RT9511
Fully Integrated Battery Charger with Two
Step-Down Converters
General Description
Features
The RT9511 is a fully integrated low cost solution with a
single-cell Li-Ion battery charger and two high efficiency
step-down DC/DC converters ideal for portable
applications.
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The Battery Charger is capable of being powered up from
AC adapter and USB (Universal Serial Bus) port inputs
which can automatically detect and select the AC adapter
and the USB port as the power source for the charger.
The Battery Charger enters sleep mode when both
supplies are removed. The Battery Charger 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 Battery Charger 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 and charge
status indicator.
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Applications
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The high-efficiency step-down DC/DC converter is capable
of delivering 1A output current over a wide input voltage
range from 2.5V to 5.5V, the step-down DC/DC converter
is ideally suited for portable electronic devices that are
powered from 1-cell Li-ion battery or from other power
sources such as cellular phones, PDAs and hand-held
devices. Two operating modes are available including :
PWM/Low-Dropout autoswitch and shut-down modes. The
Internal synchronous rectifier with low RDS(ON) dramatically
reduces conduction loss at PWM mode. No external
Schottky diode is required in practical application.
Battery Charger
` Automatic Input Supplies Selection
` 18V Maximum Rating for AC Adapter
` Integrated Selectable 100mA and 500mA USB
Charge Current
` Internal Integrated Power FETs
` Charge Status Indicator
` External Capacitor Programmable Safety Timer
` Under Voltage Protection
` Over Voltage Protection
` Automatic Recharge Feature
` Battery Temperature Monitoring
` Thermal Feedback Optimizing Charge Rate
` Power Path Controller
Step-Down DC/DC Converter
` Adjustable Output from 0.6V to VIN
` 1A Output Current
` 95% Efficiency
` No Schottky Diode Required
` 1.5MHz Fixed-Frequency PWM Operation
Small 24-Lead WQFN Package
RoHS Compliant and Halogen Free
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MP3/MP4 Player
GPS
Digital Photo Frame
Hand held Device
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
The RT9511 is available in a WQFN -24L 4x4 package.
DS9511-01 April 2011
www.richtek.com
1
RT9511
Pin Configurations
Ordering Information
(TOP VIEW)
FB1
CHG_S
ACIN
AC_ON
USB
SYS
RT9511
Package Type
QW : WQFN-24L 4x4 (W-Type)
24 23 22 21 20 19
Lead Plating System
G : Green (Halogen Free and Pb Free)
GND
EN1
VDD1
LX1
GND
FB2
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
}
Suitable for use in SnPb or Pb-free soldering processes.
18
2
17
3
16
GND
4
15
25
5
14
6
13
7
8
9
BAT_ON
BATT
TS
TIMER
EN
NC
10 11 12
GND
EN2
VDD2
LX2
ISETA
ISETU
}
1
ments of IPC/JEDEC J-STD-020.
WQFN-24L 4x4
Typical Application Circuit
System
VACIN
1µF
VUSB
1µF RSETA
VIN
2.5V to 5.5V
VDD1
2 EN1
VDD2
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2
VIN
2.5V to 5.5V
CIN2
4.7µF
LX1
LX2
10
24
IR2
VOUT2
C2
C1
COUT1
10µF
R2
9
L2
2.2µH
4
R1
Chip Enable
EN2 8
L1
2.2µH
VOUT1
CT
0.1µF
11 ISETA
3
CIN1
4.7µF
Battery Pack
+
RT9511
18
19 SYS
BAT_ON
21
AC_ON
17
BATT
23
CHG_S
12 ISETU
16
TS
22 ACIN
15
TIMER
20
USB
EN 14
FB1
FB2
R3
6
GND
1, 5, 7, 25 (Exposed Pad)
C OUT2
10µF
IR4
R4
DS9511-01 April 2011
RT9511
Functional Pin Description
Pin No.
1, 5, 7,
17 (Exposed Pad)
Pin Name
GND
Pin Function
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
2
EN1
Chip Enable Input Pin of Buck Converter 1. (Active High)
3
VDD1
Power Input Pin of Buck Converter 1.
4
LX1
Switching Output Pin of Buck Converter 1.
6
FB2
Feedback Voltage Input Pin of Buck Converter 2.
8
EN2
Chip Enable Input Pin of Buck Converter 2. (Active High)
9
VDD2
Power Input Pin of Buck Converter 2.
10
LX2
Switching Output Pin of Buck Converter 2.
11
ISETA
Adaptor Supply Charge Current Set Point.
12
ISETU
USB Supply Charge Current Set Input.
13
NC
No Internal Connection.
14
EN
Charge Enable Input Pin of Charger. (Active Low)
15
TIMER
Safe Charge Timer Setting.
16
TS
Temperature Sense Input.
