Datasheet Boost 1channel white LED driver For large LCDs BD9488F ●General Description BD9488F is a high efficiency driver for white LEDs and designed for large LCDs. This IC is built-in a boost DCDC converters that employ an array of LEDs as the light source. BD9488F has some protect function against fault conditions, such as the over-voltage protection (OVP), the over current limit protection of DCDC (OCP), LED over current protection (LEDOCP), the open detection of LED string. Therefore BD9488F is available for the fail-safe design over a wide range output voltage. ●Key Specifications Input voltage range: 9.0V to 18.0V DCDC oscillation frequency: 150kHz (RT=100kΩ) Active current consumption: 1.2mA(Typ.) Operating temperature range: -40℃ to +85℃ ●Package(s) SOP18 ●Features Current mode DCDC converter Vout discharge circuit as shutdown LED protection circuit (OPEN protection, LED OCP protection) LED protect detection as small PWM dimming signal Over-voltage protection (OVP) for the output voltage. Adjustable soft start time constant The wide range of analog dimming 0.2V-3.5V The built-in transformation circuit from pulse to DC 2 PWM dimming signal The UVLO detection for the input voltage of the power stage FAIL logic output Figure 1. W(Typ.) x D(Typ.) x H(Max.) 11.20mm x 7.80mm x 2.01mm Pin pitch 1.27mm SOP18 ●Applications TV, PC display and other LCD backlight system. ●Typical Application Circuit(s) VCC VIN VCC UVLO OVP TC54 STB GATE RT CS Css SS FAILB DIMOUT PWM1 PWM2 ISENSE ADIM_P FB ADIM GND Figure 2. Typical application circuit ○Product structure：Silicon monolithic integrated circuit .www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・14・001 ○This product is not designed protection against radioactive rays 1/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●Absolute Maximum Ratings (Ta=25℃) Symbol Ratings Unit Vccmax 20 V STB VCC V OVP, UVLO, SS, RT, ISENSE, FB, CS, TC54 7 V Parameter Input voltage STB pin voltage OVP, UVLO, SS, RT, ISENSE, FB, CS, TC54 pin voltage PWM1, PWM2, FAILB, ADIM, ADIM_P pin voltage DIMOUT, GATE pin voltage PWM1, PWM2, FAILB, ADIM, ADIM_P DIMOUT, GATE 20 V VCC V Pd 687 (*1) mW Topr -40 to +85 ℃ Tjmax 150 ℃ Tstg -55 to +150 ℃ Symbol Range Unit VCC 9.0 to 18.0 V Power Dissipation Operating Temperature Range Junction Temperature Storage Temperature Range *1 Pd derated at 5.5 mW/℃ for temperature above Ta=25℃, mounted on 70mm×70mm×1.6mm 1 layer glass-epoxy PCB. ●Operation range Parameter VCC Power source voltage DC/DC oscillation frequency fsw 50 to 800 kHz The effective range of ADIM signal VADIM 0.2 to 3.5 V PWM input frequency range FPWM 90 to 100k Hz ●Pin Configuration ●Package dimension, marking diagram OVP 1 18 TC54 UVLO 2 17 CS SS 3 16 FB RT 4 15 ISENSE PWM1 5 14 VCC PWM2 6 13 STB FAILB 7 12 GATE ADIM 8 11 DIMOUT ADIM_P 9 10 GND BD9488F Lot No. Figure 3-1. Pin configuration www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 Figure 3-2. Package dimension 2/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●1.1 Electrical character (Unless otherwise specified Ta=25℃，VCC=12V) Limit Parameter Symbol 【Total current consumption】 Min. Typ. Max. Unit Condition Circuit current Icc － 1.2 1.8 mA VSTB=3V, PWM1=PWM2=0V Standby current IST － 0 3 μA VSTB=0V VCC=SWEEP UP 【UVLO block】 Operation voltage（VCC） VUVLO_VCC 6.5 7.5 8.5 V Hysteresis Voltage（VCC） VUHYS_VCC 150 300 600 mV UVLO release voltage VUVLO 2.88 3.00 3.12 V UVLO hysteresis voltage VUHYS 250 300 350 mV VUVLO=SWEEP DOWN UVLO_LK -2 0 2 μA VUVLO=4V ISENSE threshold voltage 1 VLED1 1.47 1.50 1.53 V VADIM=1.5V ISENSE threshold voltage 2 VLED2 3.33 3.50 3.67 V VADIM=5.0V (as mask analog dimming) ISENSE threshold voltage 3 VLED3 -2 - +2 % VADIM=0.7V Oscillation frequency GATE pin MAX DUTY output GATE pin ON resistance (as source) GATE pin ON resistance (as sink) FCT 142.5 150 157. 5 KHz RT=100kohm NMAX_DUTY 90 95 99 % RT=100kohm RONSO 3.0 6.0 12.0 Ω ION=-10mA RONSI 1.2 2.5 5.0 Ω ION=10mA VRT 1.0 1.5 2.0 V RT=100kohm SS pin source current ISSSO -4.20 -3.0 -2.14 μA SS pin Low output voltage VSS_L - 0.20 0.50 V VSTB=0V, Ioss=50uA VSS_END 2.7 3.0 3.3 V FB source current IFBSO -140 -100 -60 μA FB sink current IFBSI 60 100 140 μA SS=SWEEP UP VISENSE=0.2V, VFB=1.0V VISENSE=2.0V, VFB=1.0V OCP detect voltage VCS 360 400 440 mV CS=SWEEP UP UVLO pin leak current VCC=SWEEP DOWN VUVLO=SWEEP UP 【DC/DC block】 RT pin voltage Soft start ended voltage VSS=2V VADIM=1.0V, VADIM=1.0V, 【DC/DC protection block】 OVP detect voltage OVP detect hysteresis OVP pin leak current VOVP 2.88 3.00 3.12 V VOVP_HYS 50 100 150 mV VOVP SWEEP DOWN OVP_LK -2 0 2 μA VOVP=4V www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 3/38 VOVP SWEEP UP TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●1.2 Electrical character (Unless otherwise specified Ta=25℃，VCC=12V) Limit Parameter 【LED protection block】 Symbol Min. Typ. Max. Unit LED OCP detect voltage VLEDOCP 3.8 4.0 4.2 V VISENSE=SWEEP UP VOPEN 0.05 0.10 0.15 V VISENSE=SWEEP DOWN ADIM_PH 2.0 - 3.8 V ADIM_PL -0.3 - 0.8 V ADIM_PPU 4.2 - 18 V RADIM_P 130 200 300 kΩ VADIM_P=3.0V ADIMH 3.201 3.30 3.399 V ADIM_P=3.3V ADIM_P=0.0V LED OPEN detect voltage 【Analog dimming block】 ADIM_P pin HIGH voltage ADIM_P pin LOW voltage ADIM_P pin input mask voltage ADIM_P pin pull-down resistance ADIM pin output voltage H Condition ADIM pin output voltage L ADIM pin output resistance ADIML - 0.0 0.05 V ADIMR 6.6 10 15 kΩ ADIM pin leak current ILADIM -2 0 2 μA VADIM=4V, ADIM_P=5.0V -2 0 2 μA VISENSE=4V 6.0 12.0 24.0 Ω ION=-10mA 1.7 3.5 7.0 Ω ION=10mA IO=0mA ISENSE pin leak current IL_ISENSE 【Dimming signal output block】 DIMOUT source on-resistance RONSO DIMOUT sink on-resistance RONSI 【TC54 block】 TC54 output voltage VTC54 5.2 5.4 5.6 V TC54 available current TC54_UVLO detect voltage |ITC54| 100 - - μA TC54_TH 2.232 2.4 2.568 V VSTB=H, TC54=SWEEP DOWN TC54_UVLO hysteresis TC54_HYS 50 100 200 mV VSTB=H->L, TC54=SWEEP UP TC54 discharge current 【STB block】 TC54_DIS 5 10 15 μA VSTB=H->L, TC54=4V STB pin HIGH voltage STBH 2.2 - 19 V VSTB=SWEEP UP STB pin LOW voltage STBL -0.3 - 0.8 V VSTB=SWEEP DOWN STB pin input current 【PWM block】 ISTB 2.0 3.0 4.5 μA VSTB=3.0V PWMｘ pin HIGH Voltage PWM_H PWMｘ pin LOW Voltage PWM_L PWMｘ pin Pull Down resistance RPWM 【FAIL block (OPEN DRAIN)】 2.0 - 18 V VPWMｘ=SWEEP UP -0.3 - 0.8 V VPWMｘ=SWEEP DOWN 130 200 300 kΩ VPWMｘ=3.0V FAILB pin on-resistance RFAIL 0.75 1.5 3.0 kΩ VFAIL=1.0V FAILB pin leak current ILFAIL -2 0 2 μA VFAIL=15V www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 4/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●1.3 Pin number, pin name, pin function No. name IN/OUT function rating[V] 1 OVP In Over voltage protection detection pin -0.3 to 7 2 UVLO In Under voltage lock out detection pin -0.3 to 7 3 SS Out Slow start setting pin -0.3 to 7 4 RT Out For DC/DC switching frequency setting pin 5 PWM1 In External PWM dimming signal input pin1 -0.3 to 20 6 PWM2 In External PWM dimming signal input pin2 -0.3 to 20 7 FAILB Out Abnormality detection output pin -0.3 to 20 8 ADIM In/Out ADIM signal input-output pin -0.3 to 20 9 ADIM_P In ADIM pulse signal input pin -0.3 to 20 10 GND - - 11 DIMOUT Out Dimming signal pin for driving MOSFET -0.3 to VCC 12 GATE Out DC/DC switching output pin -0.3 to VCC 13 STB In IC On/OFF pin -0.3 to VCC -0.3 to 7 14 VCC - Power supply pin 15 ISENSE In Current detection input pin -0.3 to 7 16 FB In/Out Error amplifier output pin -0.3 to 7 DC/DC output current detect pin, OCP input pin -0.3 to 7 5.4V output pin, shutdown timer pin -0.3 to 7 17 CS In 18 TC54 Out www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 -0.3 to 20 5/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●2.1.1 Pin ESD Type OVP UVLO SS Internal vol. 50k Internal vol. OVP SS 5V RT PWM1, PWM2 FAILB ADIM ADIM_P DIMOUT GATE STB ISENSE Internal vol. 10k ISENSE 5V Figure 4-1. Internal equivalent circuit www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 6/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●2.1.2 Pin ESD Type FB CS TC54 Internal vol. Internal vol. 1k TC54 FB Figure 4-2. Internal equivalent circuit ●2.2 Block diagram VCC VIN VCC UVLO OVP TC54 VCC UVLO VREG STB UVLO OVP TSD REG54 UVLO VCC OSC + RT PWM COMP GATE CONTROL LOGIC CS LEB Current sense Css SS SS VCC DIMOUT SS-FB clamper