RICHTEK RT8567A

®
RT8567A
6-CH 43V Constant Current LED Driver with PWM Dimming
Control
General Description
Features
The RT8567A is a high efficiency driver for white LEDs. It
is designed for LCD panels that employ an array of LEDs
as the lighting source. An integrated current mode Boost
controller drives six strings in parallel and supports up to
12 WLEDs per string. The internal current sinks support
a maximum of ±2% current mismatching for excellent
brightness uniformity in each string of LEDs. To provide
enough headroom for current sink operation, the Boost
controller monitors the minimum voltage of the feedback
pins and regulates an optimized output voltage for power
efficiency.
z
Wide Input Voltage : 2.7V to 24V
z High Output Voltage : Up to 43V
z Channel Current Programmable : 5mA to 40mA
z Channel Current Regulation with Accuracy ±3% and
Matching ±2%
z Dimming Controls : External PWM Input Up to 25kHz
z Adjustable Switching Frequency : 500kHz to 2MHz
z Built-In Soft-Start
z Protections
` LED Strings Open Detection
` Current Limit Protection
` Programmable Over Voltage Protection
` Over Temperature Protection
z 20-Lead WQFN Package
z RoHS Compliant and Halogen Free
The RT8567A has a wide input voltage range from 2.7V to
24V and can provide adjustable LED current from 5mA to
40mA. The internal 250mΩ, 43V power switch with current
mode control provides cycle-by-cycle over current
protection. The RT8567A also integrates PWM dimming
function for accurate LED current control. The input PWM
dimming frequency can operate from 200Hz to 25kHz
without inducing any inrush in LED current or inductor
current. The switching frequency of the RT8567A is also
adjustable from 500kHz to 2MHz, which allows flexibility
between efficiency and component size.
Applications
z
z
UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Simplified Application Circuit
L1
D1
VOUT
VIN
COUT
CIN
LX
VIN
EN
Chip Enable
RT8567A
PWM
PWM Signal
RT
ISET
RRT
RISET
GND
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8567A-00 April 2012
ROVP2
OVP
:
:
ROVP1
:
:
:
:
:
:
:
:
:
: 6 x 12 LEDs
CH1
CH2
CH3
CH4
CH5
CH6
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1
RT8567A
Pin Configurations
Ordering Information
RT8567A
(TOP VIEW)
PWM
VIN
COMP
NC
LX
Package Type
QW : WQFN-20L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
20 19 18 17 16
VDC
EN
RT
ISET
NC
Note :
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
15
2
14
3
AGND
13
4
21
12
5
11
6
7
8
PGND
OVP
NC
CH1
CH2
9 10
CH6
CH5
CH4
AGND
CH3
`
1
Suitable for use in SnPb or Pb-free soldering processes.
WQFN-20L 3x3
Marking Information
0R= : Product Code
0R=YM
DNN
YMDNN : Date Code
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
VDC
Internal Regulator Voltage. Connect a capacitor to ground.
2
EN
Chip Enable (Active High). Note that this pin is high impedance. There should
be a pull low 100kΩ resistor connected to AGND when the control signal is
floating.
3
RT
Frequency Setting. Connect a resistor between this pin and ground to set the
switching frequency of the boost converter.
4
ISET
LED Current Setting. LED current is set by the value of the resistor R ISET
connected from the ISET pin to ground. Do not short the ISET pin to ground.
VISET is typical 1V.
NC
No Internal Connection.
CH6 to CH4
Current Sink Regulation Input. This pin should be connected to the cathode
of LEDs if used. Otherwise, it should be connected to ground.
5, 13, 17
6, 7, 8,
9, 21 (Exposed Pad) AGND
Analog Ground of LED Driver. The exposed pad must be soldered to a large
PCB and connected to AGND for maximum power dissipation.
CH3 to CH1
Current Sink Regulation Input. This pin should be connected to the cathode
of LEDs if used. Otherwise, it should be connected to ground.
14
OVP
Over Voltage Protection for Boost Converter. The detecting threshold is 1.2V.
15
PGND
Power Ground of Boost Converter.
16
LX
Switching Node for Boost Converter.
18
COMP
Compensation Pin for Error Amplifier. Connect a compensation network to
ground.
