High Voltage 8 Channel LED Driver
RT8562
General Description
The RT8562 is a 40V 8-channel LED driver capable of
delivering 30mA to each channel with 10 LEDs (3.6V per
diode), total of 80 LEDs with one driver. The RT8562 is a
current mode boost converter opearated at 1MHz, wide
V
range covers from 6V to 24V and the on-chip current
IN
switch is 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 RT8562 automati-
cally detects and disconnects any unconnected and/or
broken strings during operation from PWM loop to prevent
V
from over voltage.
OUT
The 1.5% matched LED currents on all channels are simply
programmed with a resistor or a current sink. Both analog
dimming and digitally controlled PWM dimming are
supported by RT8562. Analog dimming is linearly
controlled by an external voltage. A very high contrast ratio
true digital PWM dimming can be achieved by driving PWM
pin with a PWM signal.
Features
z High V oltage : V
up to 80 x 3.6V LEDs (10 each channel)
z Channel Current Progra mma be 10mA to 30mA a nd
Matched to 1.5%
z Current Mode PWM 1MHz Boost Converter
z Easy Analog and Digital Dimming Control
z Programmable Soft Start
z Automatic Detecting Unconnected and/or Broken
Channel
z Programmable Over Voltage Protection
z Disconnects LED in Shutdown
z Providing High Accuracy Digital Dimming by PWM
Signal
z V
Under Voltage Lockout
IN
zz
z Over Temperature Protection
zz
zz
z Current Limiting Protection
zz
zz
z Small 24-Lead WQFN Package
zz
zz
z RoHS Compliant and Halogen Free
zz
up to 24V , V
IN
up to 40V , Driving
OUT
Applications
Other protecting features include programmable output
over voltage protection, LED curren limit, PWM switch
current limit and thermal shutdown.
The RT8562 is packaged with a tiny footprint package of
WQFN-24L 4x4 packages.
Ordering Information
RT8562
Package Type
QW : WQFN-24L 4x4 (W-Type)
Lead Plating System
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.
G : Green (Halogen Free and Pb Free)
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
z UMPC and Notebook Computer Backlight
z GPS, Portable DVD Backlight
z Desk Lights and Room Lighting
Pin Configurations
(TOP VIEW)
CH5 NC
LX1
LX2
18
17
16
15
14
25
13
11
CH4
ISET
EN
NC
SS
NC
GND
PWM
VDC
VIN
24 2223
1
2
3
4
5
6
7
8 9 10 12
CH8
CH7
WQFN-24L 4x4
COMP
21 20 19
GND
CH6
PGND2
PGND1
OVP
CH1
CH2
CH3
DS8562-01 April 2011 www.richtek.com
1
RT8562
Typical Application Circuit
V
IN
6V to 24V
PWM Signal
R1
1.8k
C2
3.9nF
C3
4.7µF
10
R6
R4
1µF
C6
1k
C4
0.1µF
C1
10µF
R5
1k
23
1
6
22
24
3
L
10µH
RT8562
VIN
EN5V
PWM
COMP
VDC
SS
GND
5, Exposed Pad (25)
OVP
ISET
LX1
LX2
CH1
CH2
CH7
CH8
19
20
15
14
8
7
16
11
I
LED
D1
R7
R
ISET
4.75k
(mA) =
C7
...
C5
10µF
:
:
:
:
R2
R3
20 x 4.75
Ω)
R(k
ISET
V
OUT
40V MAX
:
:
...
:
:
:
:
:
:
V
OUT
:
10 LED String
:
:
:
V
6V to 24V
Analog
Dimming
R1
1.8k
C2
3.9nF
Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control
IN
C3
4.7µF
R6
R4
10
C6
1µF
1k
R5
1k
C4
0.1µF
C1
10µF
10µH
RT8562
23
VIN
1
EN5V
6
PWM
22
COMP
24
VDC
3
SS
GND
5, Exposed Pad (25)
L
19
LX1
20
LX2
15
CH1
14
CH2
8
CH7
7
CH8
16
OVP
11
ISET
I
LED
D1
R7
...
