bq2000T
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SLUS149D – MAY 1999 – REVISED JANUARY 2010
Programmable Multi-Chemistry Fast-Charge Management IC
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FEATURES
1
•
•
•
•
•
•
•
•
Safe Management of Fast Charge for NiCd,
NiMH, or Li-Ion Battery Packs
High-Frequency Switching Controller for
Efficient and Simple Charger Design
Pre-Charge Qualification for Detecting
Shorted, Damaged, or Overheated Cells
Fast-Charge Termination by ΔT/Δt for Nickel
Chemistries, Minimum Current for Li-Ion
Chemistries, Maximum Temperature, and
Maximum Charge Time
Selectable Top-Off Mode for Achieving
Maximum Capacity in NiMH Batteries
Programmable Trickle-Charge Mode for
Reviving Deeply Discharged Batteries and for
Postcharge Maintenance
Built-in Battery Removal and Insertion
Detection
Sleep Mode for Low Power Consumption
APPLICATIONS
•
•
•
Multi-Chemistry Charger
Nickel Charger
High-Power, Multi-Cell Charger
GENERAL DESCRIPTION
The bq2000T is a programmable, monolithic IC for
fast-charge management of nickel cadmium (NiCd),
nickel metal-hydride (NiMH), or lithium-ion (Li-Ion)
batteries in single- or multi-chemistry applications.
The bq2000T chooses the proper battery chemistry
(either nickel or lithium) and proceeds with the
optimal charging and termination algorithms. This
process eliminates undesirable, undercharged, or
overcharged conditions, and allows accurate and safe
termination of fast charge.
Depending on the chemistry, the bq2000T provides a
number of charge termination criteria:
• Rate of temperature rise (ΔT/Δt) (for NiCd and
NiMH)
• Minimum charge current (for Li-Ion)
• Maximum temperature
• Maximum charge time
For safety, the bq2000T inhibits fast charge until the
battery voltage and temperature are within
user-defined limits. If the battery voltage is below the
low-voltage
threshold,
the
bq2000T
uses
trickle-charge to condition the battery. For NiMH
batteries, the bq2000T provides an optional top-off
charge to maximize the battery capacity.
The integrated high-speed comparator allows the
bq2000T to be the basis for a complete,
high-efficiency battery charger circuit for both
nickel-based and lithium-based chemistries.
8-Pin DIP or Narrow SOIC or TSSOP
spacer between para and illustration
Pin Names
SNS
Current-sense input
SNS
1
8
MOD
VSS
System ground
VSS
2
7
VCC
LED
Charge-status output
BAT
Battery-voltage input
LED
3
6
RC
TS
Temperature-sense input
BAT
4
5
TS
RC
Timer-program input
VCC
Supply-voltage input
MOD
Modulation-control output
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1999–2010, Texas Instruments Incorporated
bq2000T
SLUS149D – MAY 1999 – REVISED JANUARY 2010
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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.
PIN DESCRIPTIONS
SNS
Current-sense input
Enables the bq2000T to sense the battery current via the voltage developed on this pin by an
external sense-resistor connected in series with the battery pack
VSS
System ground
Connect to the battery’s negative terminal
LED
Charge-status output
Open-drain output that indicates the charging status by turning on, turning off, or flashing an external
LED, driven through a resistor.
BAT
Battery-voltage input
Battery-voltage sense input. A simple resistive divider, across the battery terminals, generates this
input.
TS
Temperature-sense input
Input for an external battery-temperature monitoring circuit. An external resistive divider network with
a negative temperature-coefficient thermistor sets the lower and upper temperature thresholds.
RC
Timer-program input
Used to program the maximum fast charge-time, maximum top-off charge-time, hold-off period, trickle
charge rate, and to disable or enable top-off charge. A capacitor from VCC and a resistor to ground
connect to this pin.
VCC
Supply-voltage input
Recommended bypassing is 10 µF + 0.1 µF to 0.22 µF of decoupling capacitance near the pin.
MOD
Modulation-control output
Push-pull output that controls the charging current to the battery. MOD switches high to enable
charging current to flow and low to inhibit charging-current flow.
2
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FUNCTIONAL DESCRIPTION
The bq2000T is a versatile, multi-chemistry battery charge control device. See Figure 1 for a functional block
diagram and Figure 2 for a state diagram.
TS
Voltage
Reference
BAT
OSC
Voltage
Comparators 3x
ADC
DT/Dt
ALU
Clock
Phase
Generator
Timer
Charge
Control
LED
Voltage
Comparators
MOD
RC
Internal
OSC
SNS
VCC
VSS
Figure 1. Functional Block Diagram
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VCC Reset
or
Battery Replacement at any time
4.0 V < VCC < 6.0 V
Charge
Initialization
VBAT < VSLP
VMCV < VBAT < VSLP
Battery Voltage (Voltage at BAT pin
checked continuously.)