17
BATT
Battery Charge Current Output.
18
BAT_ON
Power path controller output. This pin is used to turn on an external
19
SYS
System Voltage Detector Input Pin.
20
USB
USB Supply Voltage Input Pin.
21
AC_ON
P-MOSFET Switch Control Output (open drain).
22
ACIN
Adaptor Supply Voltage Input Pin.
23
CHG_S
Charge Status Indicator Output. (Open Drain)
24
FB1
Feedback Voltage Input Pin of Buck Converter 1.
DS9511-01 April 2011
P-MOSFET.
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3
RT9511
Function Block Diagram
ACIN
USB
OVP
Comparator
+
OVP
-
2.5V
Charge Input
Selection
SENSE
MOSFET
ISETU
USB
P-MOSFET
SENSE
MOSFET
ACIN
P-MOSFET
Timer
TIMER
USB
Current
Setting
BATT
ISETA
Temperature Fault
ACIN/USB
GND
Temperature
Sense
DRV
Loop Controller
VFB
TS
AC_ON
VREF Thermal
Sense
CHG_S
Logic
BAT_ON
EN
SYS
EN1
FB1
VDD1
+
-
Control
Logic &
VREF
LX1
VDD2
+
-
EN2
FB2
Pre-Charge Phase
Fast Charge
Phase
Control
Logic &
VREF
LX2
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
Figure 1 . Charging I-V Curve
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DS9511-01 April 2011
RT9511
RT9511
RT9511
Flow
Flow
Chart
Chart
Start-Up
Precharge Phase
Fast Charge Phase
Recharge Phase
Standby/Fault
ACIN/USB
Power Up
YES
SLEEP
UVP
DISABLE
V/CE > 1.4V ?
Start-Up
DISABLE
MODE
PFET OFF
IBATT = 0
NO
NO
VACIN < 4.3V
and
VUSB NO
< 3.9V?
YES
UVP MODE
PFET OFF
IBATT = 0
VACIN < VBATT
and
VUSB < V BATT?
YES
SLEEP MODE
PFET OFF
IBATT = 0
NO
1ms Delay
&
Start Timer
V TS > 2.5V
or
VTS < 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
NO
V BATT > 4.1 V?
IBATT = Charge
Current
/CHG_S Strong
Pull Down
YES
YES
YES
YES
V BATT > 2.8V?
NO
IBATT < 0.1 ICHG ?
TCHARGE UP?
? TCHARGE UP?
YES
STANDBY
PFET OFF
IBATT = 0
V BATT > 4.1 V?
NO
NO
DS9511-01 April 2011
NO
YES
VBATT > 2.8V?
YES
YES
TIME
FAULT
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5
RT9511
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage, ACIN -------------------------------------------------------------------------------------------- −0.3V to 18V
Supply Input Voltage, USB -------------------------------------------------------------------------------------------- −0.3V to 7V
Supply Input Voltage, EN1, EN2, FB1, FB2 ----------------------------------------------------------------------- −0.3V to 6V
VDD1, VDD2 -------------------------------------------------------------------------------------------------------------- 6.5V
Power Dissipation, PD @ TA = 25°C
WQFN-24L 4x4 ----------------------------------------------------------------------------------------------------------- 1.923W
Package Thermal Resistance (Note 2)
WQFN-24L 4x4, θJA ----------------------------------------------------------------------------------------------------- 52°C/W
WQFN-24L 4x4, θJC ----------------------------------------------------------------------------------------------------- 7°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------ 260°C
Junction Temperature --------------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range ------------------------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) --------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
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(Note 4)
Supply Input Voltage Range, ACIN ----------------------------------------------------------------------------------- 4.5V to 12V
Supply Input Voltage Range, USB ----------------------------------------------------------------------------------- 4.1V to 6V