19
VIN
Power Supply Input.
20
PWM
PWM Dimming Control Input.
10,11,12
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RT8567A
Function Block Diagram
VIN
VDC
RT
OVP
+
1.2V
-
EN
Enable
Control
OSC
S
Q
R
Q
LX
OCP &
OTP
PWM
Controller
+
+
PGND
+
EA
-
COMP
VDS
Mini LED
Selection
6
PWM
LED Open
Detection
……
CH1
CH2
CH6
+
-
1V
+
+
-
-
……
+
-
ISET
AGND
Operation
Enable Control
When VIN is higher than the UVLO rising threshold voltage
and EN pin input voltage is higher than its rising threshold,
the converter will be turned on.
temperature is higher than 150C(typically), the LX
N-MOSFET is also turned OFF until the temperature is
lower than 120C(typically).
Minimum LED Selection
OSC
The oscillator generates a clock pulse to control the LX
switching frequency according to the external resistor
connected between RT pin and GND.
This block detects all CHx voltages and selects a
minimum voltage to EA(Error Amplifier). This function can
guarantee the lowest CH voltage is around 500mV and
Vout can be boosted to the highest forward voltage of LED
strings.
PWM Controller
This controller includes some logic circuit to control the
internal power MOSFET. This block controls the minimum
ON time and max duty of LX.
OCP&OTP
When LX N-MOSFET peak current reaches 2A(typically),
the LX N-MOSFET is turned OFF immediately and resumes
again at the next clock pulse. When the junction
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LED Open Detection
When CHx is not connected to any LED strings, the voltage
of CHx is pulled low by internal current sink. If voltage of
CHx is lower than 50mV and OVP is over 1.2V, this channel
is detected as open channel and the Minimum LED
Selection function will discard it to regulate other used
channels in proper voltage.
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3
RT8567A
Absolute Maximum Ratings
z
z
z
z
z
z
z
z
z
z
(Note 1)
VIN to GND -----------------------------------------------------------------------------------------------------------------EN, PWM, VDC, ISET, COMP, RT to GND -------------------------------------------------------------------------LX to GND ------------------------------------------------------------------------------------------------------------------OVP, (CH1 to CH6) to GND --------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
−0.3V to 26.5V
−0.3V to 26.5V
−0.3V to 48V
−0.3V to 48V
WQFN−20L 3x3 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WQFN−20L 3x3, θJA -----------------------------------------------------------------------------------------------------WQFN−20L 3x3, θJC -----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) -----------------------------------------------------------------------------------------------------
1.471W
Recommended Operating Conditions
z
z
z
68°C/W
7.5°C/W
260°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- 2.7V to 24V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 4.5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
IVCC
VCOMP = 0V, No Switching
--
2
--
IVCC_LX
VCOMP = 2V, Switching
--
3
--
Shutdown Current
ISHDN
VIN = 4.5V, EN = 0
VIN Under Voltage Lockout
Threshold
VUVLO
VIN Rising
VIN Falling
----
-2.3
2.1
20
---
Logic-High VIH
VIN = 2.7V to 24V
2
--
--
Logic-Low VIL
Logic-High VIH
Logic-Low VIL
VIN = 2.7V to 24V
VIN = 2.7V to 24V
VIN = 2.7V to 24V
-1.5
---
0.8
--
--
--
0.6
-0.9
--
2
1
0.5
-1.1
--
MHz
VIN Quiescent Current
mA
μA
V
Control Input
EN Input Voltage
Threshold
PWM Input Voltage
Threshold
V
V
Boost Converter
Switching Frequency
fOSC
RRT = 25kΩ
RRT = 51kΩ
RRT = 100kΩ
LX On Resistance (N-MOSFET)
RDS(ON)
VIN > 4.5V
--
0.25
--
Ω
Minimum On Time
tMON
fOSC = 1MHz
--
120
--
ns
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RT8567A
Parameter
Symbol
Min
Typ
Max
Unit
--
94
--
%
1.6
2
2.4
A
Highest LED String, ILED = 20mA
--
0.6
--
V
ILEDA
2V > VCHx > 0.6V, RISET = 51kΩ
−3
--
3
%
LED Current Matching
ILEDM
2V > VCHx > 0.6V, RISET = 51kΩ,
Calculating
(ILEDx − IAVG )
×100%
IAVG
--
±0.5
±2
%
ISET Pin Voltage
VISET
--
1
--
V
Over Voltage Threshold
VOVP
--
1.2
--
V
OVP Fault
VOVP_FAULT
--
50
--
mV
TSD
--
150
--
°C
--
60
--
mV
Maximum Duty
DMAX
LX Current Limit
ILIM
Regulated VCHx
VCHx
Test Conditions
VCOMP = 2V, Switching
LED Current Programming
LED Current Accuracy
Fault Protection
Thermal Shutdown
Temperature
LED Channel Under Voltage
Threshold
VLSD
No-Connection
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 © 2012 Richtek Technology Corporation. All rights reserved.
