BQ25172
SLUSDY5 – JUNE 2022
BQ25172: 800-mA Linear Battery Charger for 1- to 6-Cell NiMH Batteries
1 Features
3 Description
•
•
The BQ25172 is an integrated 800-mA linear charger
for 1-cell to 6-cell NiMH batteries targeted at industrial
and medical applications. The device has a single
power output that charges the battery. The system
load can be placed in parallel with the battery, as
long as the average system load does not prevent the
battery from being charged fully within the safety timer
duration. When the system load is placed in parallel
with the battery, the charge current is shared between
the system and the battery.
•
•
•
•
•
Input voltage up to 30-V tolerant
Automatic Sleep Mode for low power consumption
– 350-nA battery leakage current
– 85-µA input leakage current when charge
disabled
Supports 1- to 6-cell NiMH with intermittentcharging
External resistor programmable operation
– VSET to set NiMH series cell-count from 1s to
6s
– ISET to set charge current from 10 mA to 800
mA
– TMR to set charge safety timer duration from
4 hr to 22 hr
High accuracy
– ±0.5% charge voltage accuracy
– ±10% charge current accuracy
Charging features
– NTC thermistor input to monitor battery
temperature
– Cold and hot temperature charging disabled
– VOUT_OVP reduced at cool temperatures
– TS pin for charging function control
– Open-drain output for status and fault indication
Integrated fault protection
– 18-V IN overvoltage protection
– VSET based OUT overvoltage protection
– 1000-mA overcurrent protection
– 125°C thermal regulation; 150°C thermal
shutdown protection
– OUT short-circuit protection
– VSET, ISET, TMR pins short/open protection
2 Applications
•
•
•
•
•
•
•
•
Fleet management, asset tracking
Gas detector
Electronic point of sales (ePOS)
Beauty and grooming
Electric toothbrush
Pulse oximeter
Blood glucose monitor
Infrared thermometer
The device charges NiMH cells in constant current
mode only and terminates the charge cycle when
the programmable timer expires or the battery
voltage exceeds the VOUT_OVP threshold. In all
charge phases, an internal control loop monitors
the IC junction temperature and reduces the charge
current if an internal temperature threshold TREG, is
exceeded.
The charger power stage and charge current sense
functions are fully integrated. The charger function
has high accuracy current, charge status display, and
timer-based charge termination. The series cell-count,
charge current, and charge timer are programmable
through external resistors. Intermittent charging allows
a NiMH battery to automatically recharge for a
reduced timer duration once its voltage falls below the
recharge threshold.
Device Information
PACKAGE(1)
PART NUMBER
BQ25172
(1)
WSON (8)
BODY SIZE (NOM)
2.0 mm x 2.0 mm
For all available packages, see the orderable addendum at
the end of the data sheet.
VIN: 3.0V ± 18V
IN
OUT
1s ± 6s NiMH
VREF
VSET
STAT
ISET
TS
GND
BQ25172
TMR
Simplified Schematic
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
BQ25172
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Table of Contents
1 Features............................................................................1
2 Applications..................................................................... 1
3 Description.......................................................................1
4 Revision History.............................................................. 2
5 Pin Configuration and Functions...................................3
6 Specifications.................................................................. 4
6.1 Absolute Maximum Ratings........................................ 4
6.2 ESD Ratings............................................................... 4
6.3 Recommended Operating Conditions.........................4
6.4 Thermal Information....................................................5
6.5 Electrical Characteristics.............................................6
6.6 Timing Requirements.................................................. 7
6.7 Typical Characteristics................................................ 8
7 Detailed Description........................................................9
7.1 Overview..................................................................... 9
7.2 Functional Block Diagram......................................... 10
7.3 Feature Description...................................................11
7.4 Device Functional Modes..........................................16
8 Application and Implementation.................................. 17
8.1 Application Information............................................. 17
8.2 Typical Applications.................................................. 17
9 Power Supply Recommendations................................20
10 Layout...........................................................................20
10.1 Layout Guidelines................................................... 20
10.2 Layout Example...................................................... 20
11 Device and Documentation Support..........................21
11.1 Device Support........................................................21
11.2 Receiving Notification of Documentation Updates.. 21
11.3 Support Resources................................................. 21
11.4 Trademarks............................................................. 21
11.5 Electrostatic Discharge Caution.............................. 21
11.6 Glossary.................................................................. 21
12 Mechanical, Packaging, and Orderable
Information.................................................................... 22
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
2
DATE
REVISION
NOTES
June 2022
*
Initial Release
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5 Pin Configuration and Functions
IN
1
8
OUT
BQ25172
ISET
2
7
VSET
TS
3
6
TMR
GND
4
5
STAT
Thermal Pad
Figure 5-1. DSG Package WSON 8-Pin Top View
Table 5-1. Pin Functions
PIN
NAME
NUMBER
I/O
DESCRIPTION
IN
1
P
Input power, connected to external DC supply. Bypass IN with a ≥1-μF capacitor to GND, placed
close to the IC.
