RT9503A
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Features
zz
zz
zAutomatic Input Supplies Selection
zz
zz
z18V Maximum Rating for AC Adapter
zz
zz
zIntegrated Selectable 100mA and 500mA USB
Charge Current
zz
zz
zInternal Integrated Power MOSFETs
zz
zz
zAC Ada pter Power Good Status Indicator
zz
zz
zCharge Status Indicator
zz
zz
zExternal Capacitor Programmable Safety Timer
zz
zz
zUnder Voltage Protection
zz
zz
zOver Voltage Protection
zz
zz
zAutomatic Recharge Feature
zz
zz
zBattery Temperature Monitoring
zz
zz
zSmall 16-Lead WQFN Package
zz
zz
zThermal Feedback Optimizing Charge Rate
zz
zz
zPower Path Controller
zz
zz
zRoHS Compliant and Halogen Free
Pin Configurations
Applications
zDigital Cameras
zCellular Phones
zPDAs , Smart Phones and MP3 Players
zPortable Instruments
Ordering Information
General Description
The RT9503A is a fully integrated low cost single-cell Li-
Ion battery charger IC ideal for portable applications. The
RT9503A is capable of being powered up via the AC adapter
and USB (Universal Serial Bus) port inputs. The RT9503A
can automatically detect and select the AC adapter and
the USB port as the power source for the charger. The
RT9503A enters sleep mode when both supplies are
removed.
The RT9503A 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 ratings of 100mA and 500mA, while the AC
adapter charge current can be programmed up to 1A with
an external resistor. The internal thermal feedback circuitry
regulates the die temperature to optimize the charge rate
for all ambient temperatures.
The RT9503A features 18V and 7V maximum rating
voltages for AC adapter and USB port inputs respectively.
Other features include external programmable safety timer,
under voltage protection, over voltage protection for AC
adapter supply, battery temperature monitoring, power
supply status indicators and charge status indicator.
(TOP VIEW)
WQFN-16L 3x3
Fully Integrated Linear Single Cell Li-Ion Battery Charger
with Power Path
Note :
Richtek products are :
` 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.
ACIN
TS
TIMER
BATT
GND
ISETU
ISETA
NC
SYS
NC
12
11
10
9
13141516
1
2
3
4
8765
GND
17
CHG_S
AC_PGOOD EN
USB
BAT_ON
AC_ON
RT9503A
Package Type
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
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Typical Application Circuit
Functional Pin Description
Pin No. Pin Name Pin Function
1 ACIN Wall Adaptor Charge Supply Input.
2 USB USB Charge Supply Input.
3 CHG_S Charge Status Indicator Output (open drain).
4 AC_PGOOD Wall Adaptor Power Good Indicator Output (open drain).
5,
17 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected
to GND for maximum power dissipation.
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 Temper ature Sense Input.
