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rt4532 ? ds4532-01 august 2015 www.richtek.com 1 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. simplified application circuit high efficiency backlight led driver general description the rt4532 is a high-efficiency led driver for backlight applications. an asynchronous boost converter with an internal schottky diode and a current source driver are designed to support 6led/channel with wide input voltage range from 2.5v to 5.5v. an i 2 c interface can provide easy backlight control in fast and high speed mode. the rt4532 supports linear mappings with 256 steps to setup the brightness of backlight leds. it also supports pwm dimming to adjust the brightness. the rt4532 provides complete protection functions such as input under-voltage lockout, over-current, output over- voltage and over-temperature protection. the ovp threshold voltage can be set at 16v and 24v for different applications. the rt4532 is available in the wl-csp-10b 0.87x2.07 package. features ? ? ? ? ? input voltage range : 2.5v to 5.5v ? ? ? ? ? internal schottky diode ? ? ? ? ? fast-speed mode i 2 c compatible interface ? ? ? ? ? drive up to 6 wleds in 4 string ? ? ? ? ? external pwm brightness control ? ? ? ? ? 550k/1.1mhz switching frequency ? ? ? ? ? built-in internal soft-start ? ? ? ? ? i 2 c programmable 256 steps linear current regulation ? ? ? ? ? up to 85% efficiency with small magnetics ? ? ? ? ? programmable 16v/24v ovp ? ? ? ? ? current accuracy 5% and current balance 3% ? ? ? ? ? uvlo, ovp, ocp, otp protection ? ? ? ? ? shutdown current : < 1 a ? ? ? ? ? temperature range : ? ? ? ? ? 40 c to 85 c applications ? cellular phones ? digital cameras ? pdas and smart phones ? portable instruments ordering information 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. rt4532 package type wsc : wl-csp-10b 0.87x2.07 (bsc) en vout vin l rt4532 lx v in fb1 fb2 c out v out c in pwm scl sda enable gnd x 6
2 rt4532 www.richtek.com ds4532-01 august 2015 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. functional pin description pin configuration (top view) pin no. pin name pin function a1 lx switch node of boost converter. connect an inductor between lx and vin. a2 gnd ground. b1 vout power output of the asynchronous boost converter for backlight leds. connect a 1 ? f or larger ceramic capacitor from vout to ground. b2 vin power input. connect this pin to the input power supply voltage. connect a 10 ? f or larger ceramic capacitor from the vin to ground. c1 pwm pwm dimming input for backlight led. c2 en enable control input (active high). the chip is in shutdown mode when the en pin is low. d1 sda i 2 c serial data input/output. an external pull-up resistor is required. d2 scl i 2 c serial clock input. an external pull-up resistor is required. e1 fb2 single output 2 for backlight led. e2 fb1 single output 1 for backlight led. fb1 fb2 scl sda en pwm vin vout lx gnd e2 e1 d2 d1 c2 c1 b2 b1 a1 a2 wl-csp-10b 0.87x2.07(bsc) marking information 2kw 2k : product code w : date code
3 rt4532 ds4532-01 august 2015 www.richtek.com ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. functional block diagram pwm current source gen. pwm logic digital control ea vslope pwm2dc v ref v fb vout lx fb1 fb2 gnd scl sda en vin + - ocp ovp otp leds operation the rt4532 is a high efficiency solution with 24 wleds in 4 parallels 6 series for backlight applications. the rt4532 optimizes the feedback regulation voltage to provide up to 85% high efficiency with as high as 8bits resolution application. linear brightness dimming the rt4532 is built-in a i 2 c 8-bit resolution brightness control with maximum 20ma/40ma selection. reg0x02<3> corresponds to full-scale led current control. reg0x04 sets 8bits resolution brightness dimming. pwm brightness dimming besides programmable built-in i 2 c backlight led current control, the rt4532 features a built-in pwm dimming current control by setting reg0x02<6> to 1, offering a linear current dimming by external clock source. in order to guarantee the pwm dimming resolution, recommending dimming frequency have to be operated at range of 400hz to 20khz. ocp protection the rt4532 features a 1.2a current limitation. once detecting current level over current limitation, the rt4532's lx witching will be forced off to avoid large current damage. otp protection the over-temperature protection function will be latched at shutdown status when the junction temperature exceeds 140 c for 2ms. after re-power on sequence, the converter will automatically resume switching. ovp protection the over-voltage protection function monitors the output voltage via the vout pin voltage. the ovp threshold voltage is 24v/16v by selecting reg0x02<7>. once the led is open, the output voltage reaches the ovp threshold, the driver will be shut down.