Sleep
Mode
Charge
Qualification
State
VSLP < VBAT < VCC
VBAT < VMCV
VTS > VHTF
Charge
Suspended
Battery Temperature
(Temperature at TS pin checked
continuously. Sampled every 8 seconds
for DT/Dt.)
VTS < VHTF
VTS < VHTF
VLBAT < VBAT < VMCV and
VHTF < VTS < VLTF
VBAT < VLBAT or
VTS > VLTF
VTS > VLTF
Battery
Conditioning
Current
Regulation
VLBAT < VBAT and
VHTF < VTS < VLTF
DT/Dt (after hold-off period),
or VTS < VTCO or
Time = MTO
NO
Trickle
Maintenance
Charge
Top-Off
Selected?
VTS > VLTF
Fast Charge State
VTS > VLTF
Time < MTO
and
VBAT reaches VMCV
Voltage
Regulation
YES
Current Taper (IBAT < Imin).
or
Time = 2 x MTO or VTS < VTCO
VTS < VLTF and
Time < MTO
VTS > VHTF
Top-Off
Time = MTO
VBAT ≥ VMCV
Done
VBAT ≥ VMCV
VTS < VHTF
Charge
Suspended
(See Note)
VTS < VHTF
VTS > VHTF
and Time < MTO
VCC Reset or Battery Replacement or Capacity Depletion (Li-lon)
NOTE: If VTS < VTCO at any time, may only return to Trickle Maintenance Charge state and not to Top-Off.
Figure 2. State Diagram
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ABSOLUTE MAXIMUM RATINGS (1)
VALUE
UNIT
–0.3 to 7
V
–0.3 to VCC
V
Operating ambient temperature
–20 to 70
°C
Storage temperature
–40 to 125
°C
260
°C
VCC
VCC relative to VSS
VT
DC voltage applied on any pin, relative to VSS
TOPR
TSTG
TSOLDER
Soldering temperature (10 s max)
(1)
Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the
Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended
periods of time may affect device reliability.
DC THRESHOLDS (1)
TA = TOPR; VCC = 5 V ± 20% (unless otherwise specified)
PARAMETER
TEST CONDITIONS
TYPICAL
TOLERANCE
UNIT
VTCO
Temperature cutoff
Voltage at the TS pin
0.225 × VCC
±5%
V
VHTF
High-temperature fault
Voltage at the TS pin
0.25 × VCC
±5%
V
VLTF
Low-temperature fault
Voltage at the TS pin
0.5 × VCC
±5%
V
VMCV
Maximum cell voltage
Voltage at the BAT pin
2.00
±0.75%
VLBAT
Minimum cell voltage
Voltage at the BAT pin
950
±5%
mV
VTHERM
TS input change for ΔT/Δt detection
Voltage at the TS pin
-VCC/161
±25%
V/min
VSNSHI
High threshold at SNS
Voltage at the SNS pin
50
±10
mV
VSNSLO
Low threshold at SNS
Voltage at the SNS pin
–50
±10
mV
VSLP
Sleep-mode input threshold
Voltage at the BAT pin
VCC–1
±0.5
V
VRCH
Recharge threshold
Voltage at the BAT pin
VMCV–0.1
±0.02
V
UNIT
(1)
V
All voltages are relative to VSS except as noted.
RECOMMENDED DC OPERATING CONDITIONS
over operating free-air temperature range (unless otherwise noted)
TEST CONDITIONS
VCC
Supply voltage
ICC
Supply current
Exclusive of external loads
ICCS
Sleep current
VBAT = VSLP
VTS
Thermistor input
VTS < 0.5 V prohibited
VOH
Output high
MOD, IOH = 10 mA
VOL
Output low
MOD, LED, IOL = 10 mA
IOZ
High-impedance leakage current
LED
Isnk
Sink current
MOD, LED
RMTO
Charge timer resistor
CMTO
Charge timer capacitor
MIN
NOM
MAX
4
5
6
V
0.5
1
mA
5
µA
VCC
V
0.5
VCC–0.4
V
0.2
V
5
µA
20
mA
2
250
kΩ
0.001
1
µF
IMPEDANCE
PARAMETER
MIN
TYP
MAX
UNIT
RBAT
Battery input impedance
10
MΩ
RTS
TS input impedance
10
MΩ
RSNS
SNS input impedance
10
MΩ
TIMING
TA = TOPR; VCC = 5 V ± 20% (unless otherwise noted)
PARAMETER
dMTO
MTO time-base variation
fTRKL
Pulse-trickle frequency
MIN
TYP
–5%
0.9
MAX
UNIT
5%
1
1.1
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bq2000T
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Initiation and Charge Qualification
The bq2000T initiates a charge cycle when it detects
• Application of power to VCC
• Battery replacement
• Exit from sleep mode
• Capacity depletion (Li-Ion only)
Immediately following initiation, the IC enters a charge-qualification mode. The bq2000T charge qualification is
based on battery voltage and temperature. If the voltage on the BAT pin is less than the internal threshold, VLBAT,
the bq2000T enters the battery conditioning state. This condition indicates the possibility of a defective or shorted
battery pack. In an attempt to revive a fully depleted pack, the bq2000T enables the MOD pin to trickle-charge at
a rate of once every 1.0s. As explained in the section "Top-Off and Pulse-Trickle Maintenance Charge," the
trickle pulse-width is user-selectable and is set by the value of the resistance connected between the RC pin and
VSS.