Supply Input Voltage Range, VDD1, VDD2 ------------------------------------------------------------------------- 2.5V to 5.5V
Junction Temperature Range ------------------------------------------------------------------------------------------ −25°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------------ −25°C to 85°C
Electrical Characteristics
(VACIN = VUSB = 5V, TA = 25°C, unless otherwise specification)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Supply Input
ACIN UVP Threshold Voltage
VU V_ACIN
Rising
4.1
4.3
4.5
V
USB UVP Threshold Voltage
VU V_USB
VBATT = 3V, Rising
3.7
3.9
4.1
V
ACIN/USB UVP Hysteresis
VU V_HYS
VBATT = 3V
40
100
140
mV
ACIN/USB Standby Current
ISTBY
VBATT = 4.5V
--
300
500
µA
ACIN/USB Shutdown Current
ISHDN
--
50
100
µA
BATT Sleep Leakage Current
ISLEEP
VEN = High
VACIN = 4V, V USB = 4V, V BATT
= 4.5V
--
5
15
µA
VR EG
IBATT = 60mA
4.158
4.2
4.242
V
Voltage Regulation
BATT Regulation Voltage
ACIN MOSFET Dropout
VBATT = 4V, ICHG = 1A
400
500
620
mV
USB MOSFET Dropout
VBATT = 4V, ISET_ USB = High
500
650
800
mV
2.43
2.48
2.53
V
Current Regulation
ISETA Set Voltage
(Fast Charge Phase)
VISETA_FCHG VBATT = 3.5V
To be continued
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6
DS9511-01 April 2011
RT9511
Parameter
Symbol
Min
Typ
Max
Unit
50
--
1000
mA
--
500
--
mA
VPRECH
2.7
2.8
2.9
V
∆V PRECH
60
100
140
mV
8
10
12
%
50
95
140
mV
Full Charge Setting Range
ICHG_AC
AC Charge Current Accuracy
ICHG_AC
Test Conditions
VBATT = 3.8V, R ISET = 1.5kΩ
Precharge
BATT Pre-charge Threshold
BATT Pre-charge Threshold
Hysteresis
Pre-Charge Current
Recharge Threshold
BATT Re-charge Falling Threshold
Hysteresis
Charge Termination Detection
Termination Current Ratio
(Note 5)
Logic Input/Output
IPCH G
VBATT = 2V
∆V RECH_L
ITERM
VBATT = 4.2V
--
10
--
%
CHG_S Pull Down Voltage
VCHG_S
ICHG_S = 5mA
--
213
--
mV
Logic-High
EN Threshold
Logic-Low
Voltage
EN Pin Input Current
VIH
1.5
--
--
V
VIL
--
--
0.4
V
IEN
--
--
1.5
µA
ISETU
Threshold
High Voltage
VISETU_HIGH
1.5
--
--
V
Low Voltage
VISETU_LOW
--
--
0.4
V
IISETU
--
--
1.5
µA
--
100
--
µs
ISETU Pin Input Current
USB Charge Current & Timing
Soft-Start Time
TSS
VISETA from 0V to 2.5V
USB Charge Current
ICHG_USB
VAC IN = 3.5V, VUSB = 5V,
VBATT =3.5V, ISETU = 5V
400
450
500
mA
USB Charge Current
ICHG_USB
VAC IN = 3.5V, VUSB = 5V,
VBATT = 3.5V, ISETU = 0V
60
80
100
mA
TIME Pin Source Current
ITIME
VTIMER = 2V
--
1
--
µA
Pre-charge Fault Time
TPCHG_F
CTIMER = 0.1µF, fC LK = 7Hz
1720
2460
3200
s
Charge Fault Time
T FC HG_F
CTIMER = 0.1µF, fCLK = 7Hz
13790
19700
25610
s
ITS
VTS = 1.5V
96
102
108
µA
Timer
Battery Temperature Sense
TS Pin Source Current
TS Pin
Threshold
High Voltage
VTS_HIGH
0.485
0.5
0.515
V
Low Voltage
VTS_LOW
2.45
2.5
2.55
V
--
125
--
°C
--
6.5
--
V
--
−20
mV
Protection
Thermal Regulation
OVP SET Voltage
Internal Default
Pow er Path Controller
BAT_ON Pull Low
As SYS Falling, V BATT = 4V,
−150
SYS-BAT
To be continued
DS9511-01 April 2011
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7
RT9511
Parameter
Symbol
BAT_ON Pull High
BAT_ON Pull Low Switch
Resistance
BAT_ON Pull High Switch
Resistance
Test Conditions
As SYS Raising,
VBATT = 4V, SYS-BAT
Min
Typ
Max
Unit
−50
--
0
mV
VBAT = 4V
--
10
--
Ω
VACIN = 5V
--
30
--
Ω
Step-Down Converter
(VDD1, 2 = 3.6V, VOUT1, 2 = 2.5V, L = 2.2µH, CIN1, 2 = 4.7µF, COUT1, 2 = 10µF, IMAX = 1A, TA = 25°C, unless otherwise
specification)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
2.5
--
5.5
V
Input Voltage Range
