® RT8302 60V, 4-CH, Programmable Current Sink LED Driver for 1D/2D/3D Dimming Applications General Description Features The RT8302 is a 4-CH constant current sink LED driver which can drive 4-CH constant current with good matching ability. z The RT8302 provides ±3% high accuracy current each channel. The range of the constant current output is programmable from 30mA to 360mA by SPI interface. It also supports the local dimming and scan dimming by 4 independent PWM generators with programmable PWM duty cycle, period and delay. The dropout voltage of output channel is 0.5V as the output constant current is 150mA which can accept wide range VF variation. Moreover, the RT8302 provides Dynamic Headroom Control (DHC) function which can generate feedback signal to DC/DC control loop and regulate the output voltage. z z z z z z z z z z z The RT8302 also provides LED open/short protection. If there is any channel open or short, the FLT pin will pull low and the output channel will be turned off individually. The RT8302 is available in the WDFN 5x5-16L and DIP-18 packages to achieve optimized solution for PCB space. Wide Input Supply Voltage Range : 5V to 26V Wide Current Range : 30mA to 360mA (8-Bit Resolution) Programmable Channel Current Low Dropout Voltage : 500mV at 150mA ±3% High Accuracy Current for 60mA to 120mA ±2% Current Matching for 60mA to 120mA Fault Detection for LED Open/Short Under-Voltage Lockout and Thermal Shutdown Integrated Dynamic Headroom Control (DHC) Support 1D/2D/3D Dimming (Programmable Channel Delay, Individual PWM Duty Control, Automatic VSYN Synchronization) Flexible Daisy-Chained SPI Interface RoHS Compliant and Halogen Free Applications z z z z z LCD TV, MNT Display Backlight DC/DC or AC/DC LED Driver Applications General Purpose Constant Current Source Architectural and Decorative LED Lighting LED Street Lighting Simplified Application Circuit L1 D1 VLED VIN CIN RT8525 DRV VIN CDC VDC M1 COUT RSLP ISW VIN RS Enable EN SS CSS PGND FB AGND RFB1 CFB RFB2 VIN COMP EN RPWMI RIF Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 LED1 LED2 LED3 LED4 VFB PWMI RC CC1 VPH CIN RFB3 MCU CS SCL VSYN MOSI MISO RPH FLT EN CS SCL VSYN SDI IFB RT8302 PWMO SDO GND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8302 Ordering Information Pin Configurations RT8302 (TOP VIEW) Package Type QW : WDFN-16L 5x5 (W-Type) N : DIP-18 Lead Plating System G : Green (Halogen Free and Pb Free) Note : SDI SCL VSYN PWMO EN VFB FLT SDO 16 15 1 2 3 4 5 6 7 8 14 13 GND 12 11 10 17 9 CS LED4 LED3 LED2 LED1 IFB VREG VIN Richtek products are : ` WDFN-16L 5x5 RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. PWMO 18 VSYN EN 2 17 SCL VFB 3 16 SDI FLT 4 15 CS SDO 5 14 GND GND 6 13 LED4 VIN 7 12 LED3 VREG 8 11 LED2 IFB 9 10 LED1 Marking Information RT8302GQW RT8302GQW : Product Number RT8302 GQW YMDNN YMDNN : Date Code RT8302GN RichTek RT8302 GNYMDNN RT8302GN : Product Number YMDNN : Date Code DIP-18 Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Functional Pin Description Pin No. Pin Name Pin Function WDFN-16L 5x5 DIP-18 1 16 SDI Serial Interface Data Input. 2 17 SCL Serial Interface Clock Input. 3 18 VSYN Video Sync Signal or External Clock Input. 4 1 PW MO PWM Output. 5 2 EN Enable Control Input (Active High). 6 3 VFB Feedback Control Voltage Output. 7 4 FLT Open-Drain Output for Fault Detection. 8 5 SDO Serial Digital Data Output. 9 7 VIN Power Supply Input. 10 8 VREG Shunt Regulator Supply. 11 9 IFB Feedback Control Current Output. 12 10 LED1 Constant Current Sink Output. 13 11 LED2 Constant Current Sink Output. 14 12 LED3 Constant Current Sink Output. 15 13 LED4 Constant Current Sink Output. 16 15 CS Chip Select. 