LEDOCP Fail detect ERROR amp PWM1 + + - OPEN FAILB ISENSE 3.5V FB PWM2 4.0V ADIM_P 1.5V + - 3.3V + 10kΩ ADIM GND Package:SOP18 Figure 5. Block diagram www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 7/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 2.0 10000 1.5 1000 frequency [kHz] ICC[mA] ●2.3 Typical performance Curves 1.0 0.5 0.0 100 10 1 7 9 11 13 15 17 10 100 RT[kΩ] Figure 7. GATE frequency vs RT 120 0 100 -20 FB source current[uA] FB sink current [uA] VCC[V] Figure 6. Operating current (ICC) vs VCC 80 60 40 20 0 0.5 1.5 2.5 3.5 -40 -60 -80 -100 -120 4.5 0.5 FB[V] 1.5 2.5 3.5 4.5 FB[V] Figure 9. FB source current vs FB voltage Figure 8. FB sink current vs FB voltage ISENSE feedback voltage [V] 1000 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 2 4 6 ADIM[V] Figure 10. ISENSE feedback voltage vs ADIM www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 8/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●2.4 Pin function description ○Pin1: OVP The OVP terminal is the input for over-voltage protection of output voltage. As OVP is more than 3.0V, the over-voltage protection (OVP) will work. At the moment of this detection, the BD9488 stops the switching of the output GATE and starts to count up the abnormal interval, but IC doesn't reach latch off state instantaneously until the detection continues up to the number of counts of GATE terminals, which depend on the kind of abnormality. (Please refer to the time chart in the section 3.5.7) The OVP pin is high impedance, because the internal resistance to a certain bias is not connected. So, the bias by the external components is required, even if OVP function is not used, because the open connection of this pin is not fixed the potential. The setting examples is separately described in the section 3.4.6, ”external components selection, how to set OVP” ○Pin2: UVLO Under voltage lock out pin for the input voltage of the power stage. More than 3.0V(typ.), IC starts the boost operation and stops lower than 2.7V(typ.). The UVLO pin is high impedance, because the internal resistance to a certain bias is not connected. So, the bias by the external components is required, even if UVLO function is not used, because the open connection of this pin is not fixed the potential. The setting examples is separately described in the section 3.4.5, ”external components selection, how to set UVLO” ○Pin3: SS The pin which sets soft start interval of DC/DC converter. It performs the constant current charge of 3.0 μA to external capacitance Css(OPEN to 4.7μF). The switching duty of GATE output will be limited during 0V to 3.0V of the SS voltage. So the equality of the soft start interval can be expressed as following 6 Css: the external capacitance of the SS pin. Tss = 1.0*10 *Css Regarding of the logic of SS=L (SS=L) = (PWM1andPWM2 have not asserted H since ResetB=L->H) or (latch off state) where ResetB = (STB=H) and (VCCUVLO=H) and (UVLO=H) and (TC54UVLO=H) As the capacitor of SS pin is smaller than about 1nF, it is necessary to notice if the inrush current I(Vin) as turning-on is too large, and if the masking interval of OPEN detection is too short. Please refer to the time chart on soft start behavior in the section 3.7.4 ○Pin4: RT DC/DC switching frequency setting pin. RT set the oscillation frequency inside IC. ○The relationship between the frequency and RT resistance value (ideal) R RT 15000 f SW [ kHz ] [ k ] The oscillation setting range from 50kHz to 800kHz. The setting examples is separately described in the section 3.4.4, ”external components selection, how to set DCDC oscillation frequency” ○Pin5, Pin6: PWM1, PWM2 The ON / OFF terminal of the LED driver. LED lights when both PWM signal are high (DIMOUT = H). The Duty signal of this pin can control the PWM dimming. The high / low level of PWM pins are following. State PWM input voltage PWM1=H or PWM2=H PWM=2.0V to 18.0V PWM1=L or PWM2=L PWM=‐0.3V to 0.8V PWM1 and PWM2 have the functional difference, and GATE pin outputs only by the logic of PWM1. This is why only boost operation continues while PWM1=H, PWM2=L. In this case, the adequate confirmation is required not to be over voltage of the output voltage Vout. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 9/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F Figure 11. PWM pin function ○Pin7: FAILB FAIL signal output pin (open drain). As abnormal, the internal NMOS turn on. Status FAILB output Normal OPEN Abnormal GND Level ○Pin8: ADIM ADIM_P input level -0.3V<ADIM_P<3.8V 4.2V <ADIM_P<18V ADIM_P pin function Pulse signal input for analog dimming ADIM_P pin function is masked. Required signal to IC DC output signal for analog dimming DC input signal for analog dimming 3.3V 0.8V/2.0V Analog dimming pulse signal ADIM pin function DUTY signal for analog dimming DC signal for analog dimming 3.3V ADIM_P 200k R1=10kohm Analog dimming DC signal C1 LED current signal 0.2V ADIM ISENSE DUTY of ADIM_P [%] 0% 6% 100% Figure 12. Analog dimming function and character Above functions enable BD9488 use both of the duty and DC signal for analog dimming. ○When the duty signal is used, that input to the pin ADIM_P with the amplitude about 3.3V. The input duty of ADIM_P needs to be larger than 6% so that the output ADIM is larger than 0.2V. In the case of the normal feedback with analog dimming, The ADIM pin voltage is equal to the ISENSE pin voltage. Therefore, please be careful that the lower ADIM voltage than 0.1V causes the OPEN abnormal detection. BD9488 ADIM PULSE ADIM_P ADIM ADIM DC BD9488 ○When the DC signal is used, ADIM_P will be pulled up more than 4.2V, and the signal input to the pin ADIM. ADIM_P In the driver module with more than two BD9488, and the analog dimming is performed by ADIM the duty signal, the architecture will be shown in the right figure. That can reduce the LED current error between the channels, because the common circuit of the pulse DC transform is used. Figure 13. the analog dimming The pulse DC transform circuit outputs DC signal to the ADIM pin with the time constant circuit as two BD9488 are used. of R1, C1 in the above diagram. More C1 value, the ripple components of the ADIM pin is decreased, on the other hand, the transient response is delayed. And please keep in mind the error voltage if the pull down resistor of ADIM pin will be connected. ○Pin9: ADIM_P The pulse signal input pin for analog dimming. Please pull up the voltage level more than 4.2V(typ.), when DC signal is www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 10/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F used for the analog dimming. In normal operation, please set the input voltage under 18.0V. For more details, please refer to <ADIM> pin descriptions. The input frequency of this pin assumed from 2kHz to 100kHz. Please keep in mind that the capacitor of ADIM pin is small considering of this input frequency, the error of LED current can be cause. ○Pin10: GND GND pin of IC. ○Pin11: DIMOUT This is the output pin for external NMOS of dimming. The below table shows the rough output logic of each operation state, and the output H level is VCC. Please refer to the time chart in the section 3.7 for detail explanations, because The DIMOUT logic has the exceptional behavior. Please insert the resistance between the dimming MOS gate to improve the over shoot of LED current, as PWM turns from low to high. Status DIMOUT output Normal PWM1 and PWM2 Abnormal GND Level ○Pin12: GATE This is the output terminal for driving the gate of the boost MOSFET. The high level is VCC of IC. Frequency can be set by the resistor connected to RT. Please refer to the <RT> pin description for the frequency setting. ○Pin13: STB ON/OFF setting terminal for IC, which can be used to perform a reset at shutdown. Please reset this pin after latch off. Regarding of the sequence of turning on, if the input logic STB turns from low to high, the internal power supply is activated. After the positive edge of PWM is input , BD9488 starts the boost operation. ○ The input voltage of STB pin toggles the IC state(IC ON/OFF). Please avoid the use of the intermediate level (from 0.8V to 2.2V). Regarding of the power down sequence, while STB=L and TC54UVLO=H, in order to discharge the output voltage, DIMOUT