UNITRODE bq2007 Technical data

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Features

Fast charging and conditioning of

➤

NiCd and NiMH batteries

Precise charging independent

-

of battery pack number of cells

Discharge-before-charge on

-

demand

Pulse trickle charge

-

conditioning

Battery undervoltage and

-

overvoltage protection

Built-in 10-step voltage-based

➤

charge status monitoring

Charge status display options

-

include seven-segment
monotonic bargraph and fully
decoded BCD digit

Display interface options for

-

direct drive of LCD or LED
segments

-

Charger state status
indicators for pending,
discharge, charge, completion,
and fault

Audible alarm for charge

-

completion and fault
conditions

Charge control flexibility

➤

Fast or Standard speed

-

charging

Top-off mode for NiMH

-

Charge rates from

-

C

to 2C

8

(30 minutes to 8 hours)

Charge termination by:

➤

Negative delta voltage (-∆V)

-

Peak voltage detect (PVD)

-

Maximum voltage

-

Maximum time

-

Maximum temperature

-

➤ High-efficiency switch-mode de-

sign

Ideal for small heat-sensitive

-

enclosures

➤ 24-pin,300-mil SOIC or DIP

bq2007

Fast-Charge IC

General Description

The bq2007 is a highly integrated
monolithic CMOS IC designed to pro
vide intelligent battery charging and
charge status monitoring for stand­alone charge systems.

The bq2007 provides a wide variety of
charge status display formats. The
bq2007 internal charge status moni
tor supports up to a seven-segment
bargraph or a single BCD digit dis
play. The bargraph display indicates
up to seven monotonic steps, whereas
the BCD digit counts in ten steps of
10% increments. The bq2007 output
drivers can direct-drive either an
LCD or LED display.

Charge action begins either by appli­cation of the charging supply or by
replacement of the battery pack. For
safety, charging is inhibited until
battery temperature and voltage are
within configured limits.

-

-

-

Pin Connections Pin Names

SEGC/ Display output segment C/
MSEL driver mode select

SEGC/MSEL

9/96 B

SEG
SEG

LED
LED

INH

COM

ALARM

VSEL
FAST

DCMD

TM

1
2

B

3

A

4

1

5

2

6
7
8
9
10
11
12

24-Pin Narrow DIP

or SOIC

24
23

22

21
20
19
18
17
16
15
14
13

PN200701.eps

SEGD/DSEL
SEGE/DSEL

SEGF/MULT
SEGG/QDSEL
MOD
V

CC

V

SS
DIS
TS
BAT
SNS
TCO

SEG

SEG

1
2

LED

LED

INH

COM Common LED/LCD output

ALARM Audio alarm output

TM Timer mode select

VSEL Voltage termination select

FAST Fast charge rate select

DCMD

TCO Temperature cutoff

Display output segment B

B

Display output segment A

A

Charge status output 1

1

Charge status output 2

2

Charge inhibit input

Discharge command

SNS Sense resistor input

BAT Battery voltage

TS Temperature sense

DIS Discharge control

V

SS

V

CC

System ground

5.0V±10% power

MOD Modulation control

SEG

/ Display output segment G/

G

QDSEL charge status display select

SEG

/ Display output segment F/

F

MULT multi-cell pack select

SEG

/ Display output segment E/

E

DSEL

SEG
DSEL

display select 2

2

/ Display output segment D/

D

display select 1

1

1

bq2007

The acceptable battery temperature range is set by an
internal low-temperature threshold and an external
high-temperature cutoff threshold. The absolute tem
perature is monitored as a voltage on the TS pin with
the external thermistor network shown in Figure 2.

The bq2007 provides for undervoltage battery protection
from high-current charging if the battery voltage is less
than the normal end-of-discharge value. In the case of a
deeply discharged battery, the bq2007 enters the
charge-pending state and attempts trickle-current condi
tioning of the battery until the voltage increases. Should
the battery voltage fail to increase above the discharge
value during the undervoltage time-out period, a fault
condition is indicated.

Discharge-before-charge may be selected to automatically
discharge the battery pack on battery insertion or with a
push-button switch. Discharge-before-charge on demand
provides conditioning services that are useful to correct or
prevent the NiCd voltage depression, or “memory” effect,
and also provide a zero capacity reference for accurate
capacity monitoring.

After prequalification and any required discharge­before-charge operations, charge action begins until one of
the full-charge termination conditions is detected. The
bq2007 terminates charging by any of the following methods:

n Negative delta voltage (-

n

Peak voltage detect (PVD)

n

Maximum absolute temperature

n

Maximum battery voltage

n

Maximum charge time-out

V)

∆

The bq2007 may be programmed for negative delta
voltage (-∆V) or peak voltage detect (PVD) charge
termination algorithms. The VSEL input pin selects -∆V
or PVD termination to match the charge rate and
battery characteristics.