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RT8567A
Typical Application Circuit
10µH
L1
VIN
3V to 8.5V
CIN
10µF C2
1µF
D1
R2
10
19
Chip Enable
2
20
PWM Signal
3
RRT
51k
1
16
LX
ROVP2
VIN
OVP 14
RT8567A
PWM
CH1 12
RT
CH2 11
CH3
VDC
:
:
:
:
:
:
:
:
:
: 6 LEDs by
:
: String
10
CH5 7
CH6 6
4 ISET
C3
10nF
:
:
:
:
:
:
CH4 8
18 COMP
C4
Open
OVP setting <24V
ROVP1
EN
CDC
0.1µF
R3
10k
VOUT
19.6V(MAX)
COUT
10µF
AGND
9, 21 (Exposed Pad)
PGND 15
RISET
51k
Figure 1. Application Circuit 1
10µH
L1
VIN
6V to 24V
CIN
10µF C2
1µF
D1
R2
10
19
Chip Enable
2
20
PWM Signal
3
RRT
51k
1
16
LX
OVP 14
RT8567A
PWM
CH1 12
RT
CH2 11
18 COMP
C4
Open
C3
10nF
ROVP1
EN
CDC
0.1µF
R3
10k
ROVP2
VIN
VDC
4 ISET
VOUT
43V(MAX)
COUT
10µF
CH3
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
: 12 LEDs by
:
: String
10
CH4 8
CH5 7
CH6 6
AGND
9, 21 (Exposed Pad)
PGND 15
RISET
51k
Figure 2. Application Circuit 2
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RT8567A
10µH
L1
VIN
3V to 8.5V
D1
CIN
10µF
16
LX
19
5V
C2
1µF
ROVP2
OVP 14
VIN
RT8567A
2
VOUT
19.6V(MAX)
COUT
10µF
ROVP1
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
: 6 LEDs by
:
: String
EN
CH1 12
20
PWM Signal
3
1
RRT
51k
PWM
RT
VDC
CDC
0.1µF
R3
10k
C3
10nF
CH3
10
CH4 8
CH5 7
18 COMP
C4
Open
CH2 11
4 ISET
RISET
51k
CH6 6
AGND
9, 21 (Exposed Pad)
PGND 15
Figure 3. Application Circuit 3
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RT8567A
Typical Operating Characteristics
Efficiency vs. Input Voltage
LED Current vs. Input Voltage
100
26
Output Current (mA)
80
Efficiency (%)
LED1
LED2
LED3
LED4
LED5
LED6
24
60
40
20
22
20
18
16
60LEDs, PWM = 3.3V, fOSC = 1MHz
10LEDs per channel, PWM = 3.3V, fOSC = 1MHz
0
14
4
8
12
16
20
24
4
8
12
Input Voltage (V)
20
24
Input Voltage (V)
LED Current vs. Temperature
ISET Voltage vs. Temperature
1.20
26
1.15
ISET Voltage (V)
24
LED Current (mA)
16
22
20
18
16
1.10
1.05
1.00
0.95
0.90
0.85
10LEDs per channel, PWM = 3.3V, fOSC = 1MHz
10LEDs per channel, fOSC = 1MHz
14
0.80
-50
-25
0
25
50
75
100
-50
125
-25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
ISET Voltage vs. Input Voltage
LED Current vs. PWM Duty Cycle
1.20
20
1.15
LED Current (mA)
ISET Voltage (V)
16
1.10
1.05
1.00
0.95
0.90
12
PWM = 200Hz
PWM = 1kHz
PWM = 10kHZ
PWM = 25kHz
8
4
0.85
10LEDs per channel, fOSC = 1MHz
0.80
10LEDs per channel, fOSC = 1MHz
0
4
8
12
16
20
Input Voltage (V)
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8
24
0
20
40
60
80
100
PWM Duty Cycle (%)
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RT8567A
Quiescent Current vs. Temperature
OVP Threshold Voltage vs. Input Voltage
3.00
Quiescent Current (mA) 1
OVP Threshold Voltage (V)
1.5
1.4
1.3
1.2
1.1
2.75
2.50
2.25
2.00
1.75
1.50
1.25
VIN = 12V, fOSC = 1MHz
10LEDs per channel, fOSC = 1MHz
1.00
1.0
4
8
12
16
20
24
-50
-25
0
25
50
75
100
Input Voltage (V)
Temperature (°C)
Line Transient Response
Line Transient Response
VIN
(5V/Div)
VIN
(2V/Div)
I LED
(50mA/Div)
I LED
(50mA/Div)
VIN = 11V to 14V, PWM = 3.3V, fOSC = 1MHz
VIN = 4.5V to 5.5V, PWM = 3.3V, fOSC = 1MHz