17 (Exposed Pad) 6, 14 GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8302 Function Block Diagram VFB 25MHz Oscillator EN SDI DHC Function LDO OTP SDO CS UVLO Daisy Chain SPI Interface SCL PWM Control VREG GND Fault Detection Channel Select VSYN VIN FLT LED1 LED2 LED3 236-step Current Setting LED4 IFB Soft-Start Circuit Constant Current Control Circuit PWMO Operation The RT8302 is a 4-CH constant current sink LED driver with 12-bit depth for PWM control. The daisy chain Serial Peripheral Interface (SPI) bus control can shift the input data into each channel buffer with dependent pixel gray scale and shift out input data to output pin SDO. The RT8302 supports local and scan dimming by PWM Control and Channel Select block. In PWM Control block, there are four independent PWM generators with programmable PWM duty cycle, period and delay. Channel Select block can decide which channel should be enabled. The RT8302 provides ±3% high accurate current for each channel by Constant Current Control Circuit block. The dropout voltage of output channel is 0.5V as the output Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 constant current is 150mA which can accept wide range VF variation. The range of the constant current output is from 30mA to 360mA which is adjusted by 236-step Current Setting block. Besides, a Dynamic Headroom Control (DHC) function is designed to generate a feedback signal for DC/DC control loop and regulate the output voltage. Furthermore, the RT8302 provides LED open/short and OTP protection by Fault Detection block. If there is any channel open/short, the FLT pin will pull low and the output channel will be turned off individually. If the internal junction temperature exceeds 150°C, all output channels will be turned off. is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------Output Voltage LED1 to LED4 -----------------------------------------------------------------------------------------Other Pins -------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-16L 5x5 -------------------------------------------------------------------------------------------------------------DIP-18 ------------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-16L 5x5, θJA -------------------------------------------------------------------------------------------------------WDFN-16L 5x5, θJC -------------------------------------------------------------------------------------------------------DIP-18, θJA ------------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------Junction Temperature -----------------------------------------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------------------- Recommended Operating Conditions z z z −0.3V to 31V −0.3V to 70V −0.3V to 28V 3.47W 1.97W 28.8°C/W 4.4°C/W 50.6°C/W 260°C 150°C −65°C to 150°C (Note 3) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 5V to 26V Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range --------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Input Power Supply Supply Current ION EN = High, VLEDx open -- 2 5 mA Shutdown Current ISHDN EN = Low -- -- 5 μA Under Voltage Lockout Threshold Voltage VUVLO VIN Rising -- 3.7 -- VIN Falling -- 3.2 -- UVLO Hysteresis VHYS -- 0.5 -- V VREG Output VREG -- 3.8 -- V V Enable EN Input Voltage Logic-High VIH TA = −40°C to 85°C 2 -- -- Logic-Low VIL TA = −40°C to 85°C -- -- 0.8 V Shutdown Delay TSHDN -- 32 -- ms EN Sink Current IIH 2 -- 20 μA Power On Reset Time tRESET -- 256 -- μs Soft-Start Time tSS -- 128 -- ms Fault Blanking Time tFB -- 256 -- ms Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8302 Parameter Symbol Test Conditions Min Typ Max Unit -- ±0.5 ±3 % Current Sink ILEDx = 60mA to 120mA; VLEDx = 0.5V Current Accuracy of Output Current IACC Channel to Channel Matching IMAT I −I IMAT = LEDx AVE × 100% IAVE -- ±0.5 ±2 % Output Current of Each Channel ILEDx Programmable 236-Step Current Setting 30 -- 360 mA Output Voltage VLEDx VLED1 to VLED4, All Channels Off -- -- 60 V Output Leakage Current IO LEAK