ISET
2
I
Programs the device charge current. External resistor from ISET to GND defines charge current
value. Expected range is 30 kΩ (10 mA) to 375 Ω (800 mA). ICHG = KISET / RISET.
TS
3
I
Temperature qualification voltage input. Connect a negative temperature coefficient (NTC)
thermistor directly from TS to GND (AT103-2 recommended). Charge suspends when the TS pin
voltage is out of range. VOUT_OVP is reduced in cool region. If TS function is not needed, connect
an external 10-kΩ resistor from this pin to GND. Pulling VTS < VTS_ENZ disables the charger.
GND
4
–
Ground pin
STAT
5
O
Open drain charge status indication output. Connect to the pullup rail via a 10-kΩ resistor. LOW
indicates charge in progress. HIGH indicates charge complete or charge disabled. When a fault
condition is detected, the STAT pin blinks at 1 Hz.
TMR
6
I
Connect to a pulldown resistor to program charge safety timer duration. Valid resistor range is 3.6
kΩ to 36 kΩ. Refer to Section 7.3.1.2.
VSET
7
I
Programs the number of series NiMH cells. Valid resistor range is 3.6 kΩ to 62 kΩ. Recommend
using a ±1% tolerance resistor with VOUT + VSLEEP, TJ = -40°C to +125°C, and TJ = 25°C for typical values (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX UNIT
QUIESCENT CURRENTS
IQ_OUT
IQ_OUT
Quiescent output current (OUT)
Quiescent output current (OUT)
OUT= 4.2V, IN floating or IN = 0V - 5V,
Charge Disabled, TJ = 25 °C
0.350
0.6
µA
OUT= 4.2V, IN floating or IN = 0V - 5V,
Charge Disabled, TJ < 105 °C
0.350
0.8
µA
OUT = 8.4V, IN floating or IN = 0V - 14V,
Charge Disabled, TJ = 25 °C
0.8
1.2
µA
OUT = 8.4V, IN floating or IN = 0V - 14V,
Charge Disabled, TJ < 105 °C
0.8
1.5
µA
IN = 5V, Charge Disabled (VTS < VTS_ENZ),
no battery
80
110
µA
ISD_IN_TS
Shutdown input current (IN) with
charge disabled via TS pin
ISTANDBY_IN
Standby input current (IN) with charge
IN = 5V, Charge Enabled, charge terminated
terminated
190
µA
ISTANDBY_IN
Standby input current (IN) with charge IN = 14V, Charge Enabled, charge
terminated
terminated
230
µA
IQ_IN
Quiescent input current (IN)
IN = 5V, OUT = 3.8V, Charge Enabled,
ICHG = 0A
0.45
0.6
mA
IQ_IN
Quiescent input current (IN)
IN = 14V, OUT = 7.6V, Charge Enabled,
ICHG = 0A
0.45
0.6
mA
18
V
INPUT
VIN_OP
IN operating range
3.0
VIN_LOWV
IN voltage to start charging
IN rising
3.05
3.09
3.15
V
VIN_LOWV
IN voltage to stop charging
IN falling
2.80
2.95
3.10
V
VSLEEPZ
Exit sleep mode threshold
IN rising, VIN - VOUT, OUT = 4V
95
135
175
mV
VSLEEP
Sleep mode threshold hysteresis
IN falling, VIN - VOUT, OUT = 4V
VIN_OV
VIN overvoltage rising threshold
IN rising
VIN_OVZ
VIN overvoltage falling threshold
IN falling
80
18.1
18.4
mV
18.7
18.2
V
V
CONFIGURATION PINS SHORT/OPEN PROTECTION
RISET_SHORT
Resistor value considered short
RISET below this at startup, charger does not
initiate charge, power cycle or TS toggle to
reset
350
Ω
RVSET_SHORT
Resistor value considered short
RVSET below this at startup, charger does
not initiate charge, power cycle or toggle to
reset
2.8
kΩ
RVSET_OPEN
Resistor value considered open
RVSET above this at startup, charger does
not initiate charge, power cycle or toggle to
