Texas Instruments BQ2013HSN-A514TR, BQ2013HSN-A514 Datasheet

Features

➤

Accurate measurement of available charge in rechargeable batteries

➤

Designed for electric assist bicycles and other applications

➤

Measures a wide dynamic current range

➤

Supports NiCd, NiMH or lead acid

➤

Designed for battery pack inte

gration

120µA typical standby current (self-discharge estimation mode)

Small size enables implementations in as little as

square inch of PCB

➤ Direct drive of LEDs for capacity

display

➤ Automatic charge and self-

discharge compensation using internal temperature sensor

➤ Simple single-wire serial commu-

nications port for subassembly testing

➤ 16-pin narrow SOIC

General Description

The bq2013H Gas Gauge IC is in

tended for battery-pack installation to maintain an accurate record of a bat

tery’s available charge. The IC moni

tors a voltage drop across a sense resis

tor connected in series between the negative battery terminal and ground to determine charge and discharge ac

tivity of the battery. The bq2013H is designed for high cpaacity battery packs used in high-discharge rate sys

tems.

Battery self-discharge is estimated based on an internal timer and tem

perature sensor. Compensations for battery temperature, rate of charge, and self-discharge are applied to the charge counter to provide available capacity information across a wide range of operating conditions. Initial battery capacity, self-discharge rate, display mode, and charge compensation are set using the PROG

1-6

pins. Actual battery capacity is automatically “learned” in the course of a discharge cycle from full to empty.

Nominal available charge may be directly indicated using a five-seg

ment LED display. These segments are used to graphically indicate nominal available charge.

The bq2013H supports a simple single-line bi-directional serial link to an external processor (common ground). The bq2013H outputs bat

tery information in response to exter

nal commands over the serial link. To support battery pack testing, the outputs may also be controlled by command. The external processor may also overwrite some of the bq2013H gas gauge data registers.

The bq2013H may operate directly from four nickel cells or three lead acid. With the REF output and an external transistor, a simple, inexpensive regulator can be built to provide V

from a greater number of cells.

Internal registers include available charge, temperature, capacity, battery ID,and battery status.

LCOM LED common output

SEG

/PROG1LED segment 1/ Program

1 input

SEG

/PROG2LED segment 2 / Program

2 input

SEG

/PROG3LED segment 3/ Program

3 input

SEG

/PROG4LED segment 4/ Program

4 input

SEG

/PROG5LED segment 5/ Program

5 input

PROG

Program 6 input

REF Voltage reference output

DONE Fast charge complete

input

HDQ Serial communications

input/output

RBI Register backup input

SB Battery sense input

DISP

Display control input

SR Sense resistor input

Supply voltage

bq2013H

Pin Connections Pin Names

PN2013.eps

16-Pin Narrow SOIC

REF

DONE

HDQ

RBI

DISP

LCOM

SEG1/PROG

SEG2/PROG

SEG3/PROG

SEG4/PROG

SEG5PROG

PROG

Gas Gauge IC for Power-

Assist Applications

SLUS120–MAY 1999 B

Pin Descriptions

LCOM

LED common

This open-drain output switches V

to source current for the LEDs. The switch is off during initialization to allow reading of PROG

1-5

pull-up or pull-down program resistors. LCOM is also high impedance when the display is off.

SEG

–

SEG

LED display segment outputs (dual func

tion with PROG

–PROG

Each output may activate an LED to sink the current sourced from LCOM.

PROG

–

PROG

Programmed full count selection inputs (dual function with SEG

- SEG5)

These three-level input pins define the pro

grammed full-count (PFC), display mode, self-discharge rate, offset compensation, overload threshold, and charge compensa

tion.

Sense resistor input

The voltage drop (V

) across the sense re-

sistor R

is monitored and integrated over time to interpret charge and discharge activity. The SR input (see Figure 1) is connected between the negative terminal of the battery and ground. V

SR>VSS

indicates charge, and

SR<VSS

indicates discharge. The effective

voltage drop, V

SRO

, as seen by the bq2013H

is V

SR+VOS.

DONE

Charge complete input

This input/output is used to communicate the status of an external charge controller to the bq2013H.

DISP

Display control input

DISP

pulled high disables the display.

DISP

floating allows the LED display to

be active during certain charge and dis

charge conditions. Transitioning DISP low activates the display.

