Texas Instruments DV2954S1L, DV2954S1H, BQ2954SNTR, BQ2954SN, BQ2954PN Datasheet
Features
➤
Safe charge of Li-Ion battery
packs
➤
Pulse-width modulation control
for current and voltage regulation
➤
Programmable high-side/low-side
current-sense
➤
Fast charge terminated by se
lectable minimum current; safety
backup termination at maximum
time
➤
Pre-charge qualification detects
shorted or damaged cells and
conditions battery
➤ Charging continuously qualified
by temperature and voltage limits
➤ Direct LED control outputs to
display charge status and fault
conditions
General Description
The bq2954 Li-Ion Charge-Manage
ment IC uses a flexible pulse-width
modulation regulator to control volt
age and current during charging.
The regulator frequency is set by an
external capacitor for design flexi
bility. The switch-mode design mini
mizes power dissipation.
For safety, the bq2954 inhibits fast
charging until the battery voltage
and temperature are within config
ured limits. If the battery voltage is
less than the low-voltage threshold,
the bq2954 provides low-current
conditioning of the battery.
For charge qualifiction, the bq2954
uses an external thermistor to measure battery temperature. Charging
begins when power is applied or the
battery is inserted
The bq2954 charges a battery in two
phases. First a constant-current
phase replenishes approximately
70% of battery capacity. Then a volt
age-regulation phase completes the
battery charge.
The bq2954 provides status indica
tions of all charger states and faults
for accurate determination of the
battery and charge-system condi
tions.
1
TM Time-out programming
input
CHG Charge active output
BAT Battery voltage input
VCOMP Voltage loop comp input
ICOMP Current loop comp input
I
TERM
Minimum current
termination select input
SNS Sense resistor input
TS Temperature sense input
1
PN295401.eps
16-Pin Narrow
DIP or SOIC
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LED2/DSEL
LED1/CSEL
MOD
V
CC
V
SS
LCOM
BTST
TPWM
TM
CHG
BAT
VCOMP
ICOMP
I
TERM
SNS
TS
TPWM Regulator timebase input
BTST Battery test output
LCOM Common LED output
V
SS
System ground
V
CC
5.0V±10% power
MOD Modulation control
output
LED
1
/ Charge status output 1/
CSEL Charge sense select
input
LED2/ Charge status output 2/
DSEL Display select input
Pin Connections
Pin Names
SLUS064–OCTOBER 1998 B
Lithium Ion Charge Management IC
with Integrated Switching Controller
bq2954
Pin Descriptions
TM Time-out programming input
Sets the maximum charge time. The resistor
and capacitor values are determined using
Equation 5. Figure 10 shows the resistor/ca
-
pacitor connection.
CHG Charge active output
An open-drain output is driven low when the
battery is removed, during a temperature
pend, when a fault condition is present, or
when charge is done. CHG can be used to
disable a high-value load capacitor to detect
quickly any battery removal.
BAT Battery voltage input
Sense input. This potential is generally de
-
veloped using a high-impedance resistor di
-
vider network connected between the posi
tive and the negative terminals of the battery. See Figures 6 and 7 and Equation 1.
VCOMP Voltage loop compensation input
Connects to an external R-C network to stabilize the regulated voltage.
ICOMP Current loop compensation input
Connects to an external R-C network to stabilize the regulated current.
I
TERM
Charge full and minimum current termi
nation select
Three-state input is used to set I
FULL
and
I
MIN
for fast charge termination. See Table 4.
SNS Charging current sense input
Battery current is sensed via the voltage devel
oped on this pin by an external sense-resistor.
TS Temperature sense input
Used to monitor battery temperature. An exter
nal resistor-divider network sets the lower and
upper temperature thresholds. (See Figures 8
and 9 and Equations 3 and 4.)
TPWM Regulation timebase input
Uses an external timing capacitor to ground
to set the pulse-width modulation (PWM)
frequency. See Equation 7.
BTST Battery test output
Driven high in the absence of a battery in or
-
der to provide a potential at the battery ter
-
minal when no battery is present.
LCOM Common LED output
Common output for LED
1-2
. This output is
in a high-impedance state during initiali
zation to read programming input on DSEL
and CSEL.
V
SS
Ground
V
CC
VCCsupply
5.0V, ±10%
MOD Current-switching control output
Pulse-width modulated push/pull output used
to control the charging current to the battery.
MOD switches high to enable current flow and
low to inhibit current flow. (The maximum
duty cycle is 80%.)
LED
1
–
LED
2
Charger display status 1–2 outputs
Drivers for the direct drive of the LED display. These outputs are tri-stated during
initialization so that DSEL and CSEL can be
read.