reset
RTMR_SHORT
Resistor value considered short
RTMR below this at startup, charger latches
off, power cycle or TS toggle to reset
RTMR_OPEN
Resistor value considered open
RTMR above this at startup, charger latches
off, power cycle or TS toggle to reset
80
kΩ
2.8
45
kΩ
kΩ
BATTERY CHARGER
ICHG_RANGE
Typical charge current regulation
range
KISET
Charge current setting factor, ICHG =
KISET / RISET
ICHG_ACC
6
Charge current accuracy
10
800
mA
10mA < ICHG < 800mA
270
300
330
AΩ
RISET = 375Ω, OUT = 3.8V
720
800
880
mA
RISET = 600Ω, OUT = 3.8V
450
500
550
mA
RISET = 3.0kΩ, OUT = 3.8V
90
100
110
mA
RISET = 30kΩ, OUT = 3.8V
9
10
11
mA
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6.5 Electrical Characteristics (continued)
3.0V < VIN < 18V and VIN > VOUT + VSLEEP, TJ = -40°C to +125°C, and TJ = 25°C for typical values (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VRECHG
Battery recharge threshold, per cell
RON
Charging path FET on-resistance
MIN
TYP
1.305
1.330
1.355
V
IOUT = 400mA, TJ = 25°C
845
1000
mΩ
IOUT = 400mA, TJ = -40 - 125°C
845
1450
mΩ
OUT falling, VSET configured for 2-cell
MAX UNIT
BATTERY CHARGER PROTECTION
VOUT_OVP
OUT overvoltage rising threshold, per
cell
VOUT rising, TS normal
1.65
1.70
1.75
V
VOUT_OVP
OUT overvoltage falling threshold, per
VOUT falling, TS normal
cell
1.40
1.45
1.50
V
VOUT_OVP_TSCOOL
OUT overvoltage rising threshold, per
cell
VOUT rising, TS in cool range
1.45
1.50
1.55
V
VOUT_OVP_TSCOOL
OUT overvoltage falling threshold, per
VOUT falling, TS in cool range
cell
1.30
1.35
1.40
V
IOUT_OCP
Output current limit threshold
0.9
1
1.1
A
IOUT rising
TEMPERATURE REGULATION AND TEMPERATURE SHUTDOWN
TREG
TSHUT
Typical junction temperature
regulation
125
°C
Thermal shutdown rising threshold
Temperature increasing
150
°C
Thermal shutdown falling threshold
Temperature decreasing
135
°C
BATTERY-PACK NTC MONITOR
ITS_BIAS
TS nominal bias current
36.5
38
39.5
µA
Cold temperature threshold
TS pin voltage rising (approx. 0°C)
0.99
1.04
1.09
V
Cold temperature exit threshold
TS pin voltage falling (approx. 4°C)
0.83
0.88
0.93
V
Cool temperature threshold; VOUT_OVP
TS pin voltage rising (approx. 10°C)
reduced
650
680
710
mV
Cool temperature exit threshold;
VOUT_OVP returns to normal
TS pin voltage falling (approx. 13°C)
580
610
640
mV
Hot temperature threshold
TS pin voltage falling (approx. 45°C)
176
188
200
mV
Hot temperature exit threshold
TS pin voltage rising (approx. 40°C)
208
220
232
mV
VTS_ENZ
Charge Disable threshold. Crossing
this threshold shall shutdown IC
TS pin voltage falling
40
50
60
mV
VTS_EN
Charge Enable threshold. Crossing
TS pin voltage rising
this threshold shall restart IC operation
65
75
85
mV
VTS_CLAMP
TS maximum voltage clamp
2.3
2.6
2.9
V
0.4
V
1
µA
VCOLD
VCOOL
VHOT
TS pin open-circuit (float)
LOGIC OUTPUT PIN (STAT)
VOL
Output low threshold level
Sink current = 5mA
IOUT_BIAS
High-level leakage current
Pull up rail 3.3V
6.6 Timing Requirements
MIN
NOM
MAX
UNIT
BATTERY CHARGER
tTS_DUTY_ON
TS turn-on time during TS duty cycle mode
tTS_DUTY_OFF
TS turn-off time during TS duty cycle mode
tOUT_OCP_DGL
Deglitch time for IOUT_OCP, IOUT rising
