MAX1644 Datasheet, PDF (23/32 Pages) Maxim Integrated Products – Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting

Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
ChargingCurrent() (POR: 0x0080)
The ChargingCurrent() command uses the Write-Word
protocol (Figure 3a). The command code for Charging-
Current() is 0x14 (0b00010100). The 16-bit binary num-
ber formed by D15–D0 represents the current-limit set
point (I0) in milliamps. However, since the MAX1645 has
64mA resolution in setting I0, the D0–D5 bits are
ignored as shown in Table 4. Figure 6 shows the map-
ping between I0 (the current-regulation-loop set point)
and the ChargingCurrent() code. All codes above 0b00
1011 1100 0000 (3008mA) result in a current overrange,
limiting the charger current to 3.008A. All codes below
0b0000 0000 1000 0000 (128mA) turn the charging cur-
rent off. A 50mΩ sense resistor (R2 in Figure 1) is
required to achieve the correct CODE/current scaling.
The power-on reset value for the ChargingCurrent() reg-
ister is 0x0080; thus, the first time a MAX1645 is pow-
ered on, the BATT current regulates to 128mA. Any time
the battery is removed, the ChargingCurrent() register
returns to its power-on reset state.
ChargingVoltage() (POR: 0x4800)
The ChargingVoltage() command uses the Write-Word
protocol (Figure 3a). The command code for
ChargingVoltage() is 0x15 (0b00010101). The 16-bit
binary number formed by D15–D0 represents the volt-
age set point (V0) in millivolts; however, since the
MAX1645 has 16mV resolution in setting V0, the D0, D1,
D2, and D3 bits are ignored as shown in Table 5.
The ChargingVoltage command is used to set the bat-
tery charging voltage compliance from 1.024V to
18.432V. All codes greater than or equal to 0b0100
1000 0000 0000 (18432mV) result in a voltage over-
range, limiting the charger voltage to 18.432V. All codes
below 0b0000 0100 0000 0000 (1024mV) terminate
charge. Figure 7 shows the mapping between V0
(the voltage-regulation-loop set point) and the
ChargingVoltage() code.
The power-on reset value for the ChargingVoltage() reg-
ister is 0x4880; thus, the first time a MAX1645 is pow-
ered on, the BATT voltage regulates to 18.432V. Any
time the battery is removed, the ChargingVoltage() reg-
ister returns to its power-on reset state. The voltage at
DAC corresponds to the set compliance voltage divided
by 4.5.
AlarmWarning() (POR: Not Alarm)
The AlarmWarning() command uses the Write-Word
protocol (Figure 3a). The command code for
AlarmWarning() is 0x16 (0b00010110). AlarmWarning()
sets the ALARM_INHIBITED status bit in the MAX1645 if
D15, D14, D13, D12, or D11 of the Write-Word protocol
data equals 1. Table 6 summarizes the Alarm-
Warning() command’s function. The ALARM_INHIBITED
status bit remains set until the battery is removed, a
ChargerMode() command is written with the
POR_RESET bit set, or new ChargingCurrent() AND
ChargingVoltage() values are written. As long as
ALARM_INHIBITED = 1, the MAX1645 switching regula-
tor remains off.
Interrupts and Alert Response Address
The MAX1645 requests an interrupt by pulling the INT
pin low. An interrupt is normally requested when there is
a change in the state of the ChargerStatus() bits
POWER_FAIL (bit 13), BATTERY_PRESENT (bit 14), or
AC_PRESENT (bit 15). Therefore, the INT pin will pull
low whenever the AC adapter is connected or discon-
nected, the battery is inserted or removed, or the charg-
er goes in or out of dropout. The interrupts from each of
the ChargerStatus() bits can be masked by an associat-
ed ChargerMode() bit POWER_FAIL_MASK (bit 6), BAT-
TERY_PRESENT_MASK (bit 5), or AC_PRESENT_MASK
(bit 4).
All interrupts are cleared by sending any command to
the MAX1645, or by sending a command to the
AlertResponse() address, 0x19, using a modified
Receive Byte protocol. In this protocol, all devices that
set an interrupt will try to respond by transmitting their
address, and the device with the highest priority, or
most leading 0’s, will be recognized and cleared. The
process will be repeated until all devices requesting
interrupts are addressed and cleared. The MAX1645
responds to the AlertResponse() address with 0x13,
which is its address and a trailing “1.”
150.4
102.4
51.2
6.4
0x0080 0x0400
128
1024
0x0800
2048
0x0BC0 0XFFFF
3008 65535
Figure 6. Average Voltage Between CSIP and CSIN vs. Charging
Current() Code
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