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RT8561D
High Voltage 8-CH LED Driver
General Description
Features
The RT8561D is a 40V 8-CH LED driver capable of delivering
30mA to each channel with 10 LEDs (3.6V per diode), for
a total of 80 LEDs per driver. The RT8561D is a currentmode Boost converter that operates at 1MHz, with a wide
VIN range from 4.5V to 24V and an on chip current switch
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High Voltage : VIN up to 24V, VOUT up to 40V
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Adjustable Channel Current from 10mA to 30mA
1.5% Channel Current Matching
Current-Mode PWM 1MHz Boost Converter
Easy and High Accuracy Digital Dimming by PWM
Signal
Adjustable Soft-Start
Automatic Detection of Unconnected and/or Broken
Channel
Adjustable Over-Voltage Protection
Disconnect Adjustable LED in Shutdown
No Power Sequence Concern
VIN Under-Voltage Lockout
Over-Temperature Protection
Current Limiting
Small 24-Lead WQFN Package
RoHS Compliant and Halogen Free
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rated at 2.5A.
The PWM output voltage loop regulates the LED pins to
0.6V with an auto adjustment circuit allowing voltage
mismatches between LED strings. The RT8561D
automatically detects and disconnects any unconnected
and/or broken strings during operation from the PWM loop
to prevent VOUT from over-voltage.
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The 1.5% matched LED currents on all channels can be
simply adjustable with a resistor or a current sink. A very
high contrast true digital PWM dimming can be achieved
by driving the PWM pin with a PWM signal.
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Other protections including adjustable programmable
output over-voltage protection, LED current limit, PWM
switch current limit and thermal shutdown are provided.
Applications
The RT8561D is available in the WQFN-24L 4x4 package.
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UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Desk Lights and Room Lighting
Simplified Application Circuit
VOUT
D1
L1
VIN
R4
C5
C1
RT8561D
LX
VCC
R7
:
:
:
:
C7
C6
R5
5V
LED1
EN
LED7
VC
R1
LED8
CREG
C3
RISET
GND
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8561D-00 May 2013
R2
OVP
SS
C4
...
...
ACTL
PWM Signal
C2
:
: 8 x 10 LED String
:
:
LED2
R6
C8
:
:
: ... :
:
:
:
:
VOUT
R3
RISET
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1
RT8561D
Ordering Information
Pin Configurations
RT8561D
(TOP VIEW)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
`
RoHS compliant and compatible with the current require-
GND
GND
GND
GND
LX
LX
Package Type
QW : WQFN-24L 4x4 (W-Type)
(Exposed Pad-Option 1)
24 23 22 21 20 19
LED1
LED2
LED3
LED4
LED5
OVP
1
18
2
17
3
15
25
5
14
13
6
7
8
9 10 11 12
VC
NC
SS
RISET
ACTL
NC
ments of IPC/JEDEC J-STD-020.
`
16
GND
4
VCC
CREG
LED8
LED7
LED6
EN
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
WQFN-24L 4x4
1N= : Product Code
1N=YM
DNN
YMDNN : Date Code
Functional Pin Description
Pin No.
Pin Name
Pin Function
1, 2, 3, 4, 5
LED1, LED2,
LED3, LED4,
LED5
LED Current Sink Output for Channel 1 to Channel 5. Leave these pins
unconnected if not used.
6
OVP
Over-Voltage Protection Sense Input. PWM Boost converter turns off when
VOVP goes higher than 1.2V.
7
VC
Compensation Node of PWM Boost Converter.
8
NC
No Internal Connection.
9
SS
Soft-Start Setting. Connect a capacitor of at least 10nF is required for
soft-start.
10
RISET
A resistor or a current from DAC on this pin programs the full LED current.
Analog/Digital Dimming Control Input. When using analog dimming,
11
ACTL
ILED (mA) = 20 x 4.75 for VACTL ≥ 1.2V.
RISET (kΩ )
12
NC
No Internal Connection.
