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Datasheet MAX1647 - Chemistry-Independent Battery Chargers - Maxim Integrated Products

Chemistry-Independent

Battery Chargers

Two sources of current in the MAX1647 charge the bat-tery: a binary-weighted linear current source sourcesfrom IOUT, and a switching regulator controls the currentflowing through the current-sense resistor (R1). IOUTprovides a small maintenance charge current to com-pensate for battery self-discharge, while the switchingregulator provides large currents for fast charging.IOUT sources from 1mA to 31mA. Table 3 shows therelationship between the value programmed with the

ChargingCurrent( ) command and IOUT source current. The CCV_LOW comparator checks to see if the outputvoltage is too high by comparing CCV to REF / 4. IfCCV_LOW = 1 (when CCV < REF / 4), IOUT shuts off,preventing the output voltage from exceeding the voltageset point specified by the ChargingVoltage( ) register.VOLTAGE_NOTREG = 1 whenever the internal clamppulls down on CCV. (The internal clamp pulls down onCCV to keep its voltage close to CCI’s voltage.)

MAX1647/MAX1648

Table 3. Relationship Between IOUT Source Current and ChargingCurrent( ) Value

Note 1:Logical AND of THERMISTOR_HOT, HOT_STOP, NOT(THERMISTOR_UR).

185

SEL = OPEN OR SEL = VL

)

EVGAm(T LNOOIVT TATLAUBG -E SR94

CT ENEGRARREUVC ANI2.94

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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