Secondary battery input

This input monitors the scaled battery volt

age through a high-impedance resistive di

vider network for the end-of-discharge volt

age (EDV) thresholds.

RBI

This input is used to provide backup poten

tial to the bq2013H registers during periods when V

< 3V. A storage capacitor can be

connected to RBI.

HDQ

Serial I/O pin

This is an open-drain bidirectional communications port.

REF

Voltage reference output for regulator

REF provides a voltage reference output for an optional micro-regulator.

Supply voltage input

Ground

bq2013H

Functional Description

General Operation

The bq2013H determines battery capacity by monitoring the amount of charge input to or removed from a recharge

able battery. The bq2013H measures discharge and charge currents, estimates self-discharge, monitors the battery for low-battery voltage thresholds, and compensates for tem

perature and charge rates. The charge measurement is made by monitoring the voltage across a small-value se

ries sense resistor between the battery’s negative terminal and ground. The available battery charge is determined by monitoring this voltage over time and correcting the measurement for the environmental and operating condi

tions.

Figure 1 shows a typical battery pack application of the bq2013H using the LED display. The bq2013H can be configured to display capacity in either a relative or an absolute display mode. The relative display mode uses the last measured discharge capacity of the battery as the battery “full” reference. The absolute display mode uses the programmed full count (PFC) as the full refer

ence, forcing each segment of the display to represent a fixed amount of charge. A push-button display feature is available for enabling the LED display.

The bq2013H monitors the charge and discharge cur

rents as a voltage across a sense resistor (see R

in Fig

ure 1). A filter between the negative battery terminal and the SR pin is required.

bq2013H

FG2013H1.eps

PROG

SEG5/PROG

SEG4/PROG

SEG3/PROG

SEG2/PROG

SEG1/PROG

DISP

REF

bq2013H

Gas Gauge IC

LCOM

RBI

HDQ

DONE

100K

Q1 ZVNL110A

H, Z, or L

To µC

0.1µF

Load

Charger

To µC or

Fast Charger

2. The battery stack voltage can be directly connect to VCC across 4 nickel cells (4.8V nominal and should not exceed 6.5V) with a resistor and a zener diode to limit voltage during charge. Otherwise, R1and Q1 are needed for regulation of > 4 nickel cells.

3. Programming resistors and ESD-protection diodes are not shown.

4. R-C on SR is required.

1. Indicates optional.

Notes:

Figure 1. Application Diagram: LED Display

The bq2013H RBI input pin is intended to be used with a storage capacitor to provide backup potential to the in

ternal bq2013H registers when V

momentarily drops be

low 3.0V. V

is output on RBI when VCCis above 3.0V.

After V

rises above 3.0V, the bq2013H checks the internal registers for data loss or corruption. If data has changed, then the NAC register is cleared, and the LMD register is loaded with the initial PFC.

Voltage Thresholds

In conjunction with monitoring VSRfor charge/discharge currents, the bq2013H monitors the battery potential through the SB pin for the end-of-discharge voltage (EDV) thresholds.

The EDV threshold levels are used to determine when the battery has reached an “empty” state.

The EDV thresholds for the bq2013H are set as follows:

EDV1 (first) = 1.00V

EDVF (final) = EDV1 - 100mV

The battery voltage divider (RB1 and RB2 in Figure 1) is used to scale these values to the desired threshold.

If VSB is below either of the two EDV thresholds for the specified delay times in Table 1, the associated flag is latched and remains latched, independent of VSB, until the next valid charge. EDV monitoring is disabled if the OVLD bit in FLGS2 is set.

Table 1. Delay Time in Seconds

Capacity

Temperature

< 10°C10°C to 30°C > 30°C

> 40% 7 6 5

20% to 40% 4 3 2

< 20% 2 2 2

Reset

The bq2013H can be reset by removing VCCand ground

ing the RBI pin for 15 seconds or with a command over the serial port. The serial port reset command sequence requires writing 00h to register PPFC (address = leh) and the writing 00h to register LMD (address = 05h.)