13
EN
Enable Control Input. When the pin is pulled low, chip is in shutdown mode.
LED6, LED7,
LED8
LED Current Sink Output for Channel 6 to Channel 8. Leave these pins
unconnected if not used.
17
CREG
4.7μF capacitor should be placed on this pin to stabilize the 5V output of the
internal regulator. This regulator is for chip internal use only.
18
VCC
Supply Voltage Input. For good bypass, a low ESR capacitor is required.
LX
Switch Node of PWM Boost Converter.
GND
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
14, 15, 16
19, 20
21, 22, 23, 24,
25 (Exposed Pad)
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is a registered trademark of Richtek Technology Corporation.
DS8561D-00 May 2013
RT8561D
Function Block Diagram
LX
OSC
VCC
-
4.2V
+
R
OVP
-
+
-
-
1.6V
+
EN
-
R
+
1.2V
CREG
LED1
S
+
LED2
Shutdown
+
-
5V
LDO
VOUT
Regulation
Unit
VC
5µA
.
.
.
LED7
+
5V
-
SS
LED8
+
ACTL
+
GND
-
-
RISET
Operation
The RT8561D integrates a current mode Boost PWM
converter and a 8-CH LED drivers. When EN and PWM
are high and VIN is higher than the UVLO threshold voltage,
the controller starts operation. In normal operation, the
LX pin goes low when the driver is set by the oscillator
and the LX pin goes high when the driver is reset by the
current comparator.
When the LX pin goes low due to the internal MOSFET
turn-on, the inductor current will rise. Once the current
reaches the level of VC pin, the current comparator will
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
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reset the driver and turn-off the internal MOSFET and LX
pin will go high. The LX pin will then go low again as set
by OSC and repeat in the next switching cycle.
The output voltage of the Boost converter supports LED
current and regulation voltage at LEDx pin. The LED current
is set by an external resistor at RISET pin.
A PWM dimming function is provided to control the LED
brightness through the ACTL pin.
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RT8561D
Absolute Maximum Ratings
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(Note 1)
Supply Voltage, VCC ----------------------------------------------------------------------------------------------------LX Voltage at Switching Off --------------------------------------------------------------------------------------------LED1 to LED8 -------------------------------------------------------------------------------------------------------------ACTL, EN ------------------------------------------------------------------------------------------------------------------OVP -------------------------------------------------------------------------------------------------------------------------LED Channel Current ----------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WQFN-24L 4x4 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WQFN-24L 4x4, θJA ------------------------------------------------------------------------------------------------------WQFN-24L 4x4, θJC -----------------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) -----------------------------------------------------------------------------------------------------
Recommended Operating Conditions
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28V
50V
50V
24V
−0.3V to 5.5V
32mA
3.57W
28°C/W
7°C/W
150°C
260°C
−65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------- 4.5V to 24V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VCC = 17V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Supply Current