V DD1, 2
Quiescent Current
IQx
IOUTx = 0mA, V FB1 , 2 = V REF + 5%
--
50
70
µA
Shutdown Current
ISHDNx
ENx = GND
--
0.1
1
µA
Reference Voltage
VREF
0.588
0.6
0.612
V
VREF
--
VDD1, 2 − 0.2V
V
Adjustable Output Range VOUT1, 2
(Note 5)
Adjustable Output
Voltage Accuracy
∆VOUT
VDD1, 2 = V OUT1, 2 + ∆V to 5.5V
(Note 6)
0A < IOU T < 1A
−3
--
3
%
FB1, 2 Input Current
IFB1, 2
V FB1, 2 = VDD1 , 2
−50
--
50
nA
P-MOSFET RON
RDS(ON)_P IOUT1, 2 = 200mA
V DD1, 2 = 3.6V
--
0.28
--
V DD1, 2 = 2.5V
--
0.38
--
N-MOSFET RON
RDS(ON)_N IOUT1, 2 = 200mA
V DD1, 2 = 3.6V
--
0.25
--
V DD1, 2 = 2.5V
--
0.35
--
Ω
Ω
P-Channel Current Limit IL IM_ P
VDD1, 2 = 2.5V to 5.5 V
1.4
1.5
--
A
EN1, 2 High-Level Input
Voltage
VEN1, 2_H
VDD1, 2 = 2.5V to 5.5V
1.5
--
--
V
EN1, 2 Low-Level Input
Voltage
VEN1, 2_L
VDD1, 2 = 2.5V to 5.5V
--
--
0.4
V
Under Voltage Lock Out
UVLO
threshold
--
1.8
--
V
Hysteresis
--
0.1
--
V
1.2
1.5
1.8
MHz
--
160
--
°C
100
--
--
%
1
--
100
µA
Oscillator Frequency
fOSC
Thermal Shutdown
Temperature
TSD
VDD1, 2 = 3.6V, IOUT1 , 2 = 100mA
Maximum Duty Cycle
LX1, 2 Current Source
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8
VDD1 , 2 = 3.6V, VL X1,2 = 0V or
VLX1, 2 = 3.6V
DS9511-01 April 2011
RT9511
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 WQFN 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. Guarantee by design.
Note 6. ∆V = IOUT x PRDS(ON)
DS9511-01 April 2011
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9
RT9511
Typical Operating Characteristics
Battery Charger
Charge Current vs. RSETA
1200
Enable Threshold Voltage vs. Input Voltage
Enable Threshold Voltage (V)
VBATT = 3.8V, ACIN = 5V
1000
Charge Current (mA)
2.0
800
600
400
200
0
VBATT = 3.8V, ICharger = 500mA
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
ISETA Voltage vs. ACIN Voltage
2.54
6
6.3
6.6
VBATT = 3.8V, ACIN = 5V, ICharger = 500mA
VBATT = 3.8V, ICharger = 500mA
2.52
2.52
ISETA Voltage (V)
ISETA Voltage (V)
5.7
ISETA Voltage vs. Temperature
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
TS Current (µA)
TS Current (µA)
5.4
Input Voltage (V)
RSETA (k
(kΩ))
102
101
100
99
98
97
102
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)
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10
6
6.3
6.6
-25 -15
-5
5
15
25
35
45
55
65
75
85
Temperature (°C)
DS9511-01 April 2011
RT9511
Regulation Voltage vs. Temperature
ISETU Threshold Voltage vs. USB Voltage
4.26
VBATT = 3.8V
Regulation Voltage (V)
ISETU Threshold Voltage (V)
2.0
1.6
Rising
1.2
0.8
Falling
0.4
ACIN = 5V, ICharger = 500mA
4.24
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
6.6
-25 -15
15
25
35
45
55
Temperature (°C)
ACIN Power On
USB Power On
VUSB
(5V/Div)
VSYS
(5V/Div)
VSYS
(5V/Div)
EN
(5V/Div)
EN
(5V/Div)
IIN
(1A/Div)
I USB
(1A/Div)
VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
Time (1ms/Div)
ACIN Power Off
USB Power Off
VUSB
(5V/Div)
VSYS
(5V/Div)
VSYS
(5V/Div)
VBATT
(5V/Div)
65
75
85
VBATT = 3.7V, ISYS = 500mA, ICharger = 500mA
Time (1ms/Div)
VACIN
(5V/Div)
VBATT
(5V/Div)
ISYS = 500mA, ICharger = 500mA
Time (500μs/Div)
DS9511-01 April 2011
5
USB Voltage (V)
VACIN
(5V/Div)
IIN
(1A/Div)
-5
IIN
(1A/Div)
ISYS = 500mA, ICharger = 500mA
Time (500μs/Div)
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11
RT9511
Step-Down Converter
Efficiency vs. Output Current
Output Voltage vs. Output Current
100
1.220
90
1.218
VIN = 3.6V
1.216
Output Voltage (V)
Efficiency (%)
80
VIN = 5V
70
60
50
40
30
20
VIN = 3.6V
1.214
1.212
VIN = 5V
1.210
1.208
1.206
1.204
10
