VHTF
72.5%
73.5%
74.5%
As percentage to VVREF
0.2%
0.4%
0.6%
Hot Temperature TS pin voltage rising
Threshold
As percentage to VVREF
46.6%
47.2%
48.8%
VTCO
Cut-off Temperature TS pin voltage falling
Threshold
As percentage to VVREF
44.2%
44.7%
45.2%
tTS_CHG_SUS
Deglitch time for Temperature Out of Range
Detection
VTS > VLTF, or VTS < VTCO, or
VTS < VHTF
tTS_CHG_RESUME
Deglitch time for Temperature in Valid Range
Detection
20
ms
VTS < VLTF – VLTF_HYS or VTS >VTCO, or VTS >
VHTF
400
ms
160%
CHARGE OVERCURRENT COMPARATOR (CYCLE-BY-CYCLE)
VOCP_CHRG
Charge Overcurrent Rising Threshold, VSRP >
2.2 V
Current as percentage of fast charge current
VOCP_MIN
Charge Overcurrent Limit Min, VSRP < 2.2 V
Measure VSRP-SRN
45
mV
VOCP_MAX
Charge Overcurrent Limit Max, VSRP > 2.2 V
Measure VSRP-SRN
75
mV
HSFET OVERCURRENT COMPARATOR (CYCLE-BY-CYCLE)
IOCP_HSFET
Current limit on HSFET
Measure on HSFET
8
11.5
Measure on V(SRP-SRN)
1
5
A
CHARGE UNDERCURRENT COMPARATOR (CYCLE-BY-CYCLE)
VUCP
Charge undercurrent falling threshold
9
mV
BAT SHORT COMPARATOR
VBATSHT
Battery short falling threshold
Measure on SRN
2
VBATSHT_HYS
Battery short rising hysteresis
Measure on SRN
200
mV
V
tBATSHT_DEG
Deglitch on both edges
1
µs
VBATSHT
Charge Current during BATSHORT
Percentage of fast charge current
VREF regulator voltage
VAVCC > VUVLO, No load
10% (2)
VREF REGULATOR
VVREF_REG
3.267
3.3
3.333
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V
9
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SLUSAD2C – NOVEMBER 2010 – REVISED APRIL 2015
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Electrical Characteristics (continued)
4.5 V ≤ V(PVCC, AVCC) ≤ 17 V, –40°C < TJ + 125°C, typical values are at TA = 25°C, with respect to AGND (unless
otherwise noted)
PARAMETER
IVREF_LIM
TEST CONDITIONS
MIN
VREF current limit
VVREF = 0 V, VAVCC > VUVLO
35
VREGN_REG
REGN regulator voltage
VAVCC > 10 V, ISET > 120 mV
5.7
IREGN_LIM
REGN current limit
VREGN = 0 V, VAVCC > 10 v, ISET > 120 mV
40
tprechrg
Precharge Safety Timer
Precharge time before fault occurs
tfastchrg
Fast Charge Timer Range
Tchg = CTTC*KTTC
TYP
MAX
90
UNIT
mA
REGN REGULATOR
6
6.3
V
120
mA
TTC INPUT
Timer Multiplier
VTTC_LOW
TTC Low Threshold
ITTC
TTC Source/Sink Current
VTTC_OSC_HI
TTC oscillator high threshold
VTTC_OSC_LO
TTC oscillator low threshold
1800
1
Fast Charge Timer Accuracy
KTTC
1620
–10%
1980
s
10
hr
10%
5.6
TTC falling
45
50
min/nF
0.4
V
55
µA
1.5
V
1
V
BATTERY SWITCH (BATFET) DRIVER
RDS_BAT_OFF
BATFET Turnoff Resistance
VAVCC > 5 V
100
Ω
RDS_BAT_ON
BATFET Turnon Resistance
VAVCC > 5 V
20
kΩ
VBATDRV_REG
BATFET Drive Voltage
VBATDRV_REG =VACN - VBATDRV when VAVCC > 5
V and BATFET is on
7
V
tBATFET_DEG
BATFET Power-up Delay to turn off BATFET
after adapter is detected
4.2
30
ms
60
µA
AC SWITCH (ACFET) DRIVER
IACFET
ACDRV Charge Pump Current Limit
VACDRV - VCMSRC = 5 V
VACDRV_REG
Gate Drive Voltage on ACFET
VACDRV - VCMSRC when VAVCC > VUVLO
RACDRV_LOAD
Maximum load between ACDRV and CMSRC
4.2
6
V
500
kΩ
AC/BAT SWITCH DRIVER TIMING
tDRV_DEAD
Dead Time when switching between ACFET
and BATFET
Driver Dead Time
10
µs
BATTERY DETECTION
tWAKE
Wake timer
Max time charge is enabled
IWAKE
Wake current
RSENSE = 10 mΩ
tDISCHARGE
Discharge timer
Max time discharge current is applied
IDISCHARGE
Discharge current
IFAULT
Fault current after a time-out fault
VWAKE
VDISCH
500
50
125
ms
200
mA
1
s
8
mA
2
mA
Wake threshold with respect to VREG To detect
battery absent during WAKE
Measure on SRN (bq24170)
100
mV/cell
Measure on FB (bq24172)
50
mV
Discharge Threshold to detect battery absent
during discharge
Measure on SRN (bq24170)
2.9
V/cell
Measure on VFB (bq24172)
1.45
V
INTERNAL PWM
fsw
PWM Switching Frequency
1360
(1)
tSW_DEAD
Driver Dead Time
RDS_HI
High-Side MOSFET ON-Resistance
RDS_LO
Low-Side MOSFET ON-Resistance
VBTST_REFRESH
Bootstrap Refresh Comparator Threshold
Voltage
1600
1840
kHz
Dead time when switching between LSFET
and HSFET no load
30
VBTST – VSW = 4.5 V
25
45
mΩ
60
110
mΩ
VBTST – VSW when low-side refresh pulse is
requested, VAVCC = 4.5 V
3
VBTST – VSW when low-side refresh pulse is
requested, VAVCC > 6 V
4
ns
V
INTERNAL SOFT START (8 steps to regulation current ICHG)
SS_STEP
Soft start steps
TSS_STEP
Soft start step time
10
8
1.6
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step
3
ms
Copyright © 2010–2015, Texas Instruments Incorporated
Product Folder Links: bq24170 bq24172
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SLUSAD2C – NOVEMBER 2010 – REVISED APRIL 2015
Electrical Characteristics (continued)