IVCC
VIN Under-Voltage Lockout
Threshold
VUVLO
Shutdown Current
ISHDN
EN Input Voltage
ACTL Input
Voltage
Test Conditions
Min
Typ
Max
Unit
VC ≤ 0.2V (Switching off)
--
3
5
mA
VIN Rising
--
4.2
4.5
Hysteresis
--
0.3
--
VEN = 0V
--
--
10
1.6
--
5
--
--
0.65
1.3
--
5
--
--
0.65
Logic-High VEN_H
Logic-Low
VEN_L
Logic-High VACTL_H
Logic-Low
EN Input Current
VACTL_L
V
μA
V
V
IEN
VEN ≤ 5V
--
--
0.1
μA
ILED
2V > VLED > 0.6V, RISET = 4.75kΩ
19
20
21
mA
2V > VLED > 0.6V, RISET = 4.75kΩ
Calculating
(I(MAX) − I(MIN)) / IAverage x 100%
--
--
1.5
%
LED Current Programming
LED Current
LEDs Current Matching
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DS8561D-00 May 2013
RT8561D
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
1.17
1.2
1.23
V
RISET Voltage
VRISET
3.6kΩ ≤ RISET ≤ 9.6kΩ, V ACTL > 1.2V
Input Current of ACTL
IACTL
V ACTL = 1.3V
--
1
2
μA
Un-connection
--
0.1
--
V
0.8
1
1.2
MHz
--
100
--
ns
0.5
0.6
0.7
V
VLED Threshold
PWM Boost Converter
Switching Frequency
Minimum On-Time
Regulated VLED
Highest Voltage LED String
Amplifier (gm) Output Current
2.4V > VC > 0.2V
--
±15
--
μA
VC Threshold
PWM Switch Off
0.1
0.2
--
V
--
0.3
0.5
Ω
ILIM
2.5
--
--
A
OVP Threshold
VOVP
1.1
1.2
1.3
V
OVP Input Current
IOVP
V OVP ≤ 3V
--
--
50
nA
Soft-Start Current
ISS
V SS ≤ 2.5V
3
5
8
μA
Thermal Shutdown Threshold
T SD
--
150
--
°C
--
20
--
°C
LX RDS(ON)
LX Current Limit
OVP & Soft-Start
Thermal Shutdown Hysteresis
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and 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 may affect
device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at 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.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
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RT8561D
Typical Application Circuit
VIN
4.5V to 24V
5V
18 VCC
R5
1k 13
:
:
:
:
7
R1
1.8k
17
9
LED1
LED2
ACTL
VC
CREG
SS
C4
0.1µF
21, 22, 23, 24,
25 (Exposed Pad)
R7
LED7
LED8
OVP
RISET
C7
:
:
: ... :
:
:
:
:
:
: 8 x 10 LED String
:
:
1
2
15
16
...
PWM Signal
11
EN
LX 19, 20
...
R6 1k
C2
3.9nF
C5
10µF
RT8561D
C6
1µF
C3
4.7µF
D1
C1
10µF
R4
10
C8
VOUT
40V MAX
L1
10µH
R2
6
10
VOUT
R3
RISET
4.75k
ILED (mA) = 20 x 4.75
GND
RISET (kΩ )
Note :
Due to the limitation of maximum duty, 5V input can support typically to VOUT = 33V.
Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control
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is a registered trademark of Richtek Technology Corporation.
DS8561D-00 May 2013
RT8561D
Typical Operating Characteristics
Efficiency vs. Input Voltage
LED Current vs. Input Voltage
100
22.0
90
21.2
LED Current (mA)
80
Efficiency (%)
21.6
80LEDs
70
60
50
40
30
20.8
20.4
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
20.0
19.6
19.2
20
18.8
10
18.4
18.0
0
4
6
8
10
12
14
16
18
20
22
4
24
6
8
10
14
16
18
20
22
24
Input Voltage (V)
Input Voltage (V)
VRISET vs. Temperature
LED Current vs. Temperature
24
1.24
23
1.22
22
1.20
21
VRISET (V)
LED Current (mA)
12
20
19
1.18
1.16
1.14
18
1.12
17
VIN = 12V
VIN = 12V
1.10
16
-50
-25
0
25
50
75
100
-50
125
-25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
LED Current vs. PWM Duty Cycle
VRISET vs. Input Voltage
25
1.25
1.24
20
LED Current (mA)
1.23
VRISET (V)
1.22
1.21
1.20
1.19
1.18
15
PWM = 200Hz
PWM = 1kHz
PWM = 10kHz
PWM = 30kHz
10
5
1.17
1.16
VPWM = 0V to 3V, VIN = 12V
0
1.15
4
6
8
10
12
14
16
18
20
22
Input Voltage (V)
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24
0
0
0.1
10
0.2
1
20 0.3
30 0.4
40 0.5
50 0.6
