TECHNICAL NOTE System Power Supply for TV Series Built-in 1ch FET Light Load Type DC/DC converters BD8622EFV ●Description BD8622EFV has realized the high performance and reliability required as a power supply for thin-screen TV. Due to the high-speed load response, it is most suitable for TV-purpose processors with increasingly high performance, and due to the wide phase margin it leaves a good margin for board pattern & constant setting and so facilitates its application design. As a high-reliability design, it has various built-in protection circuits (overcurrent protection, output voltage abnormal protection, thermal protection, and off-latch function at the time of abnormality etc.), therefore as an advantage it does not easily damage in every possible abnormal condition such as all-pin short circuit test etc. and hence most suitable for thin-screen TV which requires the high reliability. ●Features 1) High efficiency in all load area 2) 3.0A output current 3) PWM mode/PFM mode switch(automatic operation) 4) Low current mode/Rorripplmord switch with terminal MODE 5) Low RDS(ON) internal switches：75mΩ(typ.) 6) ±1% reference voltage accuracy 7) Programmable frequency : 250kHz-1MHz （Can the adjustment by an external synchronization and the terminal RT resistance.） 8) Terminal RT OPEN/SHORT detecting function 9) Over current protection function 10) Output over voltage/low voltage protection function (over : FB > VREF +60mV , low : FB < VREF -60mV) 11) Timer off latch function in abnormal circumstances 12) Thermal shutdown function 13) Under voltage protection 14) Soft start/start delay circuit 15) Soft start time out function 16) Protecting BUS function with terminal PDET 17) HTSSOP-B20 package Jul. 2008 ● Electrical characteristic (Unless otherwise noted Ta=25℃, VIN=3.3V, GND=0V) Parameter VIN supply current (operating) VIN supply current (standby) Reference voltage (VREF) Output rise detection voltage Output decrease detection voltage Terminal PDET output current Oscillation frequency Pch FET ON resistance UVLO voltage SW leak current EN terminal H threshold voltage EN terminal L threshold voltage FC sink current FC source current SS/DELAY terminal source current Terminal PDET pull-up resistor Symbol IQ_active IQ_stby VREF VOVP VLVP IPDET fOSC RPFET VUVLO ILSW VENH VENL IFCSI IFCSO ISSSO RPDET Specification value MIN TYP MAX 0.792 30 -90 0.4 500 2.35 1.1 10 2 100 210 0 0.8 60 -60 550 75 2.50 0 20 -20 4 170 350 1 0.808 90 -30 600 110 2.65 1 0.4 -10 6 250 UNIT μA μA V mV mV mA kHz mΩ V μA V V μA μA μA kΩ Condition VFB = 0.83V, VFC = 1V VEN = 0V Monitoring FB terminal Monitoring FB terminal VPDET< 0.3V RRT= 220kΩ ISW = 1A VEN= 0V, VIN = 5.5V VFB :FB terminal voltage, VEN :EN terminal voltage, VFC :FC terminal voltage, VPDET: PDET terminal voltage Current capability should not exceed Pd. 2 / 15 ● Block Diagram OSC Err AMP Detect Abnormal Voltage and Start error Shut Down en enable PWM/PFM CONTROL SVIN Predrive 10 VIN Fig1 Block diagram ● Pin Description No. Symbol 1 Description Explanation SGND Signal GND terminal Small signal system GND 2 FB Feed back terminal Output voltage detection 3 PDET Abnormal state notification and external IC Protecting BUS communication terminal abnormality detection terminal 4 NC 5 SW 6 SW 7 SW 8 SW 9 NC 10 PGND 11 VIN 12 VIN 13 VIN 14 VIN 15 NC 16 EN 17 MODE 18 19 20 Switching output terminal Power GND terminal GND for power MOSFET Power supply input terminal Power supply input. The decoupling is done to PGND Enable input ON/OFF control for device operation The operation mode is switched according to the input voltage MODE selection terminal at a light load. The soft start time is adjusted with the connected capacitor SS/DELAY Soft start adjustment capacity connection terminal FC Error amplifier output Error amplifier phase compensation point RT Frequency adjustment resistance connection terminal The switching frequency is set by the connected resistance 3 / 15 ● Pin equivalence circuit