4.5 V ≤ V(PVCC, AVCC) ≤ 17 V, –40°C < TJ + 125°C, typical values are at TA = 25°C, with respect to AGND (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
CHARGER SECTION POWER-UP SEQUENCING
tCE_DELAY
Delay from ISET above 120 mV to start
charging battery
1.5
s
INTEGRATED BTST DIODE
VF
Forward Bias Voltage
IF = 120 mA at 25°C
VR
Reverse breakdown voltage
IR = 2 µA at 25°C
0.85
20
V
V
LOGIC IO PIN CHARACTERISTICS (STAT1, STAT2, TERM_EN)
VOUT_LO
STAT Output Low Saturation Voltage
Sink Current = 5 mA
0.5
V
VCELL_LO
CELL pin input low threshold, 1 cell (bq24170)
CELL pin voltage falling edge
0.5
V
VCELL_MID
CELL pin input mid threshold, 2 cells (bq24170)
CELL pin voltage rising for MIN, falling for
MAX
0.8
1.8
V
VCELL_HI
CELL pin input high threshold, 3 cells
(bq24170)
CELL pin voltage rising edge
2.5
V
8.6 Typical Characteristics
Table 1. Table of Graphs (1)
FIGURE
(1)
DESCRIPTION
Figure 1
AVCC, VREF, ACDRV and STAT Power Up (ISET=0)
Figure 2
Charge Enable by ISET
Figure 3
Current Soft Start
Figure 4
Charge Disable by ISET
Figure 5
Continuous Conduction Mode Switching
Figure 6
Discontinuous Conduction Mode Switching
Figure 7
BATFET to ACFET Transition during Power Up
Figure 8
System Load Transient (Input Current DPM)
Figure 9
Battery Insertion and Removal
Figure 10
Battery to Ground Short Protection
Figure 11
Battery to Ground Short Transition
Figure 12
Efficiency vs Output Current (VIN = 15 V)
Figure 13
Efficiency vs Output Current (VOUT = 3.8 V)
All waveforms and data are measured on HPA610 and HPA706 EVMs.
ISET
500mV/div
AVCC
10V/div
REGN
5V/div
VREF
2V/div
STAT
10V/div
ACDRV
5V/div
IL
1A/div
STAT
10V/div
400 ms/div
20 ms/div
Figure 1. Power Up (ISET = 0)
Figure 2. Charge Enable by ISET
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ISET
500mV/div
PH
5V/div
PH
5V/div
IL
2A/div
IOUT
1A/div
2 ms/div
4 ms/div
Figure 3. Current Soft Start
Figure 4. Charge Disable by ISET
PH
5V/div
PH
5V/div
IL
1A/div
IL
1A/div
200 ns/div
200 ns/div
Figure 5. Continuous Conduction Mode Switching
Figure 6. Discontinuous Conduction Mode Switching
AVCC
10V/div
IIN
1A/div
ISYS
2A/div
ACDRV
10V/div
VSYS
10V/div
IOUT
1A/div
BATDRV
10V/div
200 ms/div
10 ms/div
Figure 7. BATFET to ACFET Transition During Power Up
12
Figure 8. System Load Transient (Input Current DPM)
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SRN
5V/div
SRN
5V/div
PH
10V/div
PH
10V/div
IL
1A/div
IL
1A/div
2 ms/div
400 ms/div
Figure 10. Battery-to-Ground Short Protection
Figure 9. Battery Insertion and Removal
96
94
SRN
5V/div
Efficiency - %
92
PH
10V/div
IL
1A/div
90
VIN 15V 3 cell
88
VIN 15V 2 cell
86
84
82
4 ms/div
80
0
Figure 11. Battery-to-Ground Short Transition
0.5
1.0
2.5
2.0
1.5
Charge Current - A
3.0
3.5
4.0
Figure 12. Efficiency vs Output Current (VIN = 15 V)
94
VIN 5V BAT 3.8V
92
VIN 9V BAT 3.8V
Efficiency - %
90
88
86
84
82
80
0
0.5
1.0
2.5
2.0
1.5
Charge Current - A
3.0
3.5
4.0
Figure 13. Efficiency vs Output Current (VOUT = 3.8 V)
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9 Detailed Description
9.1 Overview
The bq2417x device is a stand-alone switched-mode battery charger for Li-ion and Li-Polymer batteries with
power path management and integrated N-channel power MOSFETs. This fixed-frequency synchronous PWM
charger offers high accuracy regulation of input current charge current and battery regulation voltage.
9.2 Functional Block Diagram
CMSRC+6V
SLEEP
bq24170
ACN-SRN
VACN
bq24172
UVLO
3.6V
ACOV
UVLO
AVCC
ACDRV
CHARGE PUMP
VSRN+100mV
SYSTEM
POWER
SELECTOR
CONTROL
8 ACDRV
7 CMSRC
ACN
ACUV
4
19 BATDRV
VSRN+90mV
SLEEP
ACN-6V
1.35V
LOWV
VREF 12
VREF
LDO
2.05V
RCHRG
Thermal PAD
AVCC
CE
BAT_OVP
2.184V
REGN
LDO
20 REGN
21 BTST
SRN
EAI
FBO
2 PVCC
bq24170
CELL (170)
14
FB (172)
3 PVCC
1V
2.1V
LEVEL
SHIFTER
bq24172
1 SW
IC TJ
20μA
120C
ACP
6
ACN
5
EAO
PWM
PWM
CONTROL
24 SW
REGN
20xIAC
22 PGND
20X
23 PGND
5mV
ACSET 17
CE
UCP
VSRP-VSRN
OCP
VSRP-VSRN
120mV
160%xVISET/20
ISET 13
Fast-Chrg IBAT_REG
Pre-Chrg
Selection
VSW+4.2V
REFRESH
VBTST
20μA
LOWV
EN_CHARGE
9 STAT
CE
SRP 16
20xICHG
RCHRG
Charge
Termination
20X
SRN 15
Discharge
10%xVISET
Discharge
Termination
Qualification
IDISCHARGE
IQUAL
OVPSET 18
ACOV
2V
Fault
IFAULT
TTC 11
Termination
Qualification
BAT_SHORT
STATE
MACHINE
VSRN
Fast Charge Timer
(TTC)
Precharge Timer
(30 mins)
SUSPEND
Timer Fault
TCO
ACUV
IC TJ
14
HTF
10 TS
ACOV
1.6V
0.5V
VREF
LTF
ACUV
TSHUT
TSHUT
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SLEEP
UVLO
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9.3 Feature Description
Figure 14 shows a typical charging profile.
