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PDF RT8488 Data sheet ( Hoja de datos )
| Número de pieza | RT8488 | |
| Descripción | High Voltage 6-CH LED Driver Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8488 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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RT8488
High Voltage 6-CH LED Driver Controller
General Description
The RT8488 is a 6-CH LED driver controller that delivers
well matched LED current to each channel of LED string.
With external current sources, the number of LEDs per
string is only limited by the current source and the VIN/
VOUT conditions. The current mode PWM boost type
controller operates at a programmable switching frequency
of up to 1MHz, with a wide VIN range covering from 7V to
28V. The switch driver is designed to drive industrial grade
high power MOSFETs.
The PWM loop selects and regulates the LED string with
the highest voltage string to 0.7V, thus allowing voltage
mismatches between the LED strings. The RT8488
automatically detects and excludes any open and/or broken
strings during operation from the PWM loop to prevent
VOUT from over voltage.
The LED currents on all channels are simply programmed
with a resistor on each channel. Three convenient dimming
methods are provided : 1. Analog dimming is linearly
controlled by an external voltage. 2. True digitally controlled
PWM dimming can regulate the duty cycle of the LED
current. 3. For noise free PWM dimming, use an on board
output clamping amplifier as a low pass filter to convert
PWM dimming signals into analog dimming signals.
Other protection features include programmable output over
voltage protection, PWM switch current limit and thermal
shutdown.
Marking Information
RT8488GQW : Product Number
RT8488
GQWYMDNN
YMDNN : Date Code
Features
z Wide Operation Voltage Range : 7V to 28V
z Programmable Channel Current
z 3% Current Matching Accuracy between Channels
z Programmable Switching Frequency
z Easy Analog and Digital Dimming Control
z Programmable Soft-Start
z Automatic Open Channel Detection
z Programmable Output Over Voltage Protection
z Under Voltage Lockout and Thermal Shutdown
z 32-Lead WQFN Package
Applications
z Building and Street Lighting
z LED TV Backlight
z LED Monitor Backlight
z Industrial Display Backlight
Ordering Information
RT8488
Package Type
QW : WQFN-32L 5x5 (W-Type)
Note :
Lead Plating System
G : Green (Halogen Free and Pb Free)
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.
Pin Configurations
(TOP VIEW)
32 31 30 29 28 27 26 25
RSET
EN
OVP
SS
VC
ACTL
DCTL
NC
1
2
3
4
5
6
7
8
24 LED2
23 GATE2
22 SENSE2
GND
21 LED3
20 GATE3
19 SENSE3
33 18 LED4
17 GATE4
9 10 11 12 13 14 15 16
DS8488-02 April 2011
WQFN-32L 5x5
www.richtek.com
1
1 page  
RT8488
Absolute Maximum Ratings (Note 1)
z VCC --------------------------------------------------------------------------------------------------------------------------- 32V
z ISENSE
DC ------------------------------------------------------------------------------------------------------------------------------- 2V
< 200ns ------------------------------------------------------------------------------------------------------------------------ 6V
z GBIAS ------------------------------------------------------------------------------------------------------------------------- 14V
z SENSE1 to SENSE6
DC ------------------------------------------------------------------------------------------------------------------------------- 1V
< 200ns ------------------------------------------------------------------------------------------------------------------------ 6V
z LED1 - LED6 (Note 5) ---------------------------------------------------------------------------------------------------- 20V
z DCTL, ACTL, EN, OVP --------------------------------------------------------------------------------------------------- 10V
z Power Dissipation, PD@TA = 25°C
WQFN-32L 5x5 ------------------------------------------------------------------------------------------------------------- 2.778W
z Package Thermal Resistance (Note 2)
WQFN-32L 5x5, θJA -------------------------------------------------------------------------------------------------------- 36°C/W
WQFN-32L 5x5, θJC ------------------------------------------------------------------------------------------------------- 6°C/W
z Junction Temperature ------------------------------------------------------------------------------------------------------ 150°C
z Storage Temperature Range --------------------------------------------------------------------------------------------- −65°C to 150°C
z Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ----------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 4)
z Supply Voltage, VCC ------------------------------------------------------------------------------------------------------- 7V to 28V
z Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C
Electrical Characteristics
(VCC = 12V, No Load, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Overall
Supply Current
Shutdown Current
EN Threshold
Voltage
EN Input Current
Logic-High
Logic-Low
LED Current Programming
SENSE1-SENSE6 Threshold
IVCC
ISHDN
VIH
VIL
IEN
SENSE Voltage CH to CH Matching
Analog Dimming ACTL Input Current IACTL
LED Current Off Threshold at ACTL VACTL_OFF
VVC ≤ 0.4V (Switching off)
VEN ≤ 1.2V
VEN ≤ 3.3V
6V > VGATEx > 2V
V(MAX) − V(MIN)
2 × V(avg)
VACTL ≦ 6V
Min Typ Max Unit
-- 5 8 mA
-- 5 -- μA
2 -- -- V
-- -- 0.5
-- 2 -- μA
214 225 236 mV
-- 1.5 3
%
-- -- 10 μA
-- 0.4 --
V
DS8488-02 April 2011
To be continued
www.richtek.com
5
5 Page 
Power On sequence
VIN
Power Off sequence
RT8488
Abnormal Power-on sequence
UVLO
PWM
EN
VIN must be turned off earlier than
EN and PWM signal
VIN must be turned on later than
EN and PWM signal
VOUT
Soft-Start
No Soft-Start
If PWM turns on late
Figure 2. Power On Sequence Control by VIN
EN/VIN
PWM
EN and/or VIN should be pulled low
once PWM pull low for over 10 ms
10ms
Figure 3. To Prevent “hard-start”Sequence
Soft-Start
The soft-start of the RT8488 can be achieved by connecting
a capacitor from the SS pin to GND. The built in soft-start
circuit reduces the start up current spike and output voltage
overshoot. The soft-start time is determined by the external
capacitor charged by an internal 8μA constant charging
current. The SS pin directly limits the rate of voltage rise
on the VC pin, which in turn limits the peak switch current.
The soft-start interval is set by the soft-start capacitor
selection according to the equation :
tSS
=
CSS
×
3.2V
8μ A
(s)
A typical value for the soft-start capacitor is 0.1μF. The
soft-start pin reduces the oscillator frequency and the
maximum current in the switch. The soft-start capacitor
is discharged when EN/UVLO falls below its threshold,
during an over-temperature event, or during a GBIAS under
voltage event.
GBIAS Regulator Operation
The GBIAS pin requires a capacitor for stable operation
and also to store the charge for the large GATE switching
currents. Choose a 10V rated low ESR, X7R or X5R
ceramic capacitor for best performance. The value of the
DS8488-02 April 2011
www.richtek.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet RT8488.PDF ] | |
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