BQ26501_16 Datasheet, PDF (17/33 Pages) Texas Instruments – HANDHELD APPLICATIONS

Not Recommended For New Designs
bq26501
ą
SLUS586B − OCTOBER 2003 − REVISED MARCH 2004
APPLICATION INFORMATION
Digital Magnitude Filter and Self-Discharge Values (DMFSD) – Address 0x7A
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
NAME
DMF[3] DMF[2] DMF[1] DMF[0]
SD[3]
SD[2]
BIT 1
SD[1]
BIT 0
SD[0]
MODE
REGISTER
DMF[3]
DMF[2]
DMF[1]
DMF[0]
SD[3]
SD[2]
SD[1]
SD[0]
DESCRIPTION
Sets the digital magnitude filter (DMF) threshold. See Digital Magnitude Filter section for more information on the
function of the DMF. The value to be programmed is:
DMF[3
:
0]
+
Design
Threshold
6
,
mV
Sets the self-discharge rate %/day value at 25°C. NAC is reduced with an estimated self-discharge correction to
adjust for the expected self-discharge of the battery. This estimation is only performed when the battery is not
being charged. The rate programmed in EEPROM for DMFSD determines the self-discharge when 20°C
≤ TEMP < 30°C. The self-discharge estimation is doubled for each 10°C decade hotter than the 20°C−30°C
decade, up to a maximum of 16 times the programmed rate for TEMP ≥ 60°C and is halved for each 10°C
decade colder than the 20°C−30°C decade, down to a minimum of one-quarter the programmed rate for TEMP <
0°C. The self-discharge estimation is performed by reducing NAC by NAC/512 at a time interval that achieves
the desired estimation. If DMFSD is programmed with 12 decimal, the self-discharge rate is 0.195% per day in
the 20°C−30°C decade. This is accomplished by reducing NAC by NAC/512 (100/512 = 0.195%) a single time
every 24 hours. If temperature rises by 10°C, the 0.195% NAC reduction is made every 12 hours. The value to
be programmed is:
SD[3
:
0]
+
2.34
Design SD
,
%/day
Taper Current (TAPER) − Address 0x7B
This register contains the scaled end equipment design charge taper current. This value, in addition to battery
voltage, is used to determine when the battery has reached a full charge state. The equation for programming
this value is:
TAPER
+
I_TAPER
(mA) R_S
192 (mV)
(mW)
(8)
where R_S is the value of the sense resistor used in the system.
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