60 0.7
70 0.8
80 0.9
90 100
Duty Cycle (%)
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RT8561D
Shutdown Current vs. Temperature
Shutdown Current vs. Input Voltage
6
Shutdown Current (μA)1
Shutdown Current (μA)1
10
8
6
4
2
4
6
8
10
12
14
16
18
20
22
4
3
2
1
VIN = 12V, VEN = 0V
VEN = 0V
0
5
0
-50
24
-25
0
50
75
100
125
Temperature (°C)
Input voltage (V)
SS Current vs. Temperature
Switch Off Current vs. Input Voltage
4.0
8.0
3.8
7.6
3.6
7.2
3.4
6.8
SS Current (μA)
Switch Off Current (mA)
25
3.2
3.0
2.8
2.6
6.4
6.0
5.6
5.2
4.8
2.4
2.2
4.4
VCOMP = 0V
2.0
VIN = 12V, CSS = 0.1μF
4.0
4
6
8
10
12
14
16
18
20
22
-50
24
-25
0
25
50
75
100
125
Temperature (°C)
Input Voltage (V)
OVP Voltage vs. Temperature
SS Current vs. Input Voltage
6.0
1.30
1.28
1.26
OVP Voltage (V)
SS Current (μA)
5.8
5.6
5.4
5.2
1.24
1.22
1.20
1.18
1.16
1.14
CSS = 0.1μF
5.0
1.12
VIN = 12V
1.10
4
6
8
10
12
14
16
18
20
22
Input Voltage (V)
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8
24
-50
-25
0
25
50
75
100
125
Temperature (°C)
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DS8561D-00 May 2013
RT8561D
OVP Voltage (V)
OVP Voltage vs. Input Voltage
Line Transient Response
1.4
14V
1.2
12V
1.0
10V
0.8
IOUT
(100mA/Div)
0.6
0.4
0.2
VIN
VIN = 10.8V to 13.2V
0.0
4
6
8
10
12
14
16
18
20
22
24
Time (50ms/Div)
Input Voltage (V)
Power On from EN
EN
(2V/Div)
VOUT
(20V/Div)
LX
(20V/Div)
I IN
(100mADiv)
VIN = 12V
Time (10ms/Div)
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RT8561D
Applications Information
The RT8561D is a current-mode Boost converter operating
at 1MHz to power up to 80 white LEDs with a
programmable current for uniform intensity. The part
integrates current sources, soft-start, and easy analog
and digital dimming control. The protection block provides
the circuitry for over-temperature, over-voltage and current
limit protections.
Input UVLO
The input operating voltage range of the RT8561D is 4.5V
to 24V. An input capacitor at the VCC pin can reduce
ripple voltage. It is recommended to use a ceramic 10μF
or larger capacitor as the input capacitor. This IC provides
an Under-Voltage Lockout (UVLO) function to enhance the
stability during startup.
If VIN is close to VOUT and smaller than VOUT, the control
loop may turn on the power switch with minimum on time
and then skip cycles to maintain LED current regulation.
Brightness Control
The RT8561D features digital dimming control scheme.
A very high contrast ratio true digital PWM dimming can
be achieved by driving the ACTL pin with a PWM signal at
the recommended PWM frequency range from 100Hz to
10kHz.
Dimming frequency can be sufficiently adjusted from
100Hz to 30kHz. However, LED current cannot be 100%
proportional to duty cycle especially for high frequency
and low duty ratio because of physical limitation caused
by inductor rising time. Refer to Table 1 and Figure 2.
Soft-Start
The RT8561D employs a soft-start feature to limit the inrush
current. The soft-start circuit prevents excessive inrush
current and input voltage droop. The soft-start time is
determined by the capacitor, C4, which is connected to
the SS pin with 5μA constant current. The value of capacitor
C4 is user defined to satisfy the designer's requirement.
LED Connection
The RT8561D provides an 8-CH LED driver with each
channel capable of supporting up to 10 LEDs. The 8 LED
strings are connected from VOUT to pins 1, 2, 3, 4, 5, 14,
15, and 16, respectively. If one of the LED channels is not
in use, the LED pin should be tied to ground directly.