Regulation Voltage
VRECH
I CHRG
Precharge
Current
Regulation
Phase
Fastcharge Current
Regulation Phase
Fastcharge Voltage
Regulation Phase
Termination
Charge
Current
Charge
Voltage
VLOWV
10% ICHRG
Precharge
Timer
Fast Charge Safety Timer
Figure 14. Typical Charging Profile
9.3.1 Battery Voltage Regulation
The bq2417x offers a high-accuracy voltage regulator on for the charging voltage. The bq24170 uses CELL pin
to select number of cells with a fixed 4.2 V/cell. Connecting CELL to AGND sets 1-cell output, floating CELL pin
sets 2-cell output, and connecting to VREF sets 3-cell output.
Table 2. bq24170 CELL Pin Settings
CELL PIN
VOLTAGE REGULATION
AGND
4.2 V
Floating
8.4 V
VREF
12.6 V
The bq24172 uses external resistor divider for voltage feedback and regulate to internal 2.1-V voltage reference
on FB pin. Use the following equation for the regulation voltage for bq24172:
é R2 ù
VBAT = 2.1 V ´ ê1+
ë R1 úû
where
•
•
R2 is connected from FB to the battery.
R1 is connected from FB to GND.
(1)
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9.3.2 Battery Current Regulation
The ISET input sets the maximum charging current. Battery current is sensed by current sensing resistor RSR
connected between SRP and SRN. The full-scale differential voltage between SRP and SRN is 40 mV maximum.
The equation for charge current is:
VISET
ICHARGE =
20 ´ RSR
(2)
The valid input voltage range of ISET is up to 0.8 V. With 10-mΩ sense resistor, the maximum output current is
4 A. With 20-mΩ sense resistor, the maximum output current is 2 A.
The charger is disabled when the ISET pin voltage is below 40 mV and is enabled when ISET pin voltage is
above 120 mV. For 10-mΩ current sensing resistor, the minimum fast charge current must be higher than 600
mA.
Under high ambient temperature, the charge current will fold back to keep IC temperature not exceeding 120°C.
9.3.3 Battery Precharge Current Regulation
On power up, if the battery voltage is below the VLOWV threshold, the bq2417x applies the precharge current to
the battery. This precharge feature is intended to revive deeply discharged cells. If the VLOWV threshold is not
reached within 30 minutes of initiating precharge, the charger turns off and a FAULT is indicated on the status
pins.
For bq2417x, the precharge current is set as 10% of the fast charge rate set by ISET voltage.
VISET
IPRECHARGE =
200 ´ RSR
(3)
9.3.4 Input Current Regulation
The total input current from an AC adapter or other DC sources is a function of the system supply current and
the battery charging current. System current normally fluctuated as portions of the systems are powered up or
down. Without Dynamic Power Management (DPM), the source must be able to supply the maximum system
current and the maximum available charger input current simultaneously. By using DPM, the input current
regulator reduces the charging current when the summation of system power and charge power exceeds the
maximum input power. Therefore, the current capability of the AC adapter can be lowered, reducing system cost.
Input current is set by the voltage on ACSET pin using the following equation:
VACSET
IDPM =
20 ´ R AC
(4)
The ACP and ACN pins are used to sense across RAC with default value of 10 mΩ. However, resistors of other
values can also be used. A larger sense resistor will give a larger sense voltage and higher regulation accuracy,
at the expense of higher conduction loss.
9.3.5 Charge Termination, Recharge, and Safety Timers
The charger monitors the charging current during the voltage regulation phase. Termination is detected when the
SRN voltage (bq24170) or FB voltage (bq24172) is higher than recharge threshold and the charge current is less
than the termination current threshold, as calculated in Equation 5:
VISET
ITERM =
200 ´ RSR
where
•
•
VISET is the voltage on the ISET pin.
RSR is the sense resistor.
(5)
There is a 25-ms deglitch time during transition between fast charge and precharge.
As a safety backup, the charger also provides an internal fixed 30-minute precharge safety timer and a
programmable fast charge timer. The fast charge time is programmed by the capacitor connected between the
TTC pin and AGND, and is given by the formula:
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t TTC = CTTC ´ K TTC
where
•
•
A
•
•
•
CTTC is the capacitor connected to TTC.
KTTC is the constant multiplier.
(6)
new charge cycle is initiated when one of the following conditions occurs:
The battery voltage falls below the recharge threshold
A power-on-reset (POR) event occurs
ISET pin toggled below 40 mV (disable charge) and above 120 mV (enable charge)
Pull the TTC pin to AGND to disable both termination and fast charge safety timer (reset timer). Pull the TTC pin
to VREF to disable the safety timer, but allow charge termination.
9.3.6 Power Up
The charge uses a SLEEP comparator to determine the source of power on the AVCC pin because AVCC can
be supplied either from the battery or the adapter. With the adapter source present, if the AVCC voltage is
greater than the SRN voltage, the charger exits SLEEP mode. If all conditions are met for charging, the charger
then starts charge the battery (see Enable and Disable Charging). If SRN voltage is greater than AVCC, the
charger enters low quiescent current SLEEP mode to minimize current drain from the battery. During SLEEP
mode, the VREF output turns off and the STAT pin goes to high impedance.
If AVCC is below the UVLO threshold, the device is disabled.