tSAFETY
Charge safety timer accuracy, RTMR = 18kΩ
tINTERMITTENT
Commercial Intermittent charge safety timer (NiMH), as
percentage of tSAFETY
100
9.5
ms
2
s
100
µs
10
20
10.5
hr
%
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6.7 Typical Characteristics
CIN = 1 µF, COUT = 1 µF, VIN = 5 V, VOUT = 3.8 V, Temperature = Ambient (unless otherwise specified)
10
10mA
50mA
100mA
200mA
400mA
600mA
800mA
8
ICHG Accuracy (%)
6
4
2
0
-2
-4
-6
-8
-10
3.1
3.2
3.3
3.4
3.5 3.6 3.7
VOUT (V)
VIN = 5 V
3.8
3.9
4
4.1
VIN = 5 V and 12 V
Temperature = 25ºC
VOUT = 3.8 V and 7.6 V
Figure 6-1. ICHG Accuracy vs. Output Voltage
Figure 6-2. ICHG Accuracy vs. Temperature
Figure 6-3. Dropout Voltage vs. Output Current
TS Pin = LOW
VOUT = 0 V
Figure 6-4. Input Shutdown Current vs. Input Voltage
2
1
-40qC
0qC
25qC
85qC
105qC
0.9
1.6
1.4
IQ_OUT (PA)
IQ_IN (mA)
0.8
0.7
0.6
0.5
-40qC
0qC
25qC
105qC
125qC
1.8
1.2
1
0.8
0.6
0.4
0.4
0.3
0.2
0.2
0
3
5
7
9
Charge enabled
11
VIN (V)
13
15
17 18
ICHG = 0 A
2
3
4
5
6
VOUT (V)
7
8
9
10
VIN = 0 V
Figure 6-5. Input Quiescent Current vs. Input Voltage
8
1
Figure 6-6. Output Quiescent Current vs. Output Voltage
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7 Detailed Description
7.1 Overview
The BQ25172 is an integrated 800-mA linear charger for 1-cell to 6-cell NiMH battery applications. The device
has a single power output that charges the battery. When the system load is placed in parallel with the battery,
the input current is shared between the system and the battery.
The device charges a NiMH battery in constant current mode only and terminates the charge cycle when
the programmable timer, tSAFETY, expires or the battery voltage exceeds the VOUT_OVP threshold. An optional
intermittent charging phase can be programmed to automatically recharge the NiMH battery for a reduced timer
duration once its voltage falls below VRECHG.
The charger includes flexibility in programming of the charge current, charge safety timer duration, and series
cell-count. This charger is designed to work with a standard USB connection or dedicated charging adapter (DC
output).
The charger also comes with a full set of safety features: battery temperature monitoring, overvoltage protection,
charge safety timer, and configuration pin (VSET, ISET, TMR) short and open protection. Upon application of a
valid input power source, the configuration pins are checked for short and open circuits. All of these features and
more are described in detail in the following sections.
The charger is designed for a single path from the input to the output to charge the battery. Once the input
adapter has been connected, the charge current is applied and the safety timer is started. The charge current is
programmed using the ISET pin. The safety timer is programmed by the TMR pin.
Power dissipation in the IC is greatest at high charge currents and low battery voltages. If the IC temperature
reaches TREG, the IC enters thermal regulation, slows the timer clock by half, and reduces the charge current as
needed to keep the temperature from rising any further.
Further details are described in Section 7.3.