DSEL Display select input (shared pin with
LED
2
)
Three-level input that controls the LED
1–2
charge display modes.
CSEL
Charge sense-select input (shared pin
with LED
1
)
Input that controls whether current is
sensed on low side of battery or high side of
battery. A current mirror is required for
high-side sense.
2
bq2954
Functional Description
The bq2954 functional operation is described in terms of
the following (Figure 1):
■
Charge algorithm
■
Charge qualification
■
Charge status display
■
Configuring the display and termination
■
Voltage and current monitoring
■
Battery insertion and removal
■
Temperature monitoring
■
Maximum time--out
■
Charge regulation
■
Recharge after fast charge
Charge Algorithm
The bq2954 uses a two-phase fast-charge algorithm. In
phase 1, the bq2954 regulates constant current until the
voltage on the BAT pin, V
BAT
, rises to the internal
threshold, V
REG
. The bq2954 then transitions to phase 2
and regulates constant voltage (V
BAT=VREG
) until the
charging current falls below the programmed I
MIN
threshold. Fast charge then terminates, and the bq2954
enters the Charge Complete state. (See Figure 2.)
Charge Qualification
The bq2954 starts a charge cycle when power is applied
while a battery is present or when a battery is inserted.
Figure 2 shows the state diagram for the bq2954. The
bq2954 first checks that the battery temperature is
within the allowed, user-configurable range. If the temperature is out of range, the bq2954 remains in the
QUALIFICATION state (S01) and waits until the battery
temperature and voltage are within the allowed range.
If during any state of charge, a temperature excursion
occurs HOT, the bq2954 proceeds to the DONE state
(S04) and indicates this state on the LED outputs and
provides no current. If this occurs, the bq2954 remains
in the DONE state unless the following two conditions
are met:
■
Temperature falls within valid charge range
■
V
BAT
falls below the internal threshold,V
RCHG
If these two conditions are met, a new charge cycle be
-
gins. During any state of charge, if a temperature ex
-
cursion occurs COLD, the bq2954 terminates charge and
returns to the QUALIFICATION state (S01). Charge re
-
starts if V
BAT
and temperature are in valid range.
When the temperature and voltage are valid, the bq2954
enters the CONDITIONING state (S02) and regulates
current to I
COND
(=I
MAX
/10). After an initial holdoff pe
-
riod t
HO
(which prevents the IC from reacting to tran
-
sient voltage spikes that may occur when charge current
is first applied), the IC begins monitoring V
BAT
.IfV
BAT
does not rise to at least V
MIN
before the expiration of
3
bq2954
BD2954.eps
Voltage
Reference
Charge
Control
State
Machine
PWM
Regulator
Display
Control
Power-On
Reset
MTO
Timer
Oscillator
DSEL
CSEL
LED
1
LED
2
BTST
CHG
LCOM
MOD
ICOMP
V
CC
TM TPWMITERM
V
SS
TS
VCOMP
BAT
SNS
Figure 1. Functional Block Diagram
4
bq2954
Power-On
Reset
Fault
CHG = 0
Mod = 0 No Action
Latch DSEL/CSEL Inputs
Latch DSEL/CSEL Inputs
FGbg295401.eps
VCC "Up"
S01
S02
S03a
S03b
VOLTA GE
REGULATION
CURRENT
REGULATION
CONDITIONING
QUALIFICATION
DONE
Full Charge
Indication
I
SNS
= I
MIN
Temp Not Hot andV
BAT
V
RCHG
1s Hold Time after V
BAT
< V
RCHG
V
BAT
V
RCHG
V
BAT
> V
HCO
Volt Fault
V
BAT
> V
HCO
Volt Fault
V
BAT
> V
HCO
or T = MTO
Volt or Time Fault
T = MTO/25
Time Fault
Temp Not Valid
Temp Valid
Temp Not Valid
Temp Not Valid
Temp Not Valid
V
BAT
< 0.8V Reset Faults
0.8V > V
BAT
> V
HCO
Hold Time
Hold-off Faults
CHG = 0
Battst = 1
I
SNS
= I
MAX: VBAT
V
REG
T MTO
Hold Time