Time (50ms/Div)
Time (50ms/Div)
Power On from EN
Power Off from EN
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(20V/Div)
VOUT
(20V/Div)
I LED
(20mA/Div)
I LED
(20mA/Div)
VIN = 12V, PWM = 3.3V, fOSC = 1MHz
Time (5ms/Div)
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125
VIN = 12V, PWM = 3.3V, fOSC = 1MHz
Time (25ms/Div)
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RT8567A
Application Information
Input UVLO
The input operating voltage range of the RT8567A is from
2.7V to 24V. An input capacitor at the VIN pin can reduce
ripple voltage. It is recommended to use a ceramic 10μF
or larger capacitance as the input capacitor. This IC provides
an Under Voltage Lockout (UVLO) function to enhance
the stability during startup. The UVLO threshold of the
input rising voltage is set at 2.3V typically with a 0.2V
hysteresis.
Soft-Start
The function of the soft-start is defined by two periods.
The first period is capped at the peak current limit with
the time decided by the ratio of VOUT and VIN. However,
an external capacitor, VOUT, can also affect the time of
charging. The second period is defined by the slowly
ramping of the ILED current by the ISET voltage. Thus, the
inrush current is limited by the Boost converter and current
regulator.
Compensation
The control loop can be compensated by adjusting the
external components connected to the COMP pin. The
COMP pin is the output of the internal error amplifier. The
compensation capacitors, C3 and C4, will adjust the
integrator zero and pole respectively to maintain stability.
Moreover, the resistor, R3, will adjust the frequency
integrator gain for fast transient response.
Setting and Regulation of LED current
The LED current can be calculated by the following
equation :
1020
ILED =
RISET
where, RISET is the resistor between the ISET pin and
GND.
This setting is the reference for the LED current at CH1 to
CH6 and represents the sensed LED current for each string.
The DC/DC converter regulates the LED current according
to the setting.
Brightness Control
The RT8567A brightness dimming is determined by the
signal on the PWM pin with a suggested PWM frequency
range from 200Hz to 25kHz. Referring to the following curve,
the minimum dimming duty can be as low as 1% for the
frequency range from 200Hz to 1kHz. For the frequency
range from 1kHz to 10kHz, the dimming duty is at most
5%. If the frequency is increased to 25kHz, the dimming
duty will be up to 10%.
LED Current vs. PWM Duty Cycle
20
16
LED Current (mA)
The RT8567A is a current mode Boost converter capable
of powering to 72 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.
12
PWM = 200Hz
PWM = 1kHz
PWM = 10kHZ
PWM = 25kHz
8
4
0
0
20
40
60
80
100
PWM Duty Cycle (%)
Figure 1
LED Connection
Over Voltage Protection
The RT8567A equips 6-CH LED drivers with each channel
supporting up to 12 LEDs. The 6 LED strings are
connected from VOUT to pin 6, 7, 8, 10, 11, and 12
respectively. If one of the LED channels is not used, the
unused LED pin should be opened directly.
