Datasheet

MAX1667
Chemistry-Independent,
Level 2 Smart Battery Charger
______________________________________________________________________________________ 21
If reverse-polarity protection for the DC input power is
not necessary, diode D4 can be omitted. This eliminates
the power lost due to the voltage drop on diode D4.
Thermistor Characterization
Figure 11 represents the expected electrical behavior
of a 103ETB-type thermistor (nominally 10kΩ at +25°C
±5% or better) to be used with the MAX1667. The
graph is typical of the suggested thermistor’s charac-
teristics.
THERMISTOR_OR bit is set only when the thermistor
value is > 100kΩ. This indicates that the thermistor is
open.
THERMISTOR_COLD bit is set only when the thermistor
value is > 30kΩ. The thermistor indicates a cold bat-
tery.
THERMISTOR_HOT bit is set only when the thermistor
value is < 3kΩ.
THERMISTOR_UR bit is set only when the thermistor
value is < 500Ω.
Multiple bits may be set depending on the values of the
thermistor (e.g., a 450Ω thermistor will cause both the
THERMISTOR_HOT and the THERMISTOR_UR bits to
be set). The thermistor may be replaced by fixed-value
resistors in battery packs that do not require the ther-
mistor as a secondary fail-safe indicator. In this case, it
is the responsibility of the battery pack to manipulate
the resistance to obtain correct charger behavior.
Table 4. ChargingCurrent() Bit Functions
2048
DA4
1024
DA3
512
DA2
256
DA1
128
DA0
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
WEIGHT IN mA
(R
SENSE
= 40mΩ)
FUNCTION
BIT POSITION
3968*
FS* IOUT**
7**
x
0x0010–0xFFFF
0x0010–0xFFFF
0x0010–0xFFFF
0x0010–0xFFFF
0x0000–0x000F
ChargingVoltage()
0x0000
0x0001–0x0007
0x0001–0x0007
0x0008–0x007F
0x0001–0x0007
000
x
ChargingCurrent()
x
1
0
0
1
x
CCV_LOW
x
0
x
x
1
x
VOLTAGE_
NOTREG
0
0
7
7
7
0
000
000
I
OUT
OUTPUT
CURRENT (mA)
0x0010–0xFFFF
000
000
x
x0x0010–0xFFFF
x
x
0x0010–0xFFFF
0x0008–0x007F
x
0x0080–0xFFFF
x
x
000
0x0008–0x007F
1
x
x
x
x
1
1
x
x
x
x
0
7
0
0
0
0
0
0
0
100
0
000
xx1
x10
000
ALARM_
INHIBITED
(Note 1)
CHARGE_
INHIBITED
Table 5. Relationship Between IOUT Source Current and ChargingCurrent() Value
* When SEL = VL, values above 0x0F80 set the output current to 3.968A.
When SEL = OPEN, values above 0x0B80 set the output current to 2.944A.
When SEL = GND, values above 0x0380 set the output current to 0.896A.
** Values below 0x0080 set the output current to 7mA.
Note 1: THERMISTOR_HOT and HOT_STOP and NOT (THERMISTOR_UR).