TI BQ24401PW Programmable nicd/nimh fast-charge management device Datasheet

bq24401
Programmable NiCd/NiMH
Fast-Charge Management Device
Features
General Description
Ø
Safe management of fast charge
for NiCd and NiMH
Ø
High-frequency switching controller for efficient and simple
charger design
Ø
Ø
Pre-charge qualification for
detecting shorted, damaged, or
overheated cells
Fast-charge termination by
∆T/∆t maximum temperature,
and maximum charge time
Ø
Selectable top-off mode for
achieving maximum capacity in
NiMH batteries
Ø
Programmable trickle-charge
mode for reviving deeply discharged batteries and for postcharge maintenance
Ø
Built-in battery removal and insertion detection
Ø
Sleep mode for low power consumption
Pin Connections
The bq24401 is a programmable,
monolithic IC for fast-charge management of nickel cadmium (NiCd) and
nickel metal-hydride (NiMH).
Depending on the chemistry, the
b q 2 44 0 1 p r o v i de s a n u m b e r o f
charge termination criteria:
l
Rate of temperature rise, ∆T/∆t
(for NiCd and NiMH)
l
Maximum temperature
l
Maximum charge time
For safety, the bq24401 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
bq24401 uses trickle-charge to
condition the battery. For NiMH
batteries, the bq24401 provides an
optional top-off charge to maximize
the battery capacity.
The integrated high-frequency comparator allows the bq24401 to be the
basis for a complete, high-efficiency
power-conversion circuit.
Pin Names
SNS
1
8
MOD
VSS
2
7
VCC
LED
3
6
RC
BAT
4
5
TS
SNS
Current-sense input
VSS
System ground
LED
Charge-status
output
BAT
Battery-voltage
input
8-Pin DIP or Narrow SOIC
or TSSOP
PN-2000.eps
SLUS497–SEPTEMBER 2001
1
TS
Temperature-sense
input
RC
Timer-program input
VCC
Supply-voltage input
MOD
Modulation-control
output
bq24401
Pin Descriptions
SNS
RC
Current-sense input
Timer-program input
RC input used to program the maximum
charge-time, hold-off period, and trickle rate
during the charge cycle, and to disable or
enable top-off charge
Enables the bq24401 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
VCC
Supply-voltage input
LED
Charge-status output
MOD
Modulation-control output
Open-drain output that indicates the charging status by turning on, turning off, or flashing an external LED
BAT
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.
Battery-voltage input
Functional Description
Battery-voltage sense input. A simple resistive
divider, across the battery terminals, generates
this input.
TS
The bq24401 is a versatile, NiCd, NiMH battery-charge
control device. See Figure 1 for a functional block diagram and Figure 2 for the state diagram.
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.
TS
Voltage
Reference
BAT
OSC
Voltage
Comparator
ADC
∆T/∆t
ALU
Clock
Phase
Generator
Timer
Charge
Control
LED
Voltage
Comparator
MOD
RC
Internal
OSC
SNS
VCC
VSS
BD2000T.eps
Figure 1. Functional Block Diagram
2
bq24401
4.0 V < VCC < 6.0 V
Charge
Initialization
VBAT < VSLP
Sleep
Mode
Battery Voltage
(checked at all times)
VMCV < VBAT < VSLP
VSLP < VBAT < VCC
VBAT < VMCV
VTS > VHTF
Charge
Suspended
Battery Temperature
(sampled every 16
seconds for dT/dt)
VTS <VHTF
VLBAT < VBAT < VMCV and
VHTF < VTS < VLTF
VBAT < VLBAT or
VTS > VLTF
Battery
Conditioning
Current
Regulation
VLBAT < VBAT < VMCV and
VHTF < VTS < VLTF
∆T/∆t (after hold-off period),
or VTS < VTCO
or Time = MTO
VCC Reset
Maintenance
Charge
No
Top-Off
Selected?