4 rt4532 www.richtek.com ds4532-01 august 2015 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. electrical characteristics recommended operating conditions (note 4) ? supply input voltage, vin ----------------------------------------------------------------------------------------------- 2.5v to 5.5v ? junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c ? ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c parameter symbol test conditions min typ max unit input power supply input supply voltage v in 2.5 -- 5.5 v vin quiescent current i q pwm, no switching -- 0.6 -- ma shutdown current i shdn v in = 4.2v, en = gnd -- 1 3 ? a under-voltage lockout threshold v uvlo v in falling, check i q < 200 ? a -- -- 2.3 v under-voltage lockout hysteresis ? v uvlo after uvlo, v in rising, until i q > 200a -- 150 -- mv backlight led current source accuracy of output current i led_acc fb1, fb2 = 0.15v, i fb1 = i fb2 = 20ma ? 5 -- 5 % matching of output current i led_mat fb1, fb2 = 0.15v, i fb1 = i fb2 = 20ma ? 3 -- 3 % oscillator and timing operating frequency f sw reg0x03 [6] = 1 0.88 1.1 1.32 mhz maximum duty cycle d max fb1 = fb2 = 0v, check max duty 90 95 -- % brightness ramp rate t ramp reg0x03 [5:0] = 111111 209.72 262.14 314.58 ms absolute maximum ratings (note 1) ? supply input v oltage, vin ----------------------------------------------------------------------------------------------- ? 0.3v to 6v ? boost output v oltage, vout ------------------------------------------------------------------------------------------- ? 0.3v to 26v ? switching voltage, lx ---------------------------------------------------------------------------------------------------- ? 0.3v to 26v ? current source voltage, fb1, fb2 ------------------------------------------------------------------------------------ ? 0.3v to 26v ? other pins, en, pwm, scl, sda ------------------------------------------------------------------------------------ ? 0.3v to 6v ? power dissipation, p d @ t a = 25 c wl-csp-10b 0.87x2.07 (bsc) ---------------------------------------------------------------------------------------- 1w ? package thermal resistance (note 2) wl-csp-10b 0.87x2.07 (bsc), ja ---------------------------------------------------------------------------------- 99.6 c/w ? lead temperature (soldering, 10 se c.) ------------------------------------------------------------------------------- 260 c ? junction temperature ----------------------------------------------------------------------------------------------------- 150 c ? storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c ? esd susceptibility (note 3) hbm (human body model) ---------------------------------------------------------------------------------------------- 2kv mm (ma chine model) ----------------------------------------------------------------------------------------------------- 200v (v in = 3.6v, c in = 10 f, c out = 1 f, l = 10 h, t a = 25 c, unless otherwise specified)
5 rt4532 ds4532-01 august 2015 www.richtek.com ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. 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. ja is measured at t a = 25 c on a high effective thermal conductivity four-layer test board per jedec 51-7. jc 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. parameter symbol test conditions min typ max unit power switch n-mosfet on-resistance r ds(on)_n v in = 3.6v 100 200 300 m ? n-mosfet current limit i ocp 1 1.2 1.4 a n-mosfet leakage current i leak lx = 24v, no switching -- -- 1 ? a protection function over voltage protection ovp reg0x02 [7] = 0 14 16 18 v reg0x02 [7] = 1 23 24 25 v thermal shutdown threshold t sd thermal latch -- 150 -- c logic control en input voltage logic-high v enh 1.05 -- -- v logic-low v enl -- -- 0.4 pwm input voltage logic-high v pw ml 1.05 -- -- v logic-low v pw ml -- -- 0.4 scl input voltage logic-high v sclh 1.3 -- -- v logic-low v scll -- -- 0.4 sda input voltage logic-high v sdah 1.3 -- -- v logic-low v sdal -- -- 0.4 en pull-down resistance -- 400 -- k ? pwm pull-down resistance -- 400 -- k ? clock frequency of scl f scl -- -- 400 khz
6 rt4532 www.richtek.com ds4532-01 august 2015 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. typical application circuit timing diagram power sequence pwm en i(led) reg0x04 = ff as reg default reg0x04 = 00 reg0x02 = c7 pwm enable i(max) i(min) 0 duty =50% i(max)/2 note : pwm prd : count by osc : 17.6meghz > 1024 : resolution = 7bits & < 1000 : resolution = 8bits count 2^17 clock count 2^17 clock 0 reg0x02<0> = 0 dev_en disable en vout vin 2.5v to 5.5v l 3 rt4532 lx 10 8, 11 (exposed pad) 2 9 v in fb1 fb2 6 7 c out 1f v out 10h c in 10f pwm 1 scl 4 sda 5 enable gnd x 6
