RT9503

RT9503
Fully Integrated Linear Single Cell Li-Ion Battery Charger
with Power Path
General Description
Features
The RT9503 is a fully integrated low cost single-cell LiIon battery charger IC ideal for portable applications. The
RT9503 is capable of being powered up from AC adapter
and the USB (Universal Serial Bus) port inputs. The
RT9503 can automatically detect and select the AC
adapter and the USB port as the power source for the
charger. The RT9503 enters sleep mode when both
supplies are removed.
z
Automatic Input Supplies Selection
z
18V Maximum Rating for AC Adapter
Integrated Selectable 100mA and 500mA USB
Charge Current
Internal Integrated Power FETs
AC Adapter Power Good Status Indicator
Charge Status Indicator
External Capacitor Programmable Safety Timer
Under Voltage Protection
Over Voltage Protection
Automatic Recharge Feature
Battery Temperature Monitoring
Small 16-Lead WQFN Package
Thermal Feedback Optimizing Charge Rate
Power Path Controller
RoHS Compliant and 100% Lead (Pb)-Free
The RT9503 optimizes the charging task by using a control
algorithm including preconditioning mode, fast charge
mode and constant voltage mode. The charging task is
terminated as the charge current drops below the preset
threshold. The USB charge current can be selected from
preset ratings100mA and 500mA, while the AC adapter
charge current can be programmed up to 1A with an
external resister. The internal thermal feedback circuitry
regulates the die temperature to optimize the charge rate
for all ambient temperatures.
The RT9503 features 18V and 7V maximum rating voltages
for AC adapter and USB port inputs respectively. The other
features are external programmed safety timer, under
voltage protection, over voltage protection for AC adapter
supply, battery temperature monitoring, power supply
status indicators and charge status indicator.
z
z
z
z
z
z
z
z
z
z
z
z
z
Applications
z
z
z
z
Digital Cameras
Cellular Phones
PDAs and Smart Phones and MP3
Portable Instruments
Pin Configurations
RT9503
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
`
Suitable for use in SnPb or Pb-free soldering processes.
12
BATT
2
11
TS
TIMER
EN
GND
3
10
17
4
9
5
6
7
ISETU
NC
Note :
1
GND
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
16 15 14 13
ACIN
USB
CHG_S
AC_PGOOD
ISETA
Package Type
QW : WQFN-16L 3x3 (W-Type)
NC
BAT_ON
AC_ON
Ordering Information
SYS
(TOP VIEW)
8
WQFN-16L 3x3
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS9503-03 April 2011
www.richtek.com
1
RT9503
Typical Application Circuit
System
10uF
16
3
4
V IN
Adapter
1
RT9503
SYS
BAT_ON 13
CHG_S
BATT
ACIN
TS
TIMER
2
1uF
6
USB
12
1uF
AC_PGOOD
1uF
USB
Battery Pack
AC_ON
+
15
11
10
CT
0.1uF
Chip Enable
EN 9
ISETA
7 ISETU
GND
5, Exposed Pad (17)
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
ACIN
Wall Adaptor Charge Input Supply.
2
USB
USB Charge Input Supply.
3
CHG_S
Charge Status Indicator Output (open drain).
4
AC_PGOOD
Wall Adaptor Power Good Indicator Output (open drain).
5
GND
Ground.
6
ISETA
Wall Adaptor Supply Charge Current Set Point.
7
ISETU
USB Supply Charge Current Set Input (active low).
8, 14
NC
No Internal Connection.
9
EN
Charge Enable (Active Low).
10
TIMER
Safe Charge Timer Setting.
11
TS
Temperature Sense Input.
12
BATT
Battery Charge Current Output.
13
BAT_ON
Power path controller output, low to turn on the external P-MOSFET.
15
SYS
System Voltage Detecting Pin.
16
AC_ON
P-MOSFET Switch Control Output (open drain).