R
ISET
4.75k
(mA) =
C5
10µF
C7
20 x 4.75
R(k
R3
ISET
R2
Ω)
:
:
:
:
Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control
V
OUT
40V MAX
:
:
...
:
:
:
:
:
:
V
OUT
:
10 LED String
:
:
:
DS8562-01 April 2011www.richtek.com
2
V
4V to 36V
V
AVDD
6V to 24V
Analog
Dimming
R1
1.8k
C2
3.9nF
L
IN
C7
C1
1µF
10µF
R4
R5
R6
C3
4.7µF
10
1k
1k
C6
2.2µF
C4
0.1µF
23
1
6
22
24
3
10µH
RT8562
VIN
EN5V
PWM
COMP
VDC
SS
GND
5, Exposed Pad (25)
LX1
LX2
CH1
CH2
CH7
CH8
OVP
ISET
19
20
15
14
8
7
16
11
I
LED
D1
R7
R
ISET
4.75k
(mA) =
Note :
1. Due to the limitaion of maximum duty, 5V input can support typically to V
2. Due to the limitaion of maximum duty, 4V input can support typically to V
C8
...
OUT
OUT
C5
10µF
:
:
:
:
R2
R3
20 x 4.75
Ω)
R(k
ISET
= 33V.
= 26V.
V
OUT
40V MAX
:
:
...
:
:
:
:
:
:
V
OUT
:
10 LED String
:
:
:
RT8562
Figure 3. Wide Range VIN Application by Connecting VCC Pin to LCD Driver Power AVDD
Function Block Diagram
VIN
5.6V
OVP
1.2V
EN
1.6V
VDC
COMP
SS
5V
LDO
5uA
+
+
-
+
Shutdown
OSC
S
R
R
+
-
V
OUT
Regulation
Unit
LX1, LX2
5V
+
-
+
-
CH1
CH2
.
.
.
+
-
CH7
CH8
PWM
+
-
ISET
+
-
DS8562-01 April 2011 www.richtek.com
3
RT8562
Functional Pin Description
Pin No. Pin Name Pin Function
1 EN Chip enable pin, when pulled low, chip is in shutdown mode.
2, 4, 21 NC No Internal Connection.
3 SS Soft Start Pin, a capacitor of at least 10nF is required for soft start.
5,
25 (Exposed Pad)
GND
6 PWM
11 ISET A resistor or a current from DAC on this pin programs the full LED current.
10, 9, 8, 7 CH5 to CH8 Channel 5 to Channel 8 LED current sink. Leave the pin unconnected if not used.
15, 14, 13, 12 CH1 to CH4 Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not used.
16 OVP
17, 18
PGND1,
PGND2
19, 20 LX1, LX2 PWM boost converter switch node.
Ground pin of the chip. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
Analog/Digital dimming control. When using analog dimming,
I (mA) = for V 1.2V.
LED PW M
Over Voltage Protection. PWM boost converter turns off when V
20 x 4.75
R(kΩ)
ISET
≥
OVP
higher than 1.2V.
Power Ground (LX1/LX2 power return).
goes
22 COMP PWM boost converter loop compensation node.
23 VIN Power supply of the chip. For good bypass, a low ESR capacitor is required.
24 VDC
Put 1μF capacitor on this pin to stabilize the 5V output of the internal regulator.
This regulator is for chip internal use only.
