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bq2002C
NiCd/NiMH Fast-Charge Management IC
Features
(R) Fast charge of nickel cadmium or nickel-metal hydride batteries Direct LED output displays charge status Fast-charge termination by -V, maximum voltage, maximum temperature, and maximum time Internal band-gap voltage reference Selectable pulse-trickle charge rates Low-power mode 8-pin 300-mil DIP or 150-mil SOIC
General Description
The bq2002C Fast-Charge IC is a lowcost CMOS battery-charge controller providing reliable charge termination for both NiCd and NiMH battery applications. Controlling a current-limited or constant-current supply allows the bq2002C to be the basis for a costeffective stand-alone or system-integrated charger. The bq2002C integrates fast charge with pulsed-trickle control in a single IC for charging one or more NiCd or NiMH battery cells. Fast charge is initiated on application of the charging supply or battery replacement. For safety, fast charge is inhibited if the battery temperature and voltage are outside configured limits.
Fast charge is terminated by any of the following:
n n n n n
Peak voltage detection (PVD) Negative delta voltage (-V) Maximum voltage Maximum temperature Maximum time
(R) (R)
(R) (R) (R) (R)
After fast charge, the bq2002C pulsetrickles the battery per t he preconfigured limits. Fast charge may be inhibited using the INH pin. The bq2002C may also be placed in lowstandby-power mode to reduce system power consumption.
Pin Connections
Pin Names
TM LED BAT Timer mode select input Charging status output Battery voltage input System ground TS VCC INH CC Temperature sense input Supply voltage input Charge inhibit input Charge control output
TM LED BAT VSS
1 2 3 4
8 7 6 5
CC INH VCC TS
VSS
8-Pin DIP or Narrow SOIC
PN-200201.eps
SLUS136 - SEPTEMBER 1997
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bq2002C
Pin Descriptions
TM Timer mode input A three-level input that controls the settings for the fast charge safety timer, voltage termination mode, pulse-trickle, and voltage hold-off time. LED Charging output status Open-drain output that indicates the charging status. BAT Battery input voltage The battery voltage sense input. The input to this pin is created by a high-impedance resistor divider network connected between the positive and negative terminals of the battery. VSS TS System ground Temperature sense input Input for an external battery temperature monitoring thermistor. VCC Supply voltage input 5.0V 20% power input. INH Charge inhibit input When high, INH suspends the fast charge in progress. When returned low, the IC resumes operation at the point where initially suspended. CC Charge control output An open-drain output used to control the charging current to the battery. CC switching to high impedance (Z) enables charging current to flow, and low to inhibit charging current. CC is modulated to provide pulse trickle.
Functional Description
Figure 2 shows a state diagram and Figure 3 shows a block diagram of the bq2002C.
Battery Voltage and Temperature Measurements
Battery voltage and temperature are monitored for maximum allowable values. The voltage presented on the battery sense input, BAT, should represent a single-cell potential for the battery under charge. A resistor-divider ratio of RB1 =N-1 RB2 is recommended to maintain the battery voltage within the valid range, where N is the number of cells, RB1 is the resistor connected to the positive battery terminal, and RB2 is the r esistor connected to the negative battery terminal. See Figure 1. Note: This resistor-divider network input impedance to end-to-end should be at least 200k and less than 1 M. A ground-referenced negative temperature coefficient thermistor placed near the battery may be used as a lowcost temperature-to-voltage transducer. The temperature sense voltage input at TS is developed using a resistorthermistor network between VCC and VSS. See Figure 1.
VCC RT
PACK +
RB1 BAT
R3 TM
VCC TS N T C
bq2002C
VSS
RB2
R4
bq2002C
VSS
BAT pin connection
Mid-level setting for TM
Thermistor connection
NTC = negative temperature coefficient thermistor.