17 (Exposed Pad) GND
www.richtek.com
2
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
DS9503-03 April 2011
RT9503
Function Block Diagram
ACIN
USB
OVP
Comparator
+
OVP
-
2.5V
Charge Input
Selection
USB
P-MOSFET
SENSE
MOSFET
ACIN
P-MOSFET
SENSE
MOSFET
Timer
ISETA
TIMER
BATT
GND
2.5V
VREF
0.5V
Thermal
Sense
125 C
Temperature Fault
ACIN/USB
VFB
Temperature
Sense
0.25V
TS
OVP
DRV
AC_ON
Precharge
Logic
Loop Controller
1.5k
7.5k
VREF Thermal
Sense
Termination
Comparator
0.25V
+
0.9V
-
VOS
+
-
+
-
1uA
Pre-Charge Phase
CHG_S
VH
Charge
Disable BATT
1uA
EN
PGOOD
Logic
+
ISETU
VCC/USB
BAT_ON
Hys
SYS
Fast Charge
Phase
Constant Voltage
Phase &
Re-Charge Phase
Standby Phase
Programmed
Charge Current
Battery
Voltage
Charging
Current
4.1V Recharge
Threshold
1/10 Programmed
Charge Current
2.8V Precharge
Threshold
Charge
Complete
Charging I-V Curve
DS9503-03 April 2011
www.richtek.com
3
RT9503
Table
RT9503 Flow Chart
Start-Up
Precharge Phase
Fast Charge Phase
Recharge Phase
Standby/Fault
ACIN/USB
Power Up
DISABLE
UVP
SLEEP
Start-Up
DISABLE
MODE
PFET OFF
IBATT = 0
YES
V /CE > 1.4V ?
NO
NO
V ACIN < 4.3V
and
< 3.9V?
V USB NO
YES
UVP MODE
PFET OFF
IBATT = 0
V ACIN < V BATT
and
V USB < V BATT ?
YES
SLEEP MODE
PFET OFF
IBATT = 0
NO
1ms Delay
&
Start Timer
V TS > 2.5V
or
V TS < 0.5V?
OVP
MODE
NO
RECHAR
GE
YES
TEMP
FAULT
/CHG_S HIGH
IMPEDANCE
IBATT = 0.1 Charge
Current
/CHG_S Strong Pull
Down
NO
V BATT > 4.1 V?
IBATT = Charge
Current
/CHG_S Strong
Pull Down
YES
NO
YES
YES
YES
V BATT > 2.8V?
NO
IBATT < 0.1 ICHG ?
T CHARGE UP?
? TCHARGE UP?
YES
STANDBY
PFET OFF
IBATT = 0
V BATT > 4.1 V?
NO
NO
www.richtek.com
4
NO
YES
V BATT > 2.8V?
YES
YES
TIME
FAULT
DS9503-03 April 2011
RT9503
Absolute Maximum Ratings
z
z
z
z
z
z
z
z
z
z
(Note 1)
Supply Input Voltage, ACIN --------------------------------------------------------------------------------------------Supply Input Voltage, USB ---------------------------------------------------------------------------------------------CHG_SB, AC_PGOOD, AC_ON --------------------------------------------------------------------------------------Other Pins ------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WQFN-16L 3x3 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------------WQFN-16L 3x3, θJC -----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------
Recommended Operating Conditions
z
z
z
z
−0.3V to 18V
−0.3V to 7V
−0.3V to 18V
−0.3V to 5.5V
1.667W
60°C/W
8.2°C/W
260°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage Range, ACIN -----------------------------------------------------------------------------------Supply Input Voltage Range, USB ------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------
4.5V to 12V
4.1V to 6V
−20°C to 125°C
−20°C to 85°C
Electrical Characteristics
(ACIN = USB = 5V, TA = 25°C, unless otherwise specification)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
4.1
4.3
4.5
V
Supply Input
ACIN UVP Rising Threshold Voltage VUV_ACIN