1.202
VOUT = 1.2V, COUT = 10μF, L = 2.2H
0
0.001
1.200
0.01
0.1
1
0
0.1
0.2
0.3
Output Current (A)
0.5
0.6
0.7
0.8
0.9
1
Output Current (A)
Output Voltage vs. Temperature
UVLO Threshold vs. Temperature
1.25
2.1
1.24
2.0
Rising
Input Voltage (V)
1.23
Output Voltage (V)
0.4
1.22
1.21
1.20
1.19
1.18
1.9
1.8
1.7
Falling
1.6
1.5
1.17
1.4
1.16
VOUT = 1.2V, IOUT = 0A
VIN = 3.6V, IOUT = 0A
1.3
1.15
-50
-25
0
25
50
75
100
-50
125
-25
0
1.5
1.5
1.4
1.4
1.3
1.3
EN Voltage (V)
EN Voltage (V)
1.6
1.2
1.1
Rising
0.9
Falling
0.8
75
100
125
1.2
1.1
1.0
0.8
0.7
0.6
0.6
VOUT = 1.2V, IOUT = 0A
0.4
Rising
0.9
0.7
0.5
50
EN Threshold vs. Temperature
EN Threshold vs. Input Voltage
1.6
1.0
25
Temperature (°C)
Temperature (°C)
Falling
0.5
VIN = 3.6V, VOUT = 1.2V, IOUT = 0A
0.4
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
Input Voltage (V)
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12
4.9
5.2
5.5
-40
-15
10
35
60
85
110
135
Temperature (°C)
DS9511-01 April 2011
RT9511
Frequency vs. Temperature
1.60
1.55
1.55
1.50
1.50
Frequency (MHz)1
Frequency (MHz)
Frequency vs. Input Voltage
1.60
1.45
1.40
1.35
1.30
1.45
1.40
1.35
1.30
1.25
1.25
VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA
VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA
1.20
1.20
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
-40
5.5
-15
10
60
85
110
135
Current Limit vs. Temperature
Current Limit vs. Input Voltage
2.2
2.2
2.1
2.1
2.0
2.0
Output Current (A)
Output Current (A)
35
Temperature (°C)
Input Voltage (V)
1.9
1.8
1.7
1.6
1.5
1.9
1.8
1.7
VIN = 5V
VIN = 3.6V
VIN = 3.3V
1.6
1.5
1.4
1.4
1.3
1.3
VOUT = 1.2V
1.2
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
VOUT = 1.2V
1.2
-40
5.5
-15
10
35
60
85
Input Voltage (V)
Temperature (°C)
Output Ripple Voltage
Output Ripple Voltage
VIN = 3.6V, VOUT = 1.2V, IOUT = 1A
VOUT
(10mV/Div)
VLX
(5V/Div)
VLX
(5V/Div)
DS9511-01 April 2011
135
VIN = 5V, VOUT = 1.2V, IOUT = 1A
VOUT
(10mV/Div)
Time (500ns/Div)
110
Time (500ns/Div)
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13
RT9511
Power On from EN
Power On from EN
VIN = 3.6V, VOUT = 1.2V, IOUT = 10mA
VIN = 3.6V, VOUT = 1.2V, IOUT = 1A
VEN
(2V/Div)
VEN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
I IN
(500mA/Div)
I IN
(500mA/Div)
Time (100μs/Div)
Time (100μs/Div)
Power On from VIN
Power Off from EN
VIN = 3.6V, VOUT = 1.2V, IOUT = 1A
VEN = 3.6V, VOUT = 1.2V, IOUT = 1A
VEN
(2V/Div)
VIN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
I IN
(500mA/Div)
I IN
(500mA/Div)
Time (250μs/Div)
Time (100μs/Div)
Load Transient Response
Load Transient Response
VIN = 3.6V, VOUT = 1.2V
IOUT = 50mA to 1A
VIN = 3.6V, VOUT = 1.2V
IOUT = 50mA to 0.5A
VOUT
(50mV/Div)
VOUT
(50mV/Div)
IOUT
(500mA/Div)
IOUT
(500mA/Div)
Time (50μs/Div)
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14
Time (50μs/Div)
DS9511-01 April 2011
RT9511
Load Transient Response
Load Transient Response
VIN = 5V, VOUT = 1.2V
IOUT = 50mA to 1A
VIN = 5V, VOUT = 1.2V
IOUT = 50mA to 0.5A
VOUT
(50mV/Div)
VOUT
(50mV/Div)
IOUT
(500mA/Div)
IOUT
(500mA/Div)
Time (50μs/Div)
DS9511-01 April 2011
Time (50μs/Div)
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15
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 (VACIN) is
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.
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 UVP ACIN Mode
USB Mode
Q1
V ACIN < UVP
V USB > UVP
SYS
Q2
BAT_ON
AC_ON
ISYS
BATT
+
Sleep Mode
V ACIN < UVP
V USB < UVP
Figure 2. Input Power Source Operation Mode.