VLEDx = 50V, All Channels Off -- -- 0.5 μA VVFBH IVFBH = 50μA -- 3.3 -- VVFBL IVFBL = 50μA -- 0.2 -- IVFBH VVFBH = 3.3V -- 50 -- μA IVFBL VVFBL = 0.2V -- 1 -- mA 100 -- -- μA -- -- 115 μA I −I IACC = LEDx TAR ×100% ITAR Output Pins Capability Feedback Voltage of VFB pin Output Current of VFB Pin PWMO Source Current Is, PWM Output Current of IFB Pin IIFB V Protection OTP Threshold VOTP Junction Temperature -- 150 -- °C OTP Hysteresis VOTPHYS Junction Temperature -- 30 -- °C 2-Bit Programmable (Code = 00) -- 3 -- 2-Bit Programmable (Code = 01) -- 6 -- 2-Bit Programmable (Code = 10) -- 9 -- 2-Bit Programmable (Code = 11) -- 12 -- -- 50 -- LSP VLSP OLP VOLP V mV Digital Input (SPI Interface) Input Voltage High Level VIH SDI, VSYN, SCL, CS Input 2 -- -- Low Level VIL SDI, VSYN, SCL, CS Input -- -- 1 -- -- 10 MHz V Maximum SCL Frequency F_SCL Setup Time SDI, SCL ts_SDISCL SPI Interface Mode 15 -- -- ns Hold Time SCL, SDI th_SCLSDI SPI Interface Mode 15 -- -- ns Setup Time CS, SCL ts_CSSCL SPI Interface Mode 15 -- -- ns Hold Time SCL, CS th_SCLCS SPI Interface Mode 15 -- -- ns High-Level VOH SDO Output -- VREG -- Low-Level VOL SDO Output -- 0.4 -- SDO Output Voltage V VSYNC Pulse Width On-Time tVSYNC_ON 150 -- -- ns Delay Time SCL, SDI td_SCLSDI 15 -- -- ns VSYNC Pulse Width Off-Time tVSYNC_OFF 150 -- -- ns Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 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. The device is not guaranteed to function outside its operating conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 www.richtek.com 8 Copyright © 2013 Richtek Technology Corporation. All rights reserved. RFSW 56k RIF 1k VDC PWMI COMP FSW SS EN L1 33µH AGND OOVP FAULT FB PGND ISW RT8525 DRV VIN 220k Dimming Input CSS 0.33µF/16V CDC 1µF/16V R1 100 CC1 27nF/16V RC 32k Enable C1 1µF/50V CIN 10µF/50V VIN 12V RS 50m CFB 0.1µF/25V RFLT 100k RSLP 2.7k M1 D1 EN VSYN MISO CS SCL MCU MOSI ROVP2 ROVP1 RFB1 COUT 100µF/ 100V RFB2 RFB3 200pF 200 CREG 10µF/25V CVIN 0.1µF/25V 12V EN CS SCL SDI VSYN GND FLT IFB VFB SDO PWMO LED1 RT8302 LED4 Max 360mA VREG VIN VLED 60V (Max) 12V CREG 10µF/25V CVIN 0.1µF/25V RPH 47k VPH EN CS SCL SDI VSYN GND FLT IFB VFB SDO PWMO LED1 RT8302 LED4 Max 360mA VREG VIN VLED 60V (Max) RPH 47k VPH RT8302 Typical Application Circuit is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Timing Diagram SPI Interface CS SCL SDI 0 MSB 6 1 2 5 3 4 4 3 5 2 6 LSB 0 1 7 Bit Register Address SDO 7 8 9 10 11 12 13 14 15 1 R/W MSB 7 Previous Data 6 5 4 3 2 1 13 14 LSB 0 8 Bit Data Output Figure 1. Read Sequence CS SCL SDI 0 MSB 6 1 2 5 4 3 4 3 2 5 1 6 LSB 0 7 Bit Register Address SDO 7 0 8 MSB 7 9 10 6 5 7 6 5 R/W Previous Data 11 4 12 3 2 1 15 LSB 0 2 1 0 1 Bit Data Byte 4 3 Register Address Figure 2. Write Sequence CS SCL 8 Clks 8 Clks 8 Clks 8 Clks 8 Clks MOSI/SDI1 WR IC Data IC4 Data IC3 Data IC2 Data IC1 SDO1/SDI2 X WR IC Data IC4 Data IC3 Data IC2 SDO2/SDI3 X X WR IC Data IC4 Data IC3 SDO3/SDI4 X X X WRIC Data IC4 1st Execution Figure 3. Daisy Chain Write Sequence Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8302 CS SCL 8 Clks 8 Clks 8 Clks 8 Clks 8 Clks 8 Clks 8 Clks 8 Clks MOSI/SDI1 RD IC X X X X X X X SDO1/SDI2 X RD IC X X IC1 OUT X X X SDO2/SDI3 X X RD IC X IC2 OUT IC1 OUT X X SDO3/SDI4 X X X RD IC IC3 OUT IC2 OUT IC1 OUT X SDO4/MISO X X X X IC4 OUT IC3 OUT IC2 OUT IC1 OUT 1st Execution Figure 4. Daisy Chain Read Sequence (only request a read command of the same address for all ICs) ts_CSSCL th_CSSCL CS td_SCLSDI ts_SCLSDI SCL th_SCLSDI SDI MSB LSB DATA Figure 5 Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Typical Operating Characteristics VREG vs. Input Voltage 5 4 4 VREG (V) Supply Current (mA) Supply Current vs. Input Voltage 5 3 2 3 2 1 1 No current source work ILED = 120mA 0 0 5 10 15 20 5 25 10 15 LED Current vs. Input Voltage EN Level vs. Temperature 