BQ2000TS datasheet(10/18 Pages) TI

10 / 18 page

n High-temperature fault voltage: VHTF = 0.25

∗ VCC This

voltage corresponds to the temperature (HTF) at which

fast charging is allowed to begin.

n Low-temperature fault voltage: VLTF = 0.5

∗ VCC

This voltage corresponds to the minimum temperature

(LTF) at which fast charging or top-off is allowed. If the

voltage on pin TS rises above VLTF, the bq2000

suspends fast charge or top-off but does not terminate

charge. When the voltage falls back below VLTF, fast

charge or top-off resumes from the point where

suspended. Trickle-charge is allowed during this

condition.

Table 4 summarizes these various conditions.

Charge Status Display

The charge status is indicated by open-drain output

LED.

Table 5 summarizes the display output of the

bq2000.

Sleep Mode

The bq2000 features a sleep mode for low power con-

sumption. This mode is enabled when the voltage at pin

BAT is above the low-power-mode threshold, VSLP. Dur-

ing sleep mode, the bq2000 shuts down all internal cir-

cuits, drives the LED output to high-impedance state,

and drives pin MOD to low. Restoring BAT below the

VMCV threshold initiates the IC and starts a fast-charge

cycle.

bq2000

Table 5. Charge Status Display

Charge Action State

LED Status

Battery absent

High impedance

Pre-charge qualification

1Hz flash

Trickle charge (before fast charge)

1Hz flash

Fast charging

Low

Top-off or trickle (after fast charge,

NiCd, NiMH only)

High impedance

Charge complete

High impedance

Sleep mode

High impedance

Charge suspended (VTS >VLTF)

1Hz flash

Temperature

Condition

Action

VTS >VLTF

Cold battery—checked at all times

Suspends fast charge or top-off and timer

Allows trickle charge—LED flashes at 1Hz rate

during pre-charge qualification and fast charge

VHTF <VTS <VLTF

Optimal operating range

Allows charging

VTS <VHTF

Hot battery—checked during charge quali-

fication and top-off and trickle-charge

Suspends fast-charge initiation, does not allow

trickle charge—LED flashes at 1Hz rate during

pre-charge qualification and fast charge

VTS <VTCO

Battery exceeding maximum allowable

temperature—checked at all times

Terminates fast charge or top-off

Table 4. Temperature-Monitoring Conditions

2000CS.eps

BAT-

Power Supply ground

bq2000 ground

SNS

RSNS

VSS

bq2000

Figure 9. Current-Sensing Circuit

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