Yes
Time = MTO or
VTS < VTCO
VBAT > VMCV
Top-Off
Done
VBAT > VMCV
VCC Reset or Battery Replacement
Figure 2. State Diagram
3
UDG-01087
bq24401
Initiation and Charge Qualification
Charge Termination
The bq24401 initiates a charge cycle when it detects
Maximum Charge Time
l
Application of power to VCC
l
Battery replacement
l
Exit from sleep mode
The bq24401 sets the maximum charge-time through pin
RC. With the proper selection of external resistor and capacitor, various time-out values may be achieved. Figure
3 shows a typical connection.
Immediately following initiation, the IC enters a
charge-qualification mode. The bq24401 charge qualification is based on battery voltage and temperature. If
voltage on pin BAT is less than the internal threshold,
VLBAT , the bq24401 enters the charge-pending state.
This condition indicates the possiblility of a defective or
shorted battery pack. In an attempt to revive a fully
depleted pack, the bq24401 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 Charge,” the
trickle pulse-width is user-selectable and is set by the
value of the resistance connected to pin RC.
The following equation shows the relationship between
the RMTO and CMTO values and the maximum charge
time (MTO) for the bq24401:
During this period, the LED pin blinks at a 1Hz rate,
indicating the pending status of the charger.
A negative-coefficient thermistor, referenced to VSS and
placed in thermal contact with the battery, may be used
as a temperature-sensing device. Figure 4 shows a typical
temperature-sensing circuit.
MTO = RMTO ∗ CMTO ∗ 35,988
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 Tables 2 and 3 for details.)
Maximum Temperature
Similarly, the bq24401 suspends fast charge if the battery
temperature is outside the VLTF to VHTF range. (See Table 4.) For safety reasons, however, it disables the pulse
trickle, in the case of a battery over-temperature condition (i.e., VTS < VHTF). Fast charge begins when the battery temperature and voltage are valid.
During fast charge, the bq24401 compares the battery
temperature to an internal high-temperature cutoff
threshold, VTCO. As shown in Table 4, high-temperature
termination occurs when voltage at pin TS is less than
this threshold.
NiCd and NiMH Batteries
DT/Dt
Following qualification, the bq24401 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 pin BAT remains below VMCV.
When fast charging, the bq24401 monitors the voltage at
pin TS for rate of temperature change detection, ∆T/∆t.
The bq24401 samples the voltage at the TS pin every 16s
and compares it to the value measured 2 samples earlier.
This feature terminates fast charge if this voltage declines at a rate of
VCC  V 


161  Min 
Figure 4 shows a typical connection diagram.
Table 1. Charge Algorithm
Battery Chemistry
NiCd or NiMH
Charge Algorithm
1. Charge qualification
2. Trickle charge, if required
3. Fast charge (constant current)
4. Charge termination (∆T/∆t, time)
5. Top-off (optional)
6. Trickle charge
4
bq24401
Table 2. Summary of NiCd or NiMH Charging Characteristics
Parameter
Value
Maximum cell voltage (VMCV)
2V
Minimum pre-charge qualification voltage (VLBAT)
950mV
High-temperature cutoff voltage (VTCO)
0.225 ∗ VCC
High-temperature fault voltage (VHTF)
0.25 ∗ VCC
Low-temperature fault voltage (VLTF)
0.5 ∗ VCC
bq24401 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
1Hz
Trickle-charge pulse-width
See Figure 6
Table 3. Temperature-Monitoring Conditions
Temperature
Condition
Action
VTS > VLTF
Cold battery—checked at all times
Suspends fast charge or top-off and timer
Allows trickle charge—LED flashes at 1Hz rate
during pre-charge qualification and fast charge
VHTF < VTS < VLTF
Optimal operating range
Allows charging
VTS < VHTF
Suspends fast-charge initiation, does not allow
Hot battery—checked during charge qualifitrickle charge—LED flashes at 1Hz rate during
cation and top-off and trickle-charge
pre-charge qualification
VTS < VTCO
Battery exceeding maximum allowable temTerminates fast charge or top-off
perature—checked at all times
Initial Hold-Off Period
Table 4. Charge Status Display
The values of the external resistor and capacitor connected to pin RC set the initial hold-off period. During
this period, the bq24401 avoids early termination by disabling the ∆T/∆t feature. This period is fixed at the programmed value of the maximum charge time divided by
32.
