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LTC4100

4100fb

OPERATION

The ILIM 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. ILIM Trip Points and Ranges

EXTERNAL

RESISTOR

(RILIM)ILIM VOLTAGE

CONTROLLED

CHARGING

CURRENT RANGE

GRANULARITY

Short to GND

VILIM < 0.09VDD

0 < I < 1023mA

1mA

10k ±1%

0.17VVDD <

VILIM < 0.34VVDD

0 < I < 2046mA

2mA

33k ±1%

0.42VVDD <

VILIM < 0.59V

0 < I < 3068mA

4mA

Open (>250k,

or Short to VDD)

0.66VVDD <

VILIM

0 < I < 4092mA

4mA

The VLIM 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. VLIM Trip Points and Ranges (See Figure 5)

EXTERNAL

RESISTOR

(RVLIM)VLIM VOLTAGE

CONTROLLED

CHARGING VOLTAGE

(VOUT) RANGE

GRANULARITY

Short to

GND

VVLIM < 0.09VVCCP

2900mV < VOUT

< 8800mV

16mV

10k ±1%

0.17VVDD < VVLIM

< 0.34VVDD

2900mV < VOUT

< 13104mV

16mV

33k ±1%

0.42VVCCP < VVLIM

< 0.59VVDD

2900mV < VOUT

< 17408mV

16mV

100k ±1%

0.66VVDD < VVLIM

< 0.84VVDD

2900mV < VOUT

< 21712mV

16mV

Open or

Tied to VDD

0.91VVDD < VVLIM

2900mV < VOUT

< 28000mV

16mV

The Voltage DAC Block

Note that the charger output voltage is offset by VREF.

Therefore, the value of VREF is subtracted from the SMBus

ChargingVoltage() value in order for the output voltage to

be programmed properly (without offset). If the Charging-

Voltage() 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 ChargingVolt-

age() value is above the limit set by the VLIM pin, then the

charger output voltage is set to the value determined by

the VLIM resistor and the VOLTAGE_OR bit is set. These

limits are demonstrated in Figure 6.

PROGRAMMED VALUE (V)

4100 F06

RVLIM = 33k

Figure 6. Transfer Function of Charger

NOTE: THE LTC4100 CAN BE PROGRAMMED WITH ChargingVoltage() FUNCTION VALUES

BETWEEN 1.184V AND 2.9V, HOWEVER, THE BATTERY CHARGER CONTROLLER OUTPUT

VOLTAGE MAY BE ZERO WITH PROGRAMMED VALUES BELOW 2.9V.

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