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16
VACIN
ACIN
Battery
ICharger
USB
USB
Figure 4. USB Input
DS9511-01 April 2011
RT9511
CIN Over Voltage Protection
V BATT
+
A
ITS
NTC
TS
Temperature
Sense
Battery
0.1µF to 10µF
VTS = ITS × RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 5. Temperature Sensing Configuration
VBATT
+
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
RT9511 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
Battery Temperature Monitoring
The RT9511 continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9511 has an internal current source to provide the
bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 5). The
RT9511 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 RT9511 stops
charging 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 6.)
The capacitor should be placed close to TS (Pin 9) 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 a 10µF if the
layout is poor to prevent noise.
DS9511-01 April 2011
ITS
NTC
Temperature
Sense
TS
RT1
Battery
RT2
0.1µF to 10µF
RT2 × (RT1 + RNTC )
RT1 + RT2 + RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
VTS = ITS
Figure 6. Temperature Sensing Circuit
Fast-Charge Current Setting
Case 1: ACIN Mode
The RT9511 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.
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17
RT9511
1200
Charge State
Charge Current (mA)
1000
ACIN
800
USB
600
CHG_S
Charge
ON
Charge Done
OFF
Charge
ON
Charge Done
OFF
400
Temperature Regulation and Thermal Protection
200
0
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
RSETA
(k)
R
SETA(kΩ)
Figure 7. ACIN 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 the ISETU pin sets the charge current
at 100mA and a high level signal sets the charge current
at 500mA.
In order to maximize the charge rate, the RT9511 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
RT9511 throttles back on the charge current in order to
maintain a junction temperature around the thermal
regulation threshold (125°C). The RT9511 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.
Pre- Charge Current Setting
During a charge cycle if the battery voltage is below the
VPRECH threshold, the RT9511 applies a pre-charge mode
to the battery. This feature revives deeply discharged cells
and protects battery life. The RT9511 internally determines
the pre-charge rate as 10% of the fast-charge current.
Battery Voltage Regulation
The RT9511 monitors the battery voltage through the BATT
pin. Once the battery voltage level closes to the VREG
threshold, the RT9511 voltage enters constant phase and
the charging current begins to taper down. When battery
voltage is over the VREG threshold, the RT9511 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 output indicates various charger
operations as shown in the following table. These status
pin 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 is bright.
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18
External Timer
As a safety mechanism, the RT9511 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 = 0.1µF, TPRECH is ~2460 secs and TFAULT is 8 x
TPRECH. TPRECH = CTMR x 2460/0.1µ
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 RT9511 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
the input power or the EN pin. If the TIMER is shorted to
GND, the charge safety timer will be disabled.
DS9511-01 April 2011
RT9511
Selecting the Input and Output Capacitors
In most applications, the most important is the high
frequency decoupling capacitor on the input of the RT9511.
A 1µF 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 10µF
ceramic capacitor to the input. The RT9511 requires a
small output capacitor for loop stability. A 1µF ceramic
capacitor placed between the BATT pin and GND is typically
sufficient.
Step-Down DC-DC Converters
Inductor Selection
For a given input and output voltage, the inductor value
and operating frequency determine the ripple current. The
ripple current ∆IL increases with higher VIN and decreases
with higher inductance.
V
V
∆IL = OUT × 1 − OUT
VIN
f ×L
Having a lower ripple current reduces the ESR losses in
the output capacitors and the output voltage ripple. Highest
efficiency operation is achieved at low frequency with small
ripple current. This, however, requires a large inductor.
A reasonable starting point for selecting the ripple current
is ∆IL = 0.4(IMAX). The largest ripple current occurs at the
highest VIN. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation :
VOUT
VOUT
L=
× 1 − VIN(MAX)
f
×
∆
I
L(MAX)
Inductor Core Selection
Once the value for L is known, the type of inductor must
be selected. High efficiency converters generally cannot
afford the core loss found in low cost powdered iron cores,
forcing the use of more expensive ferrite or mollypermalloy
cores. Actual core loss is independent of core size for a
fixed inductor value but it is very dependent on the
inductance selected. As the inductance increases, core
losses decrease. Unfortunately, increased inductance
requires more turns of wire and therefore copper losses
will increase.
DS9511-01 April 2011
Ferrite designs have very low core losses and are preferred
at high switching frequencies, so design goals can
concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard”, which means that
inductance collapses abruptly when the peak design
current is exceeded. This results in an abrupt increase in
inductor ripple current and consequent output voltage ripple.
Do not allow the core to saturate! Different core materials
and shapes will change the size/ current and price/current
relationship of an inductor.
Toroid or shielded pot cores in ferrite or permalloy materials
are small and don't radiate energy but generally cost more
than powdered iron core inductors with similar
characteristics. The choice of which style inductor to use
mainly depends on the price vs. size requirements and
any radiated field/EMI requirements.