130 1.8 V IH 1.6 128 LED Current (mA) 1.4 EN Level 1.2 VIL 1.0 0.8 0.6 0.4 125 123 120 LED1 LED2 LED3 LED4 118 115 113 0.2 VIN = 24V ILED = 120mA, fSYNC = 120Hz 110 0.0 -50 -25 0 25 50 75 100 5 125 10 15 20 25 Input Voltage (V) Temperature (°C) LED Current vs. PWM Duty Cycle ILED vs. Temperature 60 121.0 48 120.6 36 I LED (mA) LED Current (mA) 25 Input Voltage (V) Input Voltage (V) 24 12 120.2 119.8 119.4 VIN = 24V, fSYNC = 120Hz 0 VIN = 24V, fSYNC = 120Hz 119.0 0 20 40 60 80 PWM Duty Cycle (%) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 20 October 2013 100 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8302 DHC Rising Response DHC Falling Response VFB (2V/Div) VFB (2V/Div) I LED (500mA/Div) I LED (500mA/Div) VIN = 24V, fSYNC = 120Hz VIN = 24V, fSYNC = 120Hz Time (50ms/Div) Time (50ms/Div) VSYNC Dimming Mode ILED Synchronous with VSYNC VSYNC (2V/Div) CSN (5V/Div) PWMO (5V/Div) VSYNC (2V/Div) I LED (100mA/Div) I LED (200mA/Div) VIN = 24V, fSYNC = 120Hz, no delay VIN = 24V, fSYNC = 120Hz, delay = 6.25ms Time (2.5ms/Div) Time (2.5ms/Div) Power On from EN Power Off from EN EN (5V/Div) SCL (5V/Div) EN (10V/Div) SDI (5V/Div) I LED (20mA/Div) I LED (20mA/Div) VIN = 24V, fSYNC = 120Hz Time (250μs/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 VIN = 24V, fSYNC = 120Hz Time (10ms/Div) is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Application Information The RT8302 is a 4-CH LED current source controller with SPI interface control. The RT8302 regulates the lowest voltage of the LED strings and generates a feedback control signal to a primary controller to regulate the LED current. Each channel constant current which ensures the difference in output current value of 4 channels and ICs is smaller than 3% and 3% in SYNC and ASYNC mode LED brightness control, respectively. The range of the constant current output is programmable from 30mA to 360mA by SPI interface. Moreover, the RT8302 also provides Dynamic Headroom Control (DHC) function which can generate feedback signal to DC/DC control loop and regulate the output voltage of the RT8302. The RT8302 also features several protections including Short-LED Protection (SLP), Open-LED Protection (OLP), and Over-Temperature Protection (OTP). SYNC Mode Dimming : When the PWM_Control register is set to 0x10h, the dimming mode operates in SYNC Mode. During the PWM dimming, the current source turns on/off according to the VSYNC signal. The LED current frequency is equivalent to VSYNC frequency. In this mode, the VSYNC and ILED dimming cycle will delay one period as shown in the following Figure 6. SYNC Mode and ASYNC Mode Brightness Dimming ASYNC Mode Dimming : When the PWM_Control register is set to 0x15h, the dimming mode operates in ASYNC Mode. During the PWM dimming, the current source turns on/off according to the internal clock, as shown in the following Figure 7. The LED current high time and delay time can be calculated as follows : PWM_HT_Data × Sampled CLK High Time = 4096 PWM_Delay_ Data × Sampled CLK Delay Time = 4096 The sampled CLK equals VSYNC period. PWM High + delay time can exceed VSYNC period to fulfill complex scanning requirements if PWM_HT_Data is FFFh. PWM_Delay_Data should be 000h. The RT8302 allows two ways of controlling the LED brightness. 