Table 1.
Dimming Frequency (Hz)
100 < fPWM ≤ 200
200 < fPWM ≤ 500
500 < fPWM ≤ 1k
1k < fPWM ≤ 2k
2k < fPWM ≤ 5k
5k < fPWM ≤ 10k
10k < f PWM ≤ 20k
Duty (Min.)
0.16%
0.40%
0.80%
1.60%
4.00%
8.00%
16.00%
Duty (Max.)
100%
100%
100%
100%
100%
100%
100%
Note : The minimum duty in Table 1 is based on the application
circuit and does not consider the deviation of current linearity.
LED Current vs. PWM Duty Cycle
25
Setting and Regulation of LED Current
The LED current can be calculated by the following
equation :
ILED (mA) = 20 x 4.75
RISET (kΩ)
where, RISET is the resistor between the RISET pin and
GND.
This setting is the reference for the LED current at LED1
to LED8 and represents the sensed LED current for each
string. The DC/DC converter regulates the LED current
according to the setting.
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LED Current (mA)
20
15
PWM = 200Hz
PWM = 1kHz
PWM = 10kHz
PWM = 30kHz
10
5
VPWM = 0V to 3V, VIN = 12V
0
0
0
0.1
10
0.2
1
20 0.3
30 0.4
40 0.5
50 0.6
60 0.7
70 0.8
80 0.9
90 100
Duty Cycle (%)
Figure 2. LED Current vs. PWM Dimming Duty Cycle
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DS8561D-00 May 2013
RT8561D
Over-Voltage Protection
The RT8561D equips an Over-Voltage Protection (OVP)
function. When the voltage at the OVP pin reaches a
threshold of approximately 1.2V, the MOSFET driver
output (LX) will be turned “OFF”. The MOSFET driver
output (LX) will be turned “ON” again once the voltage at
OVP drops below the threshold voltage 1.2V.
Thus, the output voltage can be clamped at a certain
voltage level as shown in the following equation :
VOUT, OVP = VOVP × ⎛⎜ 1+ R2 ⎞⎟
⎝ R3 ⎠
Hence, even when VIN is ready, the control circuit will
still wait for the arrival of PWM and EN before the LEDs
can react :
VIN
VOUT
EN
ACTL
Figure 3. EN/ACTL Prior to VIN
where
R2 and R3 are the resistors in a voltage divider connected
to the OVP pin.
VOVP is typically 1.2V.
If at least one string is in normal operation, the controller
will automatically ignore the open strings and continue to
regulate the current for the string(s) in normal operation.
UVLO
VIN
UVLO
VOUT
EN
ACTL
Current Limit
The RT8561D can limit the peak current to achieve overcurrent protection. The RT8561D senses the inductor
current through the LX pin during the switch-on period.
The duty cycle depends on the current sense signal
summed up with the internal slope compensation and
compared to the VC signal. The internal N-MOSFET will
be turned off when the current signal is larger than the
COMP signal. In the off period, the inductor current will
descend. The internal MOSFET is turned on by the
oscillator in the next beginning cycle.
Figure 4. VIN Tums Off Prior to EN/ACTL
VIN
VOUT
EN
ACTL
Figure 5. EN Prior to ACTL Signal
Over-Temperature Protection
The RT8561D has an Over-Temperature Protection (OTP)
function to prevent overheating due to excessive power
dissipation. The OTP will shut down switching operation
when the junction temperature exceeds 150°C. The main
converter will start switching again once the junction
temperature cools down approximately by 20°C.
VIN
VOUT
EN
Power Sequence
The RT8561D can apply these power-on/off sequences
among VLED, EN and ACTL as shown in the charts below.