Temperature

The bq2013H internally determines the temperature in 10°C steps centered from -35°C to +85°C. The tempera

ture steps are used to adapt charge rate compensations and self-discharge counting. The temperature range is available over the serial port in 10°C increments as shown in the following table:

TMPGG (hex) Temperature Range

0x < -30°C

1x -30°C to -20°C

2x -20°C to -10°C

3x -10°C to 0°C

4x 0°C to 10°C

5x 10°C to 20°C

6x 20°C to 30°C

7x 30°C to 40°C

8x 40°C to 50°C

9x 50°C to 60°C

Ax 60°C to 70°C

Bx 70°C to 80°C

Cx > 80°C

Layout Considerations

The bq2013H measures the voltage differential between the SR and V

pins. VOS(the offset voltage at the SR pin) is greatly affected by PC board layout. For optimal results, the PC board layout should follow the strict rule of a single-point ground return. Sharing high-current ground with small signal ground causes undesirable noise on the small signal nodes. Additionally:

■

The capacitors should be placed as close as possible to the SB and V

pins and their paths to VSSshould be as short as possible. A high-quality ceramic capacitor of 0.1µf is recommended for V

■

The sense resistor (RS) should be as close as possible to the bq2013H.

■

The R-C on the SR pin should be located as close as possible to the SR pin. The maximum R should not exceed 100K.

Gas Gauge Operation

The operational overview diagram in Figure 2 illus

trates the operation of the bq2013H. The bq2013H ac

cumulates a measure of charge and discharge currents, as well as an estimation of self-discharge. The bq2013H compensates charge current for charge rate and tem

bq2013H

perature. Discharge current is load compensated based on the value stored in location LCOMP (address = 0eh). LCOMP allows the bq2013H to automatically adjust for continuous small discharge currents. The bq2013H com

pensates self discharge for the load value as well as tem

perature.

The main counter, Nominal Available Capacity (NAC), represents the available battery capacity at any given time. Battery charging increments the NAC register, while battery discharging, self-discharge decrement the NAC register and increment the DCR (Discharge Count Register). NAC is also corrected automatically for offset error based on the value in the offset location OFFSET (address = 0bh.)

The Discharge Count Register (DCR) is used to update the Last Measured Discharge (LMD) register only if a complete battery discharge from full to empty occurs without any partial battery charges. Therefore, the bq2013H adapts its capacity determination based on the actual conditions of discharge.

The battery’s initial capacity is equal to the Pro

grammed Full Count (PFC) shown in Table 2. Until LMD is updated, NAC counts up to but not beyond this threshold during subsequent charges. This approach allows the gas gauge to be charger-independent and compatible with any type of charge regime.

1. Last Measured Discharge (LMD) or learned battery capacity:

LMD is the last measured discharge capacity of the battery. On initialization (application of V

or bat

tery replacement), LMD = PFC. During subsequent discharges, the LMD is updated with the latest measured capacity in the Discharge Count Register (DCR) representing a discharge from full to below EDV. The maximum decrease in LMD because of a DCR update is 25% of LMD. A qualified discharge is necessary for a capacity transfer from the DCR to the LMD register. The LMD also serves as the 100% reference threshold used by the relative dis

play mode.

2. Programmed Full Count (PFC) or initial bat

tery capacity:

The initial LMD and gas gauge rate values are pro

grammed by using PFC. The PFC also provides the 100% reference for the absolute display mode. The bq2013H is configured for a given application by se

lecting a PFC value from Table 2. The correct PFC may be determined by multiplying the rated battery capacity in mAh by the sense resistor value:

Battery capacity (mAh)*sense resistor (Ω) =

PFC (mVh)

Selecting a PFC slightly less than the rated capacity for absolute mode provides capacity above the full reference for much of the battery’s life.

bq2013H

FG2013H2.eps

Load and

Temperature

Compensation

Charge Current

Discharge

Current

Self-Discharge

Timer

Temperature

Translation

Nominal

Available

Charge

(NAC)

(offset corrected)

Last

Measured

Discharged

(LMD)

Discharge

Count

(DCR)

Qualified Transfer

Rate and

Temperature

Compensation

Rate and

Temperature

Compensation

Temperature Step, Other Data

Inputs

Main Counters

and Capacity

Reference (LMD)

Outputs

Serial

Port

Chip-Controlled

Available Charge

LED Display

Load

Compensation

Figure 2. Operational Overview

Example: Selecting a PFC Value

Given:

Sense resistor = 0.0075Ω Number of cells = 14 Capacity = 5000mAh, NiCd cells Current range = 1A to 30A Relative display mode with 4 second timer Self-discharge = 1% per day Trickle charge compensation = 0.85 Typical offset = -75µV Voltage drop across sense resistor = 5mV to 150mV

Therefore:

5000mAh*0.0075Ω = 37.5mVh

Select:

PFC = 448000 counts or 35mVh PROG

, PROG2=Z,L

PROG

bq2013H

Programmed

Full Count (PFC) mVh Scale PROG

PROG

27136 84.8

320

24064 75.2

320

41472 64.8

640

35072 54.8

640

28672 44.8

640

44800 35

1280

30720 24

1280

38400 15

2560

12800 5

2560

Table 2. bq2013H Programmed Full Count mVh Selections

PROG

Self-Discharge

H 1.6% per day

Z 0.8% per day

L 0.2% per day

Table 3. Programmed Self-Discharge

bq2013H

PROG

Overload Threshold Display Mode

OVLD

= -75mV Relative/4s timer after push-button release

OVLD

= -75mV Relative/4s timer after push-button release

OVLD

= -25mV Absolute/4s timer after push-button release

Table 4. Programmed Display Mode

PROG

Trickle Fast

<30°C30°C—50°C >50°C <30°C30°C—50°C >50°C

H 0.80 0.75 0.70 0.95 0.90 0.85

Z 1.00 1.00 1.00 1.00 1.00 1.00

L 0.85 0.80 0.75 0.95 0.90 0.85

Table 5. Programmed Charge Compensation

PROG

Offset

-150µV

-75µV

0µV

Table 6. Programmed Discharge Offset Adjustment

The initial full battery capacity is 35mVh (4667mAh) until the bq2013H “learns” a new capacity with a qualified dis

charge from full to EDV1.

Nominal Available Capacity (NAC):

NAC counts up during charge to a maximum value of LMD and down during discharge and self dis

charge to 0. NAC is reset to 0 on initialization and on the first valid charge following discharge to EDV1. To prevent overstatement of charge during periods of overcharge, NAC stops incrementing when NAC = LMD. When the DONE input is as

serted high, indicating full charge completion, NAC is set to LMD.

Discharge Count Register (DCR):

The DCR counts up during discharge independent of NAC and could continue increasing after NAC has decremented to 0. Prior to NAC = 0 (empty battery), both discharge and self-discharge incre

ment the DCR. After NAC = 0, only discharge in

crements the DCR. The DCR resets to 0 when NAC = LMD. The DCR does not roll over but stops counting when it reaches FFFFh.

The DCR value becomes the new LMD value on the first charge after a valid discharge to EDV1 if all of the following conditions are met:

■

No valid charge initiations (charges greater than 2 NAC updates) occurred during the period between NAC = LMD and EDV1.

■

The self-discharge count is less than 6% of NAC.

■

The temperature is≥0°C when the EDV1 level is reached during discharge.

■

VDQ is set.

Charge Counting

Charge activity is detected based on a positive voltage on the V

input. If charge activity is detected, the

bq2013H increments NAC at a rate proportional to V

SRO

(VSR+VOS) and, if enabled, activates an LED display if V

SRO

> 500µV. Charge actions increment the NAC af

ter compensation for charge rate and temperature.

The bq2013H detects charge activity with V

SRO

> 250µV.

A valid charge equates to a sustained charge activity greater than 2 NAC updates. Once a valid charge is de

tected, charge counting continues until V

SRO

drops be

low 250µV.

Discharge Counting

All discharge counts where V

SRO

< -250µV cause the

NAC register to decrement and the DCR to increment. If enabled, the display is activated when V

SRO

< -2mV.

The display remains active for 10 seconds after V

SRO

rises above - 2mV.

Self-Discharge Estimation

The bq2013H decrements NAC and increments DCR for self-discharge based on time and temperature. The selfdischarge count rate is programmed per Table 3. This is the rate for a battery temperature between 20–30°C. The NAC register cannot be decremented below 0.

Count Compensations

The bq2013H determines fast charge when the NAC up

dates at a rate of≥2 counts/s. Charge activity is com

pensated for temperature and rate before updating NAC. Self-discharge estimation is compensated for tem

perature before updating NAC or DCR.

Charge Compensation

Charge efficiency factors are selected using Table 5 for trickle charge and fast charge. Fast charge is defined as a rate of charge resulting in≥2 NAC counts/s (0.16C to

0.6C, depending on PFC selections; see Table 2).

Temperature adapts the charge rate compensation factors over three ranges between nominal, warm, and hot temperatures. Program pin 5 is used to select one of three compensation programs. These values are shown in Table 5.

bq2013H

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