Fg2002/C.eps
Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration
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bq2002C
Chip on 4.0V VCC Battery Voltage too High? VBAT < 2V Battery Voltage too Low? 0.84V < VBAT VTS > VCC/2 Battery Temperature? VTS < VCC/2 Charge Pending Fast LED = Low Trickle LED = Flash VBAT > 2V VBAT < 0.84V
VBAT > 2V
VBAT > 0.84V and VBAT < 2V and VTS > VCC/2
VBAT > 2V or VTS < VCC/2 or PVD or - V or Maximum Time Out
VBAT Trickle LED = Z
2V
SD2002C.eps
Figure 2. State Diagram
OSC
Clock Phase Generator Timing Control Sample History Voltage Reference
TM INH
Charge-Control State Machine
PVD, - V ALU
A to D Converter LBAT Check
Power-On Reset CC LED
HTF TCO Check Check TS
Power Down VCC
MCV Check
BAT
VSS
Bd2002CEG.eps
Figure 3. Block Diagram
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bq2002C
VCC = 0
Fast Charging
Pulse-Trickle
Fast Charging
CC Output
1s
See Table 1
Charge initiated by application of power Charge initiated by battery replacement LED
TD2002C1.eps
Figure 4. Charge Cycle Phases
pending state. In this state pulse trickle charge is applied to the battery and the LED flashes until the voltage and temperature come into the allowed fast charge range or VBAT rises above VMCV. Anytime VBAT VMCV, the IC enters the Charge Complete/Battery Absent state. In this state the LED is off and trickle charge is applied to the battery until the next new charge cycle begins. Fast charge continues until termination by one or more of the five possible termination conditions:
n n n n n
Starting A Charge Cycle
Either of two events starts a charge cycle (see Figure 4): 1. Application of power to VCC or 2. Voltage at the BAT pin falling through the maximum cell voltage VMCV where VMCV = 2V 5%. If the battery is within the configured temperature and voltage limits, the IC begins fast charge. The valid battery voltage range is VLBAT < VBAT < VMCV, where VLBAT = 0.175 VCC 20% The valid temperature range is VTS > VHTF where VHTF = 0.6 VCC 5%. If VBAT VLBAT or VTS VHTF, the IC enters the charge-
Peak voltage detection (PVD) Negative delta voltage (-V) Maximum voltage Maximum temperature Maximum time
Table 1. Fast-Charge Safety Time/Hold-Off Table
Typical FastCharge Time Limits (minutes) 160 80 40 Typical PVD and -V Hold-Off Time (seconds) 300 150 75 PulseTrickle Pulse Width (ms) 73 37 18 Maximum Synchronized Sampling Period (seconds) 18.7 18.7 9.4
Corresponding Fast-Charge Rate C/2 1C 2C Notes:
TM Mid Low High
Termination PVD PVD -V
PulseTrickle Rate C/32 C/32 C/32
Typical conditions = 25C, VCC = 5.0V Mid = 0.5 * VCC 0.5V Tolerance on all timing is 12%.
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bq2002C
PVD and -V Termination
There are two modes for voltage termination, depending on the state of TM. For -V (TM = high), if VBAT is lower than any previously measured value by 12mV 3mV, fast charge is terminated. For PVD (TM = low or mid), a decrease of 2.5mV 2.5mV terminates fast charge. The PVD and -V tests are valid in the range 1V < VBAT < 2V . Maximum charge time is configured using the TM pin. Time settings are available for corresponding charge rates of C/2, 1C, and 2C. Maximum time-out termination is enforced on the fast-charge phase, then reset, and enforced again on the top-off phase, if selected. There is no time limit on the trickle-charge phase.
Pulse-Trickle Charge
Pulse-trickle is used to compensate for self-discharge while the battery is idle in the charger. The battery is pulse-trickle charged by driving the CC pin active once per second for the period specified in Table 1. This results in a trickle rate of C/32.
Synchronized Voltage Sampling
Voltage sampling at the BAT pin for PVD and -V termination may be synchronized to an external stimulus using t he INH input. Low-high-low input pulses between 100ns and 3.5ms in width must be applied at the INH pin with a frequency greater than the "maximum synchronized sampling period" set by the state of the TM pin as shown in Table 1. Voltage is sampled on the falling edge of such pulses. If the time between pulses is greater than the synchronizing period, voltage sampling "free-runs" at once every 17 seconds. A sample is taken by averaging together voltage measurements taken 57s apart. The IC takes 32 measurements in PVD mode and 16 measurements in -V mode. The resulting sample periods (9.17 and 18.18ms, respectively) filter out harmonics centered around 55 and 109Hz. This technique minimizes the effect of any AC line ripple that may feed through the power supply from either 50 or 60Hz AC sources. If the INH input remains high for more than 12ms, the voltage sample history kept by the IC and used for PVD and -V termination decisions is erased and a new history is started. Such a reset is required when transitioning from free-running to synchronized voltage sampling. The response of the IC to pulses less than 100ns in width or between 3.5ms and 12ms is indeterminate. The tolerance on all timing is 12%.
TM Pin
The TM pin is a three-level pin used to select the charge timer, top-off, voltage termination mode, trickle rate, and voltage hold-off period options. Table 1 describes the states selected by the TM pin. The mid-level selection input is developed by a resistor divider between VCC and ground that fixes the voltage on TM at VCC/2 0.5V. See Figure 4.
Charge Status Indication
A fast charge in progress is uniquely indicated when the LED pin goes low. In the charge pending state, the LED pin is driven low for 500ms, then to high-Z for 500ms. The LED pin is driven to the high-Z state for all other conditions. Figure 2 outlines the state of the LED pin during charge.
Charge Inhibit
Fast charge and top-off may be inhibited by using the INH pin. When high, INH suspends all fast charge and top-off activity and the internal charge timer. INH freezes t h e c u r r e n t s t a t e of LED until inhibit is removed. Temperature monitoring is not affected by the INH pin. During charge inhibit, the bq2002C continues to pulse-trickle charge the battery per the TM selection. When INH returns low, charge control and the charge timer resume from the point where INH became active.
Voltage Termination Hold-off
A hold-off period occurs at the start of fast charging. During the hold-off time, the PVD and -V terminations are disabled. This avoids premature termination on the voltage spikes sometimes produced by older batteries when fast-charge current is first applied. Maximum voltage and temperature terminations are not affected by the hold-off period.
