RT9511 RICHTEK [Richtek Technology Corporation], RT9511 Datasheet - Page 16

• Manufacturer Part Number: RT9511
• Description: Fully Integrated Battery Charger with Two Step-Down Converters
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9511
Application Information
The RT9511 is a fully integrated low cost single-cell Li-Ion
battery charger and two high-efficiency step-down DC-DC
converters ideal for portable applications.
Battery Charger
Automatically Power Source Selection
The RT9511 can be adopted for two input power source,
ACIN and USB Inputs. It will automatically select the input
source and operate in different mode as below.
ACIN Mode : When the adapter input voltage (V
higher than the UVP voltage level (4.3V), the RT9511 will
enter ACIN Mode. In the ACIN 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 load is powered directly from the adapter
through the transistor Q1, and the battery is charged by
the RT9511. Once the ACIN voltage is higher than the
OVP or is lower than the UVP threshold, the RT9511 stops
charging, and then Q1 will be turned off and Q2 will be
turned on to supply the system by battery.
USB Mode : When ACIN voltage is lower than UVP voltage
level and USB input voltage is higher than UVP voltage
level (3.9V), the RT9511 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 RT9511 will enter Sleep Mode when
both ACIN and USB input voltage are removed. This feature
provides low leakage current from the battery during the
absence of input supply.
www.richtek.com
16
V
ACIN
Figure 2. Input Power Source Operation Mode.
> UVP
ACIN Mode
Sleep Mode
V
V
ACIN
USB
< UVP
< UVP
USB Mode
V
V
ACIN
USB
ACIN
> UVP
< UVP
) is
Power-Path Management
The RT9511 powers the system and independently
charging the battery while the input is ACIN. This feature
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 ACIN
In this case, the system load is powered directly from the
AC adapter through the transistor Q1. For the RT9511,
Q1 and Q2 act as a switch as long as the RT9511 is ready.
Once the ACIN voltage is ready (>UVP and <OVP), the
battery is charged by the RT9511 internal MOSFET and
Q1 starts regulating the output voltage supply system
(Q2 is turn off). Once the ACIN voltage is over operation
voltage (<UVP or >OVP), the RT9511 stops charging the
battery, Q1 turns off and Q2 starts to supply power for
system.
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 that in
this case, the system current over battery charge current
will lead to battery discharge.
V
V
USB
USB
ACIN
ACIN
I
SYS
Q1
Q1
I
I
Charger
Charger
Figure 3. ACIN Input
Figure 4. USB Input
SYS
AC_ON
ACIN
USB
SYS
AC_ON
ACIN
USB
RT9511
RT9511
BAT_ON
BAT_ON
BATT
BATT
DS9511-01 April 2011
+
+
Battery
Q2
Q2
Battery
System
System
I
SYS