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RT9503GQW View Datasheet(PDF) - Richtek Technology

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RT9503
Application Information
The RT9503 is a fully integrated low cost single-cell Li-
Ion battery charger for portable applications. The RT9503
can be adopted for two input power source, AC USB Input.
It will automatically select the input source and operate
in different mode as below.
AC Mode : When the AC input voltage (ACIN) is higher
than the UVP voltage level (4.3V), the RT9503 will enter
AC Mode. In the AC Mode, ACIN P-MOSFET is turned on
and USB P-MOSFET is turned off. When ACIN voltage is
between the UVP and OVP threshold levels, the switch
Q1 will be turned on and Q2 will be turned off. So, the
system oad is powered directly from the adapter through
the transistor Q1, and the battery is charged by the
RT9503. Once the ACIN voltage is higher than the OVP or
is lower than the UVP threshold, the RT9503 stops
charging, and then Q1 will be turned off and Q2 will be
turned on to supply the system by battery.
USB Mode : When AC input voltage (ACIN) is lower than
UVP voltage level and USB input voltage is higher than
UVP voltage level (3.9V), the RT9503 will operate in the
USB Mode. In the USB Mode, ACIN P-MOSFET and Q1
are turned off and USB P-MOSFET and Q2 are turned on.
The system load is powered directly from the USB/Battery
through the switch Q2. Note that in this mode, the battery
will be discharged once the system current is higher than
the battery charge current.
Sleep Mode : The RT9503 will enter Sleep Mode when
both AC and USB input voltage are removed. This feature
provides low leakage current from the battery during the
absence of input supply.
VACIN > UVP ACIN Mode
USB Mode VACIN < UVP
VUSB > UVP
Sleep Mode
VACIN < UVP
VUSB < UVP
Figure 1. Input Power Source Operation Mode
Power-Path Management
The RT9503 powers the system and independently
charging the battery while the input is AC. This features
reduces the charge time, allows for proper charge
termination, and allows the system to run with an absent
or defective battery pack.
Case 1 : Input is AC
In this case, the system load is powered directly from the
AC adapter through the transistor Q1. For RT9503, Q1
and Q2 act as a switch as long as the RT9503 is ready.
Once the AC voltage is ready (>UVP and <OVP), the
battery charge by RT9503 internal MOSFET and Q1 starts
regulating the output voltage supply system (Q2 is turn
off). Once the AC voltage over operation voltage (<UVP or
>OVP), the RT9503 stop charge battery, Q1 turns off and
Q2 starts supply power for system.
ISYS
System
RT9503
Q1
SYS
BAT_ON
Q2
AC_ON
VIN
USB
ICharger
ACIN
USB
BATT
+
Battery
Figure 2. ACIN Input
Case 2 : Input is USB
In this case, the system load is powered directly from the
battery through the switch Q2 (Q1 is turn off). Note in this
case, the system current over battery charge current will
lead to battery discharge.
System
RT9503
Q1
SYS
BAT_ON
AC_ON
Q2
ISYS
VIN
USB
ICharger
ACIN
USB
BATT
+
Battery
Figure 3. USB Input
www.richtek.com
10
DS9503-03 April 2011
 

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