9.3.7 Input Undervoltage Lockout (UVLO)
The system must have a minimum AVCC voltage to allow proper operation. This AVCC voltage could come from
either input adapter or battery because a conduction path exists from the battery to AVCC through the high-side
NMOS body diode. When AVCC is below the UVLO threshold, all circuits on the IC are disabled.
9.3.8 Input Overvoltage/Undervoltage Protection
ACOV provides protection to prevent system damage due to high input voltage. In bq2417x, once the voltage on
OVPSET is above the 1.6 V ACOV threshold or below the 0.5 V ACUV threshold, charge is disabled and input
MOSFETs turn off. The bq2417x provides flexibility to set the input qualification threshold.
9.3.9 Enable and Disable Charging
The following conditions have to be valid before charging is enabled:
• ISET pin above 120 mV.
• Device is not in UVLO mode (that is, VAVCC > VUVLO).
• Device is not in SLEEP mode (that is, VAVCC > VSRN).
• OVPSET voltage is from 0.5 V to 1.6 V to qualify the adapter.
• 1.5-s delay is complete after initial power up.
• REGN LDO and VREF LDO voltages are at correct levels.
• Thermal Shutdown (TSHUT) is not valid.
• TS fault is not detected.
• ACFET turns on (see System Power Selector for details).
One of the following conditions stops ongoing charging:
• ISET pin voltage is below 40 mV.
• Device is in UVLO mode.
• Adapter is removed, causing the device to enter SLEEP mode.
• OVPSET voltage indicates the adapter is not valid.
• REGN or VREF LDO voltage is overloaded.
• TSHUT temperature threshold is reached.
• TS voltage goes out of range, indicating the battery temperature is too hot or too cold.
• ACFET turns off.
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TTC timer expires or precharge timer expires.
9.3.10 System Power Selector
The IC automatically switches adapter or battery power to the system load. The battery is connected to the
system by default during power up or during SLEEP mode. When the adapter plugs in and the voltage is above
the battery voltage, the IC exits SLEEP mode. The battery is disconnected from the system and the adapter is
connected to the system after exiting SLEEP. An automatic break-before-make logic prevents shoot-through
currents when the selectors switch.
The ACDRV is used to drive a pair of back-to-back N-channel power MOSFETs between adapter and ACP with
sources connected together to CMSRC. The N-channel FET with the drain connected to the ACP (Q2, RBFET)
provides reverse battery discharge protection, and minimizes system power dissipation with its low-RDSON. The
other N-channel FET with drain connected to adapter input (Q1, ACFET) separates battery from adapter, and
provides a limited dI/dt when connecting the adapter to the system by controlling the FET turnon time. The
/BATDRV controls a P-channel power MOSFET (Q3, BATFET) placed between battery and system with drain
connected to battery.
Before the adapter is detected, the ACDRV is pulled to CMSRC to keep ACFET off, disconnecting the adapter
from system. /BATDRV stays at ACN - 6 V (clamp to ground) to connect battery to system if all the following
conditions are valid:
• VAVCC > VUVLO (battery supplies AVCC)
• VACN < VSRN + 200 mV
After the device comes out of SLEEP mode, the system begins to switch from battery to adapter. The AVCC
voltage must be 300 mV above SRN to enable the transition. The break-before-make logic keeps both ACFET
and BATFET off for 10 µs before ACFET turns on. This prevents shoot-through current or any large discharging
current from going into the battery. The /BATDRV is pulled up to ACN and the ACDRV pin is set to CMSRC +
6 V by an internal charge pump to turn on N-channel ACFET, connecting the adapter to the system if all the
following conditions are valid:
• VACUV < VOVPSET < VACOV
• VAVCC > VSRN + 300 mV
When the adapter is removed, the IC turns off ACFET and enters SLEEP mode.
BATFET keeps off until the system drops close to SRN. The BATDRV pin is driven to ACN - 6 V by an internal
regulator to turn on P-channel BATFET, connecting the battery to the system.
Asymmetrical gate drive provides fast turn-off and slow turnon of the ACFET and BATFET to help the breakbefore-make logic and to allow a soft start at turnon of both MOSFETs. The delay time can be further increased,
by putting a capacitor from gate to source of the power MOSFETs.
9.3.11 Converter Operation
The bq2417x employs a 1.6-MHz constant-frequency step-down switching regulator. The fixed-frequency
oscillator keeps tight control of the switching frequency under all conditions of input voltage, battery voltage,
charge current, and temperature, simplifying output filter design and keeping it out of the audible noise region.
A type III compensation network allows using ceramic capacitors at the output of the converter. An internal sawtooth ramp is compared to the internal error control signal to vary the duty cycle of the converter. The ramp
height is proportional to the AVCC voltage to cancel out any loop gain variation due to a change in input voltage,
and simplifies the loop compensation. Internal gate drive logic allows achieving 97% duty-cycle before pulse
skipping starts.
9.3.12 Automatic Internal Soft-Start Charger Current
The charger automatically soft starts the charger regulation current every time the charger goes into fast charge
to ensure there is no overshoot or stress on the output capacitors or the power converter. The soft start consists
of stepping up the charge regulation current into eight evenly divided steps up to the programmed charge
current. Each step lasts around 1.6 ms, for a typical rise time of 12.8 ms. No external components are needed
for this function.
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9.3.13 Charge Overcurrent Protection
The charger monitors top-side MOSFET current by high-side sense FET. When peak current exceeds MOSFET
limit, the charger turns off the top-side MOSFET and keeps it off until the next cycle. The charger has a
secondary cycle-to-cycle overcurrent protection. The charger monitors the charge current, and prevents the
current from exceeding 160% of the programmed charge current. The high-side gate drive turns off when either
overcurrent condition is detected, and automatically resumes when the current falls below the overcurrent
threshold.
9.3.14 Charge Undercurrent Protection
After the recharge, if the SRP-SRN voltage decreases below 5 mV, then the low-side FET is turned off for the
rest of the switching cycle. During discontinuous conduction mode (DCM), the low-side FET turns on for a short
period of time when the bootstrap capacitor voltage drops below 4 V to provide refresh charge for the capacitor.