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7.2 Functional Block Diagram
OUT
IN
ICHG
VIN
VIN_OV
INPUT
VSLEEPZ MONITOR
QBLK
CNTRL
VIN_UVLOZ
VBAT
+
VREF
ICHG_REF
TREG
+
TJ
/PG
CEN
FAULT
ISET
STAT
ICHG_REF
PIN DETECT
&
REF DAC
VSET
STAT
tSAFETY
TREG
TMR
TJSHUT
+
TJ
TSHUT
VTS
VCOOL
VRECHG
+
TS COOL
TS HOT
+
VHOT
VTS
+
RECHG
VBAT
CHARGE TS COLD
CONTROL
+
+
BATOVP
+
TMR_EXP
ITS
TS
VTS
VCOLD
tCHARGE
tSAFETY
VTS
VTS_CLAMP
VBAT
GND
VOUT_OVP
BATOCP
+
ICHG
IOUT_OCP
FAULT
10
STATE
MONITOR
STAT
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7.3 Feature Description
7.3.1 Device Power Up from Input Source
When an input source is plugged in and charge is enabled (VTS > VTS_EN), the device checks the input source
voltage to turn on all the bias circuits. It detects and sets the charge current, safety timer length, and series
cell-count before the linear regulator is started. The power-up sequence from input source is as listed:
1. ISET pin detection
2. TMR pin detection to select charge timer
3. VSET pin detection to select battery stack configuration
4. Charger power up
7.3.1.1 ISET Pin Detection
After a valid VIN is plugged in and VTS > VTS_EN, the device checks the resistor on the ISET pin for a short
circuit (RISET < RISET_SHORT). If a short condition is detected, the charger remains in the FAULT state until the
input or TS pin is toggled. If the ISET pin is open-circuit, the charger proceeds through pin detection and starts
the charger with no charge current. The ISET pin is monitored while charging and changes in RISET while the
charger is operating immediately translates to changes in charge current.
An external pulldown resistor (±1% or better is recommended to minimize charge current error) from the ISET
pin to GND sets the charge current as:
ICHG
KISET
RISET
(1)
where:
•
•
•
ICHG is the desired charge current
KISET is a gain factor found in the electrical characteristics
RISET is the pulldown resistor from the ISET pin to GND
For charge currents below 50 mA, an extra RC circuit is recommended on ISET to achieve a more stable
current signal. For greater accuracy at lower currents, part of the current-sensing FET is disabled to give better
resolution.
7.3.1.2 TMR Pin Detection
The TMR pin is used to program the safety timer using a ±1% pulldown resistor. The available pulldown resistors
and corresponding timer lengths are listed in the following table.
Table 7-1. TMR Pin Resistor Value Table
RESISTOR
CHARGE TIMER (HR)
> 45 kΩ
No charge (open-circuit)
36 kΩ
4 hr
27 kΩ
6 hr
24 kΩ
8 hr
18 kΩ
10 hr
15 kΩ
12 hr
11 kΩ
14 hr
8.2 kΩ
16 hr
6.2 kΩ
18 hr
4.7 kΩ
20 hr
3.6 kΩ
22 hr
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Table 7-1. TMR Pin Resistor Value Table (continued)
RESISTOR
CHARGE TIMER (HR)
< 3.0 kΩ
No charge (short-circuit)
If either a short- or open-circuit condition is detected, the charger stops operation and remains in the FAULT
state until the input or TS pin is toggled.
Once a value has been detected, it is latched in and the pin is not continuously monitored during operation. A
change in this pin is not acknowledged by the IC until the input supply or TS pin is toggled.
7.3.1.3 VSET Pin Detection
The VSET pin is used to program the device cell configuration using a ±1% pulldown resistor. The available
pulldown resistors and corresponding cell configurations are listed in the following table.
Table 7-2. VSET Pin Resistor Value Table
RESISTOR
CELL COUNT
> 80 Ω
No charge (open-circuit)
62 kΩ
1-cell
47 kΩ
1-cell + intermittent charge
36 kΩ
2-cell
27 kΩ
2-cell + intermittent charge
24 kΩ
3-cell
18 kΩ
3-cell + intermittent charge
15 kΩ
4-cell
11 kΩ
4-cell + intermittent charge
8.2 kΩ
5-cell
6.2 kΩ
5-cell + intermittent charge
4.7 kΩ
6-cell
3.6 kΩ
6-cell + intermittent charge
< 3.0 kΩ
No charge (short-circuit)
If either a short- or open-circuit condition is detected, the charger stops operation and remains in the FAULT
state until the input or TS pin is toggled.
Once a valid resistor value has been detected, the corresponding cell configuration is latched in and the pin is
not continuously monitored during operation. A change in this pin is not acknowledged by the IC until the input
supply or TS pin is toggled.
7.3.1.4 Charger Power Up
After ISET, TMR, and VSET pin resistor values have been validated, the device proceeds to enable the charger.
For more info see Section 7.3.2.1.
7.3.2 Battery Charging Features
When charge is enabled (VTS > VTS_EN), the device automatically completes a charging cycle according to the
settings on the ISET, TMR, and VSET pins. Charging is terminated when the charge safety timer expires or
battery voltage exceeds VOUT_OVP.