12 BATT Battery Charge Current Output.
13 BAT_ON Power Path Controller Output. Pull low to turn on the external P-MOSFET.
15 SYS System Voltage Detecting Input.
16 AC_ON P-MOSFET Switch Control Output (open drain).
Marking Information
HK=YM
DNN
HK= : Product Code
YMDNN : Date Code
RT9503A
3
4
1
BATT
TIMER
SYS
11
12
13
6
ACIN
ISETA
TS
10
15
2USB
+
Battery Pack
CTMR
0.1µF
Chip Enable
5, Exposed Pad (17)
GND
9
EN
AC_PGOOD
AC_ON
CHG_S
BAT_ON
USB
VIN
Adapter
System
7ISETU
16
10µF
1µF
1µF
1µF
RSETA
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Function Block Diagram
Pre-Charge Phase Fast Charge
Phase
Constant Voltage
Phase &
Standby Phase
Re-Charge Phase
Programmed
Charge Current
4.1V Recharge
Threshold
2.8V Precharge
Threshold
1/10 Programmed
Charge Current
Charge
Complete
Battery
Voltage
Charging
Current
Charging I-V Curve
Charge Input
Selection
ACIN/USB
ACINUSB
ISETA BATT
ACIN
P-MOSFET
SENSE
MOSFET
USB
P-MOSFET
SENSE
MOSFET
GND
Precharge
Controller
Logic
Temperature
Sense
1µA
TS
VCC/USB
EN
ISETU
1µA
7.5k
1.5k
VFB
DRV
OVP
+
-
2.5V
OVP
Comparator
-
+
+
-
BATT
SYS
VOS
VH
Hys
Logic
OVP
AC_ON
BAT_ON
CHG_S
Timer TIMER
AC_PGOOD
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Table
Start-Up Precharge Phase Fast Charge Phase Standby/Fault Recharge Phase
RT9503A Flow Chart
DISABLEUVPSLEEPStart-Up
ACIN/USB
Power Up
V/CE > 1.4V ?
NO
NO
VACIN < 3V
and
VUSB < 3V?
DISABLE
MODE
PFET OFF
IBATT = 0
YES
UVP MODE
PFET OFF
IBATT = 0
YES
VACIN < VBATT
and
VUSB < VBATT?
SLEEP MODE
PFET OFF
IBATT = 0
YES
VBATT > 2.8V?
NO
IBATT = 0.1 Charge
Current
/CHG_S Strong Pull
Down
NO
?t
CHARGE UP?
1ms Delay
&
Start Timer
VBATT > 2.8V?
NO
IBATT = Charge
Current
/CHG_S Strong
Pull Down
YES
YES
YES
NO
VTS > 2.5V
or
VTS < 0.5V?
TIME
FAULT
IBATT < 0.1 ICHG?
YES
tCHARGE UP?
NO
NO
YES
STANDBY
PFET OFF
IBATT = 0
YES
TEMP
FAULT
YES
/CHG_S HIGH
IMPEDANCE
VBATT > 4.1 V?
YES
VBATT > 4.1 V?
NO
RECHAR
GE
YES
NO
OVP
MODE
NO
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Absolute Maximum Ratings (Note 1)
zSupply Input Voltage, ACIN -------------------------------------------------------------------------------------------- −0.3V to 18V
zSupply Input Voltage, USB -------------------------------------------------------------------------------------------- −0.3V to 7V
zCHG_S, AC_PGOOD, AC_ON ---------------------------------------------------------------------------------------- −0.3V to 18V
zOther Pins ----------------------------------------------------------------------------------------------------------------- −0.3V to 5.5V
zPower Dissipation, PD @ TA = 25°C
WQFN-16L 3x3 ----------------------------------------------------------------------------------------------------------- 1.471W
zPackage Thermal Resistance (Note 2)
WQFN-16L 3x3, θJA ----------------------------------------------------------------------------------------------------- 68°C/W
WQFN-16L 3x3, θJC ----------------------------------------------------------------------------------------------------- 7.5°C/W
zLead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------- 260°C
zJunction Temperature --------------------------------------------------------------------------------------------------- 150°C
zStorage Temperature Range ------------------------------------------------------------------------------------------- −65°C to 150°C
zESD Susceptibility (Note 3)
HBM (Human Body Mode) --------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------------- 200V
Electrical Characteristics