This is important to prevent negative inductor current from causing any boost effect in which the input voltage
increases as power is transferred from the battery to the input capacitors. This can lead to an overvoltage on the
AVCC node and potentially cause damage to the system.
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9.3.15 Battery Detection
For applications with removable battery packs, IC provides a battery absent detection scheme to reliably detect
insertion or removal of battery packs. The battery detection routine runs on power up, or if battery voltage falls
below recharge threshold voltage due to removing a battery or discharging a battery.
POR or RECHARGE
Apply 8mA discharge
current, start 1s timer
VFB < VBATOWV
No
Yes
1s timer
expired
No
Yes
Battery Present,
Begin Charge
Disable 8mA
discharge current
Enable 125mA charge
current, start 0.5s timer
VFB > VRECH
Yes
Disable 125mA
charge current
No
0.5s timer
expired
No
Yes
Battery Present,
Begin Charge
Battery Absent
Figure 15. Battery Detection Flow Chart
Once the device has powered up, an 8-mA discharge current is applied to the SRN terminal. If the battery
voltage falls below the LOWV threshold within 1 second, the discharge source is turned off, and the charger is
turned on at low charge current (125 mA). If the battery voltage gets up above the recharge threshold within 500
ms, there is no battery present and the cycle restarts. If either the 500-ms or 1-second timer times out before the
respective thresholds are hit, a battery is detected and a charge cycle is initiated.
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Battery
Absent
Battery
Absent
VBAT_RE
VRECH
Battery
Present
VLOW
Figure 16. Battery Detect Timing Diagram
Ensure that the total output capacitance at the battery node is not so large that the discharge current source
cannot pull the voltage below the LOWV threshold during the 1 second discharge time. The maximum output
capacitances can be calculated according to the following equations:
IDISCH ´ tDISCH
CMAX =
(for bq24170)
(4.1 V - 2.9 V) ´ Number of cells
(7)
CMAX =
IDISCH ´ tDISCH
(for bq24172)
é R2 ù
(2.05 V - 1.45 V) ´ ê1+
ú
ë R1 û
where
•
•
•
•
CMAX is the maximum output capacitance.
IDISCH is the discharge current.
tDISCH is the discharge time.
R2 and R1 are the voltage feedback resistors from the battery to the FB pin.
(8)
9.3.15.1 Example
For a 3-cell Li+ charger, with R2 = 500 kΩ, R1 = 100 kΩ (giving 12.6 V for voltage regulation), IDISCH = 8 mA,
tDISCH = 1 second.
8 mA ´ 1 sec
CMAX =
= 2.2 mF
é 500 kW ù
0.6 V ´ ê1+
ú
ë 100 kW û
(9)
Based on these calculations, no more than 2200 µF should be allowed on the battery node for proper operation
of the battery detection circuit.
9.3.16 Battery Short Protection
When SRN pin voltage is lower than 2 V, it is considered as battery short condition during charging period. The
charger will shut down immediately for 1 ms, then soft start back to the charging current the same as precharge
current. This prevents high current may build in output inductor and cause inductor saturation when battery
terminal is shorted during charging. The converter works in nonsynchronous mode during battery short.
9.3.17 Battery Overvoltage Protection
The converter will not allow the high-side FET to turn on until the battery voltage goes below 102% of the
regulation voltage. This allows 1-cycle response to an overvoltage condition – such as occurs when the load is
removed or the battery is disconnected. A total 6-mA current sink from SRP/SRN to AGND allows discharging
the stored output inductor energy that is transferred to the output capacitors. If battery overvoltage condition lasts
for more than 30 ms, charge is disabled.
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9.3.18 Temperature Qualification
The controller continuously monitors battery temperature by measuring the voltage between the TS pin and
AGND. A negative temperature coefficient thermistor (NTC) and an external voltage divider typically develop this
voltage. The controller 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 VLTF to VHTF thresholds. If battery
temperature is outside of this range, the controller suspends charge and waits until the battery temperature is
within the VLTF to VHTF range. During the charge cycle the battery temperature must be within the VLTF to VTCO
thresholds. If battery temperature is outside of this range, the controller suspends charge and waits until the
battery temperature is within the VLTF to VHTF range. The controller suspends charge by turning off the PWM
charge MOSFETss. Figure 17 summarizes the operation.
TEMPERATURE RANGE
TO INITIATE CHARGE
TEMPERATURE RANGE
DURING A CHARGE CYCLE
VREF
VREF
CHARGE SUSPENDED
CHARGE SUSPENDED
VLTF
VLTFH
VLTF
VLTFH
CHARGE at full C
CHARGE at full C
VHTF
VTCO
CHARGE SUSPENDED
CHARGE SUSPENDED
AGND
AGND
Figure 17. TS Pin, Thermistor Sense Thresholds
Assuming a 103AT NTC thermistor on the battery pack as shown in Figure 18, the values of RT1 and RT2 can
be determined by using Equation 10 and Equation 11:
æ 1
1 ö
VVREF ´ RTHCOLD ´ RTHHOT ´ ç
÷
V
V
TCO ø
è LTF
RT2 =
æV
ö
æV
ö
RTHHOT ´ ç VREF - 1÷ - RTHCOLD ´ ç VREF - 1÷
è VLTF
ø
è VTCO
ø
(10)
VVREF
-1
VLTF
RT1 =
1
1
+
RT2
RTHCO LD
(11)
Select 0°C to 45°C range for Li-ion or Li-polymer battery,
RTHCOLD = 27.28 kΩ
RTHHOT = 4.911 kΩ
RT1 = 5.23 kΩ
RT2 = 30.1 kΩ
After selecting the closest standard resistor value, by calculating the thermistor resistance at temperature
threshold, the final temperature range can be gotten from thermistor data sheet temperature resistance table.
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VREF
bq24170
bq24172
RT1
TS
RT2
RTH
103AT
Figure 18. TS Resistor Network
9.3.19 MOSFET Short Circuit and Inductor Short Circuit Protection
The IC has a short circuit protection feature. Its cycle-by-cycle current monitoring feature is achieved through
monitoring the voltage drop across Rdson of the MOSFETs. The charger will be latched off, but the ACFET keep
on to power the system. The only way to reset the charger from latch-off status is remove adapter then plug
adapter in again. Meanwhile, STAT is blinking to report the fault condition.