7 rt4532 ds4532-01 august 2015 www.richtek.com ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. protection timing otp en senbl register sotp 2ms 2ms reg0x05 record led short en senbl register led1_f or led2_f short 2ms 2ms reg0x05 record led open reg0x05 record sovp register senbl en x 39 times 40 times
8 rt4532 www.richtek.com ds4532-01 august 2015 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. table 1. register map slave address = 0100010x ad dress address name bit label default (reset value) description 0x00 device id 7:0 dev_id 0x01 manufacture 7:2 rev 000000 revision number 1:0 vid 11 vendor id : richtek 0x02 config1 7 ovpsel 1 ovp threshold ([0] 16v, [1] 24v) 6 pwm_en 1 pwm enable : [0] ignored, [1] enable 5 pwm _set 0 pwm active setup : [0] high active, [1] low active 4 reserv ed 3 max_current 0 [0] 20ma, [1] 40ma, 2 led1_en 1 backlight led1 : [0] off, [1] on 1 led2_en 1 backlight led2 : [0] off, [1] on 0 dev_en 1 chip enable : [0] off, [1] on 0x03 timing 7 rst_sw 0 software reset : [0] disable(auto), [1] reset all registers 6 fsw 1 switching frequency ([0]550khz, [1]1.1mhz) 5:3 up_rate 000 brightness ramp-up rate : [000] 32 ? s, [001] 4.096ms, [010] 8.192ms, [011] 16.383ms, [100] 32.768ms, [101] 65.536ms, [110] 131.072ms, [111] 262.144ms 2:0 dn_rate 000 brightness ramp-down rate : [000] 32 ? s, [001] 4.096ms, [010] 8.192ms, [011] 16.383ms, [100] 32.768ms, [101] 65.536ms, [110] 131.072ms, [111] 262.144ms 0x04 linear brightness control 7:0 bright_lin 00000000 [00000000] 0.39%, [00000001] 0.39%, ?? [111111111] 100% 0x05 flag 7:4 reserved 0 3 led1_ft 0 led1 short : [0] normal, [1] fault 2 led2_ft 0 led2 short : [0] normal, [1] fault 1 ovp 0 output over voltage : [0] normal, [1] fault 0 otp 0 over temperature : [0] normal, [1] fault
9 rt4532 ds4532-01 august 2015 www.richtek.com ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. shutdown current vs. input voltage 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) shutdown current ( a) 1 typical operating characteristics pwm dimming operation 0 5 10 15 20 25 30 35 40 45 0 20406080100 dimming duty (%) led current (ma) i led = 40ma v in = 3.6v i led = 20ma switching frequency vs. input voltage 1.00 1.03 1.06 1.09 1.12 1.15 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) switching frequency (mhz) 1 c in = 10 f, c out = 1 f, l = 10 h efficiency vs. input voltage 0 10 20 30 40 50 60 70 80 90 100 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) efficiency (%) c in = 10 f, c out = 1 f, l = 10 h, i led = 20ma efficiency vs. linear brightness control 30 40 50 60 70 80 90 100 0 25 50 75 100 125 150 175 200 225 250 275 linear brightness control (step) efficiency (%) c in = 10 f, c out = 1 f, l = 10 h quiescent current vs. input voltage 0 200 400 600 800 1000 1200 1400 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) quiescent current ( a ) non-switching
10 rt4532 www.richtek.com ds4532-01 august 2015 ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. application information led short protection led short protection prevents abnormal connection to cause ic damage avoiding fb1/fb2 connecting power supply. and, if unbalanced leds series (cause fb1 or fb2 > 9.6v) is different between channel1 and channel2, ic will also occur led short event. as led short event occur more than deglitch time 2ms, ic will shut-down latch until ic is reset by en pin. soft-start the rt4532 includes a soft-start function to avoid high inrush current during start-up. the soft-start function is achieved by clamping the output voltage of the error amplifier with another voltage source that is increased slowly from zero to near vin during the soft-start period. ocp protection the rt4532 features a 1a current limitation. the current flowing through the inductor during a charging period is detected by a current sensing circuit. if the value exceeds the current limit, the n-mosfet will be turned off. the inductor will then be forced to leave charging stage and enter discharging stage. therefore, the inductor current will not increase to reach current limit. the over-temperature protection function will be latched at shutdown status when the junction temperature exceeds 140 c for 2ms. after re-power on sequence, the converter will automatically resume switching. ovp protection the chip provides over-voltage protection function to limit the output voltage in abnormal conditions. the ovp threshold voltage is 24v/16v by selecting