BQ2050H Li-Ion Power Gauge 8482 ; IC is suitable for battery packs or installed within systems to keep accurate records of available battery capacity. The IC monitors a voltage drop detection resistor connected in series between the negative battery terminal and ground to determine the charge and discharge of the active battery. Compensated battery temperature, self-discharge, and discharge rates are applied to the charge counter to provide information on the available capacity across a wide range of operating conditions.

The battery capacity is automatically recalibrated or "learned" to empty from the process of a complete discharge cycle. Nominal available capacity may be displayed directly using a five-segment LED display. These segments are used to graphically indicate available capacity. The bq2050H also supports simple

Single wire bidirectional serial link to external processor (common ground). 5kb HDQ bus interface reduces communication overhead in external controllers. Internal registers include capacity, temperature, available energy, battery ID, battery status and Li-Ion charge FET

state. External processors can also override some of the bq2050H power meter data registers.

BQ2050H can be in battery pack. The REF output and external transistor allow for a simple, inexpensive voltage regulator to power the circuit from the cell.

feature

Accurately measure the usable capacity of Li-ion batteries

Offers a low cost battery management solution for packaging credits - the complete circuit can fit as little as 1

2 square inches of PCB

- Low operating current ( 120 μA

typical)

- less than 100nA data

holding current

High-speed (5kb) single-wire communication interface (HDQ bus) for critical batteries

parameter

Monitoring and Controlling Charge FETs in Li-Ion Battery Pack Protection Circuits

Directly drive remaining capacity LEDs

automatic measurement

Compensation rate and temperature

16-Pin Narrow Body SOIC

Pin Connection Diagram

Pin Description

LCOM LED Common Output This open-drain output switches VCC to the source current of the LED. The switch is closed during initialization to allow soft pull-up or pull-down program resistors to be read. Display is off when LCOM is also high impedance.

SEG1-

SEG5

LED display segment outputs (dual function with PROG1-PROG5) Each output can activate an LED to sink current from LCOM.

PROG1-

PROG2

Programmable full count select input

(Dual function of SEG1-SEG2) These three-level input pins define the Program Full Count (PFC) threshold as described in the table below.

PROG3-

PROG4

Power Meter Scale Select Inputs (Dual Function and SEG3-SEG4) These tertiary input pins define the scale factors as shown in the table below.

PROG5 Self-discharge rate selection (dual function of SEG5) This tertiary input pin defines the self-discharge and battery compensation factors as shown in the table above.

CFC Charge FET Control Output This pin can be used as additional control to the charge FET of the Li-Ion battery pack protection circuit.

VSS ground

SR Sense Resistor Input

Monitors and integrates voltage drop across sense resistor RS (VSR)

time to explain charging and discharging activity. The SR input is connected between the negative terminal of the battery and the sense resistor. VSR VSS means charging. The effective voltage drop, VSRO, as shown on the bq2050H is VSR + VOS.

DISP display control input

DISP high level disables the LED display. Bonding DISP to VCC allows the PROGX to connect directly to VCC or VSS rather than through a pull-up or pull-down resistor. DISP float allows the LED display to activate charging during this time. DISP low activates the display. See table above.

SB Secondary Battery Input This input monitors the potential of the cell voltage across a high impedance resistive divider network for end-of-discharge voltage (EDV) threshold and battery removal detection.

RBI Register Backup Input This pin is used to provide backup potential during bq2050H register VCC≤3V. storage capacitor or battery

Can connect to RBI.

HDQ Serial Communication Input/Output This is an open-drain bidirectional communication port.

PSTAT protector status input

This input provides Li-Ion protection circuitry for overvoltage conditions. It should connect to VSS when not in use.

Reference voltage output of the REF regulator

REF provides an optional micro-regulator for the voltage reference output. VCC supply voltage input

Function Description

General operation

The bq2050H determines battery capacity by monitoring the amount of current input or removed from a rechargeable battery. The bq2050H measures discharge and charge currents, measures battery voltage, estimates self-discharge, monitors current for batteries with low battery voltage thresholds, and compensates for temperature and discharge rate. The current measurement is measured by monitoring the voltage across the small value series sense resistor between the negative of the battery and ground.

The available available energy capacity is estimated using the remaining average battery voltage and the remaining available nominal value during the discharge cycle. The scaled available energy measurement is corrected for environmental and operating conditions.

Figure 1 shows a typical battery pack application with the bq2050H using the LED display function as a charge status indicator. The bq2050H is configured to display capacity in relative display mode. Relative display mode uses the last measured discharge capacity battery as the battery "full" reference. A push button display function can be used to temporarily enable the LED display.

The bq2050H monitors the charge and discharge current as the voltage across the sense resistor. filter between negative battery terminals and requires the SR pin.

Voltmeter Operation

The operation overview diagram in the figure below illustrates the operation of the bq2050H. The bq2050H cumulatively measures charge and discharge currents, such as self-discharge estimates. The accumulated charge and discharge current temperature and rate are adjusted to provide an indication of the compensated available capacity to the host system or user.

The main counter, Nominal Available Capacity (NAC), represents the available battery capacity at any given time. Battery charging increases the NAC register, battery discharge and self-discharging decrease the NAC register and increase the DCR (discharge count register).

The Discharge Count register is used to update the Last Only Measure Discharge (LMD) register when complete without any battery being fully discharged to empty and partially charged. Therefore, the bq2050H adapts to determine its capacity based on actual emissions. The initial capacity of the battery is equal to the programmed full count before updating the LMD, and the NAC count reaches but does not exceed this threshold on subsequent charges. This approach allows the gas meter to be charger independent and compatible with any type of charging system.

Last Measured Discharge (LMD) or Learning

battery capacity:

LMD is the last measured discharge capacity battery. At initialization (VCC applied or battery replacement), LMD = PFC. On subsequent discharges, the LMD will update the latest version of the measured capacity in the discharge count register to indicate a full discharge below EDV1. The capacity required for qualifying emissions to be transferred from the DCR to the LMD register. This LMD can also be used by the relative display mode as the 100% reference threshold.

Error summary

Inaccurate capacity

LMDs are error prone when initializing, or if no updates happen. At initialization, the LMD value includes the error between the programmed full capacity and the actual capacity. This error occurs until a valid discharge occurs and the LMD is updated. Another reason for an LMD error is a drained battery. As the battery ages, the measured capacity must be adjusted to account for the actual changing battery capacity.

The maintained capacity inaccuracy counter (CPI) is incremented each time a valid charge occurs. It is reset whenever LMD is updated from DCR. Counter If the LMD has not been set, set the capacity inaccuracy flag (CI) and update it after 64 valid charges.

Current sensing error

The nonlinearity and non-repeatability errors associated with the bq2050H current sensing are shown.

The current sense error as a function of VOS is illustrated. When VSRO is between VSRQ and VSRD, the digital filter prevents the charge and discharge of the NAC register from being counted.