During charge qualification, the LED pin blinks at a 1-Hz rate, indicating the pending status of the charger.
Once battery conditioning (trickle charge) has raised the voltage on the BAT pin above VLBAT, the IC enters fast
charge, if the battery temperature is within the VLTF to VHTF range. The bq2000T stays in the battery conditioning
state indefinitely and does not progress to fast charge until the voltage on the BAT pin is above VLBAT and the
temperature is within the VLTF and VHTF range. No timer is implemented during battery conditioning.
Battery Chemistry
The bq2000T detects the battery chemistry by monitoring the battery-voltage profile during the initial stage of the
fast charge. If the voltage on the BAT pin rises to the internal VMCV reference, the IC assumes a Li-Ion battery.
Otherwise, the bq2000T assumes a NiCd/NiMH chemistry. While in the fast charge state, the LED pin is pulled
low (the LED is on).
As shown in Figure 3, a resistor voltage-divider between the battery pack's positive terminal and VSS scales the
battery voltage. A low-pass filter then smooths out this voltage to present a clean signal to the BAT pin. In a
mixed-chemistry design, a common voltage-divider is used as long as the maximum charge voltage of the
nickel-based pack is below that of the Li-Ion pack. Otherwise, different scaling is required.
BAT+
2
VSS
bq2000T
4
RB1
BAT
RB2
Figure 3. Battery Voltage Divider and Filter
Once the chemistry is determined, the bq2000T completes the fast charge with the appropriate charge algorithm
(Table 1). The user can customize the algorithm by programming the device using an external resistor and a
capacitor connected to the RC pin, as discussed in later sections.
NiCd and NiMH Batteries
Following charge qualification (which includes trickle charge, if required), the bq2000T fast-charges NiCd or
NiMH batteries using a current-limited algorithm. During the fast-charge period, it monitors charge time,
temperature, and voltage for adherence to the termination criteria. This monitoring is further explained in later
sections. Following fast charge, the battery is topped off, if top-off is selected. The charging cycle ends with a
trickle maintenance-charge that continues as long as the voltage on the BAT pin remains below VMCV.
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Lithium-Ion Batteries
The bq2000T uses a two-phase fast-charge algorithm for Li-Ion batteries (Figure 4). In phase one, the bq2000T
regulates constant current until VBAT rises to VMCV. Once VBAT = VMCV, the device identifies the cell as a Li-ion,
and changes the termination method from ΔT/Δt to minimum current. The bq2000T then moves to phase two,
regulates the battery with constant voltage of VMCV, and terminates when the charging current falls below the IMIN
threshold or the timer expires (whichever happens first). A new charge cycle is started if the cell voltage falls
below the VRCH threshold.
Current
IMAX
Charge
Qualification
VMCV
Voltage
Fast
Charge
Phase 1
VLBAT
Phase 2
Current
IMIN
Voltage
Trickle
Time
Figure 4. Lithium-Ion Charge Algorithm
During the current-regulation phase, the bq2000T monitors charge time, battery temperature, and battery voltage
for adherence to the termination criteria. During the final constant-voltage stage, in addition to the charge time
and temperature, it monitors the charge current as a termination criterion. There is no post-charge maintenance
mode for Li-Ion batteries.
Table 1 summarizes the charging process for both Nickel and Li-Ion batteries.
Table 1. Charge Algorithm
BATTERY CHEMISTRY
CHARGE ALGORITHM
1. Charge qualification
2. Trickle charge, if required
NiCd or NiMH
(VBAT < VMCV always)
3. Fast charge (constant current)
4. Fast charge termination (rate of temperature rise, maximum charge time = 1 MTO)
5. Top-off (optional)
6. Trickle charge
1. Charge qualification
2. Trickle charge, if required
Li-Ion
(VBAT ≤ VMCV )
3. Fast charge (constant current)
4. Fast charge (constant voltage)
5. Charge termination (minimum current, maximum charge time = 2 MTO)
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FAST CHARGE TERMINATION
Initial Hold-Off Period
The bq2000T incorporates a user programmable hold-off period to avoid premature fast charge termination that
can occur with brand new nickel cells at the very beginning of fast charge. The values of the external resistor and
capacitor connected to the RC pin set the initial hold-off period. During this period, the bq2000T avoids early
termination due to an initial rise in the battery temperature by disabling the rate of temperature rise (ΔT/Δt)
feature. This period is fixed at the programmed value of the maximum charge time (MTO) divided by 32.
