Features
®
Fast charge of nickel cadmium or nickel-metal hydride batter-ies
®Direct LED output displays charge status
®
Fast-charge termination by -∆V ,maximum voltage,maximum temperature,and maximum time散血莲
®Internal band-gap voltage ref-erence
®Optional top-off charge
®Selectable pulse trickle charge rates
®Low-power mode
®
8-pin 300-mil DIP or 150-mil SOIC
General Description
The bq2002E and bq2002G Fast-Charge ICs are low-cost CMOS bat-tery-charge controllers providing reli-able charge termination for both NiCd and NiMH battery applications.Con-trolling a current-limited or con-stant-current supply allows the bq2002E/G to be the basis for a cost-effective stand-alone or system-inte-grated charger.The bq2002E/G inte-grates fast charge with optional top-off and 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 re-placement.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 Peak voltage detection (PVD)n Negative delta voltage (-∆V)n Maximum voltage n Maximum temperature n
液气分离器Maximum time
After fast charge,the bq2002E/G op-tionally tops-off and pulse-trickles the battery per the pre-configured limits.Fast charge may be inhibited using the INH pin.The bq2002E/G may also be placed in low-standby-power mode to reduce system power con-sumption.
The bq2002E differs from t h e bq2002G only in that a slightly dif-ferent set of fast-charge and top-off time limits is available.All differ-ences between the two ICs are illus-trated in Table 1.
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NiCd/NiMH Fast-Charge Management ICs
bq2002E/G
TM Timer mode select input LED Charging status output BAT Battery voltage input V SS
System ground
1PN-200201.eps
8-Pin DIP or Narrow SOIC
234
8765
TM LED BAT V SS
CC INH V CC TS
TS Temperature sense input V CC Supply voltage input INH Charge inhibit input CC
Charge control output
Pin Connections
Pin Names
SLUS132 - FEBRUARY 1999
bq2002E/G Selection Guide让子弹飞
配乐
LBAT
TCO HTF LTF -∆V PVD
Fast Charge
t MTO Top-Off Maintenance
bq2002E 0.175∗
V CC 0.5∗V CC 0.6∗V CC None
C/2200None C/32 1C 80C/16C/32
2C 40None C/32bq2002G 0.175∗
V CC
0.5∗V CC
0.6∗V CC
None
C/2160None C/32 1C 80C/16C/32
2C
40
None
C/32
Pin Descriptions2013年会主题
TM Timer mode input
A three-level input that controls the settings
for the fast charge safety timer,voltage ter-
mination mode,top-off,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 re-
sistor divider network connected between
the positive and negative terminals of the
battery.
V SS System ground
TS T emperature sense input
Input for an external battery temperature
monitoring thermistor.
V CC 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 re-
sumes 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 switch-
ing to high impedance(Z)enables charging
current to flow,and low to inhibit charging
current.CC is modulated to provide top-off,
if enabled,and pulse trickle. Functional Description
Figure2shows a state diagram and Figure3shows a block diagram of the bq2002E/G.
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
RB2
= N - 1
is recommended to maintain the battery voltage within the valid range,where N is the number of cells,RB1is the resistor connected to the positive battery terminal, and RB2is the resistor connected to the negative bat-tery terminal.See Figure1.
Note:This resistor-divider network input impedance to end-to-end should be at least200kΩand less than1MΩ.
2
bq2002E/G
Figure 1.Voltage and Temperature Monitoring and TM Pin Configuration
bq2002E/G
Figure 2.State Diagram
Figure 3.Block Diagram
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A ground-referenced negative temperature coefficient ther-mistor placed near the battery may be used as a low-cost temperature-to-voltage transducer.The temperature sense voltage input at TS is developed using a resistor-thermistor network between V CC and V SS .See Figure 1.
Starting A Charge Cycle
Either of two events starts a charge cycle (see Figure 4):
1.Application of power to V CC or
2.V oltage at the BAT pin falling through the maximum cell voltage V MCV where
V MCV = 2V ±5%.
If the battery is within the configured temperature and voltage limits,the IC begins fast charge.The valid bat-tery voltage range is V LBAT <V BAT <V MCV ,where
4
bq2002E/G
Corre-sponding Fast-Charge
Rate
TM Termination
Typical Fast-Charge and Top-Off Time Limits (minutes)
Typical PVD and -∆V Hold-Off Time
(seconds)Top-Off
Rate Pulse-Trickle Rate Pulse-Trickle Width (ms)Maximum Synchro-nized Sampling Period (seconds)bq2002E bq2002G C/2Mid PVD 200160300Disabled C/327318.71C Low PVD 8080150C/16C/3237
18.72C High
-∆V
40
40
75
Disabled
C/32
18
9.4
Notes:
Typical conditions = 25°C,V CC = 5.0V Mid = 0.5*V CC ±0.5V
Tolerance on all timing is ±12%.
