TECHNICAL NOTE System Power Supply for TV Series Built-in 1ch FET Synchronous Rectification Type DC/DC converters BD8629FS ●Description BD8629FS has realized the high performance and reliability required as a power supply for thin-screen TV. With built-in FET 1ch current mode control, the DC/DC Converter series has the advantage of high-speed load response and wide phase margin. 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) 2.0A output current 3) Low RDS(ON) internal switches (PchMOS:170mΩ, NchMOS:130mΩ) 4) ±1% reference voltage accuracy 5) Programmable frequency : 250kHz-1MHz 6) Terminal RT OPEN/SHORT detecting function 7) Over current protection function 8) Output over voltage/low voltage protection function (over : FB > VREF +60mV , low : FB < VREF -60mV) 9) Timer off latch function in abnormal circumstances 10) Thermal shutdown function 11) Under voltage protection 12) Soft start/start delay circuit 13) Soft start time out function 14) SSOP-A16 package Aug. 2008 ● Electrical characteristic (Unless otherwise noted Ta=25℃, VIN=5.6V) Parameter Symbol 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 Nch FET ON resistance UVLO voltage SW leak current EN terminal H threshold voltage EN terminal L threshold voltage SS/DELAY terminal source current IQ_active IQ_stby VREF VOVP VLVP IPDET fOSC RPFET RNFET VUVLO ILSW VENH VENL ISSSO Specification value MIN TYP MAX 0.792 30 -90 1 500 3.8 2.0 2 1.3 350 0.8 60 -60 550 170 130 4.0 0 4 2.0 700 0.808 90 -30 600 240 200 4.2 1 0.5 6 UNIT mA μA V mV mV mA kHz mΩ mΩ V μA V V μA Condition VFB = 0.83V, VFC = 1V VEN = 0V Monitoring FB terminal Monitoring FB terminal VPDET< 0.5V ROSC = 220kΩ ISW = 1A ISW = -1A VEN= 0V, VIN = 6V VFB :FB terminal voltage, VEN :EN terminal voltage, VFC :FC terminal voltage, VPDET: PDET terminal voltage Current capability should not exceed Pd. Permissible loss ： PD [W] Permissible loss Fig. 1 heat decrease curve 2 / 11 ● Block Diagram Fig.2 Block diagram ● Pin description No. Description Symbol Explanation 1 SGND Signal GND terminal Small signal system GND 2 FB Feed back terminal Output voltage detection 3 PDET Off latch signal output Reset output 4 SW Output terminal Switching output 5 PGND 6 PGND Power GND terminal GND for power MOSFET 7 SW 8 SW Output terminal Power Mos output 9 VIN 10 VIN Power supply input terminal Power supply input. The decoupling is done to PGND Internal regulator Internal regulator Enable input ON/OFF control for device operation 11 VIN 12 REG 13 EN 14 The soft start time is adjusted with the connected capacitor SS/DELAY Soft start adjustment capacity connection terminal 15 FC Error amplifier output Error amplifier phase compensation point 16 RT Frequency adjustment resistance connection terminal The switching frequency is set by the connected resistance 3 / 11 ●Pin equivalence circuit diagram No. Symbol Explanation Terminal equivalent circuit diagram 1 SGND GND (connected 0V) 2 FB Output voltage detection terminal 3 PDET Off latch signal output terminal 4,7,8 SW Output terminal 5,6 PGND Power GND (Same voltage as SGND) 9,10,11 VIN Power supply input terminal 4 / 11 No. Symbol Explanation 12 REG Internal regulator output terminal 13 EN Enable terminal Terminal equivalent circuit diagram 5 / 11 No. Symbol Explanation 14 SS Soft start time adjustment terminal 15 FC Error amplifier compensation terminal 16 RT Oscillator frequency adjustment terminal Terminal equivalent circuit diagram 6 / 11 ● Operation description Enable control The device can be controlled ON/OFF by EN terminal (13 pin) voltage. An internal circuit starts when VEN reaches 1.4V. Fig. 3 ON/OFF transition wave form in EN controlling Soft start time set function As for BD8629FS, 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. 7 / 11 OSC oscillation frequency setting function The output oscillation frequency can be set by connecting resistance between terminal RT (16 pins) and SGND (range = 250kHz - 1MHz) The relation between RT terminal resistance and the oscillation frequency follows Fig.3. ス イッ チ ン グ 周 波 数 [k H z ] Frequency [kHz] 10000 1000 100 10 10 100 1000 RT 端resistance 子 抵 抗 [k Ω ][kΩ] RT terminal Fig. 4 RT resistance-oscillation frequency 8 / 11 10000 ● 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 >VIHEN SS terminal <VLVP >VLVP - >1.4V(typ) <1.4V(typ) - <VILEN Low voltage protection function FB terminal 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 >VIHEN <VILEN SS terminal Over voltage protection function FB terminal >VOVP <VOVP - >1.4V(typ) <1.4V(typ) - 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). VFB VREF＋60ｍV FB terminal voltage VREF VREF-60ｍV 0 ON Protection 500[us] 500[us] OVP LVP OFF PDET terminal HIGH LOW Fig. 5 Output voltage error detection range 9 / 11 Under voltage lock out protection (UVLO) As for BD8629FS, the power-supply voltage decrease detection protection circuit is built in. It the input voltage decrease below the UVLO voltage (4.0V typ), the device state changes to the standby mode (Moreover, to prevent the chattering of the output) hysteresis width of 300mV(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 always effective after the power supply start-up. 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, BD8629FS controls an off latch. Vo is fixed in a low level. Fig. 6 Soft start time-out Error detection (off latch) release method BD8629FS 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. Thermal shut down function Thermal shut down circuit (TSD circuit) is built into BD8629FS. 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. 10 / 11 SSOP-A16 <Dimension> <Tape and Reel information> 1 8 2500pcs Direction of feed 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) 0.15±0.1 0.1 1234 1234 1234 1234 1pin Reel （Unit:mm) 1234 1234 0.36±0.1 1234 0.8 0.3Min. 9 Embossed carrier tape Quantity 1234 6.2±0.3 1.5±0.1 4.4±0.2 0.11 6.6±0.2 16 Tape Direction of feed ※When you order , please order in times the amount of package quantity. 11 / 11 Catalog No.08T271A '08.8 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. ROHM CO.,LTD. disclaims any warranty that any use of such devices shall be free from infringement of any third party's intellectual property rights or other proprietary rights, and further, assumes no liability of whatsoever nature in the event of any such infringement, or arising from or connected with or related to the use of such devices. Upon the sale of any such devices, other than for buyer's right to use such devices itself, resell or otherwise dispose of the same, no express or implied right or license to practice or commercially exploit any intellectual property rights or other proprietary rights owned or controlled by ROHM CO., LTD. is granted to any such buyer. Products listed in this document are no antiradiation design. The products listed in this document are designed to be used with ordinary electronic equipment or devices (such as audio visual equipment, office-automation equipment, communications devices, electrical appliances and electronic toys). 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