logic can assert high, depending on the PWM logic. This discharge behavior is separately described in the time chart in the section 3.7.3, or in the section 3.4.2, ”how to shutdown and set TC54 capacitance” ○Pin14: VCC Power supply pin of IC. Input range is from 9V to 18.0V. The operation starts more than 7.5 V(TYP.) and shuts down less than 7.2 V(TYP.). ○Pin15: ISENSE This is the input terminal for the current detection. The error amplifier compares the lower voltage the analog dimming pin ADIM and 3.5V. The abnormal voltage of this pin activates the protection function of LED, such as LEDOCP, OPEN. [LED OPEN Protection Function] If OPEN state (ISENSE<0.1V) continues during 4 clocks interval of GATE terminal, BD9488 starts to count the interval of the abnormal state. If the abnormal condition continues by the completion of counting, BD9488 will be latched off. (Please refer to the time chart in the section 3.7.6.) Exceptionally the OPEN protect detection are masked in the following conditions, CASE1. When PWM = L. ISENSE is less than 0.1V even in normally, because DIMOUT = L. CASE2. In the soft-start interval. ISENSE is less than 0.1V, because of the insufficient output voltage Vout. DIMOUT Error AMP + + - [LED OCP Protection Function] More than ISENSE = 4.0V (typ.), the over current of LED (LEDOCP) will be detected. If that states continues 130k clock of GATE pin, IC will latch off. (Please refer to the time chart in the section 3.7.7.) Vout ISENSE 3.5V ADIM FB Figure 14. ISENSE pin circuit ○Pin16: FB This is the output terminal of error amplifier. Monitoring the ISENSE terminal voltage, this pin outputs the error signal with the analog dimming signal (pin ADIM) or 3.5V. After the completion of the SS, this pin outputs high impedance as the logic “PWM1 and PWM2” asserts low. FB voltage is hold to the external capacitance. (For more detail on the compensation setting is described in the section " 3.6 loop compensation".) www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 11/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F VIN ○Pin17: CS The CS pin has two functions. 9488 1. DC / DC current mode Feedback terminal The inductor current is converted to the CS pin voltage by the sense resistor RCS and this CS pin voltage controls the output voltage by compared with the error amp output. 2. Inductor current limit (OCP) terminal Id GATE The CS terminal also has a over current protection (OCP), if it voltage is more than 0.4V, the switching operation will be stopped compulsorily. CS Both of above functions are enable after 300ns (typ.) when GATE pin asserts Cs Rcs high, because the leading Edge Blanking function is included into this IC to prevent the affect noise. Please refer to the section 3.5.1 “DCDC parts selection GND / how to set OCP”, for detail explanation. If the capacitance Cs in the right figure is increased to a micro orders, please be Figure 15. CS pin circuit careful that the limited value of NMOS drain current Id is much than the simple calculation. Because the current Id flow not only Rcs but also Cs, as the CS pin voltage move according to Id. ○Pin18: TC54 This is the 5.4V (TYP.) output pin that is used for internal power supply. Available current is 100uA. TC54 can be used as a timer for the discharge of output capacitance DCDC. For detailed instructions, please refer the section 3.4.2 “how to shutdown and set TC54 capacitance” www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 12/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.1 Application circuit example The bellows are example circuits of using BD9488F. ・The basic application circuit example VCC VIN VCC UVLO OVP TC54 STB GATE RT CS Css SS FAILB DIMOUT PWM1 PWM2 ISENSE ADIM_P FB ADIM GND Figure 16. The basic application circuit example ・As for the dimming signal, the single PWM and the DC for analog dimming VCC VIN VCC UVLO OVP TC54 STB GATE RT CS Css SS FAILB PWM DIMOUT PWM1 PWM2 ISENSE ADIM_P FB Adim (DC) ADIM GND PWM1 pin and PWM2 pin are shorted. Figure 17. the circuit example with single PWM (1) www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 Figure 18. the circuit example with single PWM (2) 13/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ・Only analog dimming VCC VIN VCC UVLO OVP TC54 STB GATE RT CS Css SS FAILB DIMOUT PWM1 PWM2 ISENSE ADIM_P FB Adim (DC) ADIM GND Figure 19. the circuit example of analog dimming only ・Application example when use numerous IC The application circuit of analog dimming by external duty signal. Figure 20. the circuit example of when plural IC is used. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 14/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.2 The detection condition list of the protection (TYP. Condition) Detect condition Protection Detection pin PWM1 and pin condition SS PWM2 Release condition ISENSE > 0.1V ISENSE < 4.0V Timer operation Protection type 130k count Latch off 130k count Latch off LED OPEN ISENSE ISENSE < 0.1V H(4count) SS>3.0V LED OCP ISENSE ISENSE > 4.0V - - UVLO UVLO UVLO<2.7V - - UVLO>3.0V NO Auto recovery TC54 UVLO TC54 TC54<2.4V - - TC54>2.5V NO Auto recovery VCC UVLO VCC VCC<7.2V - - VCC>7.5V NO Auto recovery OVP OVP OVP>3.0V - - OVP<2.9V 4 count Latch off OCP CS CS>0.4V - - - NO Pulse by Pulse To reset the latch type protection, please input of STB logic to ‘L’ once. Otherwise the detection of VCCUVLO, TC54UVLO is required. The count number in the table suggests the oscillation frequency of DCDC converter. ●3.3 The behavior list of the protection The operation of the protection Dimming transistor Soft Start (DIMOUT) logic Protect Function DC/DC Gate output LED OPEN Stops after latch L after latch LED OCP Stops immediately STB Stops immediately FAILB pin discharge after latch L after latch H immediately, L after latch discharge after latch L after latch L if TC54<2.4V discharge immediately OPEN UVLO Stops immediately immediately L discharge immediately immediately L TC54 UVLO Stops immediately immediately L discharge immediately immediately L VCC UVLO Stops immediately immediately L discharge immediately immediately L OVP Stops immediately immediately L discharge after latch L after latch OCP Stops immediately Normal operation Not discharge OPEN Please refer to the timing chart in the section 3.7 for the detail. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 15/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4 External components selection ●3.4.1 The start up operation and the setting of Soft Start external capacitance The below explanations are the start up sequency of BD9488. ① STB FB SS SLOPE OSC 3uA 5V SS SLOPE VOUT Q D PWM SS COMP Css GATE DRIVER OSC ILED SS=FB Circuit PWM LED_OK ② VOUT ILED LED_OK DIMOUT FB PWM=L :STOP GATE ③ ISENSE PWM ④ ⑤ ⑥ Figure 21. the turn-on waveform Figure 22. the turn-on circuit ○The explanation of start up sequency ①When STB is H, the internal bias voltage of TC54 rising. ②With the first PWM=H, BD9488 enables output the boost pulse, and the SS start to charge to the external capacitance. At this moment, the voltage of FB will be the same as SS voltage internally regardless of the PWM logic. ③The FB=SS voltage reach the bottom voltage of saw-toothed wave and the DC/DC start to output the pulse signal. Therefore the boost of VOUT is started. ④VOUT is boosted to fixed level, and the LED current is rising. ⑤When the LED current reached to fixed level, FB is removed from SS internally. The start up operation completed. ⑥IC start the normal operation by sensing the voltage of ISENSE pin. When SS is more than 3.0V, even if the LED current does not flows, the clamped circuit of SS and FB is off, and the protect detection of OPEN starts. ○The setting method of SS external capacitance As above desribed, DC/DC stops when the PWM1=L. It means the boost operation only enabled within PWM1=H duration and SS time will be extented while boost with samll PWM duty. Also the SS time is affected by the output capacitance, the LED current and application conditions. Tss is defined as the time for the SS voltage to reach to the FB feedback voltage. Please set the Tss longer than Trise_min, which is the start up time of the minimum PWM duty. When the FB voltage during LED turns on is expressed VFB, the equality on Tss is the following. Tss Css [ F ] VFB[V ] 3[A] [Sec] So please set the external capacitance to meet the Tss>>Trise_min. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 16/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4.2 how to shutdown and set TC54 capacitance This IC is equipped the discharge function when shutdown is operated. Figure 23. the shutdown waveform and circuit ○Explanation of shutdown sequence ①When STB=L, DC/DC and TC54 are stop. ②When STB=L, TC54UVLO=H, the DIMOUT logic asserts the PWM logic. The voltage of TC54 (5.4V) will decrease by the constant current -10uA and is discharged to 2.4V. ③VOUT will be discharged and ILED decresing. ④When the voltage of TC54 pin is under 2.4V(typ.), the IC will shutdown. ○The setting method of TC54 external capacitance Please use below formula to calculate the shutdown time TOFF. TOFF CREG[ F ] 3.0 [V ] [Sec] 10 [A] As shown the above, the PWM signal is required even after STB=L. The discharge interval of VOUT is the longest in the minimum PWM duty. Please set the Creg value with a enough timing margin from the end of the VOUT discharge to shutdown. ●3.4.3 The LED current setting LED current can be adjusted by setting the resistance RISENSE which connects to ISENSE pin. ○the relationship between RISET and ILED current RISENSE ADIM [V ] [ ] I LED [ A] RISENSE 3.5[V ] [ ] I LED [ A] Without DC dimming Error AMP [setting example] If ILED current is 400mA as ADIM is 1.5V, we can calculate RISENSE as below. RISENSE DIMOUT + + - With DC dimming Vout ISENSE 3.5V ADIM RISENSE FB ADIM [V ] 1.5[V ] 3.75[] I LED [ A] 0.4[ A] Figure 24. the example of LED current setting www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 17/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4.4. how to set DCDC oscillation frequency RRT which connects to RT pin set the oscillation frequency of DCDC. ○ the relationship between OSC and RRT (ideal) R RT 15000 f SW [ kHz ] [ k ] where fsw is the oscillation frequency of DCDC [kHz] Frequency (fsw) Ideal GATE RT CS Rcs RRT GND Figure 25. RT pin setting example This equation is an ideal equation in which correction factors are not applied. The adequate verification with an actual set needs to be performed to set frequency precisely. [setting example] If DCDC oscillation frequency is 200kHz, we can calculate the RRT as below. RRT 15000 15000 75 [ k] f sw [ kHz ] 200[ kHz ] www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 18/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4.5. how to set UVLO Under voltage lock out pin for the input voltage of the power stage. More than 3.0V(typ.), IC starts boost operation and stops lower than 2.7V(typ.). The UVLO pin is high impedance, because the internal resistance to a certain bias is not connected. So, the bias by the external components is required, even if UVLO function is not used, because the open connection of this pin is not fixed the potential. The resistor value can be calculated by the below formula, if the VIN voltage is monitored, and that is divided by the resistor R1, R2 like the below diagram. ○UVLO detection equality If VIN decreases, R1, R2 value is expressed the following formula by the VINdet, the detect voltage of UVLO. R1 R 2[k] (VINDET [V ] 2.7[V ]) 2.7[V ] [k] ○UVLO release equality By using the R1, R2 in the above equality, the release voltage of UVLO can be expressed as following. VINCAN 3.0V ON/ OFF UVLO + - 2.7V/3.0V R1 R2 CUVLO ( R1[k] R2[k]) [V ] R2[k] [setting example] If the normal input voltage, VIN is 24V, the detect voltage of UVLO is 18V, R2 is 30k ohm, R1 is calculated as following. R1 R 2[k] VIN Figure 26. UVLO setting example (VINDET [V ] 2.7[V ]) (18[V ] 2.7[V ]) 170.0 [k] 30[k] 2.7[V ] 2.7[V ] By using these R1, R2, the release voltage of UVLO, VINcan can be calculated as following. VINCAN 3.0[V ] (R1[k] R 2[k]) 170.0[k] 30[k] 3.0[V ] [V ] 20.0 [V ] R 2[k] 30[k] www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 19/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4.6. how to set OVP The OVP terminal is the input for over-voltage protection of output voltage. The OVP pin is high impedance, because the internal resistance to a certain bias is not connected. So, the bias by the external components is required, even if OVP function is not used, because the open connection of this pin is not fixed the potential. The resistor value can be calculated by the below formula, if the OVP VOUT voltage is monitored, and that is divided by the resistor R1, OVP + R2 like the below diagram. - 2.9V/3.0V ○OVP detection equality If the VOUT is boosted abnormally, VOVPdet is the detect voltage of OVP, R1, R2 can be expressed by the following formula. R1 R2[k] VOUT R1 R2 COVP (VOVPDET [V ] 3.0[V ]) [k] 3.0[V ] ○OVP release equality By using the R1, R2 in the above equality, the release voltage of OVP, VOVPcan can be expressed as following. VOVPCAN 2.9V Figure 27. OVP setting example ( R1[k] R2[k]) [V ] R2[k] [setting example] If the normal output voltage, VOUT is 40V, the detect voltage of OVP is 48V, R2 is 10k ohm, R1 is calculated as following. R1 R2[k] (VOVPDET [V ] 3.0[V ]) (48[V ] 3[V ]) 10[k] 150 [k] 3.0[V ] 3[V ] By using these R1, R2, the release voltage of OVP, VOVPcan can be calculated as following. VOVPCAN 2.9[V ] 10[k] 150[k] ( R1[k] R2[k]) 2.9[V ] [V ] 46.4 [V ] 10[k] R2[k] www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 20/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.4.7. how to set the interval until latch off BD9488 built in the counter by latch off time, that is performed by counting the oscillation clock which is set by the RT pin. Since the common oscillation circuit is used for counting, the interval until latch off is corresponding to the 130k clock, which the GATE pulse output continuously. Please refer the time chart of the operation from the detect abnormality to the latch off in the section 3.7. ○latch off time BD9488 starts the counting up from the detection of each abnormal state, falls to the latch off state when the following interval has passed. Only PWM=L input does not reset the timer counter, if the abnormal state continues. LATCHTIME 217 RRT [] R [k] 130k RT 7 [sec] 10 1.5 10 1.5 10 Where LATCHTIME is the interval until latch off state RRT is the connected resistor of RT pin. [setting example] If the resistor of RT pin is 100k ohm, the timer latch interval is as following. LATCHTIME 130k www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 RRT [k] 100[k] 130 k 866[m sec] 1.5 107 1.5 107 21/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.5. DCDC parts selection 3.5.1. how to set OCP / the calculation method for the current rating of DCDC parts BD9488 stops the switching by the OCP detect, when the CS pin voltage is more than 0.4V. The resistor value of CS pin, RCS need to be considered by the coil L current. And the current rating of DCDC external parts is required more than the peak current of the coil. It is shown below that the calculation method of the coil peak current, the selection method of Rcs (the resistor value of CS pin) and the current rating of the external DCDC parts. I IN L VIN VOUT IL IOUT (the calculation method of the coil peak current, Ipeak) At first, since the ripple voltage at CS pin depend on the application condition of DCDC, those put onto the equality to calculate as following. The output voltage = VOUT [V] LED total current = IOUT [A] The DCDC input voltage of the power stage = VIN [V] The efficiency of DCDC =η[%] And then, the averaged input current IIN is calculated by the following equality fsw VOUT [V ] I OUT [ A] [ A] VIN [V ] [%] GATE CS Rcs And the ripple current of the inductor L (ΔIL[A]) can be calculated by using DCDC the switching frequency, fsw, as following. Δ IL GND (VOUT [V ] V IN [V ]) V IN [V ] [ A] L[ H ] VOUT [V ] f SW [ Hz ] (V) Ipeak I IN [ A] IL[ A] 2 [ A] … (1) N[V] On the other hand, the peak current of the inductor Ipeak can be expressed as the following equality. Therefore, the bottom of the ripple current Imin is IL[ A] Im in I IN [ A] 2 （A) (t) or 0 Ipeak VCS peak Rcs Ipeak (t) （V) 0.4V VCS[V] (the selection method of Rcs) Ipeak flows into Rcs and that cause the voltage signal to CS pin. (Please refer the right timing chart) That peak voltage VCSpeak is as following. Imin