7.3.2.1 NiMH Battery Charging Profile
The device charges NiMH batteries in constant current mode only. The charge current programmed by ISET is
the only current applied over the charging cycle, as shown in Figure 7-1. The charge termination method for
the device is timer-based. The charge safety timer, tSAFETY, sets the charging duration. Programming the charge
safety timer is done with a pulldown resistor on the TMR pin.
12
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Intermittent charging is designed to replenish the natural self-discharge of NiMH cells by restarting a short
charge cycle (20% of tSAFETY) when the output voltage falls below the VRECHG threshold. If the intermittent
charging function is disabled and a full charge cycle has been completed (safety timer expired with VOUT above
VRECHG), the device does not start a new charge cycle automatically and requires input supply or TS pin toggle
to initiate a new charge cycle.
If battery voltage is above VRECHG at power up, the battery is considered full and the device does not charge.
Once the battery voltage falls below VRECHG, the device automatically begins charging. If the intermittent
charging function is disabled, a single charge cycle is initiated with the safety timer duration programmed by
the TMR pin. If intermittent charging is enabled, an intermittent charge cycle is initiated for 20% of the TMR
programmed value.
When the charge timer (full-length or intermittent) expires, the battery voltage is checked again. If the battery
voltage is below VRECHG, a fault is reported through the STAT pin and further charging is prevented. If the charge
timer expires with VOUT above VRECHG, the STAT pin indicates charge completed. In the case where the TS fault
is within the cool threshold, VOUT_OVP is automatically reduced to VOUT_OVP_TSCOOL voltage.
If the charger is in thermal regulation during charging, the actual charging current will be less than the
programmed value. Termination by timer is still enabled, but the charging safety timer is counted at half the
clock rate. For more information, refer to Section 7.3.2.2.
OUT Over-voltage
VOUT_OVP
Battery Voltage
Charge Current
ISET
Charge Current
Constant
Current CC
Timer Expire
(Charge Done)
Charge Timer
CHM_TMR
Figure 7-1. NiMH Battery Charging Profile with Intermittent Charging Disabled
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OUT Over-voltage
VOUT_OVP
Battery Voltage
VRECHG
Charge Current
ISET
Charge Current
Constant
Current CC
Charge Timer
CHM_TMR
Charge
Done
Intermittent
Charge
20% x TMR
Figure 7-2. NiMH Battery Charging Profile with Intermittent Charging Enabled
7.3.2.2 Charging Safety Timers
The device has built-in safety timers to prevent an extended charging cycle due to abnormal battery conditions.
When the safety timer expires, the charge cycle ends.
During thermal regulation, the safety timer counts at half the clock rate as the actual charge current is likely to be
below the ISET setting. For example, if the charger is in thermal regulation throughout the whole charging cycle
and the safety timer is 10 hours, then the timer will expire in 20 hours.
During faults which disable charging, such as VIN OVP, BAT OVP, TSHUT, or TS faults, the timer is suspended.
If the charging cycle is stopped and started again, the timer is reset (toggle of the TS pin restarts the timer).
The safety timer restarts counting when the charging cycle stops and restarts. This can occur as a result of the
TS pin being toggled, the battery falling below the recharge threshold, or the input supply being toggled.
7.3.2.3 Battery Cold, Hot Temperature Qualification (TS Pin)
While charging, the device continuously monitors battery temperature by sensing the voltage at the TS pin.
A negative temperature coefficient (NTC) thermistor should be connected between the TS and GND pins
(recommend: 103AT-2). If temperature sensing is not required in the application, connect a fixed 10-kΩ resistor
from the TS pin to GND to allow normal operation. Battery charging is allowed when the TS pin voltage falls
between the VCOLD and VHOT thresholds (typically 0°C to 45°C).
If the TS pin indicates battery temperature is outside this range, the device stops charging and enters the
Standby state. Once battery temperature returns to normal conditions, charging resumes automatically.
In addition to battery temperature sensing, the TS pin can be used to disable the charger at any time by
pulling TS voltage below VTS_ENZ. The device disables the charger and consumes ISD_IN_TS from the input
supply. In order to minimize quiescent current, the TS current source (ITS_BIAS) is duty-cycled, with an on time
of tTS_DUTY_ON and an off time of tTS_DUTY_OFF. After the TS pin pulldown is released, the device may take up to
tTS_DUTY_OFF to turn ITS_BIAS back on. After the source is turned on, the TS pin voltage goes above VTS_EN and
reenables charger operation. The device treats this TS pin toggle as an input supply toggle, triggering a device
power up from input source (see Section 7.3.1).
