ltc1759cg-trpbf Linear Technology Corporation, ltc1759cg-trpbf Datasheet - Page 20

• Manufacturer Part Number: ltc1759cg-trpbf
• Description: Smart Battery Charger
• Manufacturer: Linear Technology Corporation

OPERATIO
LTC1759
When AC power is not available the thermistor block
supports the following low power operating features:
1. Only the low power THERM_OR detection circuitry is
2. The ChargeStatus() read function forces the thermistor
The thermistor impedance is interpreted according to
Table 4.
Table 4. Thermistor State Ranges
THERMISTOR
RESISTANCE
0 to 500
500 to 3k
3k to 30k
30k to 100k
Above 100k
The required values for R
Table 5.
Table 5. Thermistor External Resistor Values
Note: The maximum allowed total external capacitance on THERM and
RNR is 75pF, due to settling time requirements.
The I
The value of an external resistor connected from this pin
to GND determines one of four current limits that are used
to limit the maximum charging current value. These limits
20
kept alive to support battery present interrupts.
block to update thermistor status at the beginning of the
read. The low power mode is immediately reentered
upon completion of the read.
EXTERNAL RESISTOR
LIMIT
R
R
R
Decoder Block
WEAK
UR
NR
U
CHARGE
STATUS BITS
THERM_UR,
THERM_HOT
BATTERY_PRESENT
THERM_HOT
BATTERY_PRESENT
(NONE)
BATTERY_PRESENT
THERM_COLD
BATTERY_PRESENT
THERM_OR
THERM_COLD
WEAK
, R
UR
and R
VALUE ( )
475k 1%
10k 1%
1k 1%
NR
DESCRIPTION
Underrange
Hot
Ideal
Cold
Overrange
are shown in
provide a measure of safety with a hardware restriction on
charging current which cannot be overridden by software.
Table 6. I
EXTERNAL
RESISTOR
(R
0
10k 1%
33k 1%
Open (>250k, 0.66V
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.
DD
ILIMIT
V
Figure 5. Simplified V
)
LIMIT
R
LIMIT
)
LIMIT
LIMIT
33k
Decoder Block
V
0.17V
< 0.34V
0.42V
< 0.59V
Trip Points and Ranges
ILIMIT
I
LIMIT
12.5k
12.5k
VDD
VDD
VDD
25k
25k
25k
< 0.09V
VDD
V
VOLTAGE
DD
< V
< V
< V
LIMIT
ILIMIT
ILIMIT
ILIMIT
DD
Circuit Concept (I
+
–
+
–
+
+
–
–
CURRENT RANGE GRANULARITY
0 < I < 1023mA
0 < I < 2046mA
0 < I < 4092mA
0 < I < 8184mA
CHARGING
NOMINAL
AC_PRESENT
ENCODER
LIMIT
Is Similar)
4
1mA
2mA
4mA
8mA
V
LIM
1759 F05
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