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ACTL
Figure 6. EN Prior to ACTL Signal
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RT8561D
Diode Selection
VIN
VOUT
EN
ACTL
Figure 7. ACTL Prior to EN Signal
Schottky diode is a good choice for an asynchronous
Boost converter due to its small forward voltage. However,
when selecting a Schottky diode, important parameters
such as power dissipation, reverse voltage rating and
pulsating peak current should all be taken into
consideration. Choose a suitable diode with reverse voltage
rating greater than the maximum output voltage.
Capacitor Selection
VIN_POK
LED_ON
ACTL
EN
Figure 8
Inductor Selection
The value of the output inductor (L), where the transition
from discontinuous to continuous mode occurs is
approximated by the following equation :
L=
(VOUT − VIN ) × VIN2
2 × IOUT × f × VOUT 2
where,
VOUT = maximum output voltage.
VIN = minimum input voltage.
f = operating frequency.
IOUT = sum of current from all LED strings.
η is the efficiency of the power converter.
The Boost converter operates in discontinuous mode over
the entire input voltage range when the L1 inductor value
is less than this value L. With an inductance greater than
L, the converter operates in continuous mode at the
minimum input voltage and may be in discontinuous mode
at higher input voltages.
The inductor must be selected with a saturation current
rating greater than the peak current provided by the
following equation :
IPEAK = VOUT × IOUT + VIN × T ⎛⎜ VOUT − VIN ⎞⎟
η × VIN
2 × L ⎝ VOUT
⎠
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12
The input capacitor reduces current spikes from the input
supply and minimizes noise injection into the converter.
For most applications, a 10μF ceramic capacitor is
sufficient. A value higher or lower may be used depending
on the noise level from the input supply and the input
current to the converter.
It is recommended to choose a ceramic capacitor based
on the output voltage ripple requirements. The minimum
value of the output capacitor COUT is approximately given
by the following equation :
(VOUT − VIN ) × IOUT
COUT =
η × VRIPPLE × VOUT × f
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, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WQFN-24L 4x4 package, the thermal resistance, θJA, is
28°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 :
is a registered trademark of Richtek Technology Corporation.
DS8561D-00 May 2013
RT8561D
P D(MAX) = (125°C − 25°C) / (28°C/W) = 3.57W for
WQFN-24L 4x4 package
Layout Consideration
PCB layout is very important for designing power switching
converter circuits. Some recommended layout guides that
should be strictly be followed are shown as follows :
Maximum Power Dissipation (W)1
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 9 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
`
The power components L1, D1, CVIN1, COUT1 and COUT2
must be placed as close as possible to reduce the ac
current loop. The PCB trace between power components
must be short and wide as possible due to large current
flow these trace during operation.
`
Place L1 and D1 connected to LX pin as close as
possible. The trace should be short and wide as possible.
2.0
`
Recommend place CVIN2 close to VCC pin.
1.5
`
Pin7 is the compensation point to adjust system
stability. Place the compensation components to pin7
as close as possible, no matter the compensation is
RC or capacitance.
4.0
Four-Layer PCB
3.5
3.0
2.5
1.0
0.5
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 9. Derating Curve of Maximum Power Dissipation
Place these components
as close as possible.
COUT1
VOUT
COUT2
GND
D1
CVIN1
GND
GND
GND
GND
LX
LX
24
23
22
21
20
19
1
18
LED2
2
17
LED3
3
LED4
4
LED5
5
OVP
6
GND
9
10
11
12
SS
RISET
ACTL
NC
VC
C8
8
NC
25
R1
C2
GND
CVIN2
LED1
7
VIN
L1
R4
VCC
16
Locate the C6 as
CREG close to VCC pin as
LED8 possible.
15
LED7
14
LED6
13
EN
Locate the compensation
components to VC pin as
close as possible.
GND
Figure 10. PCB Layout Guide
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8561D-00 May 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT8561D
Outline Dimension
D2
D
SEE DETAIL A
L
1
E
E2
e
b
A3
Symbol
D2
E2
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
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
E
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
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
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
www.richtek.com
14
DS8561D-00 May 2013