60Hz, 120Hz, 180Hz, 240Hz VSYNC Sampled CLKs 1 Internal Clock (Fixed 25MHz) Sampled CLKs 2 Sampled CLKs 3 Sampled CLKs 4 CHn_Delay_VSYNC CHn Pwm data 512 CHn Pwm OUT 0 100 2000 (512/4096) x sampled CLKs_1 (100/4096) x sampled CLKs_2 PWM On Time 1000 400 PWM On Time (2000/4096) x sampled CLKs_3 PWM On Time PWM On Time tD1 tD2 tD3 tD4 Td1 = (Dn / 4096) x sampled CLKs_1 tD2 = (Dn / 4096) x sampled CLKs_2 tD3 = (Dn / 4096) x sampled CLKs_3 tD4 = (Dn / 4096) x sampled CLKs_4 Figure 6. SYNC Mode 2. Update PWM grayscale data of buffers 1. Load data from SDI 3. The next data is updated and start counting as the last data has finished one PWM period cycle. CS SCL SDI 0 1 2 3 DAddr DAddr DAddr DAddr (7) (6) (5) (4) 18 19 20 21 22 23 D(n) D(n) D(n) D(n) D(n) D(n) 5 4 3 2 1 0 Next Data Next Data VSYNC or Internal clock 500kHz CURREGX_DELAY PWM_Period Curregx_HT (Internal) CH1_4 PWM PWM Data (n - 1) PWM Data (n) CH1-4 PWM Output (n - 1) CH1-4 PWM Output (n) PWM outputs are switching according to previous data D (n - 1) (PWM outputs are finished one period cycle.) PWM outputs are switching according to data D (n) Figure 7. ASYNC Mode Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT8302 The LED current high time can be obtained as follows : High Time = VLED PWM_HT_Data × Sampled CLK PWM_Period RF1 where Converter VREF Sampled CLK : internal clock period. PWM_Period : PWM period register data RF3 VFB 0.2V to 3.3V RF2 Dynamic Headroom Control Function (DHC) The Dynamic Headroom Control (DHC) function is used to generate feedback signal to primary DC/DC control loop and regulate the LED current of the RT8302. This function can improve IC's thermal performance and efficiency. The RF1, RF2 and RF3 selection is shown in below equations : VLED(Default) = VREF × (1+ RF1 ) RF2 V − 0.2 VLED(MAX) = VLED(Default) +RF1× ( REF ) RF3 V − 3.3 VLED(MIN) = VLED(Default) +RF1× ( REF ) RF3 RF3(MIN) = VFB − VREF , IFB (typ.) VLED(MAX) − VLED(MIN) < 0.15 (typ.) 256 where VLED is converter output voltage, VREF is converter reference voltage and typical IFB is 50μA. The connection is shown as the following Figure 8. VIN 0V Figure 8 Power-On and Power-Off Sequence When power converter output voltage and supply voltage of the RT8302 are both ready, EN pulled high will enable the RT8302. Then, IC will check whether the channel is unused or not in power on reset time (256μs) in the first period. The unused channel needs to be short to GND or the FLT pin will be turned on. The second period is softstart time (128ms), and the RT8302 feedback voltage is 3.3V in this period. Then, IC gets into the third period, fault blanking time (256ms), and the fault signal would be ignored even LED in Short/Open condition. After the fault blanking time, the fault function will be turned on. As for power off sequence, IC will be shut down when the EN pin is pulled low for 32ms. The power on sequence is shown in Figure 9. 24V By CPU UVLO EN 256µs (check unused CHs Clear Registers POR Status SS 128ms Pulled low PWMO Floating Receive start-up commands LED current, PWM, etc Fault blanking 256ms Boost activated 3.3V In regulation VFB VOUT nominal DHC VOUT min BOOST VOUT 24V Assuming pull down resistor at PWMO Requested ILED ILED (Depends on DHC setting and LED string) Figure 9. Power-On Sequence Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Over-Temperature Protection (OTP) Short-LED Protection (SLP) The RT8302 has an over-temperature protection function to prevent overheating due to excessive power dissipation. The OTP will disable all channels if the junction temperature exceeds 150°C and send a fault signal. The channels are re-enabled when the junction temperature cools down by approximately 30°C. If the voltage of VLEDx is > VSLP after fault blanking period, the SLP function will be triggered. Moreover, there is an adjustable blanking time on every rising part of current regulator on. When the counter accumulates to 2μs, this short channel will be off and latched. The FLT pin will be pulled low. The fault state can only be released by current regulator off after 32ms. The operation and protection flow is shown as the following Figure 10. Open-LED Protection (OLP) If the VLEDx is < 50mV after a fault blanking period, the counter will be triggered when PWM is high. Moreover, there is an adjustable blanking time on every rising part of current regulator on. When the counter accumulates to 2μs, only