diagram No. Symbol Explanation Terminal equivalent circuit diagram 1 SGND GND (connected 0V) 2 FB Output voltage detection terminal 3 PDET Protecting BUS I/O terminal 5,6,7,8 SW Output terminal 10 PGND Power GND (Same voltage as SGND) 11,12,13 PVIN Power supply input terminal 14 SVIN Power supply input terminal 4 / 15 No. Symbol Explanation 16 EN Enable terminal 17 MODE Operation mode switch terminal at light load Terminal equivalent circuit diagram 5 / 15 No. Symbol Explanation 18 SS /DELAY Soft start time adjustment terminal 19 FC Error amplifier compensation terminal 20 RT Oscillator frequency adjustment terminal Terminal equivalent circuit diagram 6 / 15 ● Operation description Enable control The device can be controlled ON/OFF by EN terminal (16 pin) voltage. An internal circuit starts when VEN reaches 1.1V. When standing up of VIN is too steep (1msec or less), a defective start might be caused according to the state of Pascon between GND substrate pattern and power supply-when the terminal EN is short-circuited to the terminal VIN and it is used. Fig.2 ON/OFF transition wave form in EN controlling 7 / 15 Soft start time set function As for BD8622EFV, output can do soft start without overshoot by charging soft start capacity (CSS) connected between SS and SGND terminal. Also, soft start time (tss) can be set by setting soft start capacity (CSS) arbitrarily. OSC oscillation frequency setting function The output oscillation frequency can be set by connecting resistance between terminal RT (20 pins) and SGND (range = 250kHz - 1MHz) The relation between RT terminal resistance and the oscillation frequency follows Fig.4. Frequency [kHz] スイッチング周波数 [kHz] 1000 10 10 100 1000 RT端子抵抗 [kΩ] RT terminal resistance [kΩ] Fig.4 RT resistance-oscillation frequency 8 / 15 10000 Light load mode operation ・Low current mode When the terminal MODE (17 pins) is made "H", low current mode operation becomes effective. The characteristic of the efficiency valuing is obtained in low current mode operation at a light load. VOUT [20mV/DIV] SW [2V/DIV] IL [200mA/DIV] Fig.5 Low current mode operation ・Low ripple mode When the terminal MODE is made "L", the Low ripple mode operation becomes effective. It becomes operation of valuing a low ripple in the Low ripple mode operation at a light load. VOUT [20mV/DIV] SW [2V/DIV] IL [200mA/DIV] Fig.6 Low ripplemord operation 100 90 80 Low current mode ローカレントモード 60 効率[%] Efficiency [%] 70 50 ローリップルモード Low ripple mord 40 VIN=3.3V VO=1.8V Io=0～100mA SW_f=550KHz(R11=220KΩ) 30 20 10 0 1 10 負荷電流[mA] Negative overcurrent [mA] Fig7 Light load mode efficiency comparison 9 / 15 100 ● Protection function Protection circuit is effective for destruction prevention due to accident so that avoid using under continuous protection operation. Low voltage protection function (LVP) The voltage of the terminal FB (2 pins) is compared with internal reference voltage VREF. If FB terminal voltage falls below VLVP(= VREF -60mV) and the state continues for 500us, output changes to low voltage and the state is fixed. In that case , PDET (3pin) output changes to L. Table 4-1 output low voltage protection function EN terminal >VENH <VENL SS terminal >1.4V(typ) <1.4V(typ) - FB terminal Low voltage protection function ＜VLVP ＞VLVP - Effective Invalidity Invalidity Low voltage protection operation ON OFF OFF OFF ＊ Low voltage protection function is available when SS terminal voltage becomes more than 1.4V (typ) in the transition to ON control (during soft start). Over voltage protection function(OVP) The voltage of the terminal FB is compared with internal reference voltage VREF. If FB terminal voltage is over Vovp (=VREF +60mV) and the state is continues for 500usec, output changes to low voltage and the state is fixed. Table 4-2 output overvoltage protection function EN terminal >VENH <VENL SS terminal >1.4V(typ) <1.4V(typ) - FB terminal Over voltage protection function ＞VOVP ＜VOVP - Effective Invalidity Invalidity Over