Datasheet

LTC4100
19
4100fc
For more information www.linear.com/LTC4100
operaTion
The I
LIM
Decoder Block
The value of an external resistor connected from this pin
to GND determines one of four current limits that are
used for maximum charging current value. These limits
provide a measure of safety with a hardware restriction on
charging current which cannot be overridden by software.
Table 6. I
LIM
Trip Points and Ranges
EXTERNAL
RESISTOR
(R
ILIM
) I
LIM
VOLTAGE
CONTROLLED
CHARGING
CURRENT RANGE GRANULARITY
Short to GND V
ILIM
< 0.09V
DD
0 < I < 1023mA 1mA
10k ±1% 0.17V
VDD
<
V
ILIM
< 0.34V
VDD
0 < I < 2046mA 2mA
33k ±1% 0.42V
VDD
<
V
ILIM
< 0.59V
0 < I < 3068mA 4mA
Open (>250k,
or Short to V
DD
)
0.66V
VDD
<
V
ILIM
0 < I < 4092mA 4mA
The V
LIM
Decoder Block
The value of an external resistor connected from this pin
to GND determines one of five voltage limits that are ap
-
plied to the charger output value. These limits provide a
measure of safety with a hardware restriction on charging
voltage which cannot be overridden by software.
Table 7. V
LIM
Trip Points and Ranges (See Figure 5)
EXTERNAL
RESISTOR
(R
VLIM
) V
LIM
VOLTAGE
CONTROLLED
CHARGING VOLTAGE
(V
OUT
) RANGE GRANULARITY
Short to
GND
V
VLIM
< 0.09V
VCCP
2900mV < V
OUT
< 8800mV
16mV
10k ±1% 0.17V
VDD
< V
VLIM
< 0.34V
VDD
2900mV < V
OUT
< 13104mV
16mV
33k ±1% 0.42V
VCCP
< V
VLIM
< 0.59V
VDD
2900mV < V
OUT
< 17408mV
16mV
100k ±1% 0.66V
VDD
< V
VLIM
< 0.84V
VDD
2900mV < V
OUT
< 21712mV
16mV
Open or
Tied to V
DD
0.91V
VDD
< V
VLIM
2900mV < V
OUT
< 28000mV
16mV
The Voltage DAC Block
Note that the charger output voltage is offset by V
REF
.
Therefore, the value of V
REF
is subtracted from the
SMBus ChargingVoltage() value in order for the output
voltage to be programmed properly (without offset). If the
ChargingVoltage() value is below the nominal reference
voltage of the charger, nominally 1.184V, the charger
output voltage is programmed to zero. In addition, if the
ChargingVoltage() value is above the limit set by the V
LIM
pin, then the charger output voltage is set to the value
determined by the V
LIM
resistor and the VOLTAGE_OR bit
is set. These limits are demonstrated in Figure 6.
PROGRAMMED VALUE (V)
0
CHARGER V
OUT
(V)
25
20
15
10
5
0
10
20
25
4100 F06
5
15
30
35
R
VLIM
= 33k
Figure 6. Transfer Function of Charger
NOTE: THE LTC4100 CAN BE PROGRAMMED WITH ChargingVoltage() FUNCTION VALUES
BETWEEN 1.184V AND 2.9
V, HOWEVER, THE BATTERY CHARGER CONTROLLER OUTPUT
VOLTAGE MAY BE ZERO WITH PROGRAMMED V
ALUES BELOW 2.9V.