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VIN ------------------------------------------------------------------------------------------------------ 28V
z LX1, LX2 Pin Voltage at Switching Off -------------------------------------------------------------------------------- 45V
z CH1 to CH8 Pin ------------------------------------------------------------------------------------------------------------ 35V
z PWM, EN, OVP Pin Voltage ------------------------------------------------------------------------------------------- −0.3V to 5.5V
z Power Dissipation, P
WQFN-24L 4x4 ------------------------------------------------------------------------------------------------------------ 1.923W
z Package Thermal Resistance (Note 2)
WQFN-24L 4x4, θJA------------------------------------------------------------------------------------------------------- 52°C/W
WQFN-24L 4x4, θJC------------------------------------------------------------------------------------------------------ 7°C/W
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
@ TA = 25°C
D
Recommended Operating Conditions (Note 4)
z Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- 6V to 24V
z Junction Temperature Range --------------------------------------------------------------------------------------------
z Ambient Temperature Range --------------------------------------------------------------------------------------------
4
−40°C to 125°C
−40°C to 85°C
DS8562-01 April 2011www.richtek.com
RT8562
Electrical Characteristics
(VIN = 17V, T
Supply Current I
VIN Under Voltage Lockout
Threshold
Shutdown Current I
EN Pin Input Current IEN VEN ≤ 5V -- -- 0.1 μA
EN Logic Input
PWM Logic Input
L E D Curr e nt Programmi n g
LED Current I
LEDs Current Matching
ISET Pin Voltage V
Input Current of PWM I
Threshold of PWM V
V
Threshold Un-connection -- 0.1 -- V
CHx
PWM Boost Converter
Switching Frequency 0.8 1 1.2 MHz
Minimum On Time -- 100 -- ns
Regulat ed V
Amplifier (gm) Output Current 2.4V > COMP > 0.2V -- ±15 -- μA
COMP Threshold PWM Switch Off 0.1 0.2 -- V
LX1, LX2 R
LX1, LX2 Current Limit I
SW Maximum Duty -- 88 -- %
OVP & Soft Start
OVP Threshold V
OVP Input Current I
Soft Start Current ISS VSS ≤ 2.5V 3 5 8 μA
Thermal Shutdown Temperature TSD -- 150 -- °C
Thermal Shutdown Hysteresis -- 20 -- °C
= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
COMP ≤ 0.2V (Switching off) -- 3 5 mA
VIN
VIN Rising -- 5.6 5.95
V
UVLO
SHDN
High Level V
Low Level V
High Level V
Low Level V
Highest Voltage LED String 0.5 0.6 0.7 V
CHx
-- 0.3 0.5 Ω
DS(ON)
EN_H
EN_L
PWM_H
PWM_L
CHx
ISET
PWM
PWM
LIM
OVP
OVP
V
Falling -- 4.9 --
IN
VEN ≤ 0.7V -- -- 10 μA
1.6 -- 5
-- -- 1
1.3 -- 5
-- -- 0.15
2V > V
V
PWM
2V > V
V
PWM
(I
(MAX)
3.6kΩ ≤ R
0.3V ≤ V
> 0.6V, R
CHx
> 1.2V
> 0.6V, R
CHx
> 1.2V, Calculating
− I
) / I
(MIN)
ISET
PW M
Averag e
≤ 9.6kΩ, V
≤ 1.2V -- 1 2 μA
= 4.75kΩ,
ISET
= 4.75kΩ,
ISET
x 100%
PWM
19 20 21 mA
-- -- 1.5 %
> 1.2V 1.17 1.2 1.23 V
LED Current Off -- 0.2 -- V
2.5 -- -- A
1.1 1.2 1.3 V
V
≤ 3V -- -- 50 nA
OVP
V
V
V
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. θ
Note 3. Devices are ESD sensitive. Handlin
Note 4. The device is not guaranteed to function outside its operating conditions.
DS8562-01 April 2011 www.richtek.com
is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JA
JEDEC 51-7 thermal measurement standard. The case point of θ
g precaution is recommended.
is on the expose pad for the WQFN package.