voltage protection operation ON OFF OFF OFF ＊ Over voltage protection function is available when SS terminal voltage becomes more than 1.4V (typ) in the transition to ON control (during soft start). Fig.8 Output voltage error detection range 10 / 15 Under voltage lock out protection (UVLO) As for BD8622EFV, the power-supply voltage decrease detection protection circuit is built in. It the input voltage decrease below the UVLO voltage (2.5V typ), the device state changes to the standby mode (Moreover, to prevent the chattering of the output) hysteresis width of 100mV(typ) has been installed in the UVLO cancel voltage. RT terminal open/short protection function (RTO/RTS) RT terminal opening/short protection function prevent the clock from abnormal oscillation. If RT terminal open/short protection function is detected, output voltage changes to low level and is fixed. Terminal RT opening/short protection function is available if the state continue for 500usec, abnormal detection operates when the state continues about 500μsec(typ). Soft start time-out function If VSS doesn't exceed VSSTH within 64msec (typ) since a soft start began, BD8622EFV controls an off latch. Vo is fixed in a low level. Fig.9 Soft start time-out Thermal shut down function Thermal shut down circuit (TSD circuit) is built into BD8622EFV. When the temperature of the chip exceeds Tjmax=175, the DC/DC converter is fixed in a low voltage. TSD function is aimed to shut down IC from thermal reckless driving under an abnormal state to exceed Tjmax=175. It aims at neither protection nor the guarantee of the set. Therefore, please do not use this function to protect the set. Over current protection function The over current protection function has been achieved by limiting the current that flows on high side MOSFET. The current is controlled in every one cycle of the switching frequency. When an abnormal state continues for about 500μsec(typ), the output is fixed in a low level. 11 / 15 Protecting BUS function with terminal PDET The terminal PDET (3 pins) monitors whether IC is normal or not. When IC becomes abnormal, the PDET output is reduced at "L" level with the output voltage fixed “L” level at the same time. Moreover, it is possible to make the output fix in a low level by compulsorily reducing the terminal PDET at "L" level from the outside. When two or more BD8622EFV is used in the application, this function prevents the IC from destroying, because one IC error transmits all other ICs by PDET line in the condition that PDET terminals are connected each other. Fig.6 Protecting BUS communication ※Please give the terminal PDET as OPEN when you do not use protecting BUS function. Error detection (off latch) release method BD8622EFV enters the state of an off latch when the protection function operates. To release the off latch state, EN terminal voltage should be changed to low level once time. 12 / 15 ● Each characteristic reference data Vout : 100mV/div VIN = 5V Io = 3A Vout : 20mV/div Io = 1A/div 100usec/div 1usec/div Fig.11 Output load response Fig.12 Output ripple 100 90 VIN = 3.3V 80 VIN = 2V/div 70 EFFICIENCY [%] 60 VIN = 5.0V 50 VOUT = 0.5V/div 40 VOUT = 1.8V 30 fosc = 550kHz 20 LC mode SS = 2V/div 10 0 1 10 100 1000 10000 10msec/div LOAD CURRENT [mA] Fig.13 Efficiency Fig.14 Soft start 2.0 VIN = 5.0V OUTPUT VOLTAGE : Vo [V] 1.9 VOUT = 1.8V 1.8 1.7 1.6 1.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 LOAD CURRENT [A] Fig.15 Regulation 13 / 15 ERROR AMP REFERENCE VOLTAGE : VREF [V] 0.810 5.0 0.808 VIN = 3.3V VIN = 3.3V 4.8 SS CHARGE CURRENT : Iss [μA] 0.806 0.804 0.802 0.800 0.798 0.796 0.794 4.5 4.3 4.0 3.8 3.5 3.3 0.792 3.0 0.790 -25 0 25 50 75 100 125 -25 150 0 25 AMBIENT TEMPERATURE : Ta [℃] Reference voltage - Temperature characteristic Fig.16 75 100 125 150 Fig.17 SS Charging current - Temperature characteristic 600.0 600.0 590.0 590.0 Ta = 25℃ VIN = 3.3V 580.0 FREQUENCY : Fosc [kHz] 580.0 570.0 FREQUENCY : Fosc [kHz] 50 AMBIENT