Richtek RT8510GQW Schematic [ru]
43V 4-CH LED Driver
RT8510
General Description
The RT8510 is a high efficiency driver for white LEDs. It is
designed for LCD panels that employ a n array of LEDs a s
the lighting source. An integrated switch current mode
boost controller drives four strings in parallel and supports
up to 12 pieces of LED per string. The internal current
sinks support a maximum of ±2% current mismatching
for excellent brightness uniformity in ea ch string of LED.
To provide enough headroom for current sink operation
the boost controller monitors the minimum voltage of
feedback pins a nd regulates a n optimized output voltage
for power efficiency .
The RT8510 ha s a wide input voltage ra nge from 4.2V to
24V and provide a n adjustable 10mA to 40mA LED current.
The internal 200mΩ, 43V power switch with current-mode
control provides cycle-by-cycle over current protection.
RT8510 also integrates PWM dimming function for
accurate LED current control. The input PWM dimming
frequency can operate from 120Hz to 30kHz without
inducing any inrush current through the LED or inductor .
The switching frequency of the RT8510 is adjustable from
500kHz to 2MHz, allowing the user flexibility between
efficiency a nd component size.
Features
zz
Wide Input Voltage : 4.2V to 24V
z
zz
zz
z High Output V oltage : Up to 43V
zz
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z Adjustable Channel Current : 10mA to 40mA
zz
zz
z Channel Current Accuracy :
zz
zz
z Channel Current Matching :
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z PWM Dimming Frequency : 120Hz to 30kHz
zz
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z Adjustable Switching Frequency : 500kHz to 2MHz
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z Built-In Soft-Start
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z Disconnects LED in Shutdown
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z Open Current Sink Detection
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z Adjustable Over Voltage Protection
zz
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z Over Temperature Protection
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z Current Limit Protection
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z Thin 16-Lead WQFN Package
zz
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z RoHS Compliant and Halogen Free
zz
±±
±3%
±±
±±
±2%
±±
Applications
z UMPC and Notebook Computer Ba cklight
z GPS, Portable D V D Ba cklight
Pin Configurations
(TOP VIEW)
The RT8510 is available in a WQFN-16L 3x3 pa ckage.
Ordering Information
RT8510
Package Type
QW : WQFN-16L 3x3 (W-Type)
AGND
COMP
ISET
RT
CH4
CH3
CH1
CH2
13141516
1
2
GND
3
4
12
OVP
11
PGND
10
17
PGND
9
LX
8765
Lead Plating System
LX
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
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.
DS8510-03 June 2011 www.richtek.com
EN
VIN
PWM
WQFN-16L 3x3
1
RT8510
Marking Information
HU= : Product Code
HU=YM
DNN
Typical Application Circuit
V
4.2V to 24V
1nF
IN
PWM Dimming
C4
YMDNN : Date Code
C
IN
10µF
Chip Enable
R3
10k
R
C3
10nF
51k
RT
R2
10
C2
1µF
100k
R
ISET
4.75k
7
6
5
2
4
3
VIN
EN
PWM
COMP
RT
ISET
PGND
10, 11
L
10µH
RT8510
AGND
LX
OVP
CH1
CH2
CH3
CH4
1
8, 9
12
13
14
15
16
D1
R
2M
R
62k
OVP2
OVP1
C
OUT
10µF
:
:
:
:
V
OUT
43V MAX
:
:
:
:
:
:
:
:
:
10 LED String
:
:
:
PWM Dimming
C4
1nF
V
BATT
2.7V to 24V
Chip Enable
R3
10k
C3
10nF
5V
R
51k
Figure 1. General Application Circuit
RT
100k
C
10µF
C2
1µF
R
ISET
4.75k
L
10µH
IN
RT8510
7
VIN
6
EN
5
PWM
2
COMP
4
RT
3
ISET
PGND
10, 11
OVP
CH1
CH2
CH3
CH4
AGND
1
LX
12
13
14
15
16
D1
8, 9
Figure 2. Low Input V oltage Application Circuit
R
2M
R
62k
OVP2
OVP1
C
OUT
10µF
(V
depends on D
OUT
:
:
:
:
V
OUT
23V MAX
:
:
:
:
:
:
:
:
)
MAX
:
10 LED String
:
:
:
DS8510-03 June 2011www.richtek.com
2
Function Pin Description
Pin No. Pin Name Pin Function
1 AGND Analog Ground of LED Driver.
2 COMP
3 ISET
4 RT
5 PWM Dimming Control Input.
Compensation Pin for Error Amplifier. Connect a compensation network to
ground.