IL[A] As Imin>0, that operation mode is CCM (Continuous Current Mode), otherwise another mode is DCM (Discontinuous Current Mode). ΔIL IIN [V ] VCSpeak As this VCSpeak reaches to 0.4V, the DCDC output stops the switching. Therefore, Rcs value is necessary to meet the under condition. (t) Rcs Ipeak [V ] 0.4[V ] Figure 28. Coil current waveform (the current rating of the external DCDC parts) The peak current as the CS voltage reaches to OCP level (0.4V) is defined as Ipeak_det. I peak _ det 0.4[V ] [ A] Rcs[ ] … (2) The relation among Ipeak (equality (1)), Ipeak_det (equality (2)) and the current rating of parts is required to meet the following I peak I peak _ det The current rating of parts Please make the selection of the external parts to meet the above condition such as FET, Inductor, diode. [setting example] The output voltage = VOUT [V] = 40V LED total current = IOUT [A] = 0.48V The DCDC input voltage of the power stage = VIN [V] = 24V www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 22/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F The efficiency of DCDC =η[%] = 90% The averaged input current IIN is calculated as the following. I IN [ A] VOUT [V ] I OUT [ A] 40[V ] 0.48[ A] 0.89 [ A] 24[V ] 90[%] VIN [V ] [%] And the ripple current of the inductor L (ΔIL[A]) can be calculated if the switching frequency, fsw = 200kHz, the inductor, L=100μH. Δ IL (VOUT [V ] V IN [V ]) V IN [V ] ( 40[V ] 24[V ]) 24[V ] 0.48 [ A] L[ H ] VOUT [V ] f SW [ Hz ] 100 10 6 [ H ] 40[V ] 200 10 3 [ Hz ] Therefore the inductor peak current, Ipeak is Ipeak I IN [ A] IL[ A] 0.48[ A] [ A] 0.89[ A] 1.13 [ A] 2 2 The calculation result of the peak current If Rcs is assume to be 0.3 ohm VCS peak Rcs Ipeak 0.3[ ] 1.13[ A] 0.339 [V ] 0.4V The Rcs value confirmation The above condition is met. And Ipeak_det, the current OCP works is I peak _ det 0.4[V ] 1.33 [ A] 0.3[ ] If the current rating of the used parts is 2A, I peak I peak _ det The current rating 1.13[ A] 1.33[ A] 2.0[ A] The current rating confirmation of DCDC parts This inequality meets the above relationship. The parts selection is proper. And Imin, the bottom of the IL ripple current can be calculated as following. I MIN I IN [ A] IL[ A] [ A] 1.13[ A] 0.48[ A] 0.65[ A] 0 2 This inequality implies the operation is the continuous current mode. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 23/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.5.2. Inductor selection The inductor value affects the input ripple current. The equality in the section 3.5.1 is as following. Δ IL ΔIL I IN VIN (VOUT [V ] V IN [V ]) V IN [V ] [ A] L[ H ] VOUT [V ] f SW [ Hz ] VOUT [V ] I OUT [ A] [ A] VIN [V ] [%] Ipeak I IN [ A] IL L VOUT IL[ A] 2 [ A] Where L: the coil inductance [H] Vout: the DCDC output voltage [V] Vin: the input voltage [V] Iout: the output load current (the summation of LED current) [A] Iin: the input current [A] Fsw: the oscillation frequency [Hz] If in the continuous current mode, Please set ⊿IL to 30% - 50% of the output load current. RCS COUT Figure 29. the waveform and the circuit of inductor current * The current exceeding the rated current value of inductor flown through the coil causes magnetic saturation, results in decreasing in efficiency. Inductor needs to be selected to have such adequate margin that peak current does not exceed the rated current value of the inductor. * To reduce inductor loss and improve efficiency, inductor with low resistance components (DCR, ACR) needs to be selected 3.5.3. Output capacitance Cout selection Output capacitor needs to be selected in consideration of equivalent series VIN resistance required to even the stable area of output voltage or ripple voltage. Be aware that set LED current may not be flown due to decrease in LED IL terminal voltage if output ripple componet is high. Output ripple voltage ⊿VOUT is determined by Equation (4): L VOUT ΔVOUT ILMAX R ESR 1 C OUT I OUT 1 f SW [V ] ・・・・・ (4) where, RESR is the equivalent series resistance of Cout. RESR RCS COUT Figure 30. the circuit of the output capacitor * Rating of capacitor needs to be selected to have adequate margin against output voltage. * To use an electrolytic capacitor, adequate margin against allowable current is also necessary. Be aware that the LED current is larger than the set value transitionally in case that LED is provided with PWM dimming especially. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 24/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.5.4. MOSFET selection Though there is no problem if the absolute maximum rating is larger than the rated current of the inductor L, or is larger than the sum of the tolerance voltage of COUT and the rectifying diode VF. The product with small gate capacitance (injected charge) needs to be selected to achieve high-speed switching. * One with over current protection setting or higher is recommended. * The selection of one with small on resistance results in high efficiency. 3.5.5. Rectifying diode selection A schottky barrier diode which has current ability higher than the rated current of L, the reverse voltage larger than the tolerance voltage of COUT, and the low forward voltage VF especially needs to be selected. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 25/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.6. Loop compensation A current mode DCDC converter has each one pole (phase lag) fp due to CR filter composed of the output capacitor and the output resistance (= LED current) and zero (phase lead) fZ by the output capacitor and the ESR of the capacitor. Moreover, a step-up DCDC converter has RHP zero (right-half plane zero point) fZRHP which is unique with the boost converter. This zero may cause the unstable feedback. To avoid this by RHP zero, the loop compensation that the cross-over frequency fc set as following, is suggested. fc = fZRHP /5 (fZRHP: RHP zero frequency) Considering the response speed, the below calculated constant is not always optimized completely. It needs to be adequately verified with an actual device. VOUT VIN ILED L VOUT - FB gm RESR + RCS RFB1 COUT CFB2 CFB1 Figure 31. the circuit of output stage and the error amplifier i. Calculate the pole frequency fp and the RHP zero frequency fZRHP of DC/DC converter fp I LED [ Hz ] 2 VOUT COUT f ZRHP Where ILED = the summation of LED current, ii. f RHZP RCS I LED [] 5 f p gm VOUT (1 D) Where iii. (Continuous Current Mode) VOUT VIN output (fc = fZRHP/5) VOUT D Calculate the phase compensation of the error amp R FB1 VOUT (1 D) 2 [ Hz ] 2 L I LED C FB1 1 [F ] 2 RFB1 f p gm 4.0 10 4 [ S ] Calculate zero to compensate ESR (RESR) of COUT (electrolytic capacitor) C FB 2 RESR C OUT [F ] RFB1 *When a ceramic capacitor (with RESR of the order of milliohm) is used to COUT, the operation is stabilized by insertion of CFB2. To improve the transient response, RFB1 need to be increase, CFB1 need to be decrease. It needs to be adequately verified with an actual device in consideration of vary from parts to parts since phase margin is decreased. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 26/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●3.7. Timing chart 3.7.1 starting up 1 (STB inputs and PWM signal succeeds) 7.5V VCC STB PWM1 andPWM2 2.4V 2.5V 2.5V TC54 V5UVLO 3.0V 1.1V SS 1.1V GATE FAILB OFF SS STANDBY Normal OFF SS (Reset) (*1) (*2) (*3) (*4) STANDBY (*5) (*1)…TC54 starts up if STB turns from L to H. The pin SS is not charged in the state that the PWM signal is not input, the boost is not started. (*2)…The charge of the pin SS starts by the positive edge of PWM=L to H, and the soft start starts. The GATE pulse outputs only during PWM=H. And as the SS is less than 1.1V, the pulse does not output. The pin SS continues charging in spite of the assertion of PWM and OVP. (*3)…The soft start interval will end if the voltage of the pin SS, Vss reaches to 3.0V. By this time, BD9488 boost Vout where the set LED current flows. It is started to monitor the abnormal detection of OPEN. (*4)…As STB=L, instantaneously the boost operation is stopped. (GATE=L, SS=L) On the other hand, the discharge circuit works in the interval “STB=L and V5UVLO=H”. Please refer to the time chart in the section 3.7.3 for details. (*5)…As STB=H again, the boost operation restarts by the next PWM=L to H. It is the same operation as the timing of (*1). Please refer to the section 3.4.1 for the setting of soft start external capacitance. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 27/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.2 starting up 2 (PWM signal inputs and STB succeeds) VCC 7.5V STB PWM1 andPWM2 2.4V 2.5V TC54 2.5V V5UVLO 3.0V 1.1V SS 1.1V GATE FAILB OFF SS ON OFF SS (Reset) (*1) (*2) (*3) (*4) STANDBY (*5) (*1)…TC54 starts up if STB turns from L to H. (*2)…At the moment the release of V5UVLO (the UVLO of the pin TC54), or the time of the positive edge of PWM=L to H, the soft start starts. The GATE pulse outputs only during PWM1=H. And as the SS is less than 1.1V, the pulse does not output. The pin SS continues charging in spite of the assertion of PWM and OVP. (*3)…The soft start interval will end if the voltage of the pin SS, Vss reaches to 3.0V. By this time, BD9488 boost Vout where the set LED current flows. It is started to monitor the abnormal detection of OPEN. (*4)…As STB=L, instantaneously the boost operation is stopped. (GATE=L, SS=L) On the other hand, the discharge circuit works in the interval “STB=L and V5UVLO=H”. Please refer to the time chart in the section 3.7.3 for details. (*5)…As STB=H again, it is the same operation as the timing of (*1). www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 28/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.3 turn off STB PWM1 andPWM2 TC54 2.4V V5UVLO DIMOUT GATE Vout SS ON Dischange (*1) OFF (*2) (*1)…As STB pin turns High to Low, BD9488F stops the boost operation, starts the discharge of TC54. (*2)…During STB=L and V5UVLO=H, the DIMOUT asserts the same logic of PWM. TC54=5.4V is discharged until 2.4V by the constant current 10uA. And IC turns off. Vout need to be discharged adequately so that LED does not turns on drastically at the next start up. For detailed instructions, please refer the section 3.4.2 “how to shutdown and set TC54 capacitance” www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 29/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.4 the soft start function (*1)…The SS pin charge does not start by just STB=H. “PWM1=H and PWM2=H” is required to start the soft start. In the low SS voltage, the GATE pin duty is depend on the SS voltage. And as the SS is less than 1.1V, the pulse does not output. (*2)…By the low STB=L, the SS pin is discharged immediately. (*3)…As the STB recovered to STB=H, The SS charge starts immediately by the logic “PWM1 and PWM2=H” in this chart. (*4)…The SS pin is discharged immediately by the UVLO=L. (*5)…The SS pin is discharged immediately by the VCCUVLO=L (*6)…The SS pin is discharged immediately by the TC54UVLO=L (*7)…The SS pin is not discharged by the abnormal detection of the latch off type such as OVP until the latch off www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 30/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.5 the OVP detection (*1)…As OVP is detected, the output GATE=L, DIMOUT=L, and the CP counter starts (*2)…If OVP is released within 4 clock of CP counter of the GATE pin frequency, the boost operation restarts. (*3)…As the OVP is detected again, the boost operation is stopped. (*4)…As the OVP detection continues up to 4 count by the CP counter, IC will be latched off. (*5)…As the latched off, the boost operation doesn't restart even if OVP is released. (*6)…The STB=L input can make IC reset. In this chart, DIMOUT asserts high by the discharge function in the paragraph 3.7.3. (*7)…It normally starts as STB turns L to H. (*8)…The operation of the OVP detection is not related to the logic of PWM. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 31/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.6 LED OPEN detection (*1)…During starting up, even if the normality, ISENSE<0.1V because of the low Vout. Therefore the OPEN detection will be masked for the soft start period. (*2)…In the same way, as PWM=L, ISENSE<0.1V because of DIMOUT=L. OPEN will be masked, too. (*3)…Though the OPEN is detected if ISENSE<0.1V as the PWM=H, it is not judged immediately to abnormal state. The behavior of GATE, FAILB keeps the normal operation. (*4)…The CP counter will start if the OPEN detection continues 4 clock of the GATE frequency. The count stops if ISENSE>0.1V. (*5)…When the OPEN detection continues up to 130k count with the CP counter, IC will be latched off. At this time, it asserts GATE=L, DIMOUT=L, FAILB=L for the first time. (*6)…The latch off state can be reset by the STB=L. (*7)…It normally starts by STB=L to H, in this figure. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 32/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.7 LED OCP detection (*1)…If ISENSE>4.0V, LEDOCP is detected, it becomes GATE=L. To detect LEDOCP continuously, The DIMOUT is compulsorily high, regardless of the PWM dimming signal. (*2)…When the LEDOCP releases within the GATE frequency 130k counts of the CP counter, the boost operation restarts. (*3) …As the LEDOCP is detected again, the boost operation is stopped, too. (*4)…If the LEDOCP detection continues up to 130k count with the CP counter, IC will be latched off. (*5)…Once IC is latched off, the boost operation doesn't restart even if the LEDOCP releases. (*6)…The latch off state can be reset by the STB=L. In this chart, DIMOUT asserts high by the discharge function in the paragraph 3.7.3. (*7)…It normally starts by STB=L to H. (*8)…The operation of the LEDOCP detection is not related to the logic of the PWM. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 33/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F 3.7.8 the spontaneous detection OVP and OPEN. STB 3.0V 3.0V OVP 2.9V 0.1V INSENSE 0.1V SS 4count END START 4count END CP COUNTOR START 0.1V 1.1V GATE DIMOUT FAILB STATE NORMAL COUNTOR OFF Latch off NORMAL COUNTOR Latch off （Reset） (*1) (*2) (*3) (*4) (*5) (*1)…The time chart shows the OPEN detects faster and does not reach to the latch off state. The DIMOUT asserts high. (*2)…If OPEN and OVP is detected spontaneously, OVP has the priority, and GATE=L, DIMOUT=L. (*3)…IC will be latched off by the OVP factor. (*4)…The latch off state is reset by the STB=L. (*5)…The OVP has the priority too, in the case the OVP is detected first and the OPEN succeeds. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 34/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F Operational Notes 1. Reverse Connection of Power Supply Connecting the power supply in reverse polarity can damage the IC. Take precautions against reverse polarity when connecting the power supply, such as mounting an external diode between the power supply and the IC’s power supply pins. 2. Power Supply Lines Design the PCB layout pattern to provide low impedance supply lines. Separate the ground and supply lines of the digital and analog blocks to prevent noise in the ground and supply lines of the digital block from affecting the analog block. Furthermore, connect a capacitor to ground at all power supply pins. Consider the effect of temperature and aging on the capacitance value when using electrolytic capacitors. 3. Ground Voltage Ensure that no pins are at a voltage below that of the ground pin at any time, even during transient condition. 4. Ground Wiring Pattern When using both small-signal and large-current ground traces, the two ground traces should be routed separately but connected to a single ground at the reference point of the application board to avoid fluctuations in the small-signal ground caused by large currents. Also ensure that the ground traces of external components do not cause variations on the ground voltage. The ground lines must be as short and thick as possible to reduce line impedance. 5. Thermal Consideration Should by any chance the power dissipation rating be exceeded the rise in temperature of the chip may result in deterioration of the properties of the chip. The absolute maximum rating of the Pd stated in this specification is when the IC is mounted on a 70mm x 70mm x 1.6mm glass epoxy board. In case of exceeding this absolute maximum rating, increase the board size and copper area to prevent exceeding the Pd rating. 