USB UVP Rising Threshold Voltage VUV_USB
VBATT = 3V
3.7
3.9
4.1
V
ACIN/USB UVP Hysteresis
VUV_HYS
VBATT = 3V
40
100
140
mV
ACIN/USB Standby Current
ISTBY
VBA TT = 4.5V
--
300
500
uA
ACIN/USB Shutdown Current
ISHDN
VEN = High
--
50
100
uA
ISLEEP
VACIN = 4V, V USB = 4V,
VBATT = 4.5V
--
5
15
uA
VREG
IBATT = 60mA
4.158
4.2
4.242
V
BATT Sleep Leakage Current
Voltage Regulation
BATT Regulation Voltage
ACIN MOSFET Dropout
V BATT = 4V, ICHG = 1A
400
500
620
mV
ACIN MOSFET Dropout
V BATT = 4V, IUSB = High
500
650
800
mV
Current Regulation
ISETA Set Voltage
(Fast Charge Phase)
VISETA_FCHG VBATT = 3.5V
2.43
2.48
2.53
V
Full Charge Setting Range
ICHG_AC
100
--
1000
mA
AC Charge Current Accuracy
ICHG_AC
--
500
--
mA
VBATT = 3.8V, RISET = 1.5kΩ
To be continued
DS9503-03 April 2011
www.richtek.com
5
RT9503
Parameter
Symbol
Test Conditions
Min
Typ
Max
Units
V PRECH
2.7
2.8
2.9
V
ΔVPRECH
60
100
140
mV
8
10
12
%
50
95
140
mV
V BATT = 4.2V
--
10
--
%
Precharge
BATT Pre-charge Threshold
BATT Pre-charge Threshold
Hysteresis
Pre-Charge Current
IPCHG
VBATT = 2V
Recharge Threshold
BATT Re-charge Falling Threshold
ΔVRECH_L
Hysteresis
Charge Termination Detection
Termination Current Ratio
(Note5) ITERM
Logic Input/Output
CHG_S Pull Down Voltage
V CHG_S
ICHG_S = 5mA
--
213
--
mV
AC_PGOOD Pull Down Voltage
V PGOOD
IPGOOD = 5mA
--
213
--
mV
PGOOD Pull Down Voltage
V PGOOD
TBD; IPGOOD = 5mA
--
65
--
mV
EN Threshold
Logic-High Voltage
V IH
1.5
--
--
V
Logic-Low Voltage
V IL
--
--
0.4
V
IEN
--
--
1.5
uA
EN Pin Input Current
ISETU
Threshold
High Voltage
V ISETU_HIGH
1.5
--
Low Voltage
V ISETU_LOW
--
--
0.4
V
IISETU
--
--
1.5
uA
--
100
--
us
ISETU Pin Input Current
V
USB Charge Current & Timing
Soft-Start Time
TSS
VISETA from 0V to 2.5V
USB Charge Current
ICHG_USB
VACIN = 3.5V, V USB = 5V,
VBATT =3.5V, ISETU = 5V
400
450
500
mA
USB Charge Current
ICHG_USB
VACIN = 3.5V, VUSB = 5V,
VBATT = 3.5V, ISETU = 0V
60
80
100
mA
TIME Pin Source Current
ITIME
VTIMER = 2V
--
1
--
uA
Pre-charge Fault Time
T PCHG_F
CTIMER = 0.1uF, fCLK = 7Hz
1720
2460
3200
s
Charge Fault Time
T FCHG_F
CTIMER = 0.1uF, fCLK = 7Hz
13790
19700
25610
s
ITS
VTS = 1.5V
96
102
108
uA
Timer
Battery Temperature Sense
TS Pin Source Current
TS Pin
Threshold
High Voltage
V TS_HIGH
0.485
0.5
0.515
V
Low Voltage
V TS_LOW
2.45
2.5
2.55
V
--
125
--
°C
--
6.5
--
V
--
−20
mV
Protection
Thermal Regulation
OVP SET Voltage
Internal Default
Power Path Controller
BAT_ON Pull Low
As SYS Falling, VBATT = 4V,
−150
SYS-BAT
To be continued
www.richtek.com
6
DS9503-03 April 2011
RT9503
Parameter
BAT_ON Pull High
BAT_ON Pull Low Switch
Resistance
BAT_ON Pull High Switch
Resistance
Symbol
Test Conditions
As SYS Raising,
VBATT = 4V, SYS-BAT
Min
Typ
Max
Units
−50
--
0
mV
VBAT = 4V
--
10
--
Ω
VACIN = 5V
--
30
--
Ω
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard. The case point of θJC is on the expose pad for the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Guaranteed by design.