14
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7.3.3 Status Outputs (STAT)
7.3.3.1 Charging Status Indicator (STAT)
The device indicates the charging state on the open-drain STAT pin as listed in the following table. This pin can
drive an LED.
Table 7-3. STAT Pin States
CHARGING STATE
STAT PIN STATE
Charge completed (TMR_EXP), charger in Sleep mode or charge
disabled
High
Charge in progress (including intermittent charge active)
Low
Fault (VIN OVP, BAT OVP, BAT OCP, or VSET, ISET, TMR pin short
or open)
Blink at 1 Hz
7.3.4 Protection Features
The device closely monitors input and output voltages, as well as internal FET current and temperature for safe
linear regulator operation.
7.3.4.1 Input Overvoltage Protection (VIN OVP)
If the voltage at the IN pin exceeds VIN_OV, the device turns off, the safety timer suspends counting, and the
device enters Standby mode. Once the IN voltage recovers to a normal level, the charge cycle and the safety
timer automatically resume operation.
7.3.4.2 Output Overvoltage Protection (BAT OVP)
If the voltage at the OUT pin exceeds VOUT_OVP, the device immediately stops charging, the safety timer
suspends counting, and the device enters Standby mode. Once the OUT voltage recovers to a normal level, the
charge cycle and the safety timer resume operation.
7.3.4.3 Output Overcurrent Protection (BAT OCP)
During normal operation, the OUT current should be regulated to the ISET programmed value. However, if a
short circuit occurs on the ISET pin, the OUT current may rise to an unintended level. If the current at the OUT
pin exceeds IOUT_OCP, the device turns off after a deglitch, tOUT_OCP_DGL, the safety timer resets the count, and
the device remains latched off. An input supply or pin toggle is required to restart operation.
IOUT_OCP
ICHG
tOUT_OCP_DGL
RISET
Short Circuit
event on ISET
Charger
latched off
Figure 7-3. Overcurrent Protection
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7.3.4.4 Thermal Regulation and Thermal Shutdown (TREG and TSHUT)
The device monitors its internal junction temperature (TJ) to avoid overheating and to limit the IC surface
temperature. When the internal junction temperature exceeds the thermal regulation limit, the device
automatically reduces the charge current to maintain the junction temperature at the thermal regulation limit
(TREG). During thermal regulation, the safety timer runs at half the clock rate and the actual charging current is
reduced below the programmed value on the ISET pin.
Additionally, the device has thermal shutdown to turn off the linear regulator when the IC junction temperature
exceeds the TSHUT threshold. The charger resumes operation when the IC die temperature decreases below
the TSHUT falling threshold.
7.4 Device Functional Modes
7.4.1 Shutdown or Undervoltage Lockout (UVLO)
The device is in the shutdown state if the IN pin voltage is less than VIN_LOWV. The internal circuitry is powered
down, all the pins are high impedance, and the device draws from the input supply. Once the IN voltage rises
above the VIN_LOWV threshold, the IC enters Sleep mode or Active mode depending on the OUT pin voltage.
7.4.2 Sleep Mode
The device is in Sleep mode when VIN_LOWV < VIN < VOUT + VSLEEPZ. The device waits for the input voltage to
rise above VOUT + VSLEEPZ to start operation.
7.4.3 Active Mode
The device is powered up and charges the battery when the TS pin is above VTS_ENZ and the IN voltage ramps
above both VIN_LOWV and VOUT + VSLEEPZ. The device draws IQ_IN from the supply to bias the internal circuitry.
For details on the device power-up sequence, refer to Section 7.3.1.
7.4.3.1 Standby Mode
The device is in Standby mode if a valid input supply is present and charge is terminated or if a recoverable fault
is detected. The internal circuitry is partially biased, and the device continues to monitor for either VOUT to drop
below VRECHG or the recoverable fault to be removed.
7.4.4 Fault Mode
The fault conditions are categorized into recoverable and nonrecoverable as follows:
• Recoverable, from which the device should automatically recover once the fault condition is removed:
– VIN OVP
– BAT OVP
– TS HOT
– TS COLD
• Nonrecoverable, requiring pin or input supply toggle to resume operation:
– BAT OCP
– ISET pin short detected
– Charge timer expires with VOUT below VRECHG
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8 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, as well as validating and testing their design
implementation to confirm system functionality.