To provide maximum safety for battery and system,
charging terminates based on maximum temperature
cutoff (TCO), maximum cutoff voltage (MCV), and
maximum time-out (MTO). The TCO threshold is the
maximum battery temperature limit for charging. TCO
terminates charge action when the temperature sense
input voltage on the TS pin drops below the TCO pin
voltage threshold. MCV provides battery overvoltage
protection by detecting when the battery cell voltage
(V

CELL=VBAT-VSNS

) exceeds the VMCV value and ter
minates fast charge, standard charge, or top-off charge.
The maximum time-out (MTO) termination occurs when
the charger safety timer has completed during the active
charge state.

The bq2007 indicates charge state status with an audio
alarm output option and two dedicated output pins with pro
grammable display options. The DSEL1–2 inputs can select

-

one of the three display modes for the LED1–2 outputs.

Charger status is indicated for:

Charge pending

n

Charge in progress

n

Charge complete

-

n

Fault condition

n

Pin Descriptions

SEG

MSEL

DSEL
DSEL

MULT

QDSEL

LED
LED

-

INH

Display output segments A–G

A–G

State-of-charge monitoring outputs. QDSEL
input selects the bargraph or BCD digit dis
play mode. See Table 3.

Display driver mode select

Soft-programmed input selects LED or LCD
driver configuration at initialization. When
MSEL is pulled up to V

, outputs SEG

CC

LED interface levels; when MSEL is pulled
down to V

Display mode select 1–2

–

1

2

, outputs SEG

SS

are LCD levels.

A–G

Soft-programmed inputs control the LED

charger status display modes at initialization.
See Table 2.

Fixed-cell pack select

Soft-programmed input is pulled up to V

when charging multi-cell packs and is pulled
down to V

for charging packs with a fixed

SS

number of cells.

State-of-charge display select

The QDSEL input controls the SEG

state-of-charge display modes. See Table 3.

Charger status outputs 1–2

–

1

2

Charger status output drivers for direct
drive of LED displays. Display modes are
selected by the DSEL input. See Table 2.

Charge inhibit input

When low, the bq2007 suspends all charge ac
tions, drives all outputs to high impedance, and
assumes a low-power operational state. When
transitioning from low to high, a charge
cycle is initiated. See page 10 for details.

A–G

-

-

are

1—2

CC

A–G

-

2

bq2007

COM

ALARM

TM

VSEL

FAST

DCMD

TCO

SNS

BAT

Common LCD/LED output

Common output for LCD/LED display
SEG

initialization to allow reading of
soft-programmed inputs DSEL
MSEL, MULT, and QDSEL.

Audio output

Audio alarm output.

Timer mode select

TM is a three-level input that controls the set
tings for charge control functions. See Table 5.

Voltage termination select

This input switches the voltage detect
sensitivity. See Table 5.

Fast charge rate select

The FAST input switches between Fast and
Standard charge rates. See Table 4.

Discharge command

The DCMD

before-charge function. A negative-going
pulse initiates a discharge action. If DCMD
is connected to VSS, automatic discharge­before-charge is enabled. See Figure 3.

Temperature cut-off threshold input

Minimum allowable battery temperature­sensor voltage. If the potential between TS
and SNS is less than the voltage at the TCO
input, then any fast charging or top-off
charging is terminated.

Sense resistor input

SNS controls the switching of MOD output based
on an external sense resistor. This provides the
lower reference potential for the BAT pin and the
TS pin.

Battery voltage input

Battery voltage sense input referenced to SNS
for the battery pack being charged. This resis
tor divider network is connected between the
positive and the negative terminals of the
battery. See Figure 1.

. Output is high-impedance during

A—G

, DSEL2,

1

input controls the discharge-

TS

DIS

V

SS

-

V

CC

MOD

Temperature sense input

Input referenced to SNS for battery tem
perature monitoring negative temperature
coefficient (NTC) thermistor.

Discharge control

DIS is a push-pull output that controls an
external transistor to discharge the battery
before charging.

Ground

VCCsupply input

Current-switching control output

Push/pull output that controls the charging
current to the battery. MOD switches high to
enable current flow and low to inhibit current
flow.

Functional Description

Figure 1 illustrates charge control and display status
during a bq2007 charge cycle. Table 1 summarizes the
bq2007 operational features. The charge action states
and control outputs are given for possible input
conditions.

Charge Action Control

The bq2007 charge action is controlled by input pins

DCMD

, VSEL, FAST, and TM. When charge action is
initiated, the bq2007 enters the charge-pending state,
checks for acceptable battery voltage and temperature,
and performs any required discharge-before-charge
operations. DCMD
function, and VSEL, FAST, and TM select the charger
configuration. See Tables 4 and 5.

During charging, the bq2007 continuously tests for
charge termination conditions: negative delta voltage,
peak voltage detection, maximum time-out, battery
over-voltage, and high-temperature cutoff. When the
charge state is terminated, a trickle charge continues to
compensate for self-discharge and maintain the fully
charged condition.

Charge Status Indication

-

Table 2 summarizes the bq2007 charge status display
indications. The charge status indicators include the
DIS output, which can be used to indicate the discharge
state, the audio ALARM output, which indicates charge
completion and fault conditions, and the dedicated
status outputs,LED

controls the discharge-before-charge

and LED2.