DS9503-03 April 2011
www.richtek.com
7
RT9503
Typical Operating Characteristics
Charge Current vs. RSETA
Enable Threshold Voltage vs. Input Voltage
1200
2.0
1000
Charge Current (mA)
VBATT = 3.8V, ICharger = 500mA
Enable Threshold Voltage (V)
VBATT = 3.8V, ACIN = 5V
800
600
400
200
0
1.6
Rising
1.2
0.8
Falling
0.4
0.0
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
4.5
4.8
5.1
RSETA (k
ٛ)
(kΩ)
2.54
6
6.3
6.6
VBATT = 3.8V, ACIN = 5V, ICharger = 500mA
VBATT = 3.8V, ICharger = 500mA
2.52
ISETA Voltage (V)
2.52
ISETA Voltage (V)
5.7
ISETA Voltage vs. Temperature
ISETA Voltage vs. ACIN Voltage
2.54
2.50
2.48
2.46
2.44
2.50
2.48
2.46
2.44
2.42
2.42
2.40
2.40
4.5
4.8
5.1
5.4
5.7
6
6.3
-25 -15
6.6
-5
5
15
25
35
45
55
65
75
85
Temperature (°C)
ACIN Voltage (V)
TS Current vs. Input Voltage
TS Current vs. Temperature
105
105
104
104
103
103
102
102
TS Current (uA)
TS Current (uA)
5.4
Input Voltage (V)
101
100
99
98
97
101
100
99
98
97
96
VBATT = 3.8V, ICharger = 500mA
95
96
VBATT = 3.8V, ACIN = 5V, ICharger = 500mA
95
4.5
4.8
5.1
5.4
5.7
Input Voltage (V)
www.richtek.com
8
6
6.3
6.6
-25 -15
-5
5
15
25
35
45
55
65
75
85
Temperature (°C)
DS9503-03 April 2011
RT9503
ISETU Threshold Voltage vs. USB Voltage
Regulation Voltage vs. Temperature
4.26
VBATT = 3.8V
ACIN = 5V, ICharger = 500mA
4.24
1.6
Regulation Voltage (V)
ISETU Threshold Voltage (V)
2.0
Rising
1.2
0.8
Falling
0.4
4.22
4.20
4.18
4.16
4.14
0.0
4.5
4.8
5.1
5.4
5.7
6
6.3
-25 -15
6.6
ACIN Power On
15
25
35
45
VUSB
(5V/Div)
V SYS
(5V/Div)
V SYS
(5V/Div)
EN
(5V/Div)
EN
(5V/Div)
I ACIN
(1A/Div)
I USB
(1A/Div)
Time (1ms/Div)
ACIN Power Off
USB Power Off
VIN
(5V/Div)
VUSB
(5V/Div)
V SYS
(5V/Div)
V SYS
(5V/Div)
VBATT
(5V/Div)
VBATT
(5V/Div)
I ACIN
(1A/Div)
I USB
(1A/Div)
Time (500us/Div)
65
75
85
VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
Time (1ms/Div)
ISYS = 500mA, ICharger = 500mA
55
USB Power On
VACIN
(5V/Div)
DS9503-03 April 2011
5
Temperature (°C)
USB Voltage (V)
VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
-5
ISYS = 500mA, ICharger = 500mA
Time (500us/Div)
www.richtek.com
9
RT9503
Application Information
The RT9503 is a fully integrated low cost single-cell LiIon 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.
V ACIN > UVP ACIN Mode
USB 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
Q2
BAT_ON
AC_ON
BATT
ICharger
V IN
+
Battery
ACIN
USB
USB
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
V ACIN < UVP
V USB > UVP
RT9503
Q1
SYS
Q2
BAT_ON
AC_ON
ISYS
Sleep Mode
BATT
V ACIN < UVP
V USB < UVP
+
ACIN
V IN
Battery
ICharger
USB
USB
Figure 1. Input Power Source Operation Mode
Figure 3. USB Input
www.richtek.com
10
DS9503-03 April 2011
RT9503
ACIN Over-Voltage Protection
V BATT
+
The ACIN input voltage is monitored by an internal OVP
comparator. The comparator has an accurate reference of
2.5V from the band-gap reference. The OVP threshold is
set by the internal resistive. The protection threshold is
set to 6.5V, but ACIN input voltage over 18V still leads the
RT9503 to damage. When the input voltage exceeds the
threshold, the comparator outputs a logic signal to turn
off the power P-MOSFET to prevent the high input voltage
from damaging the electronics in the handheld system.