CIN and COUT Selection
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the top MOSFET. To
prevent large ripple voltage, a low ESR input capacitor
sized for the maximum RMS current should be used. RMS
current is given by :
V
IRMS = IOUT(MAX) OUT
VIN
VIN
−1
VOUT
This formula has a maximum at VIN = 2VOUT , where
I RMS = I OUT /2. This simple worst-case condition is
commonly used for design because even significant
deviations do not offer much relief. Choose a capacitor
rated at a higher temperature than required. Several
capacitors may also be paralleled to meet size or height
requirements in the design.
The selection of COUT is determined by the effective series
resistance (ESR) that is required to minimize voltage ripple
and load step transients, as well as the amount of bulk
capacitance that is necessary to ensure that the control
loop is stable. Loop stability can be checked by viewing
the load transient response as described in a later section.
The output ripple, ∆VOUT , is determined by :
1
∆VOUT ≤ ∆IL ESR+
8fCOUT
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19
RT9511
The output ripple is highest at maximum input voltage
since ∆IL increases with input voltage. Multiple capacitors
placed in parallel may be needed to meet the ESR and
RMS current handling requirements. Dry tantalum, special
polymer, aluminum electrolytic and ceramic capacitors are
all available in surface mount packages. Special polymer
capacitors offer very low ESR but have lower capacitance
density than other types. Tantalum capacitors have the
highest capacitance density but it is important to only
use types that have been surge tested for use in switching
power supplies. Aluminum electrolytic capacitors have
significantly higher ESR but can be used in cost-sensitive
applications provided that consideration is given to ripple
current ratings and long term reliability. Ceramic capacitors
have excellent low ESR characteristics but can have a
high voltage coefficient and audible piezoelectric effects.
The high Q of ceramic capacitors with trace inductance
can also lead to significant ringing.
Using Ceramic Input and Output Capacitors
Higher values, lower cost ceramic capacitors are now
becoming available in smaller case sizes. Their high ripple
current, high voltage rating and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at the input and
output. When a ceramic capacitor is used at the input
and the power is supplied by a wall adapter through long
wires, a load step at the output can induce ringing at the
input, VIN. At best, this ringing can couple to the output
and be mistaken as loop instability. At worst, a sudden
inrush of current through the long wires can potentially
cause a voltage spike at VIN large enough to damage the
part.
Output Voltage Programming
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown in Figure 8.
V OUT
R1
FB
RT9511
R2
GND
Figure 8. Setting the Output Voltage
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20
For adjustable voltage mode, the output voltage is set by
an external resistive divider according to the following
equation :
VOUT = VREF(1 + R1 )
R2
where VREF is the internal reference voltage (0.6V typ.)
Efficiency Considerations
The efficiency of a switching regulator is equal to the output
power divided by the input power times 100%. It is often
useful to analyze individual losses to determine what is
limiting the efficiency and which change would produce
the most improvement. Efficiency can be expressed as :
Efficiency = 100% - (L1+ L2+ L3+ ...)
where L1, L2, etc. are the individual losses as a percentage
of input power. Although all dissipative elements in the
circuit produce losses, two main sources usually account
for most of the losses: VIN quiescent current and I2R
losses.
The VIN quiescent current loss dominates the efficiency
loss at very low load currents whereas the I 2R loss
dominates the efficiency loss at medium to high load
currents. In a typical efficiency plot, the efficiency curve
at very low load currents can be misleading since the
actual power lost is of no consequence.
1. The VIN quiescent current appears due to two factors
including : the DC bias current as given in the electrical
characteristics and the internal main switch and
synchronous switch gate charge currents. The gate charge
current results from switching the gate capacitance of the
internal power MOSFET switches. Each time the gate is
switched from high to low to high again, a packet of charge
∆Q moves from VIN to ground.
The resulting ∆Q/∆t is the current out of VIN that is typically
larger than the DC bias current. In continuous mode,
IGATECHG = f (QT + QB)
where QT and QB are the gate charges of the internal top
and bottom switches. Both the DC bias and gate charge
losses are proportional to VIN and thus their effects will
be more pronounced at higher supply voltages. 2. I2R
losses are calculated from the resistances of the internal
switches, RSW and external inductor RL. In continuous
DS9511-01 April 2011
RT9511
RSW = RDS(ON)TOP x DC + RDS(ON)BOT x (1-DC)
The RDS(ON) for both the top and bottom MOSFETs can be
obtained from the Typical Performance Characteristics
curves. Thus, to obtain I2R losses, simply add RSW to RL
and multiply the result by the square of the average output
current.
Other losses including CIN and COUT ESR dissipative
losses and inductor core losses generally account for less
than 2% of the total loss.
resistance θJA is 52°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 :
PD(MAX) = (125°C − 25°C) / (52°C/W) = 1.923W for
WQFN-24L 4x4 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For RT9511 packages, the Figure 9 of
derating curves allows designers to see the effect of rising
ambient temperature on the maximum power dissipation
allowed.