hold-off period =
Charge Action State
Battery absent
maximum time - out
32
5
LED Status
High impedance
Pre-charge qualification
1Hz flash
Trickle charge (before fast charge)
1Hz flash
Fast charging
Low
Top-off or trickle
High impedance
Charge complete
High impedance
Sleep mode
High impedance
Charge suspended (VTS > VLTF)
1Hz flash
bq24401
2
VCC
VSS
7
bq24401
bq2000T
CMTO
RC
6
RMTO
F2000T RCI.eps
Figure 3. Typical Connection for the RC Input
VCC
2
VSS
7
VCC
bq24401
bq2000T
RT1
5
TS
RT2
N Battery
T Pack
C
F2000TTMC.eps
Figure 4. Temperature Monitoring Configuration
BAT+
2
VSS
bq24401
bq2000T
4
RB1
BAT
RB2
F2000TBVD.eps
Figure 5. Battery Voltage Divider
6
bq24401
Charge Current Control
Top-Off and Pulse-Trickle Charge
The bq24401 controls the charge current through the
MOD output pin. The current-control circuit supports a
switching-current regulator with frequencies up to
500kHz. The bq24401 monitors charge current at the
SNS input by the voltage drop across a sense-resistor,
RSNS, in series with the battery pack. See Figure 8 for a
typical current-sensing circuit. RSNS is sized to provide
the desired fast-charge current (IMAX):
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 to pin RC (Figure 3) should be greater than
0.13µF, and the value of the resistor connected to this pin
should be less than 15kΩ. To disable top-off, the capacitance value should be less than 0.07µF. The tolerance of
the capacitor needs to be taken into account in component selection.
IMAX =
Once enabled, the top-off is performed over a period
equal to the maximum charge time at a rate of 1 16 that of
fast charge.
0.05
RSNS
If the voltage at the SNS pin is greater than VSNSLO or
less than VSNSHI, the bq24401 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
bq24401 switches the MOD output low to shut off charging current to the battery. Figure 7 shows a typical
multi-chemistry charge circuit.
Following top-off, the bq24401 trickle-charges the battery
by enabling the MOD 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, which is on pin RC.
Figure 6 shows the relationship between the trickle
pulse-width and the value of RMTO. The typical tolerance
of the pulsewidth below 150kΩ is ±10%.
Voltage Input
As shown in Figure 5, a resistor voltage-divider between
the battery pack’s positive terminal and VSS scales the
battery voltage measured at pin BAT.
During top-off and trickle-charge, the bq24401 monitors
battery voltage and temperature. These functions are
suspended if the battery voltage rises above the
maximum cell voltage (V MCV ) or if the temperature
exceeds the high-temperature fault threshold (VHTF).
The resistor values RB1 and RB2 are calculated by the following equation:
RB1
= N−1
RB2
where N is the number of cells in series. The end-to-end
input impedance of this resistive divider network should
be at least 200kΩ and no more than 1MΩ.