1

-

3

bq2007

Charge

Pending

(Pulse-Trickle)

Dis-

charge

(Optional)

DIS

MOD

or
MOD

(Switching

Configuration)

(External

Regulation)

Mode 1, LED2 Status Output

Mode 1, LED1 Status Output

Mode 2, LED2 Status Output

Mode 2, LED1 Status Output

Mode 3, LED2 Status Output

Fast Charging

Top-Off

(Optional)

260 s

2080 s

260 s

2080 s

Pulse-Trickle

Note

260 s

Note

260 s

Mode 3, LED1 Status Output

Battery discharged to V
temperature/voltage limits. (Discharge-before-charge not
qualified by temperature.)

Low-voltage fault: Battery voltage less than V

Charge initiated. Battery outside temperature/voltage limits.

Note: See Table 4 for pulse-trickle period.

Figure 1. Example Charging Action Events

4

or battery within

EDV

for under-voltage time-out.

EDV

TD200701.eps

bq2007

Outputs LED

selected at initialization by the input pins DSEL
DSEL

. The DSEL1and DSEL2input pins, when pulled

2

down to V
simple two-LED system. LED
status (i.e., charge pending and discharge) and LED

have three display modes that are

1–2

, are intended for implementation of a

SS

indicates the precharge

2

and

1

indi

1

cates the charge status (i.e., charging and completion).
DSEL

pulled up to VCCand DSEL2pulled down to V

1

mode is for implementation of a single tri-color LED such
that discharge, charging, and completion each have a unique
color. DSEL
V

allows for fault status information to be displayed.

CC

pulled down to VSSand DSEL2pulled up to

1

Audio Output Alarm

The bq2007 audio alarm output generates an audio tone
to indicate a charge completion or fault condition. The
audio alarm output is a symmetrical duty-cycle AC sig
nal that is compatible with standard piezoelectric alarm
elements. A valid battery insertion is indicated by a sin

gle high-tone beep of
charge completion and fault conditions are indicated by
a 9.5- to 15-second high-tone sequence of
cal duration at a 2-second typical repetition rate.

Charge Action

State Conditions MOD Output DIS Output

Battery absent V

Charge initiation

Discharge-before­charge

Charge pending

Fast charging

Standard charging

Charge complete

Top-off pending

Top-off charging

Trickle charging

Fault

Definitions: V

1

-second typical duration. The

2

1

2

Table 1. bq2007 Operational Summary

applied and V

CC

V

applied or V

CC

from≥V

DCMD

high-to-low transition or to VSSon charge

initiation and V

Charge initiation occurred and V

V

Charge pending complete and FAST = V

Charge pending complete and FAST = V

-∆V termination or V

-3mV/cell or maximum time-out or V
VSEL = V

or V

VSEL = V

time-out not exceeded and V

Charge complete and top-off disabled or

Charge pending state and charge pending

= V

V

CELL

LTF

= 0.5*VCC.

BAT

- V

V

≤

TEMP

CC

TCO

, charge complete and V

V

≤

TEMP

and charge complete and

CC

V

CELL

top-off complete or pending

time-out (t

SNS;VMCV

= 0.8*VCC;V

-second typi-

CELL

CELL

to < V

MCV

< V

EDV

CELL

or V

CELL

< V

TEMP

TCO

PEND

or V

CELL

< V

MCV

) complete

TCO

TEMP

Charge Status Monitoring

The bq2007 charge status monitor may display the bat
tery voltage or charge safety timer as a percentage of
the full-charged condition. These options are selected

-

with the MULT soft-programmed input pin.

When MULT is pulled down to V

SS

status is displayed as a percentage of the battery
voltage, and the single-cell battery voltage at the BAT
pin is compared with internal charge voltage reference
thresholds. When V
thresholds of V

20,V40,V60

is greater than the internal

BAT

,orV80, the respective 20%,
40%, 60%, or 80% display outputs are activated. The
battery voltage directly indicates 20% charge
increments, while the 10% charge increments use a
timer that is a function of the charge safety timer.

­When MULT is pulled down to V

exceeds V20during charging, the 20% charge indication

­is activated and the timer begins counting for a period

equal to
When the timer count is completed, the 30% charge

1

1

to

64

of the charge safety time-out period.

32

indication is activated. Should V
the timer count completion, the charge status monitor
activates the 30% and 40% indications. This technique

V

≥

MCV

drops

MCV

< V

MCV

≥

TEMP

< V

EDV

or PVD≥0 to

CELL

TEMP

< V

EDV

> V

TCO

V

LTF

> V

≥

Trickle charge per Table 4 Low

- Low

Low High

or

Trickle charge per Table 4 Low

CC

SS

V

and

Low if V
high if V

Low if V
high if V

MCV

LTF

Trickle charge per Table 4 Low

Activated per V

73ms of every 585ms Low

SNS

SNS

SNS

SNS

--

Trickle charge per Table 4 Low

Trickle charge per Table 4 Low

= 0.262*VCCor 0.4*VCC;V

EDV

, the battery charge

SS

SS

exceed V40prior to

BAT

> 250mV;

< 200mV

> 250mV;

< 200mV

for

SNS

= VTS- V

TEMP

and when V

SNS

-

BAT

Low

Low

;

5