MAX1667 Maxim, MAX1667 Datasheet - Page 19

• Manufacturer Part Number: MAX1667
• Description: Chemistry-Independent / Level 2 Smart Battery Charger
• Manufacturer: Maxim

Figure 8. SMBus a) Write-Word and b) Read-Word Protocols
The ChargerStatus() command uses Read-Word proto-
col (Figure 8b). The command code for ChargerStatus()
is 0x13 (0b00010011). The ChargerStatus() command
returns information about thermistor impedance and the
MAX1667’s internal state. The Read-Word protocol
returns D15–D0. Table 8 describes the meaning of the
individual bits. The latched bits, THERMISTOR_HOT
and ALARM_INHIBITED, are cleared whenever BAT-
TERY_PRESENT = 0 or ChargerMode() is written with
POR_RESET = 1.
An interrupt is triggered (INT goes low) whenever power
is applied to DCIN, the BATTERY_PRESENT bit changes,
or the POWER_FAIL bit changes. BATTERY_PRESENT
and POWER_FAIL have interrupt masks that can be set
a) Write-Word Format
b) Read-Word Format
S
S
Legend:
S = Start Condition or Repeated Start Condition
ACK = Acknowledge (logic low)
W = Write Bit (logic low)
0b0001001
0b0001001
ADDRESS
ADDRESS
MSB LSB
MSB LSB
Preset to
Preset to
SLAVE
SLAVE
7 bits
7 bits
MASTER TO SLAVE
SLAVE TO MASTER
______________________________________________________________________________________
1b
1b
W
W
0
0
ACK
ACK
Alert-Response Address
1b
1b
ChargerStatus() =
ChargerMode() = 0x12
ChargingCurrent() = 0x14
ChargerVoltage() = 0x15
AlarmWarning() = 0x16
COMMAND
COMMAND
MSB LSB
MSB LSB
BYTE
BYTE
Interrupts and the
8 bits
8 bits
0x13
ChargerStatus()
ACK
ACK
Level 2 Smart Battery Charger
1b
1b
S
S
P = Stop Condition
NACK = NOT Acknowledge (logic high)
R = Read Bit (logic high)
0b0001001
D7
ADDRESS
MSB LSB
MSB LSB
Preset to
SLAVE
7 bits
DATA
BYTE
7 bits
LOW
Chemistry-Independent,
or cleared via the ChargerMode() command. INT stays
low until the interrupt is cleared. There are two methods
for clearing the interrupt: issuing a ChargerStatus() com-
mand, and using a modified Receive Byte protocol with a
0x19 (0b0011001) Alert-Response address. The
MAX1667 responds to the Alert-Response address with
its address (0x13) left justified as the most significant bits
of the returned byte.
In most portable equipment, the DC power to charge
batteries enters through a two-conductor cylindrical
power jack. It is easy for the end user to add an
adapter to switch the DC power’s polarity. Polarized
capacitor C6 would be destroyed if a negative voltage
were applied. Diode D4 in Figure 7 prevents this from
happening.
D0
__________Applications Information
ACK
1b
R
1b
1
ACK
D15
MSB LSB
1b
Negative Input Voltage Protection
DATA
BYTE
HIGH
8 bits
D7
MSB LSB
D8
DATA
BYTE
8 bits
LOW
ACK
1b
D0
ACK
1b
P
D15
MSB LSB
DATA
BYTE
HIGH
8 bits
D8
NACK
1b
P
19