160
140
120
Shows Tolerance
Pulsewidth—ms
100
80
60
40
20
4
3
2
1
2
4
6
8
10
50
100
150
200
250
RMTO—kΩ
2000PNvB3.eps
Figure 6. Relationship Between Trickle Pulse-Width and Value of RMTO
7
bq24401
DC+
L1
47 mH
Q1
FMMT718
D4
S1A
BAT+
+
D3
MMSD914LT
R7
1 kW
C6
47 mF
D2
ZHCS1000
D5
MMSD914LT C8
1000 PF
VCC
+ C3
10 mF
R2
2 kW
Q2
MMBT3904LT1
C7
4.7 PF
C9
0.33 mF
R9
120 W
R1
100kW
R4
210 kW
R13
10.5 kW
+
C5
10 mF
C4
0.0022 mF
BQ24401
1
SNS
MOD
8
2
VSS
VCC
7
3
LED
RC
6
Q3
MMBT3904LT1
D1
RED
R8
220 W
R5
105 kW
R12
100 kW
4
D6
BZT52-C5V1
C2
0.1 mF
BAT
TS
THERM
5
C1
0.1 mF
R10
1.1 kW
R11
6.81 kW
C10
0.01 mF
R14
23.2 kW
BAT-
R3
0.05 W
Notes:
1. DC input voltage: 9 V to 16 V
2. Charge current: 1 A
3. L1: 3L global P/N PKSMD-1005-470K-1A
Figure 7. Three-Cell NiCd/NiMH 1A Charger
8
bq24401
Temperature Monitoring
Sleep Mode
The bq24401 measures the temperature by the voltage at
the TS pin. This voltage is typically generated by a negative-temperature-coefficient thermistor. The bq24401
compares this voltage against its internal threshold
voltages to determine if charging is safe.
The bq24401 features a sleep mode for low power consumption. This mode is enabled when the voltage at pin
BAT is above the low-power-mode threshold, VSLP. During sleep mode, the bq24401 shuts down all internal circuits, drives the LED output to high-impedance state,
and drives pin MOD to low. Restoring BAT below the
VMCV threshold initiates the IC and starts a fast-charge
cycle.
These thresholds are the following:
l
l
l
High-temperature cutoff voltage: VTCO = 0.225 ∗ VCC
This voltage corresponds to the maximum temperature
(TCO) at which fast charging is allowed. The bq24401
terminates fast charge if the voltage on pin TS falls
below VTCO.
High-temperature fault voltage: VHTF = 0.25 ∗ VCC This
voltage corresponds to the temperature (HTF) at which
fast charging is allowed to begin.
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 pin TS rises above VLTF, the bq24401
suspends fast charge or top-off but does not terminate
charge. When the voltage falls back below VLTF, fast
charge or top-off resumes from the point where
suspended. Trickle-charge is allowed during this
condition.
Rf
RSNS
1 SNS
Cf
2
BAT-
VSS
bq2000T
bq24401
Power Supply ground
bq2000 ground
bq24401
2000TCS.eps
Table 3 summarizes these various conditions.
Charge Status Display
The charge status is indicated by open-drain output LED.
Table 4 summarizes the display output of the bq24401.
Figure 8. Current-Sensing Circuit
Absolute Maximum Ratings
Minimum
Maximum
Unit
VCC
Symbol
VCC relative to VSS
-0.3
+7.0
V
VT
DC voltage applied on any pin, excluding VCC relative to VSS
-0.3
+7.0
V
TOPR
Operating ambient temperature
-20
+70
°C
TSTG
Storage temperature
-40
+125
°C
TSOLDER
Soldering temperature
-
+260
°C
Note:
Parameter
Notes
10s max.
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.
