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UDG−04096

+

PACK−

PACK+

HDQ

ESDProtection

D2

5.6V

R7

100 Ω

R8

100 Ω

R1

1kΩ

C1

0.1 µF

R2

1kΩ

0.02 Ω

R4

10kΩ

C2

0.1 µF

C3

0.1 µF

C4

0.1 µF

C3

0.1 µF

R3

1kΩ

Li-IonProtector

Li-Ion

or

Li-Pol

PGM TP

1

2

3

4

9

8

7

6

GPIO

SRP

SRN

BAT

RBI

VCC

VSS

D/C

bq27010DRK

5

HDQ

10

PGM

11

Measurements

Charge and Discharge Coulometric and Current Measurements

bq27010, bq27210

SLUS707B – APRIL 2006 – REVISED JANUARY 2007

FUNCTIONAL DESCRIPTION (continued)

Figure 3 shows a typical application circuit. Differential sense of the voltage across the current sense resistor,

R

3-µA pull-down on the HDQ or SDA and SCL lines ensures that the device detects a logic 0 on the

communication lines and allows the device to automatically enter the low-power sleep mode when the system

power is switched off or the pack is removed. A 100 k

Ω pullup to V

this feature needs to be disabled. The bqJUNIOR can operate directly from a single Li-Ion or Li-Pol cell.

Figure 3. Typical Application Circuit (bq27010)

As shown in the functional block diagram, the bqJUNIOR uses a dedicated fully differential Delta-Sigma

Coulomb Counter (DSCC) for charge and discharge current and coulometric measurements and an

analog-to-digital converter (ADC) for battery voltage and temperature measurements. Both DSCC and ADC are

automatically compensated for offset. No user calibration or compensation is required. An EEPROM offset value

can be programmed to compensate for contributions to the DSCC offset due to the PCB layout.

The bqJUNIOR uses a DSCC to perform a continuous integration of the voltage waveform across a small value

sense resistor in the negative lead of the battery, as shown in Figure 3. The integration of the voltage across the

sense resistor is the charge added or removed from the battery. Because the DSCC does a direct integration of

the waveform, the shape of the current waveform through the sense resistor does not have any effect on the

coulometric measurement accuracy. The low-pass filter that feeds the sense resistor voltage to the bqJUNIOR

SRP and SRN inputs filters out system noise and does not affect the coulometric measurement accuracy,

because the low-pass filter does not change the integrated value of the waveform. The bqJUNIOR also uses the

DSCC to measure current. The reported current is determined by the average voltage across the sense resistor

over a 5.12 second interval.

8

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