8.1 Application Information
A typical application consists of the device configured as a standalone battery charger for a 1-cell to 6-cell NiMH
battery. The charge voltage and number of cells is configured using a pulldown resistor on the VSET pin. The
charge current is configured using a pulldown resistor on the ISET pin. A battery thermistor may be connected
to the TS pin to allow the device to monitor battery temperature and control charging. Pulling the TS pin below
VTS_ENZ disables the charging function. The safety timer is programmable through a pullown resistor on the TMR
pin. Faults are indicated through the STAT pin.
8.2 Typical Applications
8.2.1 NiMH Charger Design Example
VIN: 3.0V ± 18V
IN
OUT
1s ± 6s NiMH
VREF
VSET
STAT
ISET
TS
GND
BQ25172
TMR
Figure 8-1. BQ25172 Simple Schematic
8.2.1.1 Design Requirements
The design requirements include the following:
•
•
•
•
•
•
•
Input supply up to 18 V
Battery: 4-cell NiMH, RVSET = 11 kΩ
Fast charge current: ICHG = 30 mA
Recharge voltage for intermittent cycles: VRECHG = 1.33V x 4 = 5.32 V
Charge safety timer: RTMR = 8.2 kΩ, tSAFETY: 16 hr
TS – Battery temperature sense = 10-kΩ NTC (103AT-2)
TS can be pulled low to disable charging
8.2.1.2 Detailed Design Procedure
The regulation voltage is set via the VSET pin to 2s NiMH, the input voltage is 5 V and the charge current is
programmed via the ISET pin to 500 mA.
RISET = [KISET / ICHG]
from electrical characteristics table. . . KISET= 300 AΩ
RISET = [300 AΩ/0.5 A] = 600 Ω
Selecting the closest 1% resistor standard value, use a 604-Ω resistor between ISET and GND, for an expected
ICHG 497 mA.
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8.2.1.3 Application Curves
CIN = 1 µF, COUT = 1 µF, VIN = 5 V, VOUT = 3.8 V (unless otherwise specified)
RISET = 0.6 kΩ
RISET = 0.6kΩ OUT = open-circuit
Figure 8-2. Power Up with Battery
VIN = 5 V → 0 V
Figure 8-3. Power Up without Battery
TS pulled LOW
Figure 8-4. Power Down with Battery
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TS pin released
VIN = 5 V → 10 V
Figure 8-6. Charge Enable
Figure 8-7. Input OVP Response
VIN = 20 V → 10 V
ISET = 0 Ω
Figure 8-8. Input OVP Recovery
Figure 8-9. ISET Short-Circuit Then Power Up
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9 Power Supply Recommendations
The device is designed to operate from an input voltage supply range between 3 V and 18 V (tolerant up to 30 V)
and current capability of at least the maximum designed charge current. If located more than a few inches from
the IN and GND pins, a larger capacitor is recommended.
10 Layout
10.1 Layout Guidelines
To obtain optimal performance, the decoupling capacitor from the IN pin to the GND pin and the output filter
capacitor from the OUT pin to the GND pin should be placed as close as possible to the device, with short trace
runs to both IN, OUT, and GND.
•
•
All low current GND connections should be kept separate from the high current charge or discharge paths
from the battery. Use a single-point ground technique incorporating both the small signal ground path and the
power ground path.
The high current charge paths into the IN pin and from the OUT pin must be sized appropriately for the
maximum charge current in order to avoid voltage drops in these traces.
10.2 Layout Example
OUT
GND
VREF
0402
0402
TMR
/PG
STAT
IN
OUT
ISET
VSET
TS
TMR
GND
STAT
0402
VSET
0402
0402
GND
0402
IN
GND
Figure 10-1. BQ25172 Layout Example
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. Click on
Subscribe to updates to register and receive a weekly digest of any product information that has changed. For
change details, review the revision history included in any revised document.
11.3 Support Resources
TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight
from the experts. Search existing answers or ask your own question to get the quick design help you need.
Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do
not necessarily reflect TI's views; see TI's Terms of Use.
11.4 Trademarks
TI E2E™ is a trademark of Texas Instruments.
All trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled
with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric changes could cause the device not to meet its published
specifications.
11.6 Glossary
TI Glossary
This glossary lists and explains terms, acronyms, and definitions.
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12 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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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)
Samples
(4/5)
(6)
BQ25172DSGR
ACTIVE
WSON
DSG
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
B172
(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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