CM9112 Datasheet, PDF (8/18 Pages) California Micro Devices Corp – Dual Inputs Dual Outputs High Accurate Fast Charger

PRELIMINARY
CM9112
Application Information
The CM9112 is an integrated charger with a charging
profile tailored for single-cell graphite electrode (anode)
Li-ion batteries. This linear charger can be powered
from either an AC voltage-source adapter or a USB
port. When both are applied it will automatically select
the AC Adaptor source.
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 battery temperature monitoring, volt­
age and current monitoring and charging time limits.
Two charging status indicators provide charge state
information.
Two different external resistors Riset1,Riset2 allow two
different charging current to be programmed for either
USB adaptor or AC Adaptor. This method allows an
accurate control of USB input current.
Under AC Adaptor input both VSYS (host system) and
VOUT (battery) are simultaneously supplied with the
current required by each oh them, independently.
When the absolute over current limit protection is
reached (1.5A), CM9112 goes into shutdown, latched
mode.
Under USB supply, with AC Adaptor out, CM9112 pro­
vide power only to VOUT. The total current available for
VOUT is externally programmed by Riset1.
USB/AC adapter dual input
The CM9112 can support inputs from either a USB bus
or a 5V AC wall adapter.
The USB standard specifies a 5.0V +/-5% bus voltage,
capable of 500mA (High Power peripheral configura­
tion) of current. Since desktop and mobile PCs are
equipped with USB or USB2 connectors for interfacing
with peripherals and digital consumer electronics, it is
advantageous to tap the USB’s power to charge porta­
ble devices such as cell phones.
When using USB input power, the CM9112 will auto­
matically select external resistor Riset1 to fix the total
input current. This goes only into VOUT pin and is
intended to charge the battery. However, the system is
connected to the battery through a Schottky diode.
This makes possible some current flowing into VOUT
pin to go not only into Battery but into System too. A
longer charging time will be the result of this. That’s
why, under USB input, timeout for charger are disabled.
When using AC Adaptor power, CM9112 will automati­
cally select the resistor Riset2 for charging current. In
addition of this it will provide a free current to VSYS
directly from Adaptor input through a power LDO. This
will be limited to 450mA either by power dissipated on
the chip, or absolute current limit.
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. When a valid AC adapter voltage
between 4.75V and 6.5V is detected on the VAD pin,
an external MOSFET, Q1 is turn ON and VAD and VIN
are connected together. An internal power MOSFET
used for USB supply, is turned OFF, so there is no
residual voltage on USB pin due to VAD supply. The
same, when USB is used as input. No residual voltage
in VAD pin.
Charging Li-ion Batteries
Once the CM9112 detects the presence of either a
valid AC adapter or USB input voltage, and checks that
the battery voltage at BSEN is less then V_IN and that
the battery temperature is within the correct range, it is
ready to charge the Li-ion battery. The controller’s
internal counter is reset.
If the battery voltage is deeply discharged (less than
3.2V), the CM9112 will start in the Precharge mode,
charging at 10% of the programmed Fast-charge cur­
rent level. See Figure 1. While the battery is charging,
the status pins will be set to STAT1=0 and STAT2=0.
The Precharge current will gradually bring the battery
voltage to above 3.2V. If the battery does not reach the
3.2V level, indicative of a defective Li-ion cell, the
CM9112 will turn off the charging process after a Pre-
charge timeout period (Timeout1, 30 minutes per
0.1µF of CT capacitance). In this case, the status pins
will be set to STAT1=V_IN and STAT2=V_IN.
© 2006 California Micro Devices Corp. All rights reserved.
8 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 lTel: [phone] lFax: [phone] lwww.cmd.com
07/06/06