MAX1645-MAX1645A Maxim, MAX1645-MAX1645A Datasheet - Page 24

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

MAX1645A respond to the AlertResponse() address
with 0x13, which is their address and a trailing “1.”
The MAX1645/MAX1645A include a timer that termi-
nates charge if the charger has not received a
ChargingVoltage() or ChargingCurrent() command in
175sec. During charging, the timer is reset each time a
ChargingVoltage() or ChargingCurrent() command is
received; this ensures that the charging cycle is not ter-
minated.
If timeout occurs, charging will terminate and both
ChargingVoltage() and ChargingCurrent() commands
are required to restart charging. A power-on reset will
also restart charging at 128mA.
Advanced Chemistry-Independent, Level 2
Battery Chargers with Input Current Limiting
Figure 7. ChargingVoltage() Code to Voltage Mapping
24
______________________________________________________________________________________
12.592V
18.432V
16.800V
8.400V
4.192V
1.024V
0
0
V
VDCIN > 20V
REF
0x0400
= 4.096V
Charger Timeout
0x106x
ChargingVoltage() D15–D0 DATA
0x20Dx
The MAX1645/MAX1645A employ a buck regulator with
a boot-strapped NMOS high-side switch and a low-side
NMOS synchronous rectifier.
The control scheme is a constant off-time, variable fre-
quency, cycle-by-cycle current mode. The off-time is
constant for a given BATT voltage; it varies with V
to keep the ripple current constant. During low-dropout
operation, a maximum on-time of 10ms allows the con-
troller to achieve >99% duty cycle with continuous con-
duction. Figure 8 shows the controller functional
diagram.
0x313x
0x41A0
0x4800
DC-to-DC Converter
0xFFFF
DC-DC Controller
BATT