MAX1645-MAX1645A Maxim, MAX1645-MAX1645A Datasheet - Page 14

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

The MAX1645/MAX1645A change their operation
depending on the voltages at DCIN, BATT, V
THM. Several important operating states follow:
• AC Present. When DCIN is > 7.5V, the battery is
• Power Fail. When DCIN is < BATT + 0.3V, the part is
• Battery Present. When THM is < 91% of V
• Battery Undervoltage. When BATT < 2.5V, the bat-
• V
The MAX1645/MAX1645A receive control inputs from
the SMBus interface. The serial interface complies with
the SMBus specification (refer to the System
Management Bus Specification from Intel Corporation).
Charger functionality complies with the Intel/Duracell
Smart Charger Specification for a Level 2 charger.
The MAX1645/MAX1645A use the SMBus Read-Word
and Write-Word protocols to communicate with the bat-
tery being charged, as well as with any host system
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
14
considered to be in an AC Present state. In this con-
dition, both the LDO and REF will function properly
and battery charging is allowed. When AC is pre-
sent, the AC_PRESENT bit (bit 15) in the
ChargerStatus() register is set to “1.”
in the Power Fail state, since the charger doesn’t
have enough input voltage to charge the battery. In
Power Fail, the PDS input PMOS switch is turned off
and the POWER_FAIL bit (bit 13) in the
ChargerStatus() register is set to “1.”
battery is considered to be present. The MAX1645/
MAX1645A use the THM pin to detect when a battery
is connected to the charger. When the battery is pre-
sent, the BATTERY_PRESENT bit (bit 14) in the
ChargerStatus() register is set to “1” and charging
can proceed. When the battery is not present, all of
the registers are reset. With no battery present, the
charger will perform a "Float" charge to minimize
contact arcing on battery connection. "Float" charge
will still try to regulate the BATT pin voltage at 18.32V
with 128mA of current compliance.
tery is in an undervoltage state. This causes the
charger to reduce its current compliance to 128mA.
The content of the ChargingCurrent() register is unaf-
fected and, when the BATT voltage exceeds 2.7V,
normal charging resumes. ChargingVoltage() is unaf-
fected and can be set as low as 1.024V.
ply is in an undervoltage state, and the SMBus inter-
face will not respond to commands. Coming out of
the undervoltage condition, the part will be in its
Power-On Reset state. No charging will occur when
V
DD
DD
______________________________________________________________________________________
is under voltage.
Undervoltage. When V
Operating Conditions
DD
SMBus Interface
< 2.5V, the V
DD,
DD
DD
, the
sup-
and
that monitors the battery-to-charger communications as
a Level 2 SMBus charger. The MAX1645/MAX1645A
are SMBus slave devices and do not initiate communi-
cation on the bus. They receive commands and
respond to queries for status information. Figure 3
shows examples of the SMBus Write-Word and Read-
Word protocols, and Figures 4 and 5 show the SMBus
serial-interface timing.
Each communication with these parts begins with the
MASTER issuing a START condition that is defined as a
falling edge on SDA with SCL high and ends with a
STOP condition defined as a rising edge on SDA with
SCL high. Between the START and STOP conditions,
the device address, the command byte, and the data
bytes are sent. The MAX1645/MAX1645As’ device
address is 0x12 and supports the charger commands
as described in Tables 1–6.
The ChargerSpecInfo() command uses the Read-Word
protocol (Figure 3b). The command code for
ChargerSpecInfo() is 0x11 (0b00010001). Table 1 lists
the functions of the data bits (D0–D15). Bit 0 refers to
the D0 bit in the Read-Word protocol. The
MAX1645/MAX1645A comply with level 2 Smart Battery
Charger Specification Revision 1.0; therefore, the
ChargerSpecInfo() command returns 0x01.
The ChargerMode() command uses the Write-Word
protocol (Figure 3a). The command code for
ChargerMode() is 0x12 (0b00010010). Table 2 lists the
functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the Write-Word protocol.
To charge a battery that has a thermistor impedance in
the HOT range (i.e., THERMISTOR_HOT = 1 and THER-
MISTOR_UR = 0), the host must use the Charger
Mode() command to clear HOT_STOP after the battery
is inserted. The HOT_STOP bit returns to its default
power-up condition (“1”) whenever the battery is
removed.
The ChargerStatus() command uses the Read-Word
protocol (Figure 3b). The command code for Charger
Status() is 0x13 (0b00010011). Table 3 describes the
functions of the data bits (D0–D15). Bit 0 refers to the
D0 bit in the Read-Word protocol.
The ChargerStatus() command returns information
about thermistor impedance and the MAX1645/
MAX1645A’s internal state. The latched bits, THERMIS-
TOR_HOT and ALARM_INHIBITED, are cleared when-
Battery Charger Commands
ChargerSpecInfo()
ChargerStatus()
ChargerMode()