®
RT9455
Switch-Mode Single Cell Li-Ion Battery Charger
with USB-OTG
General Description
The RT9455 is a switch-mode single cell Li-Ion/Li-Polymer
battery charger for portable applications. It integrates a
synchronous PWM controller, power MOSFETs, input
current sensing, high accuracy voltage regulation and
charge termination circuits. The RT9455 also features USB
On-The-Go (OTG).
The RT9455 optimizes the charging task by using a control
algorithm to vary the charge rate via different modes,
including pre-charge mode, fast charge mode, and constant
voltage mode. The key charge parameters can be
programmed via the I
2
C interface. The RT9455 resumes
the charge cycle whenever the battery voltage falls below
an internal threshold and automatically enters sleep mode
when the input power supply is removed.
Other features include under-voltage protection, over-
voltage protection, thermal regulation and reverse leakage
protection.
The RT9455 is available in the small WL-CSP-16B
1.7x1.77 (BSC) package.
Features
Support Quick Start for Charger
High Accuracy Voltage/Current Regulation
Input Current Regulation : 100mA/500mA/700mA/
1A
Minimum Input Voltage Regulation : 4V/4.25V/4.5V
Charge Voltage Regulation Accuracy :
±
1% (0 to
85°C)
°
Charge Current Regulation Accuracy :
±
5%
Built-In Input Current Sensing and Limiting
Integrated Power MOSFETS for up to 1.55A Charge
Rate
Integrated Sensing Resistors for Charging Current
Sensing
Synchronous 1.5MHz Fixed Frequency PWM
Controller with up to 95% Duty Cycle
Reverse Leakage Protection to Prevent Battery
Drainage
Thermal Regulation and Protection
Over-Temperature Protection
Input Over-Voltage Protection
IRQ Output for Communication with I
2
C
Automatic Charging
RoHS Compliant and Halogen Free
Marking Information
1A : Product Code
1AW
W : Date Code
Applications
Cellular Telephones
Personal Information Appliances
MP3 Players
Portable Instruments
Simplified Application Circuit
To Adaptor/USB
VIN
VMID
RT9455
LX
ISNSIN
OTG
SCL
SDA
IRQ
BATS
GND
+
Battery
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9455-00 April 2014
www.richtek.com
1
RT9455
Ordering Information
RT9455
Package Type
WSC : WL-CSP-16B 1.7x1.77 (BSC)
Note :
Richtek products are :
½
A1
VIN
B1
VMID
C1
LX
D1
Pin Configurations
(TOP VIEW)
A2
VIN
B2
VMID
C2
LX
D2
A3
IRQ
B3
OTG
C3
AGND
D3
BOOT
A4
BATS
B4
ISNSIN
C4
SCL
D4
SDA
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
½
PGND PGND
WL-CSP-16B 1.7x1.77 (BSC)
Functional Pin Description
Pin No.
A1, A2
A3
A4
B1, B2
B3
B4
C1, C2
C3
C4
D1, D2
D3
D4
Pin Name
VIN
IRQ
BATS
VMID
OTG
ISNSIN
LX
AGND
SCL
PGND
BOOT
SDA
Power Input.
IRQ Output Node.
Feedback Voltage Input for Battery.
Connection Point Between Reverse Blocking MOSFET and High-Side
MOSFET.
Boost Mode Control Input or Current Regulation Setting for Average Input
Current.
Charge Current Sense Input.
Switch Node.
Analog Ground.
Clock Input for I C. Open-drain output, connect a 10k pull-up resistor.
Power Ground for Switching Charger.
Bootstrap Supply for High-Side MOSFET. Connect a capacitor between BOOT
and LX.
Data Input for I C. Open-drain output, connect a 10k pull-up resistor.
2
2
Pin Function
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS9455-00 April 2014
RT9455
Function Block Diagram
VIN
Protection
OVP, UVLO,
OTP, Timer
Base
VDD, Ibias,
VREF, OSC
Loop
Control
Gate
Driver 1
VMID
BOOT
Gate
Driver 2
LX
PGND
SCL
SDA
OTG
I C
2
State
Machine
Current
Sense
ISNSIN
BATS
AGND
IRQ
Operation
The RT9455 is a switch mode charger with USB-OTG
support for single cell Li-Ion battery in portable applications.
Base Circuits
Base circuits provide the internal power, VDD and reference
voltage and bias current.
Current Sense
Current sense circuit regulates the output current up to
1.5A to battery
Protection Circuits
The protection block includes the OVP, UVLO, OTP, Timer
and other circuits. It turns off the charging when the charger
IC or input power is in abnormal level.
Loop Controller and PWM and Driver
The multi-loop controller controls the PWM signal during
the charging process. The PWM circuit controls the power
stage through the driver. It makes sure that the battery is
well-charged with suitable current, voltage and die-
temperature.
I
2
C Interface
The I
2
C interface is used to program the charging
parameters, ex : output current and output voltage.
State Machine
The State Machine controls the operation of the switching
charger and outputs the interrupt via the IRQ pin if there is
any fault be triggered.
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9455-00 April 2014
www.richtek.com
3
RT9455
Flow Charts
Yes
Any I C?
Yes
No
2
Charge Start
TMR_EN = 1?
Yes
Reset Timer
---------------------
T32
min
mode
Any I C?
2
No
32 min?
Yes
Timer Fault
-----------------------
Disable Charging
No
Yes
No
Any state
No
V
IN
,V
BATS
< 2.4V
POR Reset
No
V
IN
> 2.4V and
V
BATS
> 2.4V ?
Yes
V
IN
> 3.3V ?
Yes
Charge Configure
(I C is Programmable)
2
No
Clean I C
2
Any State If V
IN
< 2.4V and
V
BATS
< 2.4V
Power On
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS9455-00 April 2014
RT9455
Charger Flow
Power on
disable charge
-----------------
Charge Configure Mode
Load I C with default
settings
2
Yes
32 min timer fault?
Any state
No
V
BATS
> V
PREC
?
No
PreCharge Mode
Yes
Fast-Charge to CV mode
No
TE is enabled?
Yes
No
I
CHRG
< I
EOC
?
No
Yes
Yes
Yes
Sink 0.5mA from battery
----------------------------------
Start 262ms timer
BATD_EN is enabled?
262ms timer expired?
No
Yes
Charge done
No
V
BATS
< V
REC
?
No
Yes
V
BATS
< V
REC
?
Battery Detection Mode
(Detect every 2s)
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9455-00 April 2014
www.richtek.com
5
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