Texas Instruments DV2007S1, BQ2007STR, BQ2007S, BQ2007PN Datasheet

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

to 2C

(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

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.

PN200701.eps

24-Pin Narrow DIP

or SOIC

2 3 4 5

6 7 8

24 23

21 20 19 18

17 9 10

15 11 12

SEGC/MSEL

SEG

LED

INH

COM

ALARM

TM VSEL FAST

DCMD

SEGD/DSEL

SEGE/DSEL

SEGF/MULT SEGG/QDSEL MOD V

SS DIS TS BAT SNS TCO

Fast-Charge IC

bq2007

Pin Connections Pin Names

SEGC/ Display output segment C/ MSEL driver mode select

SEG

Display output segment B

SEG

Display output segment A

LED

Charge status output 1

LED

Charge status output 2

INH

Charge inhibit input

COM Common LED/LCD output

ALARM Audio alarm output

TM Timer mode select

VSEL Voltage termination select

FAST Fast charge rate select

DCMD

Discharge command

TCO Temperature cutoff

SNS Sense resistor input

BAT Battery voltage

TS Temperature sense

DIS Discharge control

System ground

5.0V±10% power

MOD Modulation control

SEG

/ Display output segment G/

QDSEL charge status display select

SEG

/ Display output segment F/

MULT multi-cell pack select

SEG

/ Display output segment E/

DSEL

display select 2

SEG

/ Display output segment D/

DSEL

display select 1

9/96 B

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 (-

∆

Peak voltage detect (PVD)

Maximum absolute temperature

Maximum battery voltage

Maximum charge time-out

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

Charge in progress

Charge complete

Fault condition

Pin Descriptions

SEG

A–G

Display output segments A–G

State-of-charge monitoring outputs. QDSEL input selects the bargraph or BCD digit dis

play mode. See Table 3.

MSEL

Display driver mode select

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

, outputs SEG

A–G

are LED interface levels; when MSEL is pulled down to V

, outputs SEG

A–G

are LCD levels.

DSEL

–

DSEL

Display mode select 1–2

Soft-programmed inputs control the LED

1—2

charger status display modes at initialization. See Table 2.

MULT

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

number of cells.

QDSEL

State-of-charge display select

The QDSEL input controls the SEG

A–G

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

LED

–

LED

Charger status outputs 1–2

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

INH

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.

bq2007

COM

Common LCD/LED output

Common output for LCD/LED display SEG

A—G

. Output is high-impedance during initialization to allow reading of soft-programmed inputs DSEL

, DSEL2,

MSEL, MULT, and QDSEL.

ALARM

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.

VSEL

Voltage termination select

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

FAST

Fast charge rate select

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

DCMD

Discharge command

The DCMD

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

TCO

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.

SNS

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.

BAT

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.

Temperature sense input

Input referenced to SNS for battery tem

perature monitoring negative temperature coefficient (NTC) thermistor.

DIS

Discharge control

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

Ground

VCCsupply input

MOD

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

controls the discharge-before-charge 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

and LED2.

bq2007

Fast Charging

Top-Off

(Optional)

TD200701.eps

Dis-

charge

(Optional)

Charge

Pending

(Pulse-Trickle)

DIS

MOD

Mode 1, LED2 Status Output

Charge initiated. Battery outside temperature/voltage limits.

Battery discharged to V

EDV

or battery within temperature/voltage limits. (Discharge-before-charge not qualified by temperature.)

Pulse-Trickle

(Switching

Configuration)

(External

Regulation)

Mode 1, LED1 Status Output

Mode 2, LED2 Status Output

Mode 2, LED1 Status Output

Mode 3, LED2 Status Output

260 s

2080 s

260 s

2080 s

260 s

Note

260 s

Note

Note: See Table 4 for pulse-trickle period.

Mode 3, LED1 Status Output

Low-voltage fault: Battery voltage less than V

EDV

for under-voltage time-out.

Figure 1. Example Charging Action Events

Outputs LED

1–2

have three display modes that are

selected at initialization by the input pins DSEL

and

DSEL

. The DSEL1and DSEL2input pins, when pulled

down to V

, are intended for implementation of a

simple two-LED system. LED

indicates the precharge

status (i.e., charge pending and discharge) and LED

indi

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

pulled up to VCCand DSEL2pulled down to V

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

pulled down to VSSand DSEL2pulled up to

allows for fault status information to be displayed.

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

-second typical duration. The charge completion and fault conditions are indicated by a 9.5- to 15-second high-tone sequence of

-second typi-

cal duration at a 2-second typical repetition rate.

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

, the battery charge 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

BAT

is greater than the internal

thresholds of V

20,V40,V60

,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

and when V

BAT

exceeds V20during charging, the 20% charge indication is activated and the timer begins counting for a period equal to

of the charge safety time-out period. When the timer count is completed, the 30% charge indication is activated. Should V

BAT

exceed V40prior to the timer count completion, the charge status monitor activates the 30% and 40% indications. This technique

bq2007

Charge Action

State Conditions MOD Output DIS Output

Battery absent V

applied and V

CELL

≥

MCV

Trickle charge per Table 4 Low

Charge initiation

applied or V

CELL

drops

from≥V

MCV

to < V

MCV

- Low

Discharge-beforecharge

DCMD

high-to-low transition or to VSSon charge

initiation and V

EDV

< V

CELL

< V

MCV

Low High

Charge pending

Charge initiation occurred and V

TEMP

≥

LTF

TEMP

≤

TCO

or V

CELL

< V

EDV

Trickle charge per Table 4 Low

Fast charging

Charge pending complete and FAST = V

Low if V

SNS

> 250mV;

high if V

SNS

< 200mV

Low

Standard charging

Charge pending complete and FAST = V

Low if V

SNS

> 250mV;

high if V

SNS

< 200mV

Low

Charge complete

-∆V termination or V

TEMP

< V

TCO

or PVD≥0 to

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

CELL

> V

MCV

Top-off pending

VSEL = V

, charge complete and V

TEMP

≥

LTF

or V

TEMP

≤

TCO

or V

CELL

< V

EDV

Trickle charge per Table 4 Low

Top-off charging

VSEL = V

and charge complete and

time-out not exceeded and V

TEMP

> V

TCO

and

CELL

< V

MCV

Activated per V

SNS

for

73ms of every 585ms Low

Trickle charging

Charge complete and top-off disabled or

top-off complete or pending

Trickle charge per Table 4 Low

Fault

Charge pending state and charge pending

time-out (t

PEND

) complete

Trickle charge per Table 4 Low

Definitions: V

CELL

= V

BAT

- V

SNS;VMCV

= 0.8*VCC;V

EDV

= 0.262*VCCor 0.4*VCC;V

TEMP

= VTS- V

SNS

;

LTF

= 0.5*VCC.

Table 1. bq2007 Operational Summary

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