JC
5
RT8562
Typical Operating Characteristics
Efficiency vs. Input Voltage
100
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
8 1012141618202224
Input Voltage (V)
LED Current vs. Tem perature
24
23
22
21
20
19
LED Current (mA)
18
80LEDs
LED Current v s. Input Voltage
26
24
22
20
18
16
LED Current (mA)
14
12
10
8 10 12141618202224
Input Voltage (V)
V
vs. Temperature
1.24
1.22
1.20
1.18
(V)
ISET
1.16
V
1.14
ISET
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
17
16
-40 -15 10 35 60 85 110 135
Temperature
V
vs. Input Voltage
1.25
1.24
1.23
1.22
(V)
1.21
ISET
V
1.20
1.19
1.18
1.17
8 1012141618202224
ISET
(°C)
Input Voltage (V)
V
IN
= 12V
1.12
1.10
-40 -15 10 35 60 85 110 135
Temperature
(°C)
V
LED Curre nt vs. PWM Duty Cycle
25
20
15
PWM = 200Hz
10
LED Current (mA)
5
V
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0 10 20 30 40 50 60 70 80 90 100
PWM
Duty Cycle (%)
PWM = 1kHz
PWM = 10kHz
PWM = 30kHz
= 0V to 3V, V
IN
IN
= 12V
= 12V
DS8562-01 April 2011www.richtek.com
6
RT8562
LED Current vs. PWM Analog Voltage
28
24
20
16
12
8
LED Current (mA)
4
0
0 0.25 0.5 0.75 1 1.25 1.5
PWM Analog Voltage(V)
Shutdown Current vs. Input Voltage
10
8
6
4
2
Shutdown Current (uA)
0
6 8 10 12 14 16 18 20 22 24
Input Voltage (V)
V
V
IN
EN
= 12V
= 0V
Frequency vs. Input Voltage
1100
1060
1020
980
Frequency (kHz)
940
900
8 1012141618202224
Input Voltage (V)
Switch Off Current vs. Input Voltage
4.0
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
Switch Off Current (mA)
3.1
3.0
8 10 1214 1618202224
Input Voltage (V)
COMP = 0V
SS Current vs. Temperature
8.0
7.6
7.2
6.8
6.4
6.0
5.6
5.2
SS Current (uA)
4.8
4.4
4.0
-40 -15 10 35 60 85 110 135
Temperature
V
IN
= 12V, C
(°C)
= 0.1μF
SS
9
8
7
6
5
SS Current (uA)
4
3
2
SS Current vs. Input Voltage
C
= 0.1μF
SS
8 1012141618202224
Input Volatge (V)
DS8562-01 April 2011 www.richtek.com
7
RT8562
OVP Voltage vs. Temperature
1.30
1.28
1.26
1.24
1.22
1.20
1.18
1.16
OVP Voltage (V)
1.14
1.12
1.10
-40 -15 10 35 60 85 110 135
Temperature
(°C)
V
IN
= 12V
PWM SW-OFF Threshold Voltage vs. Temperature
0.22
0.21
0.20
OVP Voltage vs. Input Volatge
1.3
1.2
1.1
1.0
OVP Voltage (V)
0.9
0.8
8 1012141618202224
Input Voltage (V)
Line Transient Response
V
= 10.8V to 13.2V
IN
0.19
0.18
0.17
0.16
0.15
0.14
PWM SW-OFF Threshold Voltage (V)
V
EN
(2V/Div)
V
OUT
(20V/Div)
I
IN
(500mADiv)
V
= 12V
IN
-40 -15 10 35 60 85 110 135
Temperature
(°C)
Power On from EN
V
= 12V, C
IN
= 0.1μF
SS
V
IN
(5V/Div)
I
OUT
(100mA/Div)
V
IN
(10V/Div)
V
OUT
(50V/Div)
LX1, LX2
(50V/Div)
Time (50ms/Div)
OVP
V
= 12V, All LED Pin Open
IN
Time (10ms/Div)
Time (2.5ms/Div)
DS8562-01 April 2011www.richtek.com
8
Applications Information
RT8562
The RT8562 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 protection features.
Input UVLO
The input operating voltage range of the RT8562 is 6V to
24V. An input capacitor at the VIN pin can reduce ripple
voltage. It is recommended to use a ceramic 10uF or larger
capacitance as the input capacitor. This IC provides an
under voltage lockout (UVLO) function to enhance the
stability when startup. The UVLO threshold of input rising
voltage is set at 5.6V typically with a 0.7V hysteresis.