The RT8567A equips an Over Voltage Protection (OVP)
function. When the voltage at the OVP pin reaches a
threshold of approximately 1.2V, the MOSFET driver turns
off. The MOSFET driver turns on again once the voltage
at OVP drops below the threshold voltage. Thus, the
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RT8567A
output voltage can be clamped at a certain voltage level.
This voltage level can be calculated by the following
equation :
R
VOUT, OVP = VOVP × (1+ OVP2 )
ROVP1
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.
where ROVP1 and ROVP2 are the resistors in the voltage
divider connected to the OVP pin. 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.
The selected inductor must be selected with saturation
current rating greater than the peak current provided by
the following equation :
V
×I
V
− VIN
V ×T
IPEAK = ( OUT OUT ) + ( IN
) × ( OUT
)
η x VIN
2×L
VOUT
Current Limit Protection
Diode Selection
The RT8567A can limit the peak current to achieve over
current protection. The RT8567A senses the inductor
current through LX pin in the ON period. The duty cycle
depends on the current sense signal summed with the
internal slope compensation and 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 starting
cycle.
Schottky diode is a good choice for any asynchronous
Boost converter due to its small forward voltage and fast
switching Speed. However, when selecting a Schottky
diode, important parameters such as power dissipation,
reverse voltage rating and pulsating peak current must all
be taken into consideration. Choose a suitable diode with
reverse voltage rating greater than the maximum output
voltage.
Over Temperature Protection
The RT8567A has an over temperature protection (OTP)
function to prevent excessive power dissipation from
overheating the device. The OTP will shut down switching
operation when the junction temperature exceeds 150°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 :
L=
Capacitor Selection
The input capacitor reduces current spikes from the input
supply and minimizes noise injection to 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, can be
calulated by the following equation :
COUT =
(VOUT − VIN ) × IOUT
η × VRIPPLE × VOUT × f
(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
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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
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RT8567A
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-20L 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-20L 3x3 package
PCB layout is very important for designing switching power
converter circuits. The following layout guides should be
strictly followed for best performance of the RT8567A.
`
The power components L1, D1, CIN, COUT must be placed
as close to the IC as possible to reduce current loop.
The PCB trace between power components must be as
short and wide as possible.
`
Place L1 and D1 as close to the LX pin as possible. The
trace should be as short and wide as possible.
`
The compensation circuit should be kept away from
the power loops and shielded with a ground trace to
prevent any noise coupling. Place the compensation
components as close to the COMP pin as possible.
`
The exposed pad of the chip should be connected to
ground plane for thermal consideration.
The compensation circuit should be kept away from The power loops
and shielded with a ground trace to prevent any noise coupling.
1.6
Four-Layer PCB
Place the power
components as
Close as possible.
The traces should
be wide and short
especially for the
high current loop.
1.4
VIN
GND
1.2
CIN
1.0
C2
GND
C3
0.8
0.4
Locate RISET as
close to ISET
as possible.
0.2
0.0
25
50
75
100
RISET
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
GND
D1
VOUT
COUT
20 19 18 17 16
VDC
EN
RT
ISET
NC
1
15
2
14
3
AGND
4
21
5
13
12
11
6
7
8
PGND
OVP
NC
CH1
CH2
9 10
CH6
CH5
CH4
AGND
CH3
0
L1
R3
Locate the C2 as
close to VIN as
possible.
0.6
C4
PWM
VIN
COMP
NC
LX
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 2 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Layout Considerations
Figure 3. PCB Layout Guide
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS8567A-00 April 2012
RT8567A
Outline Dimension
1
1
2
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
0.150
0.250
0.006
0.010
D
2.900
3.100
0.114
0.122
D2
1.650
1.750
0.065
0.069
E
2.900
3.100
0.114
0.122
E2
1.650
1.750
0.065
0.069
e
L
0.400
0.350
0.016
0.450
0.014
0.018
W-Type 20L QFN 3x3 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.
DS8567A-00 April 2012
www.richtek.com
13