(ACIN = USB = 5V, TA = 25°C, unless otherwise specification)
To be continued
Recommended Operating Conditions (Note 4)
zSupply Input Voltage Range, ACIN ----------------------------------------------------------------------------------- 4.5V to 12V
zSupply Input Voltage Range, USB ----------------------------------------------------------------------------------- 4.1V to 6V
zJunction Temperature Range ------------------------------------------------------------------------------------------ −20°C to 125°C
zAmbient Temperature Range ------------------------------------------------------------------------------------------ −20°C to 85°C
Parameter Symbol Test Conditions Min Typ Max Unit
Supply Input
ACIN UVP Rising Threshold Voltage VUV_ACIN -- 3 -- V
USB UVP Rising Threshold Voltage VUV_USB V
BATT = 3V -- 3 -- V
ACIN/USB UVP Hysteresis VUV _HYS V
BATT = 3V -- 100 -- mV
ACIN/USB Standby Current ISTBY V
BATT = 4.5V -- 300 500 μA
BATT Sleep Leakage Current ISLEEP VACIN = 4V, VUSB = 4V,
VBATT = 4.5V -- 5 15 μA
Voltage Regulation
BATT Regulation Voltage VREG I
BATT = 60mA 4.138 4.2 4.262 V
ACIN MOSFET Dropout VBATT = 4V, ICHG_AC = 1A 400 500 620 mV
USB MOSFET Dropout VBATT = 4V, ICHG_USB = High 500 650 800 mV
Cur rent Regu l ation
ISETA Set Voltage
(Fast Charge Phase) VISETA_FCHG V
BATT = 3.5V 2.43 2.48 2.53 V
Full Charge Setting Range ICHG_AC 100 -- 1000 mA
AC Charge Current Accuracy ICHG_AC V
BATT = 3.8V, RISET = 1.5kΩ -- 500 -- mA
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Parameter Symbol Test Conditions Min Typ Max Unit
Precharge
BATT Pre-charge Threshold VPRECH 2.7 2.8 2.9 V
BATT Pre-charge Threshold
Hysteresis ΔVPRECH 60 100 140 mV
Pre-Charge Current IPCHG V
BATT = 2V 8 10 12 %
R echarge Threshold
BATT Re-charge Falling Threshold
Hysteresis ΔVRECH_L 50 95 140 mV
Charge Term ination Detection
Termination Current Ratio (Note5) ITERM V
BATT = 4.2V -- 10 -- %
Logic Input/Output
CHG_S Pull Down Voltage VCHG_S I
CHG_S = 5mA -- 213 -- mV
AC_PGOOD Pull Down Voltage VP GOOD I
PGOOD = 5mA -- 213 -- mV
PGOOD Pull Down Voltage VPGOOD
I
PGOOD = 5mA -- 65 -- mV
Logic-High VIH 1.5 -- -- V
EN Threshold
Voltage Logic-Low VIL -- -- 0.4 V
EN Pin Input Current IEN -- -- 1.5 μA
High Voltage VISETU_HIGH 1.5 -- V
ISETU Threshold Low Voltage VISETU_LOW -- -- 0.4 V
ISETU Pin Input Current IISETU -- -- 1.5 μA
USB Charge C urren t & Timing
Soft-Start Time tSS V
ISETA from 0V to 2.5V -- 100 -- μs
USB Charge Current ICHG_USB VACIN = 2.5V, VUSB = 5V,
VBATT =3.5V, VIS ETU = 5V 400 450 500 mA
USB Charge Current ICHG_USB VACIN = 2.5V, VUSB = 5V,
VBATT = 3.5V, VISETU = 0V 60 80 100 mA
Timer
TIMER Pin Source Current ITIME V
TIMER = 2V -- 1 -- μA
Pre-charge Fault Time tPCHG_F C
TIMER = 0.1μF, fCLK = 7Hz 1720 2460 3200 s
Charge Fault Time tFCHG_F C
TIMER = 0.1μF, f CLK = 7Hz 13790 19700 25610 s
B attery Temperature Sense
TS Pin Source Current ITS V
TS = 1.5V -- 102 -- μA
High Voltage VTS_HIGH 0.485 0.5 0.515 V
TS Pin
Threshold Low Voltage VTS_LOW 2.45 2.5 2.55 V
Protection
Thermal Regulation -- 125 -- °C
OVP SET Voltage Internal Default -- 6.5 -- V
Power Pa th Cont ro ller
BAT _ON Pull Low As SYS Falling, VBATT = 4V,
SYS-BAT −150 -- −20 mV
To be continued
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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 thermal conductivity four-layer test board of
JEDEC 51-7 thermal measurement standard. The measurement case position of θJC is on the exposed pad of 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.