MTO
hold-off period =
32
(1)
Maximum Charge Time (NiCd, NiMH, and Li-Ion)
The bq2000T sets the maximum charge-time through the RC pin. With the proper selection of external resistor
and capacitor values, various time-out values may be achieved. If the timer expires while still in constant-current
charging, the bq2000T assumes a Nickel chemistry and proceeds to top-off charge (if top-off is enabled) or trickle
maintenance charge. Figure 5 shows a typical connection.
2
VSS
VCC
7
bq2000T
CMTO
RC
6
RMTO
Figure 5. Typical Connection for the RC Input
The following equation shows the relationship between the RMTO and CMTO values and the maximum charge time
(MTO) for the bq2000T:
MTO = RMTO ´ CMTO ´ 35,988
(2)
MTO is measured in minutes, RMTO in ohms, and CMTO in farads. (Note: RMTO and CMTO values also determine
other features of the device. See Table 4 and Table 5 for details.)
If, during fast charge, VTS > VLTF, then the timer is paused and the IC enters battery conditioning charge until VTS
< VLTF. Since the IC is in the battery conditioning state, the LED flashes at the 1 Hz rate. Once VTS< VLTF, fast
charge restarts and the timer resumes from where it left off with no change in total fast charge time.
For Li-Ion cells, when the battery reaches the constant-voltage phase of fast charge, the bq2000T adds an
additional MTO of time to whatever time was left over from the constant current fast charge timer. Thus, the pack
could spend longer than 1 MTO in constant-voltage fast charge, but is always limited to 1 MTO in
constant-current fast charge. This feature provides the additional charge time required for Li-Ion cells.
For Nickel cells, if top-off is enabled, the timer is reset on the completion of fast charge before beginning top-off
charge.
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Maximum Temperature (NiCd, NiMH, Li-Ion)
A negative-coefficient thermistor, referenced to VSS and placed in thermal contact with the battery, may be used
as a temperature-sensing device. Figure 6 shows a typical temperature-sensing circuit.
VCC
2
VCC 7
VSS
RT1
bq2000T
TS
5
RT2
N Battery
T Pack
C
Figure 6. Temperature Monitoring Configuration
During fast charge, the bq2000T compares the battery temperature to an internal high-temperature cutoff
threshold, VTCO, and a low-temperature threshold, VLTF. During fast charge only, the VHTF fault comparator is
disabled. When the voltage at the TS pin is lower than VTCO, the bq2000T terminates fast charge, moves to the
charge suspended state, and turns off the LED. When VTS rises above VHTF, the bq2000T resumes charging in
the trickle maintenance charge state, per Figure 2. In fast charge (either constant current or constant voltage fast
charge), when the voltage on the TS pin is higher than VLTF, the charger enters the battery conditioning state, as
described in the previous section. Fast charge is resumed when VTS is less than VLTF.
Rate of Temperature Rise (NiCd, NiMH)
The bq2000T uses a rate of temperature rise (ΔT/Δt) scheme to terminate fast charge for NiCd and NiMH
batteries. During fast charge, it samples the TS pin voltage every 8 seconds and compares it to the value
measured 2 samples earlier. This feature terminates fast charge if this voltage declines at a rate of VCC/161
(V/min). Figure 6 shows a typical connection diagram. In preparation for sampling the TS pin voltage, the
bq2000T briefly turns off most circuits (the MOD and RC pins both go low) in order to get the cleanest possible,
noise-free measurement. While the monitoring of the TS pin voltage is continuous, the sampling of the TS pin
voltage with the internal ADC only occurs during the constant current regulation phase of fast charge. If the cell
voltage reaches VMCV, the pack is assumed to be Li-Ion and the TS pin voltage sampling is disabled, as ΔT/Δt is
not a termination criterion for Lithium cells.
Minimum Current (Li-Ion Only)
The bq2000T monitors the charging current during the voltage-regulation phase of Li-Ion batteries. Fast charge is
terminated when the current is tapered off to 7% of the maximum charging current. Note that this threshold is
different for the bq2000.
Once constant-current fast charge has ended, the bq2000T either measures the value of the CMTO capacitor (in
the case of Nickel batteries) and then proceeds to either top-off or trickle maintenance charge or simply
completes the constant-voltage stage of fast charge (in the case of a Li-Ion cell).
Top-Off and Pulse-Trickle Maintenance Charge
An optional top-off charge is available for NiCd or NiMH batteries. Top-off may be desirable on batteries that
have a tendency to terminate charge before reaching full capacity. To enable this option, the capacitance value
of CMTO connected between the RC pin and VCC (Figure 5) should be greater than 0.13 µF , and the value of the
resistor connected to this pin should be less than 250 kΩ . To disable top-off, the capacitance value should be
less than 0.07 µF. The tolerance of the capacitor needs to be taken into account in component selection.