9.3.20 Thermal Regulation and Shutdown Protection
The QFN package has low thermal impedance, which provides good thermal conduction from the silicon to the
ambient, to keep junctions temperatures low. The internal thermal regulation loop will fold back the charge
current to keep the junction temperature from exceeding 120°C. As added level of protection, the charger
converter turns off and self-protects whenever the junction temperature exceeds the TSHUT threshold of 150°C.
The charger stays off until the junction temperature falls below 130°C.
9.3.21 Timer Fault Recovery
The IC provides a recovery method to deal with timer fault conditions. The following summarizes this method:
Condition 1: The battery voltage is above the recharge threshold and a time-out fault occurs.
Recovery Method: The timer fault will clear when the battery voltage falls below the recharge threshold, and
battery detection will begin. A POR or taking ISET below 40 mV will also clear the fault.
Condition 2: The battery voltage is below the recharge threshold and a time-out fault occurs.
Recovery Method: Under this scenario, the IC applies the fault current to the battery. 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, the IC disabled the fault current and
executes the recovery method described in Condition 1. A POR or taking ISET below 40 mV will also clear the
fault.
9.3.22 Inductor, Capacitor, and Sense Resistor Selection Guidelines
The IC provides internal loop compensation. With this scheme, the best stability occurs when the LC resonant
frequency, fo, is approximately 15 kHz to 25 kHz for the IC.
1
fo =
2p LC
(12)
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Table 3 summarizes typical LC components for various charge currents.
Table 3. Typical Values as a Function of Charge Current
CHARGE CURRENT
1A
2A
3A
4A
Output inductor L
6.8 µH
3.3 µH
3.3 µH
2.2 µH
Output capacitor C
10 µF
20 µF
20 µF
30 µF
9.3.23 Charge Status Outputs
The open-drain STAT outputs indicate various charger operations as listed in Table 4. These status pins can be
used to drive LEDs or communicate with the host processor. OFF indicates that the open-drain transistor is
turned off.
Table 4. STAT Pin Definition
CHARGE STATE
STAT
Charge in progress (including recharging)
ON
Charge complete, Sleep mode, Charge disabled
OFF
Charge suspend, Input overvoltage, Battery overvoltage, timer fault, , battery absent
BLINK
9.4 Device Functional Modes
The bq2417x is a stand-alone switched-mode charger with power path selector. The device can operate from
either a qualified adapter or supply system power from the battery. Dynamic Power Management (DPM) mode
allows for a smaller adapter to be used effectively in systems with more dynamic system loads.
The bq2417x device provides power path selector gate driver ACDRV/CMSRC on input NMOS pair ACFET (Q1)
and RBFET (Q2), and BATDRV on a battery PMOS device (Q3). When the qualified adapter is present, the
system is directly connected to the adapter. Otherwise, the system is connected to the battery. In addition, the
power path prevents battery from boosting back to the input.
The bq2417x features DPM to reduce the charge current when the input power limit is reached to avoid
overloading the adapter. A highly accurate current-sense amplifier enables precise measurement of input current
from adapter to monitor overall system power.
The total input current from an AC adapter or other DC sources is a function of the system supply current and
the battery charging current. System current normally fluctuated as portions of the systems are powered up or
down. Without DPM, the source must be able to supply the maximum system current and the maximum available
charger input current simultaneously. By using DPM, the input current regulator reduces the charging current
when the summation of system power and charge power exceeds the maximum input power. Therefore, the
current capability of the AC adapter can be lowered, thus reducing system cost.
Although the bq2417x is a stand-alone charger, external control circuitry can effectively be used to change pin
settings such as ISET, ACSET, and enable Battery Learn mode to accommodated for dynamic charging
conditions.
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10 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
A typical application consists of a bq24170 or bq24172 with power path management and from 1- to 3-cell series
Li-ion or Li-polymer battery in a wide variety of portable applications. The bq24170 provides a fixed 4.2 V/cell
(programmable through CELL pin) with highest accuracy and low leakage while the bq24172 provides a
programmable battery voltage (through the FB) pin to allow customized battery regulation voltage.
10.2 Typical Application
Q2
Q1
RAC: 10 m
System
12-V Adapter
C12: 0.1 µ
RIN
2
C11: 0.1 µ
C4:: 10 µ
CIN
2.2 µ
R12
4.02 k
R11
4.02 k
VBAT
PVCC
CMSRC
BATDRV
L: 3.3 mH RSR:10 m
VREF
R2
232 k
VREF
R1
10
bq24170
R3
32.4 k
R5
22.1k
BTST
ACSET
RT
103AT
R9
30.1 k
SRP
C3: 0.1 m
R8
5.23 k
R10
1.5k
TTC
SRN
TS
CELL
Float
THERMAL
STAT
VREF
C9, C10
10 m 10 m
PGND
OVPSE T
VREF
C8
0.1 m
C6
1m
C1
1µ
R6
1000 k
C7
0.1 m
REGN
AVCC
R7
100 k
C5
0.047 m
ISET
R4
100 k
VBAT
SW
VREF
D1
Q3
R14
1k
ACDRV
C2: 1 µ
D2
ACN
ACP
D3
PAD
12-V input, 2-cell battery 8.4 V, 2-A charge current, 0.2-A precharge/termination current, 3-A DPM current, 18-V input
OVP, 0 – 45°C TS
Figure 19. Typical Application Schematic
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Typical Application (continued)
10.2.1 Design Requirements
For this design example, use the parameters listed in Table 5 as the input parameters.
Table 5. Design Parameters
PARAMETER
EXAMPLE VALUE
Input Voltage Range
4.5 V - 17 V
Input Current DPM Limit
600 mA min
Battery Voltage
13.5 V max
Charge Current
4 A max
10.2.2 Detailed Design Procedure
10.2.2.1 Inductor Selection
The bq2417x has a 1600-kHz switching frequency to allow the use of small inductor and capacitor values.