reg0x02 <7>. once the led is open, the output voltage reaches the ovp threshold, the driver will be shut down. under-voltage lockout an under-voltage lockout circuit prevents the operation of the device at input voltages below under-voltage threshold (2.3v maximum). when the input voltage is below the led led, full code i = i 255 ? where i led, full : the full-scale led current set by reg0x02 <3>. code : the 8bit brightness code reg0x04 <7:0> programmed by i 2 c interface. pwm brightness dimming besides programmable built-in i 2 c backlight led current control, the rt4532 features a built-in pwm dimming current control by setting reg0x02 <6> to 1, offering a linear current dimming by external clock source. in order to guarantee the pwm dimming resolution (7 bit at > 15khz application), recommending dimming frequency have to be operated at range of 400hz to 20khz. inductor selection the recommended inductor value for dual-channel 6 wleds applications is 10 h. when selecting the inductor, the inductor rated saturation current should be higher than the peak current at maximum load. small size and better efficiency are major concerns for portable devices. the inductor should have low core loss at 1.1mhz and low dcr for better efficiency. capacitor selection 10 f input ceramic capacitor and 1 f output ceramic capacitor are recommended for driving dual-channel 6 wleds applications. for better voltage filtering, ceramic capacitors with low esr are recommended. x5r and x7r types are suitable because of their wide voltage and temperature ranges. threshold, the device is shut down. if the input voltage rises by under-voltage lockout hysteresis (200mv typical), the ic restarts. linear brightness dimming the chip is built-in an i 2 c 8-bit resolution brightness control with maximum 20ma/40ma selection. reg0x02 <3> corresponds to full-scale led current control. reg0x04 <7:0> sets 8bits resolution brightness dimming control.
11 rt4532 ds4532-01 august 2015 www.richtek.com ? copyright 2015 richtek technology corporation. all rights reserved. is a registered trademark of ric htek technology corporation. 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 : p d(max) = (t j(max) ? t a ) / ja where t j(max) is the maximum junction temperature, t a is the ambient temperature, and ja 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, ja , is layout dependent. for wl-csp-10b 0.87x2.07 (bsc) package, the thermal resistance, ja , is 99.6 c/w on a standard jedec 51-7 four-layer thermal test board. the maximum power dissipation at t a = 25 c can be calculated by the following formula : p d(max) = (125 c ? 25 c) / (99.6 c/w) = 1w for wl-csp-10b 0.87x2.07 (bsc) package the maximum power dissipation depends on the operating ambient temperature for fixed t j(max) and thermal resistance, ja . the derating curve in figure 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. layout consideration as for all switching power supplies, the layout is an important step in the design, especially at high peak currents and switching frequencies. if the layout is not carefully done, the regulator might expose noise problems and duty cycle jitter. therefore, use wide and short traces for high current paths. the input capacitor should be placed as close as possible to the input pin for good input voltage filtering. the inductor should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits. the output capacitor needs to be placed directly from the vout pin to gnd rather than across the leds. this reduces the ripple current in the trace to the leds. when doing the pcb layout, the bold traces should be routed first, as well as placement of the inductor, and input and output capacitors. figure 1. derating curve of maximum power dissipation 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0 25 50 75 100 125 ambient temperature (c) maximum power dissipation (w) 1 four-layer pcb
12 rt4532 www.richtek.com ds4532-01 august 2015 richtek technology corporation 14f, no. 8, tai yuen 1 st 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 furnish ed 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 infringeme nts 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 r ichtek or its subsidiaries. outline dimension 10b wl-csp 0.87x2.07 package (bsc) min max min max. a 0.500 0.600 0.020 0.024 a1 0.170 0.230 0.007 0.009 b 0.240 0.300 0.009 0.012 d 2.020 2.120 0.080 0.083 d1 e 0.820 0.920 0.032 0.036 e1 e symbol dimensions in millimeters dimensions in inches 1.600 0.063 0.400 0.016 0.400 0.016

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