this open channel will be off but not latched. The FLT pin will be pulled low. VIN and PWMI Power-On Start (RESET) PWMI = low after 32ms or VIN < UVLO Disable this Channel Un-used VFB = 0.2 Status of Channel is VLEDx Floating? (Un-used channel need short to GND) 4 channels open LED OLP Soft-Start Function and ILED Turn-On (128ms) Over-Temperature Protection ? Tj >140°C Turn-Off All Channel FLT Pulled Low Follow the Normal Flow SLP : Fault pulled low, only this channel off and latch OLP : Fault pulled low, only this channel off and non-latch VFB = 3.3V OLP = SLP = L Fault Blacking Time VFB = 0.2V to 3.3V (256ms) OLP = SLP = L Tj < 90°C Auto-recovery Normal Operation TF <2µs TF > 2µs Open / Short Detection Time 4 channels DHC open LED Short / Open Latch Protection ? Figure 10 Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 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 WDFN-16L 5x5 package, the thermal resistance, θJA, is Maximum Power Dissipation (W)1 RT8302 4.0 Four-Layer PCB WDFN-16L 5x5 3.2 2.4 DIP-18 1.6 0.8 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 11. Derating Curve of Maximum Power Dissipation 28.8°C/W on a standard JEDEC 51-7 four-layer thermal test board. For DIP-18 package, the thermal resistance, θJA, is 50.6°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) / (28.8°C/W) = 3.47W for WDFN-16L 5x5 package PD(MAX) = (125°C − 25°C) / (50.6°C/W) = 1.97W for DIP-18 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 11 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 16 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Layout Consideration Place the current sensing register as close as possible to IC PGND. Place the power components as close as possible. The traces should be wide and short especially for the high-current loop. VIN PGND L1 VOUT The compensation circuit should be kept away from the power loops and should be shielded with a ground trace to prevent any noise coupling. D1 CIN COUT RT8525 1 VDC 2 VIN DRV M1 14 RS RC CC1 PGND 13 3 COMP EN 12 4 SS ISW 11 5 FSW PGND RSLP IFB RIF 6 AGND PWMO 7 PWMI ROVP1 OOVP 10 FB VFB RFB1 9 FAULT 8 CFB ROVP2 RFB2 AGND The feedback voltage-divider resistors must near the feedback pin. The divider center trace must be short and avoid the trace near any switching nodes. CS MOSI MCU VOUT SCL VSYN EN RT8302 MISO 1 SDI 2 SCL LED4 15 CS 3 VSYN LED3 14 PWMO4 PWMO The SPI signals path must be kept away from noise and be short enough to connect to the RT8302. 16 LED2 13 GND VFB RFB3 5 EN 6 VFB 7 FLT 8 SDO LED1 12 IFB 11 CREG IFB VREG 10 PGND VIN 9 PGND CVIN VIN Locate the CVIN and CREG as close to VIN as possible. Figure 12. PCB Layout Guide for WDFN-16L 5x5 Package Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 17 RT8302 Place the power components as close as possible. The traces should be wide and short especially for the high-current loop. VIN L1 VOUT PGND The compensation circuit should be kept away from the power loops and should be shielded with a ground trace to prevent any noise coupling. D1 CIN M1 COUT RT8525 1 VDC 2 DRV 14 PGND 13 VIN 3 COMP EN 12 4 ISW 11 SS 5 FSW ROVP1 RS PGND OOVP 10 RC 6 AGND CC1 RFB1 RSLP FB 7 PWMI 9 FAULT 8 ROVP2 RIF RFB3 RFB2 0 The feedback voltage-divider resistors must near the feedback pin. The divider center trace must be short and avoid the trace near any switching nodes. CFB EN VSYN PWMO 1 18 VSYN EN 2 17 SCL SCL MCU VFB 3 16 SDI MOSI FLT 4 15 CS CS SDO 5 14 GND GND 6 13 LED4 VIN 7 12 LED3 VREG 8 11 LED2 IFB 9 10 LED1 RT8302 CVIN CREG Locate the CVIN and CREG as close to VIN as possible. The IFB trace must be placed close to compensation circuit for reducing noise coupling. The SPI signals path must be kept away from noise and be Short enough to connect to the RT8302. Place the currentsensing resistor as close as possible to IC PGND. Figure 13. PCB Layout Guide