MAX1645-MAX1645A Maxim, MAX1645-MAX1645A Datasheet - Page 23

• Manufacturer Part Number: MAX1645-MAX1645A
• Description: Advanced Chemistry-Independent / Level 2 Battery Chargers with Input Current Limiting
• Manufacturer: Maxim

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/MAX1645A have 64mA resolution in setting
I0, the D0–D5 bits are ignored as shown in Table 4.
Figure 6 shows the mapping 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 current off. A 50mΩ sense
resistor (R2 in Figure 1) is required to achieve the cor-
rect CODE/current scaling.
The power-on reset value for the ChargingCurrent() reg-
ister is 0x0080; thus, the first time a MAX1645/
MAX1645A is powered on, the BATT current regulates
to 128mA. Any time the battery is removed, the
ChargingCurrent() register returns to its power-on reset
state.
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/MAX1645A have 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/
MAX1645A are powered on, the BATT voltage regulates
to 18.432V. Any time the battery is removed, the
ChargingVoltage() register returns to its power-on reset
state. The voltage at DAC corresponds to the set com-
pliance voltage divided by 4.5.
The AlarmWarning() command uses the Write-Word
protocol (Figure 3a). The command code for
AlarmWarning() is 0x16 (0b00010110). AlarmWarning()
Battery Chargers with Input Current Limiting
Advanced Chemistry-Independent, Level 2
______________________________________________________________________________________
AlarmWarning() (POR: Not Alarm)
ChargingCurrent() (POR: 0x0080)
ChargingVoltage() (POR: 0x4800)
sets the ALARM_INHIBITED status bit in the
MAX1645/MAX1645A if D15, D14, D13, D12, or D11 of
the Write-Word protocol data equals 1. Table 6 summa-
rizes the Alarm-Warning() command’s function. The
ALARM_INHIBITED status bit remains set until the bat-
tery 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/MAX1645A
switching regulators remain off.
The MAX1645/MAX1645A request an interrupt by
pulling the INT pin low. An interrupt is normally request-
ed when there is a change in the state of the
ChargerStatus()
BATTERY_PRESENT (bit 14), or AC_PRESENT (bit 15).
Therefore, the INT pin will pull low whenever the AC
adapter is connected or disconnected, the battery is
inserted or removed, or the charger goes in or out of
dropout. The interrupts from each of the ChargerStatus()
bits can be masked by an associated ChargerMode()
bit POWER_FAIL_MASK (bit 6), BATTERY_PRE-
SENT_MASK (bit 5), or AC_PRESENT_MASK (bit 4).
All interrupts are cleared by sending any command to
the MAX1645/MAX1645A, 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/
Figure 6. Average Voltage Between CSIP and CSIN vs. Charging
Current() Code
Interrupts and Alert Response Address
150.4
102.4
51.2
6.4
0x0080
128
0x0400
1024
bits
POWER_FAIL
0x0800
2048
0x0BC0
3008
(bit
0XFFFF
65535
13),
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