MAX1647 Datasheet, PDF (19/24 Pages) Maxim Integrated Products – Chemistry-Independent Battery Chargers

Chemistry-Independent
Battery Chargers
Two sources of current in the MAX1647 charge the bat-
tery: a binary-weighted linear current source sources
from IOUT, and a switching regulator controls the current
flowing through the current-sense resistor (R1). IOUT
provides a small maintenance charge current to com-
pensate for battery self-discharge, while the switching
regulator provides large currents for fast charging.
IOUT sources from 1mA to 31mA. Table 3 shows the
relationship between the value programmed with the
ChargingCurrent( ) command and IOUT source current.
The CCV_LOW comparator checks to see if the output
voltage is too high by comparing CCV to REF / 4. If
CCV_LOW = 1 (when CCV < REF / 4), IOUT shuts off,
preventing the output voltage from exceeding the voltage
set point specified by the ChargingVoltage( ) register.
VOLTAGE_NOTREG = 1 whenever the internal clamp
pulls down on CCV. (The internal clamp pulls down on
CCV to keep its voltage close to CCI’s voltage.)
Table 3. Relationship Between IOUT Source Current and ChargingCurrent( ) Value
CHARGE_
INHIBITED
0
0
0
0
0
0
0
0
0
0
1
(NOTE 1)
0
0
0
0
0
0
0
0
x
1
x
ALARM_
INHIBITED
ChargingVoltage( )
ChargingCurrent( )
CCV_LOW
VOLTAGE_
NOTREG
0
0x0010–0xFFFF
0x0001–0x001F
0
x
0
0x0010–0xFFFF
0x0001–0x001F
1
0
0
0x0010–0xFFFF
0x0001–0x001F
1
1
0
0x0010–0xFFFF
0x0020–0xFFFF
0
x
0
0x0010–0xFFFF
0x0020–0xFFFF
1
0
0
0x0010–0xFFFF
0x0020–0xFFFF
1
1
0
x
0x0000
x
x
0
0x0000–0x000F
x
x
x
1
x
x
x
x
x
x
x
x
x
x
x
x
x
x
IOUT
OUTPUT
CURRENT
1mA–31mA
0mA
1mA–31mA
31mA
0mA
31mA
0mA
0mA
0mA
0mA
0mA
Note 1: Logical AND of THERMISTOR_HOT, HOT_STOP, NOT(THERMISTOR_UR).
185
SEL = OPEN OR SEL = VL
94
2.94
0b000001
0b100000
0b111111
CURRENT DAC CODE, DA5–DA0 BITS
Figure 9. Average Voltage Between CS and BATT vs. Current DAC Code
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