When the input over Voltage condition is removed (ACIN
< 6V), the comparator re-enables the output by running
through the soft-start.
A
ITS
NTC
TS
Temperature
Sense
Battery
0.1uF to 10uF
VTS = ITS × RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 4. Temperature Sensing Configuration
V BATT
+
Battery Temperature Monitoring
A
The RT9503 continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9503 has an internal current source to provide the
bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 4). The
RT9503 compares the voltage on the TS pin against the
internal VTS_HIGH and VTS_LOW thresholds to determine
if charging is allowed. When the temperature outside the
VTS_HIGH and VTS_LOW thresholds is detected, the
device will immediately stop the charge. The RT9503 stops
charge and keep monitoring the battery temperature when
the temperature sense input voltage is back to the
threshold between VTS_HIGH and VTS_LOW, the charger
will be resumed. Charge is resumed when the temperature
returns to the normal range. However the user may modify
thresholds by the negative-temperature coefficient thermal
resistor or adding two external resistors. (see Figure 5.)
The capacitor should be placed close to TS (Pin 9) and
connected to the ground plane. The capacitance value
(0.1uF to 10uF) should be selected according to the quality
of PCB layout. It is recommended to use 10uF if the layout
is poor if prevent noise.
DS9503-03 April 2011
ITS
NTC
Temperature
Sense
TS
R T1
Battery
R T2
0.1uF to 10uF
RT2 × (RT1 + RNTC )
RT1 + RT2 + RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
VTS = ITS
Figure 5. Temperature Sensing Circuit
Fast-Charge Current Setting
Case 1: ACIN Mode
The RT9503 offers ISETA pin to determine the ACIN charge
rate from 100mA to 1.2A. The charge current can be
calculated as following equation.
Icharge_ac = K SET
VSET
RSETA
The parameter KSET = 300 ; VSET = 2.5V. RSETA is the
resistor connected between the ISETA and GND.
www.richtek.com
11
RT9503
indicates the open-drain transistor is turned on and LED
bright.
1200
Charge Current (mA)
1000
Charge State
800
CHG_S
AC_PGOOD
Charge
ON
ON
Charge Done
OFF
ON
Charge
ON
OFF
Charge Done
OFF
OFF
ACIN
600
USB
400
200
Temperature Regulation and Thermal Protection
0
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
(k)
RRSETA
SETA(kΩ)
Figure 6. AC Mode Charge Current Setting
Case 2 : USB Mode
When charging from a USB port, the ISETU pin can be
used to determine the charge current of 100mA or 500mA.
A low-level signal of ISETU pin sets the charge current at
100mA and a high level signal sets the charge current at
500mA.
Pre- Charge Current Setting
During a charge cycle if the battery voltage is below the
VPRECH threshold, the RT9503 applies a pre-charge mode
to the battery. This feature revives deeply discharged cells
and protects battery life. The RT9503 internal determines
the pre-charge rate as 10% of the fast-charge current.
Battery Voltage Regulation
The RT9503 monitors the battery voltage through the BATT
pin. Once the battery voltage level closes to the VREG
threshold, the RT9503 voltage enters constant phase and
the charging current begins to taper down. When battery
voltage is over the VREG threshold, the RT9503 will stop
charge and keep to monitor the battery voltage. However,
when the battery voltage decreases 100mV below the
VREG, it will be recharged to keep the battery voltage.
Charge Status Outputs
The open-drain CHG_S and AC_PGOOD outputs indicate
various charger operations as shown in the following table.
These status pins can be used to drive LEDs or
communicate to the host processor. Note that ON
www.richtek.com
12
In order to maximize charge rate, the RT9503 features a
junction temperature regulation loop. If the power
dissipation of the IC results in a junction temperature
greater than the thermal regulation threshold (125°C), the
RT9503 throttles back on the charge current in order to
maintain a junction temperature around the thermal
regulation threshold (125°C). The RT9503 monitors the
junction temperature, TJ, of the die and disconnects the
battery from the input if TJ exceeds 125°C. This operation
continues until junction temperature falls below thermal
regulation threshold (125°C) by the hysteresis level. This
feature prevents the maximum power dissipation not
exceeded typical design conditions.
External Timer
As a safety mechanism the RT9503 has a userprogrammable timer that monitors the pre-charge and fast
charge time. This timer (charge safety timer) is started at
the beginning of the pre-charge and fast charge period.