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Once top-off is started, the timer is reset and top-off proceeds until the timer expires, VMCV is reached, or there is
a temperature fault. During top-off, current is delivered to the battery in pulses that occur each second. The fixed
pulse width allows an average current of 1/16 of the fast charge current to be delivered to the battery every
second. The LED is always off during top-off and trickle maintenance charge.
During top-off, there are three different temperature faults that can occur. If VTS > VLTF, top-off is suspended, the
timer is paused, and trickle charge is started. When VTS falls below VLTF, top-off is resumed. If VTS < VHTF, all
charging stops, but the timer keeps counting. When VTS > VHTF, top-off is resumed, if there is still time remaining
on the timer. If there is not time left, trickle maintenance charge is entered. If VTS < VTCO, all charging stops. Only
trickle maintenance charge may resume after VTS > VHTF.
Pulsewidth - ms
Following top-off, the bq2000T trickle-charges the battery by enabling the MOD pin to charge at a rate of once
every 1.0 second. The trickle pulse-width is user-selectable and is set by the value of the resistor RMTO,
connected between the RC pin and VSS. Figure 7 shows the relationship between the trickle pulse-width and the
value of RMTO. The typical tolerance of the pulsewidth below 150 kΩ is ±10%.
200
180
160
140
120
100
80
60
40
20
4
3
2
1
Shows Tolerance
2
4
6
8
10
50
100
RMTO - kW
150
200
250
Figure 7. Relationship Between Trickle Pulse-Width and Value of RMTO
Note that with an RMTO value around 150 kΩ, the trickle charge pulse width is nearly identical to the top-off pulse
width of 62.5 ms (1/16 of a second for a 1A fast charge current). With RMTO values near 150 kΩ, it can be difficult
to tell which state the IC is in (top-off or trickle charge). The best way to tell if the bq2000T is in top-off or trickle
charge is to look at the RC pin when the temperature is between the LTF and HTF. In top-off, the RC pin is
counting and has a sawtooth waveform on it. In trickle charge, there is no timer and the RC pin is at a DC value.
The RC pin contains valuable information in determining what state the bq2000T is in, since it always operates in
one of three modes. If the RC pin is low (around VSS potential), the IC is in sleep mode. (If the RC pin is low for
brief instants during fast charge, the bq2000T is sampling the TS pin for ΔT/Δt). If the RC pin is at some DC
value (usually around 1 V to 2 V), then the IC has paused the timer or the timer is inactive. If the RC pin is a
sawtooth waveform (similar to Figure 15), then the timer is running and the RC pin is considered “active.” Lastly,
the RC pin can be loaded by too large of a C or too small of an R. This sometimes makes the usual sawtooth
waveform look like a triangle waveform on an oscilloscope (the rise time is lengthened), or the RC signal could
have the appearance of being clipped (flat top or bottom). The timer is unreliable under these conditions and the
bq2000T should not be operated in this manner. Table 2 summarizes the different states of the RC pin.
Table 2. RC Pin Status
bq2000T CHARGE STATE
TS PIN STATE
RC PIN BEHAVIOR
Battery absent
N/A
1-V to 2-V DC level
Sleep mode
N/A
Ground (VSS)
Charge qualification (including battery
conditioning (trickle charge) and charge
suspended)
N/A
1-V to 2-V DC level
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Table 2. RC Pin Status (continued)
bq2000T CHARGE STATE
TS PIN STATE
RC PIN BEHAVIOR
VTS < VLTF
Active
VTS > VLTF (in battery conditioning state)
1-V to 2-V DC level (timer is paused and
resumes when VTS < VLTF)
VTS > VLTF (in trickle maintenance charge
state)
1-V to 2-V DC level (timer is paused and
resumes when VTS < VLTF)
VLTF > VTS > VHTF
Active
VHTF > VTS > VTCO
Active (timer is still counting, even though
charging is suspended)
Trickle maintenance charge (after fast charge)
N/A
1-V to 2-V DC level
Charge complete
N/A
Active
Fast charge (current and voltage regulation)
Top-off charge
Both top-off and trickle maintenance charge are terminated and the pack never receives any more charge (until a
charge initialization occurs) if the voltage on the BAT pin reaches VMCV. During trickle maintenance charge,
charging is suspended if VTS < VHTF. It resumes when VTS > VHTF. The bq2000T is designed to remain in trickle
maintenance charge forever (excluding the two faults just mentioned) in order to keep a Nickel pack full.
Charge Current Control
The bq2000T implements a hysteretic control loop that regulates the current being delivered to the battery pack
to a user programmable value that is set by the value of the RSNS resistor. A second, outer control loop reduces
the average current delivered to the pack in order to clamp the voltage at the BAT pin to a maximum of VMCV.
The bq2000T controls the MOD pin to regulate the current and voltage of the pack. The bq2000T monitors
charge current at the SNS input by sensing the voltage drop across a sense-resistor, RSNS, in series with the
battery pack. See Figure 8 for a typical current-sensing circuit.