Parameter Symbol Test Conditions Min Typ Max Uni
BAT_ON Pull High As SYS Raising,
VBATT = 4V, SYS-BAT −50 -- 0 mV
BAT_ON Pull Low Switch
Resistance V
BATT = 4V -- 10 -- Ω
BAT_ON Pull High Switch
Resistance V
ACIN = 5V -- 30 -- Ω
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Typical Operating Characteristics
ISETA Voltage vs. Temperature
2.40
2.42
2.44
2.46
2.48
2.50
2.52
2.54
-25-15-5 5 1525354555657585
Temperature
ISETA Voltage (V)
VBATT = 3.8V, ACIN = 5V, ICharger = 500mA
(°C)
Charge Current vs. RSETA
0
200
400
600
800
1000
1200
0.51.52.53.54.55.56.57.58.59.5
RSETA (kٛ)
Charge Current (mA)
VBATT = 3.8V, ACIN = 5V
(kΩ)
Enable Threshold Voltage vs. Input Voltage
0.0
0.4
0.8
1.2
1.6
2.0
4.5 4.8 5.1 5.4 5.7 6 6.3 6.6
Input Voltage (V)
Enable Threshold Voltage (V)
VBATT = 3.8V, ICharger = 500mA
Rising
Falling
ISETA Voltag e vs. ACIN Voltage
2.40
2.42
2.44
2.46
2.48
2.50
2.52
2.54
4.5 4.8 5.1 5.4 5.7 6 6.3 6.6
ACIN Voltage (V)
ISETA Voltage (V)
VBATT = 3.8V, ICharger = 500mA
TS Current vs. Temperature
95
96
97
98
99
100
101
102
103
104
105
-25-15-5 5 1525354555657585
Temperature
TS Current (μA)
VBATT = 3.8V, ACIN = 5V, ICharger = 500mA
(°C)
TS Current v s. Input Voltage
95
96
97
98
99
100
101
102
103
104
105
4.5 4.8 5.1 5.4 5.7 6 6.3 6.6
Input Voltage (V)
TS Current (μA)
VBATT = 3.8V, ICharger = 500mA
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USB Power Off
Time (500μs/Div)
VBATT
(5V/Div)
VSYS
(5V/Div)
VUSB
(5V/Div)
IUSB
(1A/Div) ISYS = 500mA, ICharger = 500mA
ISETU Threshold Voltage vs. USB Voltage
0.0
0.4
0.8
1.2
1.6
2.0
4.5 4.8 5.1 5.4 5.7 6 6.3 6.6
USB Voltage (V)
ISETU Threshold Voltage (V)
VBATT = 3.8V
Rising
Falling
Regulation Voltage vs. Temperature
4.14
4.16
4.18
4.20
4.22
4.24
4.26
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Temperature
Regulation Voltage (V)
ACIN = 5V, ICharger = 500mA
(°C)
ACIN Power Off
Time (500μs/Div)
VBATT
(5V/Div)
VSYS
(5V/Div)
VIN
(5V/Div)
IACIN
(1A/Div) ISYS = 500mA, ICharger = 500mA
USB Power On
Time (1ms/Div)
EN
(5V/Div)
VSYS
(5V/Div)
VUSB
(5V/Div)
IUSB
(1A/Div) VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
ACIN Power On
Time (1ms/Div)
EN
(5V/Div)
VSYS
(5V/Div)
VACIN
(5V/Div)
IACIN
(1A/Div) VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
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Application Information
The RT9503A is a fully integrated low cost single-cell Li-
Ion battery charger for portable applications. The RT9503A
can be adopted for two input power source including AC
and USB inputs. 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 (3V), the RT9503A 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
below 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 RT9503A. Once
the ACIN voltage is higher than the OVP, the RT9503A
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 removed
and USB input voltage is higher than UVP voltage level
(3V), the RT9503A will operate in the USB Mode. In the
USB Mode, ACIN P-MOSFET is turned off while 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 RT9503A 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.