Power Sequence
Please refer to the below Figure 4 and 5. The
recommended power-on sequence is that the PWM ready
before EN and/or VIN ready. If not, the Soft-Start function
will be disabled. As to power-off sequence, the EN/VIN
must be pulled low within 10ms to prevent “Hard-Start”
shown as Figure 6.
Abnormal Poweron sequence
UVLO
No Soft-Start
If PWM turns
on late
VIN
PWM
EN
VOUT
Power-on
sequence
EN must be turned
on late than VIN
and PWM signal
Soft-Start
Power-off
sequence
EN must be turned
off early than VIN
and PWM signal
Figure 4. Power-On Sequence Control by EN
Power-on
sequence
VIN
PWM
EN
VOUT
Power-off
sequence
VIN must be turned
off early than EN and
PWM signal
Soft-Start
VIN must be
turned on late
than EN and
PWM signal
Abnormal Poweron sequence
UVLO
No Soft-Start
If PWM turns
on late
Figure 5. Power-On Sequence Control by VIN
EN/VIN
PWM
10ms
EN and/or VIN should be
pulled low once PWM pull low
for over 10 ms
Figure 6. To Prevent “Hard-Start” Sequence
Soft Start
The RT8562 employs a soft start feature to limit the inrush
current. The soft-start circuit prevents the excessive inrush
current and input voltage droop. The soft-start time is
determined by capacitor CSS connected to SS pin with
5uA constant current to charge CSS. The value of capacitor
CSS is user-defined to satisfy the designer's requirement.
The recommended soft-start capacitor is 0.1uF.
LED connection
The RT8562 equips 8 channel LED drivers and each channel
supports up to 10 LEDs. The 8 LED strings are connected
from VOUT to pin 7, 8, 9, 10, 12, 13, 14, and 15
respectively. If one of the LED channel is not used, the
LED pin should be opened directly.
Setting and Regulation of LED current
The LED current can be calculated by the following
equation :
I(mA) =
LED
DS8562-01 April 2011 www.richtek.com
20 x 4.75
R(kΩ)
ISET
9
RT8562
Where, the R
is the resister between ISET pin and
ISET
GND.
This setting is the reference for the LED current at CH1 to
CH8 and represents the sensed LED current for each string.
The DC/DC converter regulates the LED current according
to the setting.
If VIN is close to V
and smaller than V
OUT
, the control
OUT
loop may turn on the power switch with minimum on time
and then skip cycles to maintain LED current regulation.
Brightness Control
The RT8562 features both analog and digital dimming
control. Analog dimming is linearly controlled by an
external voltage (0.3V to 1.2V) at PWM pin. A very high
contrast ratio true digital PWM dimming can be achieved
by driving PWM pin with a PWM signal and the
recommended PWM frequency is 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 Figure 7, the minimum
dimming duty can be as low as 1% for the frequency range
from 100Hz to 300Hz. For the dimming frequency from
300Hz to 1kHz, the duty is about 5%. If the frequency is
increased to 1kHz to 30kHz, the duty will be about 10%.
LED Curre nt vs. PWM Duty Cycle
25
20
Over Voltage Protection
The RT8562 equips over voltage protection (OVP) function.
When the voltage at the OVP pin reaches a threshold of
approximately1.2V, the MOSFET driver output (LX1, LX2)
will be turned “OFF”. The MOSFET driver output (LX1,
LX2) will be turned “ON” again once the voltage at OVP
drops below the threshold voltage 1.2V.
So, the output voltage can be clamped at a certain voltage
level and it can be calculated by the following equation :
R2
V = V1+
OUT, OVP OVP
⎛⎞
×
⎜⎟
R3
⎝⎠
Where
R2 and R3 are the voltage divider connected to OVP pin.
