Datasheet

LTC4099
23
4099fd
operaTion
The battery charger current settings are decoded in
Table 3. The battery charger current settings are adjusted
by selecting one of the eight servo voltages for the PROG
pin. Recall that the programmed charge current is given
by the expression:
I
CHG
=
V
PROG
R
PROG
•1030
The default state for the battery charger current settings is
000, giving the lowest available servo voltage of 500mV.
The COVERX1 and COVERX0 bits are decoded in Table 4.
The C/x
setting controls the PROG pin level that the
LTC4099’s C/x comparator uses to report full capacity
charge. For example, if the 100mV setting is chosen, then
the LTC4099 reports that its PROG pin voltage has fallen
below 100mV. For the 50mV setting, LTC4099 reports
that its PROG pin voltage has fallen below 50mV. The C/x
settings are adjusted by comparing the PROG pin voltage
with the values shows in Table 4. The default value for the
C/x setting is 00, giving 100mV detection.
The second byte of data at sub address 0x01 controls the
three batter
y charger safety timer bits, TIMER2-TIMER0,
the DISABLE_CHARGER bit, the ENABLE_BATTERY_
CONDITIONER bit,
the V
FLOAT
= 4.2V control bit and the
T
REG
= 85°C control bit.
The TIMER2–TIMER0 bits control the duration of the bat-
tery
charger safety timer. The safety timer starts once the
LTC4099 reaches the 4.100V or the 4.200V float voltage.
As long as input power is available, charging will con
-
tinue
in float voltage mode until the safety timer expires.
Table 1. LTC4099 Input Data Bytes
SUB ADDRESS 0 SUB ADDRESS 1 SUB ADDRESS 2
COMMAND
REGISTER 0
COMMAND
REGISTER 1
IRQ MASK
REGISTER
Bit
7 I
LIM2
TIMER2 USBGOOD
Bit 6 I
LIM1
TIMER1 WALLGOOD
Bit 5 I
LIM0
TIMER0 BADCELL
Bit 4 I
CHARGE2
DISABLE_CHARGER THERMAL_ REG
Bit 3 I
CHARGE1
ENABLE_ BATTERY_
CONDITIONER
THERMISTOR_
ST
ATUS
Bit 2 I
CHARGE0
V
FLOAT
= 4.2V CHARGER_STATUS
Bit 1 COVERX1 T
REG
= 85°C Not Used
Bit 0 COVERX0 Not
Used Not Used
Table 2. I
LIM2
– I
LIM0
Decode
USB INPUT CURRENT LIMIT SETTINGS
I
LIM2
I
LIM1
I
LIM0
I
USB
0 0 0 100mA*
0 0 1 500mA
0 1 0 620mA
0 1 1 790mA
1 0 0 1000mA
1 0 1 1200mA
1 1 0 Suspend
Low (500µA)
1 1 1 Suspend
High (2.5mA)
*Default Setting
Table 3. I
CHARGE2
– I
CHARGE0
Decode
BATTERY CHARGER CURRENT LIMIT SETTINGS
I
CHARGE2
I
CHARGE1
I
CHARGE0
V
PROG
CHARGE CURRENT
R
PROG
= 1.02k
0 0 0 500mV* 500mA
0 0 1 600mV 600mA
0 1 0 700mV 700mA
0 1 1 800mV 800mA
1 0 0 900mV 900mA
1 0 1 1000mV 1000mA
1 1 0 1100mV 1100mA
1 1 1 1200mV 1200mA
*Default
Setting
Table 4. C/x Decode
C/x INDICATION SETTINGS
COVERX1 COVERX0 V
PROG
FULL CAPACITY CHARGE
INDICATION
R
PROG
= 1.02k
0 0 100mV* 100mA*
0 1 50mV 50mA
1 0 200mV 200mA
1 1 500mV 500mA
*Default
Setting