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PVD and -∆V Termination

There are two modes for voltage termination, depending on

the state of TM. For - V (TM = high), if V

∆

BAT

is lower than any

previously measured value by 12mV ±3mV, fast charge is

terminated. For PVD (TM = low or mid), a decrease of 2.5mV

±2.5mV terminates fast charge. The PVD and - V tests are

∆

Synchronized Voltage Sampling

Voltage sampling at the BAT pin for PVD and - V termi

∆

nation

may be synchronized to an external stimulus using the INH

input. Low-high-low input pulses between 100ns and 3.5ms in

width must be applied at the INH pin with a frequency

greater than the “maximum synchronized sampling period”

set by the state of the TM pin as shown in Table 1. Voltage is

sampled on the falling edge of such pulses. If the time between

pulses is greater than the synchronizing period, voltage

sampling “free-runs” at once every 17 seconds. A sample is

taken by averaging together voltage measurements taken

57µs apart. The IC takes 32 measurements in PVD mode and

16 measurements in - V mode. The resulting sample periods

∆

(9.17 and 18.18ms, respectively) filter out harmonics centered

around 55 and 109Hz. This technique minimizes the effect of

any AC line ripple that may feed through the power supply

from either 50 or 60Hz AC sources. If the INH input remains

high for more than 12ms, the voltage sample history kept by

the IC and used for PVD and - V termination decisions is

∆

erased and a new history is started. Such a reset is required

when transitioning from free-running to synchronized voltage

sampling. The response of the IC to pulses less than 100ns in

width or between 3.5ms and 12ms is indeterminate. The

tolerance on all timing is ±12%.

Voltage Termination Hold-off

A hold-off period occurs at the start of fast charging. During

the hold-off time, the PVD and - V terminations are disabled.

∆

This avoids premature termination on the voltage spikes

sometimes produced by older batteries when fast-charge

current is first applied. Maximum voltage and temperature

terminations are not affected by the hold-off period.

Maximum Voltage, Temperature, and Time

Any time the voltage on the BAT pin exceeds the maximum

Maximum temperature termination occurs anytime the

voltage on the TS pin falls below the temperature cut-off

Maximum charge time is configured using the TM pin. Time

settings are available for corresponding charge rates of C/2,

1C, and 2C. Maximum time-out termination is enforced on the

fast-charge phase. There is no time limit on the trickle-charge

phase.

Pulse-Trickle Charge

Pulse-trickle is used to compensate for self-discharge while

the battery is idle in the charger. The battery is pulse-trickle

charged by driving the CC pin active once per second for the

period specified in Table 1. This results in a trickle rate of

C/32.

TM Pin

The TM pin is a three-level pin used to select the charge

timer, voltage termination mode, trickle rate, and voltage

hold-off period options. Table 1 describes the states selected

by the TM pin. The mid-level selection input is developed by a

Charge Status Indication

A fast charge in progress is uniquely indicated when the LED

pin goes low. In the charge pending state, the LED pin is

driven low for 500ms, then to high-Z for 500ms. The LED pin

is driven to the high-Z state for all other conditions. Figure 2

outlines the state of the LED pin during charge.

Charge Inhibit

Fast charge may be inhibited by using the INH pin. When

high, INH suspends all fast charge activity and the internal

charge timer. INH freezes the current state of LED until

inhibit is removed. Temperature monitoring is not affected by

the INH pin. During charge inhibit, the bq2002C continues to

pulse-trickle charge the battery per the TM selection. When

INH returns low, charge control and the charge timer resume

from the point where INH became active.

Low-Power Mode

Both the CC pin and the LED are driven to the high-Z state.

The operating current is reduced to less than 1µA in this

trickle charges until the next new charge cycle begins.

bq2002C

5