for DIP-18 Package Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 18 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Name Page Addr Write Default Addr. Reg Control1 02h EFh Feedback Control 04h 01h Voltage Fault 1 09h 00h Curreg_Control 0Dh 00h Reference_DAC _Voltage 0Eh 00h PWM-Control 0Fh 15h PWM_Period_LSB 10h FFh PWM_Period_MSB 11h 00h Curreg1_HT_LSB 12h 22h 00h Curreg1_HT_MSB 13h 23h 00h Curreg2_HT_LSB 14h 24h 00h Curreg2_HT_MSB 15h 25h 00h Curreg3_HT_LSB 16h 26h 00h Curreg3_HT_MSB 17h 27h 00h Curreg4_HT_LSB 18h 28h 00h Curreg4_HT_MSB 19h 29h 00h Curreg1_Delay_LSB 32h 42h 00h Curreg1_Delay_MSB 33h 43h 00h Curreg2_Delay_LSB 34h 44h 00h Curreg2_Delay_MSB 35h 45h 00h Curreg3_Delay_LSB 36h 46h 00h Curreg3_Delay_MSB 37h 47h 00h Curreg4_Delay_LSB 38h 48h 00h Curreg4_Delay_MSB 39h 49h 00h DHC Timing Control 54h 00h Overtemp Control 55h 00h B7 October 2013 B5 B4 B3 Curreg4 _ON IC Version B2 B1 Fault _Reg4 Fault_Reg3 Peak current with VSYNC B0 Curreg3 Curreg2 Curreg1 _ON _ON _ON SHORT_LED SHORT OPEN Detect _LED _LED Voltage _DET_ON _DET_ON Fault_Reg2 Feedback _ON Fault_Reg1 SR_Control Vref_DAC_Code Scrambled PWM Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 B6 Hysteretic VSYNC PWM _INVERT _INT/EXT PWM_MODE PWM_Period_LSB PWM_Period_MSB Curreg1_HT_LSB Curreg1_HT_MSB Curreg2_HT_LSB Curreg2_HT_MSB Curreg3_HT_LSB Curreg3_HT_MSB Curreg4_HT_LSB Curreg4_HT_MSB Curreg1_Delay_LSB Curreg1_Delay_MSB Curreg2_Delay_LSB Curreg2_Delay_MSB Curreg3_Delay_LSB Curreg3_Delay_MSB Curreg4_Delay_LSB Curreg4_Delay_MSB DHC_T ov_temp is a registered trademark of Richtek Technology Corporation. www.richtek.com 19 RT8302 Current Regulator On/Off Control Addr : 02h Bit Bit Name 3:0 Curreg1_ON to Curreg4_ON 7:4 IC Version RT8302 Register Control This Register enables or disable the curreg1 to curreg4 Default Access Description Enables or disables the current regulators 1111 R/W 1 = regulator on 0 = regulator off Define the IC version 1110 R/W 1110 = RT8302 Feedback Mode Control Addr : 04h Bit Bit Name 0 Feedback on 2 Open_LED_Det_on 3 Short_det_on 5:4 Short LED Detect Voltage (VSL) RT8302 Feedback Control Enables and Disables the Different Feedback modes Default Access Description 1 = Feedback Circuit is Active 1 R/W 0 = The entire feedback loop is disabled Enables open LED detection comparators 0 R/W 0 = Open LED Detection enabled 1 = Open LED Detection disabled Enables short LED detection 0 R/W 0 = Short LED Detection on. 1 = Short LED Detection off. Short LED detection trip voltage (de-bounced 3ms) 00 = 3V 00 R/W 01 = 6V 10 = 9V 11 =12V Voltage Fault Register Status Read RT8302 Voltage Fault Addr : 09h This register shows a fault on any LED string Bit Bit Name Default Access Description Shows an error on any LED string 00 = no fault 1 : 0 Fault_Reg 1 00 R 01 = open LED 10 = short LED 11 = channel un-used Shows an error on any LED string 00 = no fault 3 : 2 Fault_Reg 2 00 R 01 = open LED 10 = short LED 11 = channel un-used Shows an error on any LED string 00 = no fault 5 : 4 Fault_Reg 3 00 R 01 = open LED 10 = short LED 11 = channel un-used Shows an error on any LED string 00 = no fault 7 : 6 Fault_Reg 4 00 R 01 = open LED 10 = short LED 11 = channel un-used Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 20 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Current Regulator Slew Rate Control Addr : 0Dh Bit 3 :2 7 Bit Name RT8302 Curreg Control Controls Rise and Fall times of the Curreg. Default Access SR_Control 00 R/W Peak current with VSYNC 0 R/W Description SLEW_RATE_Control. Adjusts the rise and fall time of the current switching 00 = typ. 1μs 01 = typ. 2μs 10 = typ. 4μs 11 = typ. 8μs 0 = Update Synchronous with next VSYNC 1 = Update Directly after CS Transition Reference DAC Voltage Control RT8302 Ref_DAC_Voltage Addr : 0Eh The Regulation Current can be chosen in this register Bit 7:0 Bit Name Ref_DAC_Voltage Default 00000000 Access R/W Description 00000000 = 30mA ….. 