2.0
Maximum Power Dissipation (W)
mode, the average output current flowing through inductor
L is “chopped” between the main switch and the
synchronous switch. Thus, the series resistance looking
into the LX pin is a function of both top and bottom
MOSFET RDS(ON) and the duty cycle (DC) as follows :
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to ∆ILOAD (ESR), where ESR is the effective series
resistance of COUT . ∆ILOAD also begins to charge or
discharge COUT generating a feedback error signal used
by the regulator to return VOUT to its steady-state value.
Four Layers PCB
1.8
1.6
1.4
WQFN-24L 4x4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
During this recovery time, VOUT can be monitored for
overshoot or ringing that would indicate a stability problem.
25
50
75
100
125
Ambient Temperature (°C)
Figure 9. Derating Curves for RT9511 Packages
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
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.
For recommended operating conditions specification of
the RT9511, the maximum junction temperature is 125°C.
The junction to ambient thermal resistance θJA is layout
dependent. For WQFN-24L 4x4 packages, the thermal
DS9511-01 April 2011
Layout Consideration
The RT9511 is a fully integrated solution for portable
applications including a single-cell Li- Ion battery charger
and two ideal high-efficiency step-down DC-DC converters
ideal. Careful PCB layout is necessary. For best
performance of the RT9511, the following guidelines should
be strictly followed.
}
Input capacitors should be placed close to the IC and
connected to ground plane.
}
The GND and Exposed Pad should be connected to a
strong ground plane for heat sinking and noise protection.
}
The connection of RSETA should be isolated from other
noisy traces. The short wire is recommended to prevent
noise coupling.
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21
RT9511
}
Output capacitors should be placed close to the IC and
connected to ground plane to reduce noise coupling.
}
Keep the main current traces as possible as short and
wide.
}
LX node of step-down DC-DC converter is with high
frequency voltage swing. It should be kept at a small
area.
}
Place the feedback components as close as possible
to the IC and keep away from the noisy devices.
The capacitors should be
placed close to the IC pin
and connected to ground
plane.
AC_ON
USB
SYS
FB1
CHG_S
ACIN
SYS
24 23 22 21 20 19
1
18
2
17
3
16
GND
4
15
14
5
25
6
9
13
BAT_ON
BATT
TS
TIMER
EN
NC
Battery
10 11 12
ISETU
8
GND
EN2
VDD2
7
LX2
ISETA
V OUT1
GND
EN1
VDD1
LX1
GND
FB2
R SETA
V OUT2
The connection of R SETA should be
isolated from other noisy traces. The
short wire is recommended to prevent
EMI and noise coupling
GND
The GND should be connected
to a strong ground plane for heat
sinking and noise protection.
Figure 10. PCB Layout Guide
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22
DS9511-01 April 2011
RT9511
Table 1. Recommended Inductors
Inductance
Current Rating (mA)
(µH)
Supplier
DCR
(mΩ)
Dimensions
(mm)
Series
TAIYO YUDEN
2.2
1480
60
3.00 x 3.00 x 1.50
NR 3015
GOTREND
2.2
1500
58
3.85 x 3.85 x 1.80
GTSD32
Sumida
2.2
1500
75
4.50 x 3.20 x 1.55
CDRH2D14
Sumida
4.7
1000
135
4.50 x 3.20 x 1.55
CDRH2D14
TAIYO YUDEN
4.7
1020
120
3.00 x 3.00 x 1.50
NR 3015
GOTREND
4.7
1100
146
3.85 x 3.85 x 1.80
GTSD32
Table 2. Recommended Capacitors for CIN and COUT
Supplier
Capacitance
(µF)
Package
Part Number
TDK
4.7
603
C1608JB0J475M
MURATA
4.7
603
GRM188R60J475KE19
TAIYO YUDEN
4.7
603
JMK107BJ475RA
TAIYO YUDEN
10
603
JMK107BJ106MA
TDK
10
805
C2012JB0J106M
MURATA
10
805
GRM219R60J106ME19
MURATA
10
805
GRM219R60J106KE19
TAIYO YUDEN
10
805
JMK212BJ106RD
DS9511-01 April 2011
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23
RT9511
Outline Dimension
D2
D
SEE DETAIL A
L
1
E
E2
e
b
1
1
2
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A
A3
A1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
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
3.950
4.050
0.156
0.159
D2
2.300
2.750
0.091
0.108
E
3.950
4.050
0.156
0.159
E2
2.300
2.750
0.091
0.108
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 24L QFN 4x4 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: 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.
www.richtek.com
24
DS9511-01 April 2011
工商网监
湘ICP备2023018690号