CHG = 1
V
BAT
< V
MIN: ISNS
= I
MAX/
10
Hold Time
CHG = 1
V
BAT
= V
REG: I
MAX
> ISNS
> I
TRMN
T MTO
CHG = 1
V
BAT
> V
RCHG
Hold-off MOD
V
RCHG
< V
BAT
< V
HCO
CHG = 1
V
HCO
< V
BAT
>0.8V
Reset MTO
V
BAT
V
MIN
Reset MTO
V
BAT
= V
REG
T = MTO
I
SNS
= I
TRM
Temp Hot
Battery Removal
Volt or
Time Fault
S04
<
<
<
<
<
>
V
BAT
Voltages:
V
RCHG
= 1.92V 0.5V
V
MIN
= 1.50V 0.5V
V
REG
= 2.05V
V
HCO
= 2.30V
Volt Fault: When V
BAT
> V
HCO
Time Fault: When T = MTO/4 in State S02 or T = MTO in S03a
Hold Time: A V
HCO
Fault or State charge held off for 0.740s to 1.12s
Figure 2. bq2954 Charge Algorithm
5
bq2954
BAT+
R14
RB1
C11
10uF
20V
PCS4106
L2
47uH
D5
B130DI
L1
10 uH
R1
1K
5V
C2
1uF
R2
4.7K
R5
10K
Q1
FMMT3906
Q2
FMMt3904
Q5
FZT789A
D1
1N4148
VDC
C3
1uF
25V
R4
10K
C10
47uF
25V
OUT
G
N
D
IN
U2
ZMR500
D4
B130DI
8-24VDC ±10%
5V
C4
0.1 uF
R6
10K
R9
220
R10
62K
Q3
FMMT451
R7
1K
BAT-
R8
0.25 5%
0.5W
R15
RB2
TEM+
R12
8.45K
1%
C1
0.1uF
2954sch9/23/98
5V
C7
0.01uF
C8
1000pF
R11
4.32K
1%
TM
1
CHG
2
BAT
3
VCOMP
4
ICOMP
5
ITERM
6
SNS
7
TS
8
TPWM
9
BTST
10
LCOM
11
VSS
12
VCC
13
MOD
14
LED1/CSEL
15
LED2/DSEL
16
U1
bq2954
C5
0.1uF
C9
470pF
R3
10K
C6
0.1 uF
Q4
FMMT3904
R13
1K
D2
GRREN
D3
RED
3. TEMP = 0-45˚C,
4. Frequency = 200kHz
2. MTO = 3 HRS, I
FULL
= I
MAX
/5, I
TERM
= I
MAX
/10
1. I
MAX
= 1.0A, Vreg = 4.2V ± 1% PER CELL
Figure 3. High-Efficiency Li-Ion Charger for 1–4 Cells
time-out limit tQT(i.e., the battery has failed short), the
bq2954 enters the Fault state. Then t
QT
is set to 25% of
t
MTO
.IfV
MIN
is achieved before expiration of the time
limit, the bq2954 begins fast charging.
Once in the Fault state, the bq2954 waits until V
CC
is cy
cled or a new battery insertion is detected. It then starts a
new charge cycle and begins the qualification process again.
Charge Status Display
Charge status is indicated by the LED driver outputs
LED
1
–LED2. Three display modes (Tables 1– 3) are avail
able in the bq2954 and are selected by configuring pin
DSEL. Table 1 illustrates a normal fast charge cycle, Ta
ble 2 a recharge-after-fast-charge cycle, and Table 3 an ab
normal condition.
Configuring the Display Mode, I
FULL/IMIN
,
and I
SENSE
DSEL/LED
2
and CSEL/LED1are bi-directional pins
with two functions: as LED driver pins (output) and as
programming pins (input). The selection of pull-up,
pull-down, or no-resistor programs the display mode on
DSEL as shown in Tables 1 through 3. A pull-down or
no-resistor programs the current-sense mode on CSEL.
The bq2954 latches the programming data sensed on
the DSEL and CSEL input when V
CC
rises to a valid
level. The LEDs go blank for approximately 400ms (typi
-
cal) while new programming data are latched.
When fast charge reaches a condition where the charg
-
ing current drops below I
FULL
, the LED1 and LED2
outputs indicate a full-battery condition. Fast charge
terminates when the charging current drops below the
6
bq2954
GR295401.eps
V
BAT
I
BAT
V
REG
I
MAX
V
MIN
I
COND
I
FULL
I
MIN
Battery
Absent
Qualification
Charge
Complete
Low
Low
Low
Low
Low
Low
Low
High
Low
High
MTO
Fast Charge
Current
Regulate
LED1
LED2
LED1
LED2
LED1
LED2
CHG
BTST
CHG
BTST
High
Low
High
Low
High
Low
High
Low
High
High
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
High
High
Low
High
Low
Low
High
Low
High
Low
High
High
Low
High
Low
Low
High
Low
High
Low
High
Low
Low
Low
Low
Mode 1
(DSEL = 0)
Mode 2
(DSEL = 1)
Mode 3
(DSEL = F)
Mode 1
and 2
Mode 3
Time
Voltage
Regulate
Current
Taper
I
FULL
Detect
Table 1. Normal Fast Charge Cycle
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