Inductor saturation current should be higher than the charging current (ICHG) plus half the ripple current (IRIPPLE):
ISAT ³ ICHG +(1/2)IRIPPLE
(13)
Inductor ripple current depends on input voltage (VIN), duty cycle (D = VOUT/VIN), switching frequency (fs), and
inductance (L):
V ´ D ´ (1 - D)
IRIPPLE = IN
fs × L
(14)
The maximum inductor ripple current happens with D = 0.5 or close to 0.5. Usually inductor ripple is designed in
the range of 20% to 40% of the maximum charging current as a trade-off between inductor size and efficiency for
a practical design.
10.2.2.2 Input Capacitor
The input capacitor should have enough ripple current rating to absorb input switching ripple current. The worst
case RMS ripple current is half of the charging current when duty cycle is 0.5. If the converter does not operate
at 50% duty cycle, then the worst case capacitor RMS current ICIN occurs where the duty cycle is closest to 50%
and can be estimated by the following equation:
ICIN = ICHG ´ D ´ (1 - D)
(15)
A low ESR ceramic capacitor such as X7R or X5R is preferred for the input decoupling capacitor and should be
placed as close as possible to the drain of the high-side MOSFET and source of the low-side MOSFET. The
voltage rating of the capacitor must be higher than the normal input voltage level. A 25-V rating or higher
capacitor is preferred for a 15-V input voltage. A 20-μF capacitance is suggested for a typical 3-A to 4-A charging
current.
10.2.2.3 Output Capacitor
The output capacitor also should have enough ripple current rating to absorb output switching ripple current. The
output capacitor RMS current ICOUT is given as:
I
ICOUT = RIPPLE » 0.29 ´ IRIPPLE
2 ´ 3
(16)
The output capacitor voltage ripple can be calculated as follows:
DVO =
VOUT æ
V
ç 1 - OUT
2 ç
VIN
8LCfs è
ö
÷
÷
ø
(17)
At certain input and output voltages and switching frequencies, the voltage ripple can be reduced by increasing
the output filter LC.
26
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The bq2417x has an internal loop compensator. To achieve good loop stability, the resonant frequency of the
output inductor and output capacitor should be designed from 15 kHz to 25 kHz. The preferred ceramic capacitor
has a 25-V or higher rating, X7R or X5R.
10.2.2.4 Input Filter Design
During adapter hot plug-in, the parasitic inductance and the input capacitor from the adapter cable form a
second-order system. The voltage spike at the AVCC pin may be beyond the IC maximum voltage rating and
damage the IC. The input filter must be carefully designed and tested to prevent an overvoltage event on the
AVCC pin.
There are several methods to damping or limiting the overvoltage spike during adapter hot plug-in. An electrolytic
capacitor with high ESR as an input capacitor can damp the overvoltage spike well below the IC maximum pin
voltage rating. A high current capability TVS Zener diode can also limit the overvoltage level to an IC safe level.
However, these two solutions may not be lowest cost or smallest size.
A cost-effective and small-size solution is shown in Figure 20. R1 and C1 are composed of a damping RC
network to damp the hot plug-in oscillation. As a result, the overvoltage spike is limited to a safe level. D1 is used
for reverse voltage protection for the AVCC pin. C2 is the AVCC pin decoupling capacitor and it should be placed
as close as possible to the AVCC pin. R2 and C2 form a damping RC network to further protect the IC from high
dv/dt and high voltage spike. The C2 value should be less than the C1 value so R1 can dominant the equivalent
ESR value to get enough damping effect for hot plug-in. R1 and R2 must be sized enough to handle in-rush
current power loss according to the resistor manufacturer’s data sheet. The filter component values always need
to be verified with a real application and minor adjustments may be needed to fit in the real application circuit.
If the input is 5 V (USB host or USB adapter), the D1 can be saved. R2 must be 5 Ω or higher to limit the current
if the input reversely inserted.
D1
R2(1206)
4.7 - 30 W
R1(2010)
2W
Adapter
Connector
AVCC pin
C1
2.2 mF
C2
0.1 - 1 mF
Figure 20. Input Filter
10.2.2.5 Input ACFET and RBFET Selection
N-type MOSFETs are used as input ACFET(Q1) and RBFET(Q2) for better cost effective and small size solution,
as shown in Figure 21. Normally, there is a total capacitance of 50 µH connected at PVCC node: 10-µF capacitor
for buck converter of bq2417x and 40-µF capacitor for system side. There is a surge current during Q1 turnon
period when a valid adapter is inserted. Decreasing the turnon speed of Q1 can limit this surge current in
desirable range by selecting a MOSFET with relative bigger CGD and/or CGS. If Q1 turns on too fast, we must add
external CGD and/or CGS. For example, 4.7-nF CGD and 47-nF CGS are adopted on EVM while using NexFET
CSD17313 as Q1.
RIN
2
CIN
2. ?
2.2?
Q2
Q1
ADAPTER
SYS
RSNS
C4 1m
RGS
499k
CGS
CGD
R11
4.02k
R12
4.02k
CSYS
40?
