MAX1667 Datasheet, PDF (17/28 Pages) Maxim Integrated Products – Chemistry-Independent, Level 2 Smart Battery Charger

Chemistry-Independent,
Level 2 Smart Battery Charger
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When the master has finished communicating with the
slave, the master issues a STOP condition, which is a
low-to-high transition on SDA while SCL is high. The
bus is then free for another transmission. Figures 1 and
2 show timing diagrams for signals on the SMBus inter-
face. The address byte, control byte, and data bytes
are transmitted between the START and STOP condi-
tions. Data is transmitted in 8-bit words, and after each
byte either the slave or the master issues an acknowl-
edgment (Figure 2); therefore, nine clock cycles are
required to transfer each byte. The SDA state is allowed
to change only while SCL is low, except for the START
and STOP conditions.
The MAX1667 7-bit address is preset to 0b0001001.
The eighth bit indicates a Write-Word (W = 0) or a
Read-Word (R = 1) command. This can also be denot-
ed by the hexadecimal number 0x12 for a Write-Word
command or a 0x13 for a Read-Word command.
The following commands use the Write-Word protocol
(Figure 8a): ChargerMode(), ChargingVoltage(),
ChargingCurrent(), and AlarmWarning(). The
ChargerStatus command uses the Read-Word protocol
(Figure 8b).
ChargerMode()
The ChargerMode() command uses Write-Word protocol
(Figure 8a). The command code for ChargerMode() is
0x12 (0b00010010). Table 3 describes the functions of
the 16 data bits (D0–D15). Bit 0 refers to the D0 bit in the
Write-Word protocol.
Whenever the BATTERY_PRESENT status bit (bit 14) of
ChargerStatus() is clear, the HOT_STOP bit is set,
regardless of any previous ChargerMode() command.
To charge a battery that has a thermistor impedance
in the HOT range (i.e., THERMISTOR_HOT = 1 and
THERMISTOR_UR = 0), the host must use the
ChargerMode() 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.
ChargingVoltage()
The ChargingVoltage() command uses Write-Word proto-
col (Figure 8a). The command code for ChargingVoltage()
is 0x15 (0b00010101). The 16-bit binary number formed
by D15–D0 represents the voltage set point (V0) in milli-
volts; however, since the MAX1667 has only 16mV of reso-
lution in setting V0, the D0, D1, D2, and D3 bits are
ignored.
The maximum voltage delivered by the MAX1667 is
18.416V, corresponding to a ChargingVoltage() value of
0x47F0. This is also the floating voltage set by the
power-on reset (POR). ChargingVoltage() values above
0x47F0 deliver the floating voltage and set the VOLT-
AGE_OR status bit. Any time the BATTERY_PRESENT
status bit is clear, the ChargingVoltage() register
returns to its POR state.
Figure 9 shows the mapping between V0 (the voltage-
regulation-loop set point) and the ChargingVoltage()
data.
ChargingCurrent()
The ChargingCurrent() command uses Write-Word proto-
col (Figure 8a). The command code for ChargingCurrent()
is 0x14 (0b00010100). The 16-bit binary number formed
by D15–D0 represents the current-limit set point (I0) in
milliamps (Table 4). Connecting SEL to AGND selects a
0.896A maximum setting for I0. Leaving SEL open selects
a 2.944A maximum setting for I0. Connecting SEL to VL
selects a 3.968A maximum setting for I0.
Two sources of current in the MAX1667 charge the bat-
tery: a linear current source begins from IOUT, and a
switching regulator controls the current flowing through
the current-sense resistor (R1). IOUT provides a trickle-
charge current to compensate for battery self-discharge,
while the switching regulator provides large currents for
fast charging.
IOUT sources 7mA, while the switching regulator
sources from 128mA to 3968mA with a 5-bit resolution
(LSB = 5.12mV / RSENSE = 128mA with a 40mΩ sense
resistor). In Table 4, DA4–DA0 denotes the bits in the
current DAC code. Table 5 shows the relationship
between the value programmed with the Charging-
Current() command and IOUT source current. The
CCV_LOW comparator checks to see if the output volt-
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