Rf
RSNS
1 SNS
Cf
2
BAT-
VSS
bq2000T
Power Supply ground
bq2000T ground and BAT-
Figure 8. Current-Sensing Circuit
RSNS is sized to provide the desired fast-charge current (IMAX).
0.05
IMAX =
RSNS
(3)
If the voltage at the SNS pin is greater than VSNSLO or less than VSNSHI, the bq2000T switches the MOD output
high to pass charge current to the battery. When the SNS voltage is less than VSNSLO or greater than VSNSHI, the
bq2000T switches the MOD output low to shut off charging current to the battery. A hysteresis capacitor (CHYS) is
required between the CMOD pin and the SNS pin to add a healthy amount of hysteresis to the current sense
signal. Typical hysteresis values are between 5 mV and 25 mV. The amount of hysteresis can be calculated by
examining the capacitive divider formed by CHYS and Cf.
CHYS
Hysteresis (V) = VCC ´
(C HYS + Cf )
(4)
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Being a hysteretic controller, the switching frequency of the bq2000T is determined by the values of several of
the external circuit components. The components that affect the switching frequency are: input voltage, RSNS
value, inductor value, hysteresis capacitor value (CHYS), and the value of the filter on the current sense signal (Rf
and Cf values). Rf and Cf have the most impact on the switching frequency and are also the components that are
easiest to change to adjust the frequency, as they do not affect anything else in the circuit (besides, of course,
the cleanliness and quality of the current sense signal being fed to the bq2000T). In general, increasing the input
voltage and/or inductor value or decreasing CHYS and/or the Rf × Cf filter corner frequency increases the
switching frequency. Figure 9 and Figure 10 show empirical data on the variation in switching frequency based
on adjusting Rf and Cf. This data was taken with an input voltage of 12 V, inductor value of 220 µH, RSNS value
of 50 mΩ, and CHYS value of 4.7 pF. Typical switching frequencies for the bq2000T are between 100 and 200
kHz, though it is possible to achieve switching frequencies in excess of 300 kHz.
180
160
fs - Switching Frequency - kHz
Rf = 748W
140
120
100
80
60
40
20
0
220
720 1220 1720 2220 2720 3220 3720 4220
Cf - pF
Figure 9. Switching Frequency vs Capacitance
210
fs - Switching Frequency - kHz
190
Cf = 1000pF
170
150
130
110
90
70
50
200 300 400 500 600 700 800 900 1000 1100 1200
Rf - W
Figure 10. Switching Frequency vs Resistance
12
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SLUS149D – MAY 1999 – REVISED JANUARY 2010
BATTERY VOLTAGE INPUT
As shown in Figure 3, a resistor voltage-divider between the battery pack's positive terminal and VSS scales the
battery voltage measured at the BAT pin.
For Li-Ion battery packs, the resistor values RB1 and RB2 are calculated by the following equation:
RB1
RB2
æ
V
= ç N ´ CELL
VMCV
è
ö
÷ -1
ø
(5)
where N is the number of cells in series and VCELL is the manufacturer-specified charging voltage. RB1 + RB2
should be at least 200 kΩ and no more than 1 MΩ.
A NiCd or NiMH battery pack consisting of N series cells may benefit by the selection of the RB1 value to be N–1
times larger than the RB2 value. This sets the per cell regulation voltage (VCELL) equal to VMCV. It is critical that
VCELL be set high enough that the nickel pack not reach voltage regulation, thus allowing proper termination by
ΔT/Δt. The typical VCELL setting for a nickel pack is between 1.7 V and 2 V.
In a mixed-chemistry design, a common voltage-divider is used as long as the maximum charge voltage of the
nickel-based pack is below that of the Li-Ion pack. Otherwise, different scaling is required. See Figure 11 for an
example.
Q1
FMMT718
D4
DC+
S1A
D3
MMSD914LT
C6
47 mF
D5
MMSD914LT
L1
BAT+
47 mH
Q2
MMBT3904LT1
D2
ZHCS1000
R12
120 W
C9
R10
1 kW
1000 pF
Q3
MMBT3904LT1
VCC
C3
10 mF
R2
2 kW
D6
BZT52-C5V1
C7
C4
4.7 pF
0.0022 mF
R1
D1
U1
1 SNS
2 VSS
3 LED
4
BAT
RED
R11
220 W
C2
C8
0.33 mF
C5
10 mF
R4
12.4 kW
100 kW
8
7
6
5
MOD
VCC
RC
TS
THERM
bq2000T
0.1 mF
R6
210 kW
C1
0.1 mF
R8
6.81 kW
R9
R5
20 kW
CHEMISTRY
221 kW
BATR7
200 kW
R13
1.1 kW
R3
0.05 W
DCNOTES:
1. For Li-Ion, CHEMISTRY is left floating.
For NiCd/NiMH, CHEMISTRY is tied to BAT2. DC input voltage: 9–16V
3. Charge current: 1A
4. L1: 3L Global P/N PKSMD-1005-470K-1A
Figure 11. Single-Cell Li-Ion, 3-Cell NiCd/NiMH 1-A Charger
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SLUS149D – MAY 1999 – REVISED JANUARY 2010
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TEMPERATURE MONITORING
The bq2000T measures the temperature by the voltage at the TS pin. This voltage is typically generated by a
negative-temperature-coefficient thermistor. The bq2000T compares this voltage against its internal threshold
voltages to determine if charging is safe. These thresholds are the following:
• High-temperature cutoff voltage: VTCO = 0.225 × VCC . This voltage corresponds to the maximum temperature
(TCO) at which any charging is allowed. The bq2000T terminates charging if the voltage on the TS pin falls
below VTCO.
• High-temperature fault voltage: VHTF = 0.25 × VCC . This voltage corresponds to a maximum allowed pack
temperature (HTF) in all states except for fast charge. During fast charge, HTF faults are disabled to allow for
a normal increase in pack temperature.
• Low-temperature fault voltage: VLTF = 0.5 × VCC . This voltage corresponds to the minimum temperature
(LTF) at which fast charging or top-off is allowed. If the voltage on the TS pin rises above VLTF, the bq2000T
suspends either fast charge or top-off and begins a trickle charge. When the voltage falls back below VLTF,
fast charge or top-off resumes from the point where suspended. If VTS > VLTF, the charger is always in trickle
charge.
Table 3 summarizes these various conditions.
Table 3. Temperature-Monitoring Conditions and Actions
TEMPERATURE
CONDITION
ACTION
During charge qualification, no effect
VTS > VLTF
Cold battery – checked at all times
VHTF < VTS < VLTF
Optimal charging range
During fast charge, suspends fast charge and moves into charge
qualification, pauses timer, and flashes LED
During top-off, suspends top-off and moves into trickle maintenance
charge and pauses timer
During trickle maintenance charge, no effect
Allows all stages of charging
During charge qualification, stops charging
VTS < VHTF
Hot battery – checked at all times,
except during fast charge
During fast charge, no effect
During top-off, stops charging
During trickle maintenance charge, stops charging
During charge qualification, stops charging
VTS < VTCO
Battery exceeding maximum
allowable temperature – checked at
all times
During fast charge, terminates fast charge and stops charging, turns off
LED
During top-off, terminates top-off and stops charging
During trickle maintenance charge, stops charging
Table 4. Summary of NiCd or NiMH Charging Characteristics
VALUE (1)
PARAMETER
Maximum cell voltage (VMCV)
2V
Minimum pre-charge qualification voltage (VLBAT)
950 mV
High-temperature cutoff voltage (VTCO)
0.225 × VCC
High-temperature fault voltage (VHTF)
0.25 × VCC
Low-temperature fault voltage (VLTF)
0.5 × VCC
bq2000T fast-charge maximum time out (MTO)
RMTO × CMTO × 35,988
Fast-charge charging current (IMAX)
0.05/RSNS
Hold-off period
MTO/32
Top-off charging current (optional)
IMAX/16
Top-off period (optional)
MTO
Trickle-charge frequency
1 Hz
Trickle-charge pulse-width
(1)
14
See Figure 7
See the DC Thresholds Specification for details.
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Table 5. Summary of Li-Ion Charging Characteristics
VALUE (1)
PARAMETER
Maximum cell voltage (VMCV)
2V
Minimum pre-charge qualification voltage (VLBAT)
950 mV
High-temperature cutoff voltage (VTCO)
0.225 × VCC
High-temperature fault voltage (VHTF)
0.25 × VCC
Low-temperature fault voltage (VLTF)
0.5 × VCC
2 × RMTO × CMTO × 35,988
(See Maximum Charge Time section for full explanation)
bq2000T fast-charge maximum time out (MTO)
Fast-charge charging current (IMAX)
0.05/RSNS
Hold-off period
MTO/32
Minimum current (for fast-charge termination)
IMAX/14
Trickle-charge frequency (before fast charge only)
1 Hz
Trickle-charge pulse-width (before fast charge only)
(1)
See Figure 7
See the DC Thresholds Specification for details.
Charge Status Display
The charge status is indicated by open-drain output LED. Table 6 summarizes the display output of the bq2000T.
A temperature fault or timer expiring changes the charge state immediately (according to Figure 2) and thus
changes the LED status immediately and accordingly.
Table 6. Charge Status Display
bq2000T CHARGE STATE
LED STATUS
Charge qualification (including battery conditioning and charge suspended)
1-Hz flash
Fast charge (current and voltage regulation)
Low
Top-off charge
Trickle maintenance charge (after fast charge)
Charge complete
High impedance
Battery absent
Sleep mode
Sleep Mode
The bq2000T features a sleep mode for low power consumption. This mode is enabled when the voltage at the
BAT pin is above the low-power-mode threshold, VSLP. During sleep mode, the bq2000T shuts down all
unnecessary internal circuits, drives the LED output to high-impedance state, and drives the MOD pin low.