Figure 1. Input Power Source Operation Mode
Power-Path Management
The RT9503A powers the system and independently
charging the battery while the input source is AC. This
feature reduces the charge time, allows for proper charge
termination, and allows the system to run with an absent
or defective battery pack.
Ca se 1 : Input Source is AC
In this case, the system load is powered directly from the
AC adapter through the transistor Q1. For RT9503A, Q1
and Q2 act as a switch as long as the RT9503A is ready.
Once the AC voltage is ready (<OVP), the battery charge
by the RT9503A internal MOSFET and Q1 starts regulating
the output voltage supply system (Q2 is turn off). Once
the AC voltage is higher than the operation voltage (>OVP),
the RT9503A stop charging battery, Q1 turns off and Q2
starts to supply power for system.
Figure 2. ACIN Input
Case 2 : In put Source is USB
In this case, the system load is powered directly from the
battery through the switch Q2. Note that in this case, the
system current over battery charge current will lead to
battery discharge.
Figure 3. USB Input
ACIN Mode USB Mode VACIN removed
VUSB > UVP
Sleep Mode
Both VACIN and
VUSB removed
VACIN > UVP
RT9503A
BATT
SYS
ACIN
USB
Battery
AC_ON
BAT_ON
USB
System
+
Q1 Q2
VIN
ICharger
ISYS
RT9503A
BATT
SYS
ACIN
USB
Battery
AC_ON
BAT_ON
USB
System
+
Q1 Q2
VIN
ICharger
ISYS
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ACIN Over-V oltage Protection
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 resistor. The protection threshold is
set to 6.5V, but ACIN input voltage over 18V still leads the
RT9503A 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.
Battery Temperature Monitoring
The RT9503A continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9503A has an internal current source to provide
the bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 4). The
RT9503A 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 charging. The RT9503A stops
charging and keeps monitoring the battery temperature
when the temperature-sense 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 via the negative-temperature coefficient
thermal resistor or by adding two external resistors. (see
Figure 5.)
The capacitor should be placed close to TS (Pin 11) and
connected to the ground plane. The capacitance value
(0.1μF to 10μF) should be selected according to the quality
of PCB layout. It is recommended to use 10μF if the layout
is poor for noise prevention.
Figure 4. Temperature Sensing Configuration
TS TS NTC
TS TS
V = I R
Turn off when V 2.5V or V 0.5V
×
≥≤
Figure 5. Temperature Sensing Circuit
T2 T1 NTC
TS TS T1 T2 NTC
TS TS
R(R + R)
V = I R + R + R
Turn off when V 2.5V or V 0.5V
×
≥≤
Fa st-Charge Current Setting
Ca se 1: ACIN Mode
The ISETA pin is used to determine the ACIN charge rate
from 100mA to 1A. The charge current can be calculated
as following equation.
_SET
CHG AC SET SETA
V
I = K
R
The parameter KSET = 300 ; VSET = 2.5V. RSETA is the
resistor connected between ISETA and GND.
+
0.1µF to 10µF
Battery
A
TS
Temperature
Sense
ITS
VBATT
NTC
+
RT2
Battery
A
TS
Temperature
Sense
ITS
VBATT
NTC
RT1
0.1µF to 10µF
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0
200
400
600
800
1000
1200
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5
RSETA (k)
Charge Current (mA)
RSETA (kΩ)
Figure 6. AC Mode Charge Current Setting
Ca se 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 RT9503A applies a pre-charge mode
to the battery. This feature revives deeply discharged cells
and protects battery life. The RT9503A internally
determines the pre-charge rate as 10% of the fast-charge
current.
Battery Voltage Regulation
The RT9503A monitors the battery voltage through the
BATT pin. Once the battery voltage level closes in on the
VREG threshold, the RT9503A voltage enters constant
phase and the charging current begins to taper down.