9
bq24401
DC Thresholds
(TA = TOPR; VCC = 5V ±20% unless otherwise specified)
Symbol
VTCO
VHTF
VLTF
Parameter
Temperature cutoff
High-temperature fault
Low-temperature fault
Rating
0.225 * VCC
0.25 * VCC
0.5 * VCC
Tolerance
±5%
±5%
±5%
Unit
V
V
V
VMCV
Maximum cell voltage
2.00
±2.5%
V
VLBAT
Minimum cell voltage
±5%
mV
VTHERM
TS input change for ∆T/∆t detection
950
VCC
−
161
±25%
V/Min
50
±10
mV
Voltage at pin SNS
-50
±10
mV
Voltage at pin SNS
VSLP
High threshold at SNS, resulting in
MOD-low
Low threshold at SNS, resulting in
MOD-high
Sleep-mode input threshold
VRCH
Recharge threshold
VSNSHI
VSNSLO
Notes
Voltage at pin TS
Voltage at pin TS
Voltage at pin TS
VBAT > VMCV inhibits
fast charge
Voltage at pin BAT
VCC - 1
±0.5
V
Applied to pin BAT
VMCV - 0.1
±0.02
V
At pin BAT
Impedance
Symbol
Parameter
Minimum
Typical
Maximum
Unit
RBAT
Battery input impedance
10
-
-
MΩ
RTS
TS input impedance
10
-
-
MΩ
RSNS
SNS input impedance
10
-
-
MΩ
Minimum
Typical
Maximum
Unit
Timing
Symbol
(TA = TOPR; VCC = 5V ±20% unless otherwise specified)
Parameter
dMTO
MTO time-base variation
-5
-
+5
%
fTRKL
Pulse-trickle frequency
0.9
1.0
1.1
Hz
10
bq24401
Recommended DC Operating Conditions (TA = TOPR)
Symbol
Condition
Minimum
Typical
Maximum
Unit
Notes
VCC
Supply voltage
4.0
5.0
6.0
V
ICC
Supply current
-
0.5
1
mA
Exclusive of external loads
ICCS
Sleep current
-
-
5
µA
VBAT = VSLP
VTS
Thermistor input
0.5
-
VCC
V
VTS < 0.5V prohibited
VOH
Output high
VCC - 0.2
-
-
V
MOD, IOH = 20mA
VOL
Output low
-
-
0.2
V
MOD, LED, IOL = 20mA
IOZ
High-impedance leakage
current
-
-
5
µA
LED
Isnk
Sink current
-
-
20
mA
MOD, LED
RMTO
Charge timer resistor
2
-
250
kΩ
CMTO
Charge timer capacitor
0.001
-
1.0
µF
Note:
All voltages relative to VSS except as noted.
Ordering Information
bq24401
Package Option:
P = 8-pin narrow plastic DIP
D = 8-pin narrow SOIC
PW = 8-pin TSSOP
Device:
bq24401 NiCd/NiMH Fast-Charge IC with ∆T/∆t Detection
11
bq24401
8-Pin DIP (P)
0.400 (10,60)
0.355 (9,02)
8
5
0.260 (6,60)
0.240 (6,10)
1
4
0.070 (1,78) MAX
0.325 (8,26)
0.300 (7,62)
0.020 (0,51) MIN
0.015 (0,38)
Gage Plane
0.200 (5,08) MAX
Seating Plane
0.010 (0,25) NOM
0.125 (3,18) MIN
0.100 (2,54)
0.021 (0,53)
0.015 (0,38)
0.430 (10,92)
MAX
0 .010 (0 ,2 5) M
4040082/D 05/98
NOTES:
A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-001
12
bq24401
8-Pin SOIC Narrow (D)
14 PINS SHOWN
0.050 (1,27)
0.020 (0,51)
0.010 (0,25) M
0.014 (0,35)
14
8
0.008 (0,20) NOM
0.244 (6,20)
0.228 (5,80)
0.157 (4,00)
0.150 (3,81)
Gage Plane
0.010 (0,25)
1
7
05- 85
A
0.044 (1,12)
0.016 (0,40)
Seating Plane
0.069 (1,75) MAX
0.010 (0,25)
0.004 (0,10)
0.004 (0,10)
PINS **
8
14
16
A MAX
0.197
(5,00)
0.344
(8,75)
0.394
(10,00)
A MIN
0.189
(4,80)
0.337
(8,55)
0.386
(9,80)
DIM
4040047 / D 10/96
NOTES:
A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).
D. Falls within JEDEC MS-012
13
bq24401
8-Pin TSSOP ~ PW Package Suffix
14 PINS SHOWN
0,30
0,65
0,19
14
0,10 M
8
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
0,25
1
7
05- 85
A
0,75
0,50
Seating Plane
0,15
0,05
1,20 MAX
PINS **
DIM
0,10
8
14
16
20
24
28
A MAX
3,10
5,10
5,10
6,60
7,90
9,80
A MIN
2,90
4,90
4,90
6,40
7,70
9,60
4040064/F 01/97
NOTES:
A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion not to exceed 0,15.
D. Falls within JEDEC MO-153
14
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15
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