Table 1.Fast-Charge Safety Time/Hold-Off/Top-Off Table
Figure 4.Charge Cycle Phases
V LBAT= 0.175∗V CC±20%
The valid temperature range is V TS>V HTF where
V HTF= 0.6∗V CC±5%.
If the battery voltage or temperature is outside of these limits,the IC pulse-trickle charges until the next new charge cycle begins.
If V MCV<V BAT<V PD(see“Low-Power Mode”)when a new battery is inserted,a delay of0.35to0.9s is imposed before the new charge cycle begins.
Fast charge continues until termination by one or more of the five possible termination conditions:
n Peak voltage detection(PVD)
n Negative delta voltage(-∆V)
n Maximum voltage
n Maximum temperature
n Maximum time
PVD and-∆V Termination
There are two modes for voltage termination,depending on the state of TM.For-∆V(TM=high),if V BAT is lower than any previously measured value by12mV±3mV,fast charge is terminated.For PVD(TM=low or mid),a de-crease of2.5mV±2.5mV terminates fast charge.The PVD and-∆Vtests are valid in the range1V<V BAT<2V. Synchronized Voltage Sampling
V oltage sampling at the BAT pin for PVD and-∆V termi-nation may be synchronized to an external stimulus us-ing the INH input.Low-high-low input pulses between 100ns and3.5ms in width must be applied at the INH pin with a frequency greater than the“maximum syn-chronized sampling period”set by the state of the TM pin as shown in Table1.V oltage is sampled on the fal-ling edge of such pulses.
If the time between pulses is greater than the synchro-nizing period,voltage sampling“free-runs”at once every 17seconds.A sample is taken by averaging together voltage measurements taken57µs apart.The IC takes 32measurements in PVD mode and16measurements in-∆V mode.The resulting sample periods(9.17and 18.18ms,respectively)filter out harmonics centered around55and109Hz.This technique minimizes the ef-fect of any AC line ripple that may feed through the power supply from either50or60Hz AC sources.
If the INH input remains high for more than12ms,the voltage sample history kept by the IC and used for PVD and-∆V termination decisions is erased and a new his-tory is started.Such a reset is required when transition-ing from free-running to synchronized voltage sampling.
The response of the IC to pulses less than100ns in width or between3.5ms and12ms is indeterminate.Tol-erance on all timing is±12%.
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 terminatio
n 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.
Maximum Voltage,Temperature,and Time
Any time the voltage on the BA T pin exceeds the maxi-mum cell voltage,V MCV,fast charge or optional top-off charge is terminated.
Maximum temperature termination occurs anytime the voltage on the TS pin falls below the temperature cut-off threshold V TCO where
V TCO= 0.5∗V CC±5%.
Maximum charge time is configured using the TM pin.
Time settings are available for corresponding charge rates of C/2,1C,and2C.Maximum time-out termina-tion 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.
Top-off Charge
An optional top-off charge phase may be selected to follow fast charge termination for1C and C/2rates.
This phase may be necessary on NiMH or other bat-tery chemistries that have a tendency to terminate charge before reaching full capacity.With top-off en-abled,charging continues at a r educed r ate after fast-charge termination for a period of time selected by the TM pin.(See Table1.)During top-off,the CC pin is modulated at a duty cycle of73ms active for every1097ms inactive.This modulation results in an average rate1/16th that of the fast charge rate.Maxi-mum voltage,time,and temperature are the only ter-mination methods enabled during top-off.
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 every1.17s for the period specified in Table1.This re-sults in a trickle rate of C/32.
TM Pin
The TM pin is a three-level pin used to select the charge timer,top-off,voltage termination mode,trickle 5
bq2002E/G
rate,and voltage hold-off period options.Table1de-scribes the states selected by the TM pin.The mid-level selection input is developed by a resistor di-vider between V CC and ground that fixes the voltage on TM at V CC/2±0.5V.See Figure4.
Charge Status Indication
A fast charge in progress is uniquely indicated when the LED pin goes low.The LED pin is driven to the high-Z state for all conditions other than fast charge.Figure2 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 the current state of LED until inhibit is removed. Temperature monitoring is not affected by the INH pin. During charge inhibit,the bq2002E/G 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.
Low-Power Mode
The IC enters a low-power state when V BAT is driven above the power-down threshold(V PD)where
V PD= V CC- (1V±0.5V)
chengreiBoth the CC pin and the LED pin are driven to the high-Z state.The operating current is reduced to less than1µA in this mode.When V BAT returns to a value below V PD,the IC pulse-trickle charges until the next new charge cycle begins.
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bq2002E/G
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