Low-Power Mode
The IC enters a low-power state when VBAT is driven above the power-down threshold (VPD) where VPD = VCC - (1V 0.5V) Both the CC pin and the LED pin are driven to the high-Z state. The operating current is reduced to less than 1A in this mode. When VBAT returns to a value below VPD, the IC pulse-trickle charges until the next new charge cycle begins.
Maximum Voltage, Temperature, and Time
Any time the voltage on the BAT pin exceeds the maximum cell voltage, VMCV, fast charge is terminated. Maximum temperature termination occurs anytime the voltage on the TS pin falls below the temperature cut-off threshold VTCO, where VTCO = 0.5 VCC 5%.
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bq2002C
Absolute Maximum Ratings
Symbol VCC VT TOPR TSTG TSOLDER TBIAS Note: Parameter VCC relative to VSS DC voltage applied on any pin excluding VCC relative to VSS Operating ambient temperature Storage temperature Soldering temperature Temperature under bias Minimum -0.3 -0.3 0 -40 -40 Maximum +7.0 +7.0 +70 +85 +260 +85 Unit V V C C C C 10 sec max. Commercial Notes
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
Symbol VTCO VHTF VMCV VLBAT -V PVD
(TA = 0 to 70C; VCC 20%)
Parameter Temperature cutoff High-temperature fault Maximum cell voltage Minimum cell voltage BAT input change for -V detection BAT input change for PVD detection
Rating 0.5 * VCC 0.6 VCC 2 0.175 VCC -12 -2.5
Tolerance 5% 5% 5% 20% 3 2.5
Unit V V V V mV mV
Notes VTS VTCO inhibits/terminates fast charge VTS VHTF inhibits fast charge start VBAT VMCV inhibits/terminates fast charge VBAT VLBAT inhibits fast charge
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bq2002C
Recommended DC Operating Conditions (TA = 0 to 70C)
Symbol VCC VDET VBAT VTS VIH Condition Supply voltage -V, PVD detect voltage Battery input Thermistor input Logic input high Logic input high VIM Logic input mid Minimum 4.0 1 0 0.5 0.5 VCC - 0.5 VCC 2 VIL Logic input low Logic input low VOL VPD Logic output low Power down - 0.5 VCC - 1.5 Typical 5.0 VCC 2 Maximum 6.0 2 VCC VCC + 0.5 Unit V V V V V V V VTS < 0.5V prohibited INH TM TM Notes
0.1 0.5 0.8 VCC - 0.5
V V V V
INH TM LED, CC, IOL = 10mA VBAT VPD max. powers down bq2002C; VBAT < VPD min. = normal operation. Outputs unloaded, VCC = 5.1V VCC = 5.1V, VBAT = VPD @ OL = VSS + 0.8V V INH, CC, V = VSS to VCC LED, CC
I CC
Supply current
-
-
500
A A mA A A
I SB I OL IL I OZ
Standby current LED, CC sink Input leakage Output leakage in high-Z state All voltages relative to VSS.
10 -5
-
1 1 -
Note:
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bq2002C
Impedance
Symbol RBAT RTS Parameter Battery input impedance TS input impedance Minimum 50 50 Typical Maximum Unit M M
Timing
Symbol dFCV Note:
(TA = 0 to +70C; VCC 10%)
Parameter Time base variation
Minimum -12
Typical -
Maximum 12
Unit %
Notes
Typical is at TA = 25C, VCC = 5.0V.
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bq2002C
8-Pin DIP (PN)
8-Pin PN (0.300" DIP)
Inches
D
Millimeters Min. 4.06 0.38 0.38 1.40 0.20 8.89 7.62 5.84 7.62 2.29 2.92 0.51 Max. 4.57 1.02 0.56 1.65 0.33 9.65 8.26 7.11 9.40 2.79 3.81 1.02
Dimension A A1
Min. 0.160 0.015 0.015 0.055 0.008 0.350 0.300 0.230 0.300 0.090 0.115 0.020
Max. 0.180 0.040 0.022 0.065 0.013 0.380 0.325 0.280 0.370 0.110 0.150 0.040
E1 E A1 L C A B1
B B1 C D E E1 e
S B G
e
G L S
9
bq2002C
8-Pin SOIC Narrow (SN)
8-Pin SN (0.150" SOIC)
Inches Dimension A A1 B C D E e H L Min. 0.060 0.004 0.013 0.007 0.185 0.150 0.045 0.225 0.015 Max. 0.070 0.010 0.020 0.010 0.200 0.160 0.055 0.245 0.035 Millimeters Min. 1.52 0.10 0.33 0.18 4.70 3.81 1.14 5.72 0.38 Max. 1.78 0.25 0.51 0.25 5.08 4.06 1.40 6.22 0.89
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bq2002C
Data Sheet Revision History
Change No. 1 Note: Page No. All Description Revised format and outline of this data sheet
Change 1 = Sept. 1997 B changes from Dec. 1995.
Ordering Information
bq2002C
Package Option:
PN = 8-pin plastic DIP SN = 8-pin narrow SOIC
Device:
bq2002C Fast-Charge IC
11
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