The safety charge timeout value is set by the value of an
external capacitor connected to the TMR pin (CTMR), if pin
TMR is short to GND, the charge safety timer is disabled.
As CTMR = 0.1uF, TPRECH is ~2460 secs and TFAULT is 8 x
TPRECH. TPRECH = CTMR x 2460/0.1u
As timer fault, re-plug-in power or pull high and re-pull low
EN can release the fault condition.
As a safety mechanism, the RT9503 has a userprogrammable timer that monitors the pre-charge and fast
charge time. This timer(charge safe timer) is started at
the beginning of the pre-charge and fast-charge period.
The safety charge timeout value is set by an external
capacitor (CT) connected between TIMER pin and GND.
The timeout fault condition can be released by resetting
DS9503-03 April 2011
RT9503
Selecting the Input and Output Capacitors
In most applications, the most important is the high
frequency decoupling capacitor on the input of the RT9503.
A 1uF ceramic capacitor, placed in close proximity to input
pin and GND pin is recommended. In some applications
depending on the power supply characteristics and cable
length, it may be necessary to add an additional 10uF
ceramic capacitor to the input. The RT9503 requires a
small output capacitor for loop stability. A 1uF ceramic
capacitor placed between the BATT pin and GND is typically
sufficient.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = ( TJ(MAX) - TA ) / θJA
1.8
Maximum Power Dissipation (W)
the input power or the EN pin. If the TIMER is shorted to
GND, the charge safety timer will be disabled.
Four Layers PCB
1.6
1.4
1.2
WQFN-16L 3x3
1.0
0.8
0.6
0.4
0.2
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 7. Derating Curves for RT9503 Package
Layout Consideration
The RT9503 is a fully integrated low cost single-cell LiIon battery charger ideal for portable applications. Careful
PCB layout is necessary. The following guidelines should
be strictly followed to achieve best performance of RT9503.
` Input capacitor should be placed close to the IC and
connected to the ground plane. The trace of the input in
the PCB should be placed far away from the sensitive
devices or shielded by the ground.
Where T J(MAX) is the maximum operation junction
temperature 125°C, TA is the ambient temperature and
the θJA is the junction to ambient thermal resistance.
` The GND should be connected to a strong ground plane
for heat sinking and noise protection.
For recommended operating conditions specification,
where TJ(MAX) is the maximum junction temperature of the
die (125°C) and TA is the ambient temperature. The junction
to ambient thermal resistance θJA is layout dependent.
For WQFN-16L 3x3 packages, the thermal resistance θJA
is 60°C/W on the standard JEDEC 51-7 four layers thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by following formula :
` Output capacitor should be placed close to the IC and
connected to ground plane to reduce noise coupling.
` The connection of the RSETA should be isolated from
other noisy traces. The short wire is recommended to
prevent EMI and noise coupling.
PD(MAX) = (125°C − 25°C) / (60°C/W) = 1.667W for
WQFN-16L 3x3 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For WQFN-16L 3x3 package, the Figure
7 of derating curves allows the designer to see the effect
of rising ambient temperature on the maximum power
allowed.
DS9503-03 April 2011
www.richtek.com
13
RT9503
The capacitors should be
placed close to the IC and
connected to ground plane.
SYS
NC
BAT_ON
AC_ON
SYS
16 15 14 13
ACIN 1
USB 2
CHG_S 3
12
BATT
Battery
TS
GND
10 TIMER
17 9 EN
11
AC_PGOOD 4
6
7
8
GND
ISETA
ISETU
NC
5
RSETA
The GND should be connected
to a strong ground plane for heat
sinking and noise protection.
The connection of R SETA
should be isolated from other
noisy traces.
Figure 8
www.richtek.com
14
DS9503-03 April 2011
RT9503
Outline Dimension
D
SEE DETAIL A
D2
L
1
E
E2
e
b
A3
Symbol
1
2
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A
A1
1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
2.950
3.050
0.116
0.120
D2
1.300
1.750
0.051
0.069
E
2.950
3.050
0.116
0.120
E2
1.300
1.750
0.051
0.069
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 16L QFN 3x3 Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
DS9503-03 April 2011
www.richtek.com
15