Restoring BAT below the VMCV threshold initiates the IC and starts a fast-charge cycle. Normally, the bq2000T
only enters sleep mode when there is no battery connected on the output and the charger is idling with nothing to
charge. In addition, VIN needs to be high enough such that when VIN is present on the output, VBAT would be
greater than VSLP. In sleep mode, the output voltage decays to VMCV at which point the bq2000T turns on and
pulses the MOD pin several times. With no battery connected, the output rises to near VIN at which point the
bq2000T re-enters sleep mode. During sleep mode, the RC pin is at VSS potential. A typical sleep mode
waveform is shown in Figure 18.
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TYPICAL CHARACTERISTICS
CH1 = RC pin, 2V/div
CH1 = RC pin, 2V/div
1
CH2 = MOD pin, 5V/div
CH2 = MOD pin, 5V/div
Voltage - V
Voltage - V
2
CH3 = VO, 5V/div
2
CH3 = VI, 5V/div
3
CH4 = LED pin, 5V/div
1
CH4 = LED pin, 5V/div
4
3
4
Time - 0.2s/div
Time - 0.2s/div
Figure 12. bq2000T Start-up on Battery Insertion
Figure 13. bq2000T Start-up on Vin
CH1 = VO, 5V/div
CH2 = RC pin, 1V/div
CH1 = VO, 5V/div
1
Voltage - V
Voltage - V
1
CH2 = BAT pin, 1V/div
CH3 = MOD pin, 5V/div
3
2
CH3 = MOD pin, 5V/div
3
CH4 = LED pin, 1V/div
Time - 0.5s/div
4
Time - 0.5ms/div
Figure 14. Battery Removal During Fast Charge
16
2
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Figure 15. bq2000T in Fast Charge
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TYPICAL CHARACTERISTICS (continued)
CH1 = VO, 5V/div
1
CH2 = RC pin, 1V/div
CH1 = SNS pin, 20mV/div
CH3 = MOD pin, 5V/div
2
Voltage - V
Voltage - V
1
CH2 = MOD pin, 5V/div
3
2
4
CH4 = LED pin, 1V/div
Time - 2ms/div
Time - 10ms/div
Figure 16. bq2000T in Fast Charge
Figure 17. bq2000T Fast Charge SNS and MOD Waveforms
CH1 = VO, 10V/div
Voltage - V
1
CH2 = BAT pin, 1V/div
CH3 = RC pin, 2V/div
2
3
4
CH4 = MOD pin, 5V/div
Time - 1s/div
Figure 18. bq2000T Cycling In and Out of Sleep Mode (No battery present)
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REVISION HISTORY
Changes from Original (January 1999) to Revision 1
Page
•
Changed the device status From: Preliminary To: Final ....................................................................................................... 1
•
Added state diagram ............................................................................................................................................................. 4
•
Changed minimum current termination From: 14% To: 7% ................................................................................................. 9
•
Changed capacitor value for enabling top-off From: 0.13 µF To: 0.26 µF ........................................................................... 9
•
Changed Figure 11 ............................................................................................................................................................. 13
•
Changed VTCO ..................................................................................................................................................................... 14
•
Changed VHTF ..................................................................................................................................................................... 14
•
Changed VLTF ...................................................................................................................................................................... 14
Changes from Revision 1 (May 1999) to Revision 2
•
Page
Changed minimum current (for fast-charge termination) From: IMAX/7 To: IMAX/14 ............................................................. 15
Changes from Revision 2 (February 2000) to Revision 3
Page
•
Changed ordering information .............................................................................................................................................. 1
•
Changed Figure 1 - connection added between TS and ADC and connection deleted between BAT and ADC ................ 3
•
Changed Figure 2 - battery temperature From: (checked at all times) To: (sampled every 16 seconds for ΔT/Δt) ............ 4
Changes from Revision 3 (February 2001) to Revision 4
•
Changed resistor value From: 15 kΩ To: 250 kΩ ................................................................................................................. 9
Changes from Revision 4 (January 2008) to Revision D
•
18
Page
Page
Changed the data sheet throughout ..................................................................................................................................... 1
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PACKAGE OPTION ADDENDUM
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2-Dec-2022
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)
BQ2000TPN-B5
ACTIVE
PDIP
P
8
50
RoHS &
Non-Green
NIPDAU
N / A for Pkg Type
-20 to 70
2000T-B5
Samples
BQ2000TPW
ACTIVE
TSSOP
PW
8
150
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-20 to 70
BQ20T
Samples
BQ2000TPWR
ACTIVE
TSSOP
PW
8
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-20 to 70
BQ20T
Samples
BQ2000TSN-B5
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-20 to 70
2000T
Samples
BQ2000TSN-B5TR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-20 to 70
2000T
Samples
(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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