V
is typically 1.2V.
OVP
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.
Current Limit Protection
The RT8562 can limit the peak current to achieve over
current protection. RT8562 senses the inductor current
through LX1, LX2 pins in the switch-on period. The duty
cycle depends on the current sense signal summing with
the internal slope compensation compared to the COMP
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 begining
cycle.
15
PWM = 200Hz
10
LED Current (mA)
5
V
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0 10 20 30 40 50 60 70 80 90 100
PWM
Duty Cycle (%)
PWM = 1kHz
PWM = 10kHz
PWM = 30kHz
= 0V to 3V, V
IN
= 12V
Figure 7. LED Current vs. PWM Dimming Duty Cycle
10
Over Temperature Protection
The RT8562 has over temperature protection (OTP)
function to prevent the excessive power dissipation from
overheating. The OTP will shut down switching operation
while the junction temperature exceeds 150°C. Main
converter starts switching when junction temperature
cooling down approximately 20°C.
Inductor Selection
The value of the output inductor (L), where the transition
from discontinuous to continuous mode occurs is
approximated by the following equation :
2
(V V V
OUT IN IN
L =
2I f V
×××
OUT OUT
)
−×
2
DS8562-01 April 2011www.richtek.com
RT8562
Where,
V
= maximum output voltage.
OUT
VIN = minimum input voltage.
f = operating frequency.
I
= sum of current from all LED strings.
OUT
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 discontinuous at higher
voltages.
The inductor must be selected with a saturation current
rating greater than the peak current provided by the
following equation :
I =
PEAK
××−
OUT OUT IN OUT IN
η
××
+
V2LV
IN OUT
⎛⎞
⎜⎟
⎝⎠
VI VTV V
Diode Selection
Schottky diode is a good choice for an asynchronous
Boost converter due to the small forward voltage. However,
for power dissipation, reverse voltage rating and pulsating
peak current are the important parameters of Schottky
diode consideration. Choose a suitable diode whose
reverse voltage rating is greater than the maximum output
voltage.
Capacitor Selection
The input capacitor reduces current spikes from the input
supply and minimizes noise injection to the converter. For
most applications, a 10uF 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.
Layout Guideline
PCB layout is very important to design power switching
converter circuits. The following layout guide lines should
be strictly followed for best performance of the RT8562.
` The power components L, D1, C1, C
OUT1
and C
OUT2
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
through these trace during operation.
` Place L and D1 connected to LX pin as close as possible.
The trace should be short and wide as possible.
` It is recommend to place C6 close to VIN pin.
` Pin22 is the compensation point to adjust system
stability. Place the compensation components to pin22
as close as possible.
V
C2
R1
COMP
GND
CH6
IN
C1
L
LX2
21 20 19
25
11
CH5 NC
ISET
Place power components
as close as possible.
GND
C
D1
LX1
CH4
18
17
16
15
14
13
C
OUT1
PGND2
PGND1
OVP
CH1
CH2
CH3
OUT2
V
OUT
Locate the compensation
components to COMP
pin as close as possible.
Locate the C
close to VIN pin as
possible.
VIN2
as
EN
NC
SS
NC
GND
PWM
R4
C6
1
2
3
4
5
6
C
VDC
24 2223
7
CH8
VC2
VIN
8 9 10 12
CH7
Figure 8
It is recommended to choose a ceramic capacitor bases
on the output voltage ripple requirements. The minimum
value of the output capacitor C
is approximately given
OUT
by the following equation :
(V V ) I
−×
C =
OUT
DS8562-01 April 2011 www.richtek.com
OUT IN OUT
VVf
η
×××
RIPPLE OUT
11
RT8562
Outline Dimension
D
E
A
A3
A1
D2
SEE DETAIL A
1
be
E2
L
1
2
1
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
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 0.500 0.020
L 0.350 0.450
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
0.014 0.018
W-Type 24L QFN 4x4 Package
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.
DS8562-01 April 2011www.richtek.com
12
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