CM9100 Datasheet, PDF (7/11 Pages) California Micro Devices Corp – Basic Compact Cost-effective Fast-Charger

PRELIMINARY
CM9100
Application Information
The CM9100 is an integrated charger with a charging
profile tailored for single-cell graphite electrode (anode)
Li-ion batteries. With single resistor charge current pro-
gramming, the CM9100 can provide charge currents
up to 1000mA, or limited to 100mA/500mA for USB
input applications.
The charger features the three modes required for a
safe and reliable Li-ion charging profile; Precharge,
Fast-charge, and Termination charge. Extensive safety
features include voltage and current monitoring. A sta-
tus indicator provides charge state information.
From
USB
VIN
500 mA
100 mA
6.19k ISET
CM9100
Charger
VOUT
nmos
Q1
25.5k
Figure 1. USB Input Circuit
Linear Charger vs. Switching Charger
A Li-ion battery charger can be either a switching or a
linear regulator. A switching regulator type charger
achieves higher efficiency, typical 90% or better, over a
wide range of load and line conditions and generally
offers a faster charging speed. However, a switching
charger requires an external power inductor, which
occupies substantial PC board space with added
weight. Another issue with switching regulators is the
switching noise and the potential EMI it generates.
In contrast, The CM9100 linear charger is implemented
with a single IC, without the use of an inductor. The
CM9100 provides a complete Li-ion charging control
system, with integrated power MOSFETs and several
important features, requiring just a few external resis-
tors and capacitors for a compact system design. A
sophisticated thermal management system addresses
the concerns commonly associated with linear charg-
ers.
Input
When using a constant-voltage, 5VDC nominal, AC
adapter, the semi-regulated voltage to the charger,
after accounting for the conduction losses through the
power cord and connector contacts, is a voltage in the
range of 5.0V to 6.0V.
The USB standard specifies a 5.0V +/-5% bus voltage,
capable of 500mA (High Power peripheral configura-
tion) of current. When using a USB input, the charging
current must be limited to <500mA, which is set with
the R_SET resistor. In a system that requires 100mA
starting current until told by the host controller to go
into High Power mode, the circuit in Figure 1 can be
used. Q1 can be the output of the controller.
Charging Li-ion Batteries
Once the CM9100 detects the presence of a valid AC
adapter, and checks that the battery voltage at V_OUT is
less then V_IN, it is ready to charge the Li-ion battery.
If the battery voltage is deeply discharged (less than
3.2V), the CM9100 will start in the Precharge mode,
charging at 10% of the programmed Fast-charge cur-
rent level. See Figure 2. While the battery is charging,
the status pins will be set to STAT=0. The Precharge
current will gradually bring the battery voltage to above
3.2V.
Pre-
Charge
0.8A
0.4A
CC
Mode
CV
Mode
Charging
Voltage
4.0V
Charging
Current
3.0V
2.0V
Figure 2. Typical Li-ion Battery Charging Process
Once the battery voltage exceeds the 3.3V threshold,
the CM9100 enters the Fast-charge, constant-current
(CC) mode. The status pins will be set to STAT=0. Dur-
ing the CC mode, the charging current is limited by the
maximum charging current, programmed with a single
resistor between I_SET and ground, R_ISET:
I_FASTCHG(max)
=
2----.-5----V------×_{----1----0---0----0-}
R_ISET
© 2006 California Micro Devices Corp. All rights reserved.
06/30/06 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 l Tel: [phone] l Fax: [phone] l www.cmd.com
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