6. Recommended Operating Conditions These conditions represent a range within which the expected characteristics of the IC can be approximately obtained. The electrical characteristics are guaranteed under the conditions of each parameter. 7. Inrush Current When power is first supplied to the IC, it is possible that the internal logic may be unstable and inrush current may flow instantaneously due to the internal powering sequence and delays, especially if the IC has more than one power supply. Therefore, give special consideration to power coupling capacitance, power wiring, width of ground wiring, and routing of connections. 8. Operation Under Strong Electromagnetic Field Operating the IC in the presence of a strong electromagnetic field may cause the IC to malfunction. 9. Testing on Application Boards When testing the IC on an application board, connecting a capacitor directly to a low-impedance output pin may subject the IC to stress. Always discharge capacitors completely after each process or step. The IC’s power supply should always be turned off completely before connecting or removing it from the test setup during the inspection process. To prevent damage from static discharge, ground the IC during assembly and use similar precautions during transport and storage. 10. Inter-pin Short and Mounting Errors Ensure that the direction and position are correct when mounting the IC on the PCB. Incorrect mounting may result in damaging the IC. Avoid nearby pins being shorted to each other especially to ground, power supply and output pin. Inter-pin shorts could be due to many reasons such as metal particles, water droplets (in very humid environment) and unintentional solder bridge deposited in between pins during assembly to name a few. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 35/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F Operational Notes – continued 11. Unused Input Pins Input pins of an IC are often connected to the gate of a MOS transistor. The gate has extremely high impedance and extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it. The small charge acquired in this way is enough to produce a significant effect on the conduction through the transistor and cause unexpected operation of the IC. So unless otherwise specified, unused input pins should be connected to the power supply or ground line. 12. Regarding the Input Pin of the IC This monolithic IC contains P+ isolation and P substrate layers between adjacent elements in order to keep them isolated. P-N junctions are formed at the intersection of the P layers with the N layers of other elements, creating a parasitic diode or transistor. For example (refer to figure below): When GND > Pin A and GND > Pin B, the P-N junction operates as a parasitic diode. When GND > Pin B, the P-N junction operates as a parasitic transistor. Parasitic diodes inevitably occur in the structure of the IC. The operation of parasitic diodes can result in mutual interference among circuits, operational faults, or physical damage. Therefore, conditions that cause these diodes to operate, such as applying a voltage lower than the GND voltage to an input pin (and thus to the P substrate) should be avoided. Figure xx. Example of monolithic IC structure 13. Ceramic Capacitor When using a ceramic capacitor, determine the dielectric constant considering the change of capacitance with temperature and the decrease in nominal capacitance due to DC bias and others. 14. Area of Safe Operation (ASO) Operate the IC such that the output voltage, output current, and power dissipation are all within the Area of Safe Operation (ASO). 15. Thermal Shutdown Circuit(TSD) This IC has a built-in thermal shutdown circuit that prevents heat damage to the IC. Normal operation should always be within the IC’s power dissipation rating. If however the rating is exceeded for a continued period, the junction temperature (Tj) will rise which will activate the TSD circuit that will turn OFF all output pins. When the Tj falls below the TSD threshold, the circuits are automatically restored to normal operation. Note that the TSD circuit operates in a situation that exceeds the absolute maximum ratings and therefore, under no circumstances, should the TSD circuit be used in a set design or for any purpose other than protecting the IC from heat damage. 16. Over Current Protection Circuit (OCP) This IC incorporates an integrated overcurrent protection circuit that is activated when the load is shorted. This protection circuit is effective in preventing damage due to sudden and unexpected incidents. However, the IC should not be used in applications characterized by continuous operation or transitioning of the protection circuit. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 36/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F ●Ordering Information B D 9 4 8 8 F Part Number XX Package F:SOP18 Packaging and forming specification XX: Please confirm the formal name to our sales. ●Physical Dimension Tape and Reel Information SOP18 <Tape and Reel information> 11.2 ± 0.2 (MAX 11.55 include BURR) 10 1 Tape Embossed carrier tape Quantity 2000pcs Direction of feed 0.3MIN 7.8±0.3 5.4±0.2 18 E2 The direction is the 1pin of product is at the upper left when you hold ( reel on the left hand and you pull out the tape on the right hand ) 9 0.11 1.8±0.1 0.15 ± 0.1 0.1 1.27 0.4 ± 0.1 1pin Reel (Unit : mm) Direction of feed ∗ Order quantity needs to be multiple of the minimum quantity. ●Marking Diagram (TOP VIEW) SOP18(TOP VIEW) Part Number Marking B D 9 4 8 8 F LOT Number 1PIN MARK www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 37/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet BD9488F Revision History Date Revision 11.Jul.2012 001 29.Dec.2013 002 27. May 2014 003 Changes New Release p.2 The rating of STB pin is changed from 20V to VCC. p.5 The rating of STB pin is changed from 20V to VCC. p.6 In the equivalent circuit of STB pin, the Diode of VCC side is added. p.9,20 In OVP explanation, “over-voltage protection and short circuit protection” is changed to “over-voltage protection”. www.rohm.com © 2012 ROHM Co., Ltd. All rights reserved. TSZ22111・15・001 38/38 TSZ02201-0F1F0C100040-1-2 27.May 2014 Rev.003 Datasheet Notice Precaution on using ROHM Products 1. Our Products are designed and manufactured for application in ordinary electronic equipments (such as AV equipment, OA equipment, telecommunication equipment, home electronic appliances, amusement equipment, etc.). If you (Note 1) , transport intend to use our Products in devices requiring extremely high reliability (such as medical equipment equipment, traffic equipment, aircraft/spacecraft, nuclear power controllers, fuel controllers, car equipment including car accessories, safety devices, etc.) and whose malfunction or failure may cause loss of human life, bodily injury or serious damage to property (“Specific Applications”), please consult with the ROHM sales representative in advance. Unless otherwise agreed in writing by ROHM in advance, ROHM shall not be in any way responsible or liable for any damages, expenses or losses incurred by you or third parties arising from the use of any ROHM’s Products for Specific Applications. (Note1) Medical Equipment Classification of the Specific Applications JAPAN USA EU CHINA CLASSⅢ CLASSⅡb CLASSⅢ CLASSⅢ CLASSⅣ CLASSⅢ 2. ROHM designs and manufactures its Products subject to strict quality control system. However, semiconductor products can fail or malfunction at a certain rate. Please be sure to implement, at your own responsibilities, adequate safety measures including but not limited to fail-safe design against the physical injury, damage to any property, which a failure or malfunction of our Products may cause. The following are examples of safety measures: [a] Installation of protection circuits or other protective devices to improve system safety [b] Installation of redundant circuits to reduce the impact of single or multiple circuit failure 3. Our Products are designed and manufactured for use under standard conditions and not under any special or extraordinary environments or conditions, as exemplified below. Accordingly, ROHM shall not be in any way responsible or liable for any damages, expenses or losses arising from the use of any ROHM’s