LTC4100 Linear Technology, LTC4100 Datasheet - Page 16

• Manufacturer Part Number: LTC4100
• Description: Smart Battery Charger Controller
• Manufacturer: Linear Technology

LTC4100
OPERATIO
Table 4. SafetySignal State Ranges
SafetySignal
RESISTANCE
0 to 500
500 to 3k
3k to 30k
30k to 100k
Above 100k
Note: The underrange detection scheme is a very important feature of the
LTC4100. The R
well above the 0.047 • V
pull-up. A system using a 10k pull-up would not be able to resolve the
important underrange to hot transition point with a modest 100mV of
ground offset between battery and SafetySignal detection circuitry. Such
offsets are anticipated when charging at normal current levels.
The required values for R
Table 5.
Table 5. SafetySignal External Resistor Values
C
and GND. C
immunity from transients in the application. C
exceed 1nF if the LTC4100 is to properly sense the value
of R
The I
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 charg-
ing current which cannot be overridden by software.
16
SS
EXTERNAL RESISTOR
represents the capacitance between the SafetySignal
SafetySignal
LIM
Decoder Block
R
R
THA
THB
SS
THA
.
/R
may be added to provide additional noise
SafetySignal
U
DD
CHARGE
STATUS BITS
RES_UR,
RES_HOT
BATTERY_PRESENT
RES_HOT
BATTERY_PRESENT
BATTERY_PRESENT
RES_COLD
BATTERY_PRESENT
RES_OR
RES_COLD
(140mV) threshold of a system using a 10k
divider trip point of 0.333 • V
THA
and R
VALUE ( )
54.9k 1%
1130 1%
THB
are shown in
DESCRIPTION
Underrange
Hot
Ideal
Cold
Overrange
SS
DD
(1V) is
can not
Table 6. I
EXTERNAL
RESISTOR
(R
Short to GND
10k 1%
33k 1%
Open (>250k,
or Short to V
The V
The value of an external resistor connected from this pin
to GND determines one of five voltage limits that are
applied to the charger output value. These limits provide
a measure of safety with a hardware restriction on charg-
ing voltage which cannot be overridden by software.
Table 7. V
EXTERNAL
RESISTOR
(R
Short to
GND
10k 1%
33k 1%
100k 1%
Open or
Tied to V
The Voltage DAC Block
Note that the charger output voltage is offset by V
Therefore, the value of V
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
pin, then the charger output voltage is set to the value
determined by the V
is set. These limits are demonstrated in Figure 6.
ILIM
VLIM
)
)
LIM
DD
LIM
LIM
DD
Decoder Block
V
0.42V
0.17V
0.66V
0.91V
Trip Points and Ranges
VLIM
)
V
Trip Points and Ranges (See Figure 5)
LIM
< 0.34V
< 0.59V
< 0.84V
0.17V
0.42V
0.66V
V
VCCP
< 0.09V
VDD
VDD
VDD
I
ILIM
VOLTAGE
LIM
< 0.34V
< 0.59V
< V
< V
< V
VDD
VDD
VDD
< V
VOLTAGE
VDD
VDD
VDD
< 0.09V
LIM
VLIM
VLIM
VLIM
VCCP
VLIM
< V
< V
< V
VDD
resistor and the VOLTAGE_OR bit
REF
ILIM
ILIM
ILIM
DD
CHARGING VOLTAGE
is subtracted from the SMBus
2900mV < V
2900mV < V
2900mV < V
2900mV < V
2900mV < V
CURRENT RANGE GRANULARITY
(V
CONTROLLED
< 13.104mV
< 17.408mV
< 21.712mV
0 < I < 1023mA
0 < I < 2046mA
0 < I < 3068mA
0 < I < 4092mA
< 28000mV
CONTROLLED
< 8800mV
OUT
CHARGING
) RANGE
OUT
OUT
OUT
OUT
OUT
GRANULARITY
sn4100 4100is
1mA
2mA
4mA
4mA
16mV
16mV
16mV
16mV
16mV
REF
LIM
.