TEMPERATURE : Ta [℃] 560.0 550.0 540.0 530.0 570.0 560.0 550.0 540.0 530.0 520.0 520.0 510.0 510.0 500.0 500.0 2.5 3 3.5 4 4.5 5 -25 5.5 0 25 Fig.18 50 75 100 125 150 AMBIENT TEMPERATURE : Ta [℃ ] INPUT VOLTAGE : Vin [V] Fig.19 Switching frequency-power-supply voltage characteristic 100.0 Switching frequency-temperature characteristic 110.00 90.0 Ta = 25℃ VIN = 3.3V 100.00 ON‐RESISTANCE: Ron [mΩ] ON‐RESISTANCE: Ron [mΩ] 80.0 70.0 60.0 50.0 40.0 30.0 20.0 90.00 80.00 70.00 60.00 50.00 40.00 10.0 30.00 0.0 2.5 3 3.5 4 4.5 5 -25 5.5 0 25 Fig.20 PMOS on resistance-power-supply voltage 75 100 125 150 Fig.21 PMOS on resistance-temperature characteristic 400.0 1.00 VIN = 3.3V 0.90 350.0 0.80 Ta = 25℃ 300.0 CIRCUIT CURRENT: Icc [uA] EN VOLTAGE HIGH: VENH [V] 50 AMBIENT TEMPERATURE : Ta [℃ ] INPUT VOLTAGE : Vin [V] 0.70 0.60 0.50 0.40 0.30 0.20 250.0 200.0 150.0 VFB = 0.83V 100.0 VFC = 1.0V SW = H 50.0 0.10 0.0 0.00 -25 0 25 50 75 100 125 150 2.5 3 3.5 4 4.5 5 5.5 INPUT VOLTAGE : Vin [V] AMBIENT TEMPERATURE : Ta [℃ ] Fig.22 Terminal EN H voltage-temperature characteristic Fig.23 Circuit current-power-supply voltage characteristic 14 / 15 HTSSOP-B20 <Dimension> <Tape and Reel information> 6.5 ± 0.1 11 6.4 ± 0.2 4.4 ± 0.1 0.5 ± 0.15 1.0 ± 0.2 20 1 10 Embossed carrier tape Quantity 2500pcs Direction 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) of feed 0.17 +0.05 −0.03 S 0.08 S 1234 1234 1234 1pin 1234 （Unit:mm) 1234 Reel 1234 0.2 +0.05 −0.04 1234 0.65 1234 1.0Max. 0.85 ± 0.05 0.08 ± 0.05 0.325 Tape Direction of feed ※When you order , please order in times the amount of package quantity. Catalog No.08T274A '08.7 ROHM © Appendix Notes No technical content pages of this document may be reproduced in any form or transmitted by any means without prior permission of ROHM CO.,LTD. The contents described herein are subject to change without notice. The specifications for the product described in this document are for reference only. Upon actual use, therefore, please request that specifications to be separately delivered. Application circuit diagrams and circuit constants contained herein are shown as examples of standard use and operation. Please pay careful attention to the peripheral conditions when designing circuits and deciding upon circuit constants in the set. Any data, including, but not limited to application circuit diagrams information, described herein are intended only as illustrations of such devices and not as the specifications for such devices. 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Should you intend to use these products with equipment or devices which require an extremely high level of reliability and the malfunction of which would directly endanger human life (such as medical instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers and other safety devices), please be sure to consult with our sales representative in advance. It is our top priority to supply products with the utmost quality and reliability. However, there is always a chance of failure due to unexpected factors. Therefore, please take into account the derating characteristics and allow for sufficient safety features, such as extra margin, anti-flammability, and fail-safe measures when designing in order to prevent possible accidents that may result in bodily harm or fire caused by component failure. ROHM cannot be held responsible for any damages arising from the use of the products under conditions out of the range of the specifications or due to non-compliance with the NOTES specified in this catalog. Thank you for your accessing to ROHM product informations. More detail product informations and catalogs are available, please contact your nearest sales office. ROHM Customer Support System www.rohm.com Copyright © 2008 ROHM CO.,LTD. THE AMERICAS / EUROPE / ASIA / JAPAN Contact us : webmaster@ rohm.co. jp 21 Saiin Mizosaki-cho, Ukyo-ku, Kyoto 615-8585, Japan TEL : +81-75-311-2121 FAX : +81-75-315-0172 Appendix1-Rev2.0