00010100 = 30mA ….. 10000000 = 181.4mA ….. 11111111= 360mA PWM Mode Control Addr : 0Fh Bit Bit Name RT8302 PWM Mode Control the different PWM modes and internal or external PWM Default Access 1 :0 PWM_MODE 01 R/W 2 PWM INT/EXT 1 R/W 3 VSYNC_INVERT 0 R/W 5 :4 PWM Hysteretic Control 01 R/W 7 :6 Scrambled PWM 00 R/W Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 Description 00 SYNC mode 01 ASYNC mode 10 not used 11 not used Note : SYNC mode can only be used with PWM INT = 0. 0 PWM generator uses external H and VSYNC clock 1 PWM generator uses internal 500kHz clock. 0 VSYNC active high (PWM triggers on rising edge) 1 VSYNC active low (PWM triggers on falling edge) 00 : No Hysteretic 01 : PWM varied range < ± 1 clock cycle 10 : PWM varied range < ± 2 clock cycle 11 : PWM varied range < ± 3 clock cycle 00 : 1 times refresh rate 01 : 2 times refresh rate 10 : 4 times refresh rate 11 : 8 times refresh rate is a registered trademark of Richtek Technology Corporation. www.richtek.com 21 RT8302 PWM Period Control Addr : 10h Bit Bit Name 7:0 PWM_PERIOD _LSB RT8302 PWM Period-LSB Defines PWM – Period Default Access 11111111 R/W Description Defines the period of the PWM PWM Period Control Addr : 11h RT8302 PWM Period-MSB Defines PWM – Period Bit Bit Name Default Access 3:0 PWM_PERIOD_MSB 0000 R/W Description Defines the period of the PWM PWM High Time Control Addr : 12h, 14h, 16h, 18h Bit 7:0 Bit Name CurregX_HT_LSB Addr : 13h, 15h, 17h, 19h Bit 3:0 Bit Name CurregX_HT_MSB RT8302 CURREGX PWM-High Time-LSB Defines High Time of PWM Default Access 00000000 R/W Description Defines PWM high time RT8302 CURREGX PWM-High Time-MSB Defines High Time of PWM Default Access 0000 R/W Description Defines PWM high time PWM Delay Time Control Addr : 32h, 34h, 36h, 38h Bit 7:0 Bit Name CurregX_DELAY RT8302 CURREGX Delay Time-LSB Defines delay of the different PWM’s Default Access 00000000 R/W Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 22 Description Defines the delay time of the PWM is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Addr : 33h, 35h, 37h, 39h Bit 3:0 Bit Name CurregX_DELAY RT8302 CURREGX Delay Time-MSB Defines delay of the different PWM’s Default Access 0000 R/W Description Defines the delay time of the PWM DHC Timing Control Addr : 54h Bit 5 Bit Name DHC_T RT8302 DHC Timing Control Enable, disable and timing setup some function of RT8302 Default Access 0 R/W Description DHC one step time 0 = 1ms 1 = 128μs Over Temperature Control Addr : 55h Bit 1 Bit Name ov_temp RT8302 Over Temperature Control Controls the temperature function Default 0 Access R/W Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8302-01 October 2013 Description Displays temperature status 0 = Normal operation 1 = Over temperature shutdown is a registered trademark of Richtek Technology Corporation. www.richtek.com 23 RT8302 Outline Dimension 2 1 2 1 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 0.200 0.300 0.008 0.012 D 4.900 5.100 0.193 0.201 D2 4.350 4.450 0.171 0.175 E 4.900 5.100 0.193 0.201 E2 3.650 3.750 0.144 0.148 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 16L DFN 5x5 Package Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 24 is a registered trademark of Richtek Technology Corporation. DS8302-01 October 2013 RT8302 Symbol Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 3.700 5.330 0.146 0.210 A1 0.381 0.710 0.015 0.028 A2 3.200 3.600 0.126 0.142 b 0.360 0.560 0.014 0.022 b1 1.143 1.778 0.045 0.070 D 22.350 23.368 0.880 0.920 E 6.200 6.600 0.244 0.260 E1 7.620 8.255 0.300 0.325 2.540 e L 2.920 0.100 3.800 0.115 0.150 18-Lead DIP Plastic Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st 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. DS8302-01 October 2013 www.richtek.com 25