LED Current Set Pin. LED current is set by the value of the resistor R
connected from the ISET pin to ground. Do not short the ISET pin. V
typic al ly 0.6V.
I =
LED
R
95
ISET
Frequency Adj ust Pin. This pin allows setting the switching frequency with a
resistor to 500kHz to 2MHz.
RT8510
ISET
is
ISET
6 EN
Chip Enable (Active High). Note that this pin is high impedance. There should be
a pull low 100kΩ resistor connected to GND when the control signal is floating.
7 VIN Power Supply Input.
8, 9 LX Switching Pin of Boost Converter.
10, 11 PGND P ower Ground of Boost Co nverter.
12 OVP Sense Input for Over Voltage Protection. The detecting threshold is 1.2V.
13, 14, 15, 16 CH1 to CH 4 Current Sink for LED. Leave the pin unconnected, if not used.
17 (Exposed Pad) GND
Th e e xpo se d p ad m us t be s old er e d to a large PC B and c on nec ted to G N D f o r
max imu m pow er dis si pat ion .
Function Block Diagram
RT
COMP
PWM
OSC
PWM
Controller
+
1.2
-
QS
R
Q
+
-
+
EA
-
+
0.6V
+
-
-
0.4V
LXOVP
+
-
EN
Regulator
LED
Detection
OCP
OTP
VIN
:
4
+
:
-
PGND
CH1
CH2
CH3
CH4
ISET
AGND
DS8510-03 June 2011 www.richtek.com
3
RT8510
Absolute Maximum Ratings (Note 1)
z Supply Input V oltage to GND------------------------------------------------------------------------------------------ −0.3V to 26.5V
z EN, PWM, ISET, COMP, RT to GND -------------------------------------------------------------------------------- −0.3V to 26.5V
z LX, OVP , CH1, CH2, CH3, CH4 to GND ---------------------------------------------------------------------------- −0.3V to 48V
z Power Dissipation, P
WQFN-16L 3x3----------------------------------------------------------------------------------------------------------- 1.471W
z Package Thermal Resistance (Note 2)
WQF N-16L 3x3, θJA----------------------------------------------------------------------------------------------------- 68°C/W
WQF N-16L 3x3, θJC----------------------------------------------------------------------------------------------------- 7.5°C/W
z Lead T emperature (Soldering, 10 sec.) ----------------------------------------------------------------------------- 260°C
z Junction T emperature --------------------------------------------------------------------------------------------------- 150°C
z Storage T emperature Range------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM ------------------------------------------------------------------------------------------------------------------------ 2kV
MM-------------------------------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 4)
@ T
D
= 25°C
A
z Supply Input Voltage, V
z Junction T emperature Range ------------------------------------------------------------------------------------------ −40°C to 125°C
z Ambient T emperature Range ------------------------------------------------------------------------------------------ −40°C to 85°C
---------------------------------------------------------------------------------------------- 4.2V to 24V
IN
Electrical Characteristics
(V
= 4.5V, T
IN
VIN Quiesce nt Current IQ
VIN Shutdown Current I
VIN Under Voltage Lockout UVLO
Control Input
EN, PWM Threshold
Voltage
PWM Dimming Frequency f
EN, PWM Leakage Current I
EN Shutdown Delay tEN R
Boost Converte r
LX On Resistance (N-MOSFET) R
M inimu m O N Time t
M aximum Duty D
LX Current Limit I
= 25°C unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
V
V
VIN = 4.5V , EN = 0V -- -- 10 μA
SHDN
Rising -- 2.2 -Falling -- 2.1 --
Logic-High VIH 2 -- -Logic-Low V
IL
PWM
2 -- 6 μA
LKG
V
120 -- 30k Hz
= 0V, No Switching -- 1 1.5
COMP
= 2V, Switching 2 3
COMP
mA
V
= 4.2V to 24V
IN
= 51kΩ -- 32 -- ms
RT
-- -- 0.8
V
RRT = 25kΩ -- 2 --
OSC
DS(ON)_N VIN
-- 120 -- ns
MON
MAX
-- 2 -- A
LIM
RRT = 51kΩ -- 1 -- Switching Frequency f
= 102kΩ -- 0.5 --
R
RT
> 4.5V -- 0.2 0.32 Ω
V
COMP
= 2V, Switching -- 90 -- %
MHz
T o be continued
DS8510-03 June 2011www.richtek.com
4
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