Products under any special or extraordinary environments or conditions. If you intend to use our Products under any special or extraordinary environments or conditions (as exemplified below), your independent verification and confirmation of product performance, reliability, etc, prior to use, must be necessary: [a] Use of our Products in any types of liquid, including water, oils, chemicals, and organic solvents [b] Use of our Products outdoors or in places where the Products are exposed to direct sunlight or dust [c] Use of our Products in places where the Products are exposed to sea wind or corrosive gases, including Cl2, H2S, NH3, SO2, and NO2 [d] Use of our Products in places where the Products are exposed to static electricity or electromagnetic waves [e] Use of our Products in proximity to heat-producing components, plastic cords, or other flammable items [f] Sealing or coating our Products with resin or other coating materials [g] Use of our Products without cleaning residue of flux (even if you use no-clean type fluxes, cleaning residue of flux is recommended); or Washing our Products by using water or water-soluble cleaning agents for cleaning residue after soldering [h] Use of the Products in places subject to dew condensation 4. The Products are not subject to radiation-proof design. 5. Please verify and confirm characteristics of the final or mounted products in using the Products. 6. In particular, if a transient load (a large amount of load applied in a short period of time, such as pulse. is applied, confirmation of performance characteristics after on-board mounting is strongly recommended. Avoid applying power exceeding normal rated power; exceeding the power rating under steady-state loading condition may negatively affect product performance and reliability. 7. De-rate Power Dissipation (Pd) depending on Ambient temperature (Ta). When used in sealed area, confirm the actual ambient temperature. 8. Confirm that operation temperature is within the specified range described in the product specification. 9. ROHM shall not be in any way responsible or liable for failure induced under deviant condition from what is defined in this document. Precaution for Mounting / Circuit board design 1. When a highly active halogenous (chlorine, bromine, etc.) flux is used, the residue of flux may negatively affect product performance and reliability. 2. In principle, the reflow soldering method must be used; if flow soldering method is preferred, please consult with the ROHM representative in advance. For details, please refer to ROHM Mounting specification Notice – GE © 2013 ROHM Co., Ltd. All rights reserved. Rev.002 Datasheet Precautions Regarding Application Examples and External Circuits 1. If change is made to the constant of an external circuit, please allow a sufficient margin considering variations of the characteristics of the Products and external components, including transient characteristics, as well as static characteristics. 2. You agree that application notes, reference designs, and associated data and information contained in this document are presented only as guidance for Products use. Therefore, in case you use such information, you are solely responsible for it and you must exercise your own independent verification and judgment in the use of such information contained in this document. ROHM shall not be in any way responsible or liable for any damages, expenses or losses incurred by you or third parties arising from the use of such information. Precaution for Electrostatic This Product is electrostatic sensitive product, which may be damaged due to electrostatic discharge. Please take proper caution in your manufacturing process and storage so that voltage exceeding the Products maximum rating will not be applied to Products. Please take special care under dry condition (e.g. Grounding of human body / equipment / solder iron, isolation from charged objects, setting of Ionizer, friction prevention and temperature / humidity control). Precaution for Storage / Transportation 1. Product performance and soldered connections may deteriorate if the Products are stored in the places where: [a] the Products are exposed to sea winds or corrosive gases, including Cl2, H2S, NH3, SO2, and NO2 [b] the temperature or humidity exceeds those recommended by ROHM [c] the Products are exposed to direct sunshine or condensation [d] the Products are exposed to high Electrostatic 2. Even under ROHM recommended storage condition, solderability of products out of recommended storage time period may be degraded. It is strongly recommended to confirm solderability before using Products of which storage time is exceeding the recommended storage time period. 3. Store / transport cartons in the correct direction, which is indicated on a carton with a symbol. Otherwise bent leads may occur due to excessive stress applied when dropping of a carton. 4. Use Products within the specified time after opening a humidity barrier bag. Baking is required before using Products of which storage time is exceeding the recommended storage time period. Precaution for Product Label QR code printed on ROHM Products label is for ROHM’s internal use only. Precaution for Disposition When disposing Products please dispose them properly using an authorized industry waste company. Precaution for Foreign Exchange and Foreign Trade act Since our Products might fall under controlled goods prescribed by the applicable foreign exchange and foreign trade act, please consult with ROHM representative in case of export. Precaution Regarding Intellectual Property Rights 1. All information and data including but not limited to application example contained in this document is for reference only. ROHM does not warrant that foregoing information or data will not infringe any intellectual property rights or any other rights of any third party regarding such information or data. ROHM shall not be in any way responsible or liable for infringement of any intellectual property rights or other damages arising from use of such information or data.: 2. No license, expressly or implied, is granted hereby under any intellectual property rights or other rights of ROHM or any third parties with respect to the information contained in this document. Other Precaution 1. This document may not be reprinted or reproduced, in whole or in part, without prior written consent of ROHM. 2. The Products may not be disassembled, converted, modified, reproduced or otherwise changed without prior written consent of ROHM. 3. In no event shall you use in any way whatsoever the Products and the related technical information contained in the Products or this document for any military purposes, including but not limited to, the development of mass-destruction weapons. 4. The proper names of companies or products described in this document are trademarks or registered trademarks of ROHM, its affiliated companies or third parties. Notice – GE © 2013 ROHM Co., Ltd. All rights reserved. Rev.002 Datasheet General Precaution 1. Before you use our Pro ducts, you are requested to care fully read this document and fully understand its contents. ROHM shall n ot be in an y way responsible or liabl e for fa ilure, malfunction or acci dent arising from the use of a ny ROHM’s Products against warning, caution or note contained in this document. 2. All information contained in this docume nt is current as of the issuing date and subj ect to change without any prior notice. Before purchasing or using ROHM’s Products, please confirm the la test information with a ROHM sale s representative. 3. The information contained in this doc ument is provi ded on an “as is” basis and ROHM does not warrant that all information contained in this document is accurate an d/or error-free. ROHM shall not be in an y way responsible or liable for an y damages, expenses or losses incurred b y you or third parties resulting from inaccur acy or errors of or concerning such information. Notice – WE © 2014 ROHM Co., Ltd. All rights reserved. Rev.001 Datasheet BD9488F - Web Page Buy Distribution Inventory Part Number Package Unit Quantity Minimum Package Quantity Packing Type Constitution Materials List RoHS BD9488F SOP18 2000 2000 Taping inquiry Yes