PVCC
CMSRC
ACDRV
Figure 21. Input ACFET and RBFET
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10.2.3 Application Curve
96%
VIN=12 V, 2 S
94%
Efficiency (%)
92%
90%
88%
86%
84%
82%
80%
0
0.5
1
1.5
2
2.5
IOUT (A)
3
3.5
4
D001
Figure 22. Charge Efficiency
10.3 System Examples
RevFET
Q4
RAC: 20m
Adapter
Or USB
System
0.1µ
0.1µ
1µ
VREF
Selectable input
current limit
R5B
8.06k
ILIM_500mA
R11
5
R4
100k
R5A
32.4k
VREF
ACN
PVCC
ACP
CMSRC
BATDRV
4.7µ
ACDRV
3.3mH
VREF
R2
100k
RSR: 10m
VBAT
SW
bq24170
ISET
0.047m
R3
32.4k
BTST
ACSET
REGN
0.1m
0.1m
D1
Optional
10m 10m
1m
R6
845k
C1
1µ
AVCC
PGND
OVPSET
R7
100k
RT
103AT
SRP
VREF
R8
6.81k
R9
133k
R10
1.5k
TTC
SRN
TS
CELL
STAT
VREF
D3
THERMAL
PAD
USB or adapter with input OVP 15 V, up to 4-A charge current, 0.4-A precharge current, 2-A adapter current or 500mA USB current, 5 – 40°C TS, system connected before sense resistor
Figure 23. Typical Application Schematic With Single-Cell Unremovable Battery
28
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System Examples (continued)
Q2
Q1
C12: 0.1µ
RIN
2
C11: 0.1µ
CIN
2.2m
R11
4.02k
VBAT
ACN
ACP
CMSRC
R12
4.02k
D1
R21
100k
VREF
R4
100k
C1
1µ
VREF
R20
599k
R21
499k
FB
LEARN
bq24172
R8
5.23k
R17
49.9k
RT
103AT
R9
30.1k
R10
1.5k
VREF
D3
C5
0.047m
C7
0.1m
REGN
VBAT
C8
0.1m
C9, C10
m 10m
20m
C6
1m
AVCC
PGND
C3: 0.1m
VREF
RSR:10m
BTST
OVPSET
R7
49.9k
L: 2.2mH
ISET
ACSET
R6
499k
Q3
R14
1k
SW
R22
32.4k
R5
32.4k
C4
10µ
BATDRV
VREF
R20
10
Battery LEARN
PVCC
ACDRV
C2: 1µ
D2
System
RAC: 10m
15-V Adapter
SRP
TTC
SRN
TS
FB
R2
499k
THERMAL
STAT
PAD
R1
100k
15-V input, 3-cell battery 12.6 V, 4-A charge current, 0.4-A precharge/termination current, 4-A DPM current, 0 – 45°C
TS
Figure 24. Typical Application Schematic With Battery Learn Function
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System Examples (continued)
5-V Adapter
System
PVCC
ACN
ACP
CMSRC
1µ
VREF
Selectable
current limit
R5B
12.1k
12.1
ILIM_500mA
R11
5
4.7µ
BATDRV
ACDRV
VREF
3.3mH
VREF
bq24172
R4
100k
ISET
0.047m
BTST
R5A
12.1k
RSR: 20m
VBAT
SW
ACSET
REGN
0.1m
0.1m
D1
Optional
10m10m
1m
R6
400k
C1
1µ
AVCC
PGND
OVPSET
R7
100k
RT
103AT
SRP
VREF
TTC
R8
5.23k
R9
30.1k
STAT
D3
R2
100k
FB
TS
R10
1.5k
VREF
SRN
THERMAL
PAD
R1
100k
USB with input OVP 8 V, selectable charge current limit of 900 mA or 500 mA, 0 – 45°C TS, system connected after
sense resistor
Figure 25. Typical Application Schematic With Single-Cell Unremovable Battery
30
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11 Power Supply Recommendations
In order to provide an output voltage on SYS, the bq24171 requires a power supply from 4.5 V to 17 V input with
ideally more than 500-mA current rating connected to VBUS; or, a single-cell Li-Ion battery with voltage >
VBATUVLO connected to BAT.
12 Layout
12.1 Layout Guidelines
The switching node rise and fall times should be minimized for minimum switching loss. Proper layout of the
components to minimize the high-frequency current path loop (see Figure 26) is important to prevent electrical
and magnetic field radiation and high-frequency resonant problems. The following is a PCB layout priority list for
proper layout. Layout of the PCB according to this specific order is essential.
1. Place the input capacitor as close as possible to the PVCC supply and ground connections and use the
shortest copper trace connection. These parts should be placed on the same layer of the PCB instead of on
different layers and using vias to make this connection.
2. Place the inductor input terminal as close as possible to the SW terminal. Minimize the copper area of this
trace to lower electrical and magnetic field radiation but make the trace wide enough to carry the charging
current. Do not use multiple layers in parallel for this connection. Minimize parasitic capacitance from this
area to any other trace or plane.
3. The charging current sensing resistor should be placed right next to the inductor output. Route the sense
leads connected across the sensing resistor back to the IC in the same layer, close to each other (minimize
loop area) and do not route the sense leads through a high-current path (see Figure 27 for Kelvin connection
for best current accuracy). Place decoupling capacitor on these traces next to the IC.
4. Place the output capacitor next to the sensing resistor output and ground.
5. Output capacitor ground connections must be tied to the same copper that connects to the input capacitor
ground before connecting to system ground.
6. Route analog ground separately from power ground and use a single ground connection to tie charger power
ground to charger analog ground. Just beneath the IC use analog ground copper pour but avoid power pins
to reduce inductive and capacitive noise coupling. Use the thermal pad as a single ground connection point
to connect analog ground and power ground together, or use a 0-Ω resistor to tie analog ground to power
ground. A star-connection under the thermal pad is highly recommended.
7. It is critical to solder the exposed thermal pad on the backside of the IC package to the PCB ground. Ensure
that there are sufficient thermal vias directly under the IC, connecting to the ground plane on the other layers.
8. Decoupling capacitors must be placed next to the IC pins and make trace connection as short as possible.
9. The number and physical size of the vias must be enough for a given current path.
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12.2 Layout Examples
SW
L1
R1
High
Frequency
VIN
C1
Current
Path
VBAT
BAT
PGND
C2
C3
Figure 26. High-Frequency Current Path
Current Direction
R SNS
Current Sensing Direction
To SRP and SRN pin
Figure 27. Sensing Resistor PCB Layout
32
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13 Device and Documentation Support
13.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 6. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
bq24170
Click here
Click here
Click here
Click here
Click here
bq24172
Click here
Click here
Click here
Click here
Click here
13.2 Trademarks
All trademarks are the property of their respective owners.
13.3 Electrostatic Discharge Caution
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.
13.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
14 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
BQ24170RGYR
ACTIVE
VQFN
RGY
24
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ24170
BQ24170RGYT
ACTIVE
VQFN
RGY
24
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ24170
BQ24172RGYR
ACTIVE
VQFN
RGY
24
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ24172
BQ24172RGYT
ACTIVE
VQFN
RGY
24
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ24172
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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