When battery voltage is over the VREG threshold, the
RT9503A will stop charging but continue to monitor the
battery voltage. However, when the battery voltage
decreases 100mV below VREG, it will be recharged to
preserve 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
indicates the open-drain transistor is turned on and LED
bright.
Charg e St ate CHG_S AC_PGOOD
Charge ON ON
ACIN Charge Done OFF ON
Charge ON OFF
USB
Charge Done OFF OFF
Temperature Regulation and Thermal Protection
In order to maximize the charge rate, the RT9503A 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
RT9503A throttles back on the charge current in order to
maintain a junction temperature around the thermal
regulation threshold (125°C). The RT9503A 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 from
exceeding typical design conditions.
External Timer
As a safety mechanism, the RT9503A provides a user-
programmable 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 TIMER pin (CTMR), if
the TIMER pin is short to GND, the charge safety timer is
disabled.
As CTMR = 0.1μF, t PCHG_F is ~2460 secs and tFCHG_F is 8
x tPCHG_F. tPCHG_F = CTMR x 2460/0.1μ
When timer faults, re-plug-in power or pull high and then
pull low EN to release the fault condition.
Selecting the Input and Output Capacitors
In most applications, the most important is the high
frequency decoupling capacitor on the input of the
RT9503A.
A 1μF ceramic capacitor, placed in close proximity to input
RT9503A
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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 10μF
ceramic capacitor to the input. The RT9503A requires a
small output capacitor for loop stability. A 1μF ceramic
capacitor placed between the BATT pin and GND is typically
sufficient.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
Where TJ(MAX) is the maximum junction temperature, TA
is the ambient temperature, and θJA is the junction to
ambient thermal resistance.
For recommended operating condition specifications of
RT9503A, the maximum junction temperature is 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
68°C/W on a standard JEDEC 51-7 four-layer thermal test
board. The maximum power dissipation at TA = 25°C can
be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (68°C/W) = 1.471W for
WQFN-16L 3x3 package
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, θJA. For RT9503A package, the derating curve
in Figure 7 allows the designer to see the effect of rising
ambient temperature on the maximum power dissipation.
Figure 7. Derating Curves for RT9503A Package
Layout Consideration
The RT9503A is a fully integrated low cost single-cell Li-
Ion battery charger ideal for portable applications. Careful
PCB layout is necessary. The following guidelines should
be strictly followed to achieve best performance of the
RT9503A.
`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.
`The GND should be connected to a strong ground plane
for heat sinking and noise protection.
`Connection of the RSETA should be isolated from other
noisy traces. A short wire is recommended to prevent
EMI and noise coupling.
`Output capacitor should be placed close to the IC and
connected to ground plane to reduce noise coupling.
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 25 50 75 100 125
Ambient Temperature (°C)
Maximum Power Dissipation (W) 1
Four-Layer PCB
RT9503A
14
DS9503A-01 April 2011www.richtek.com
Figure 8. PCB Layout Guide
GND
ACIN
TS
TIMER
BATT
GND
ISETU
ISETA
NC
SYS
NC
12
11
10
9
13141516
1
2
3
4
8765
17
CHG_S
AC_PGOOD EN
USB
BAT_ON
AC_ON
SYS
Battery
RSETA
The capacitors should be
placed close to the IC and
connected to ground plane.
Connection of RSETA should
be isolated from other noisy
traces.
The GND should be connected
to a strong ground plane for heat
sinking and noise protection.
RT9503A
15
DS9503A-01 April 2011 www.richtek.com
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 95, Minchiuan Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
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.
Outline Dimension
A
A1 A3
D
E
1
D2
E2
L
b
e
SEE DET AIL A
Dimensions In Millimeters Dimensions In Inches
Symbol 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 0.500 0.020
L 0.350 0.450
0.014 0.018
W-Type 16L QFN 3x3 Package
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
DETAIL A
Pin #1 ID and Tie Bar Mark Options
1
1
22
