1/4 STRUCTURE PRODUCT NAME ： ： Silicon Monolithic Integrated Circuit Synchronous rectification with built-in FET type DC/DC converter IC MODEL NAME ： BD8643FV FEATURES ： ・Synchronous rectification with built-in FET type DC/DC converter ・Output current 3A ・Reference voltage accuracy FB 0.8V±1% ・Switching frequency 100kHz～600kHz ・Over current protection circuit ・Thermal shutdown ・Input low voltage detection UVLO ・Soft start / Start delay circuit ・Programmable OFFLATCH time ◎ABSOLUTE MAXIMUM RATING Parameter Input supply voltage BOOT terminal voltage EN terminal voltage Input terminal voltage SW terminal voltage Output switch current Power dissipation Operating temperature Storage temperature （Ta=25℃） Symbol VIN VBOOT VEN VINP*1 VSW IOUT Pd Topr Tstg Limits 20 28 GND-0.3 ～ VIN+0.3 GND-0.3 ～ 7 GND-0.3 ～ VIN+0.3 3.5*2 2.06*3 -20 ～ 85 -55 ～ 150 Unit V V V V V A Ｗ ℃ ℃ 150 ℃ Maximum Junction Tjmax Temperature ＊1 VINP Application terminal： SS/DELAY, FB, FC, RT, PSET ＊2 Do not however exceed Pd. ＊3 （70mm×70mm, thickness 1.6mm, and four layer glass epoxy substrates）When mounting substrate and the package back exposure part are connected with solder. Operating at higher than Ta=25℃, 9.5mW shall be reduced per 1 ◎Operation condition Parameter Input supply voltage Output switch current Symbol VIN IOUT MIN 4.5 - This product is not designed for protection against radioactive rays. REV. A TYP - MAX 18.0 3.0 Unit Ｖ A 2/4 ◎Electrical characteristic (Unless otherwise noted Ta=25℃, VIN=12V, VEN = 3V) Parameter VIN supply current (operating) VIN supply current (standby) Reference voltage Oscillation frequency High side FET ON resistance Low side FET ON resistance UVLO voltage SW leak current EN terminal H threshold voltage EN terminal L threshold voltage SS/DELAY terminal source current SS/DELAY – FB Offset voltage PSET terminal source current PSET terminal threshold voltage Symbol IQ active IQ ｓｔｂｙ VFB ｆOSC RHFET RLFET VUVLO ILSW VENH VENL ISSSO VSSFBOST IPSET VPSET MIN 0.792 270 3.8 1.6 2.8 450 3 0.8 Specification value TYP 1.5 0.8 0.8 300 110 110 4.0 0 4 600 5 1.0 MAX 2.5 1.2 0.808 330 160 160 4.2 5 0.4 5.2 750 7 1.2 UNIT mA mA V kHz mΩ mΩ V μA V V μA mV μA V Condition VFB = 0.75V VEN = 0V FB-FC Short RRT= 56kΩ ISW = -1A ISW = 1A VIN Sweep VEN= 0V VSS= 1V VSS= 1V VPSET= 2V ●VFB :FB terminal voltage、VEN :EN terminal voltage、VSS :SS/DELAY terminal voltage, VPSET :PSET terminal voltage, RRT :RT resistor ●Current capability should not exceed Pd. REV. A 3/4 ◎BLOCK DIAGRAM FB GND 11 10 FC SS 12 Softstart/Delay 9 RT NC 13 OSC 8 5V PSET 14 Protect time 15 EN CURRENT DET BOOT 7 EN SW 6 PWM CONTROL NC SW 16 5 NC VOUT SW 17 4 18 3 19 2 20 1 VIN PGND VIN PGND VIN PGND ◎PIN ASSIGNMENT No. Symbol 1 2 PGND PGND 3 PGND Description No. Symbol Power GND terminal Power GND terminal 11 12 FB FC Power GND terminal 13 RT Description Feedback terminal Phase amends terminal Frequency adjustment resistance connection terminal 4 SW Switching output terminal 14 PSET 5 SW Switching output terminal 15 EN Enable input 6 SW Switching output terminal 16 NC - 7 BOOT Boot strap terminal 17 NC - 8 NC - 18 VIN Power supply input terminal 19 VIN Power supply input terminal 20 VIN Power supply input terminal 9 SS/DELAY 10 GND Soft start adjustment capacity connection terminal Signal GND terminal ◎PACKAGE OUTLINE Product number BD8643 1PIN MARK Lo No. SSOP-B20W (UNIT：mm) REV. A Adjust OFF LATCH time terminal 4/4 ◎NOTE ON USE 1．About the absolute maximum rating Attention is brushed off enough to the quality control, it is likely to destroy when the absolute maximum rating such as impressed voltages (VCC_IN,DCIN) and ranges (Topr) of the operating temperature as it is exceeded, the mode of breakings of the short or the opening, etc. cannot be specified, and examine it in this IC to give physical measures for safety such as fuses when a special mode that exceeds the absolute maximum rating is assumed. 2．GND pin voltage GND terminal should be connected the lowest voltage, under all conditions. And all terminals except SW should be under GND terminal voltage under all conditions including transient situations. If a terminal exists under GND,it should be inserting a bypass route. 3．Power dissipation If IC is used on condition that the power loss is over the power dissipation, the reliability will become worse by heat up, such as reduced output current capability. Also, be sure to use this IC within a power dissipation range allowing enough of margin. 4．Input supply voltage Input supply pattern layout should be as short as possible. 5．About the short and the miss-installation between terminals Note the direction and the miss-registration of IC enough when you install it in the set substrate. IC might destroy it as well as reversely connecting the power supply connector when installing it by mistake. Moreover, there is fear of destruction when the foreign body enters between terminals, the terminal, the power supply, and grandeur and it is short-circuited. 6．About operation in strong electromagnetic field In use in strong electromagnetic field, note that there is a possibility of malfunctioning. 7．About the inspection by the set substrate It is likely to suffer stress to IC and discharge electricity every one process when you connect the capacitor with the pin with low impedance when inspecting it in the set substrate. Moreover, detach it after connecting after the power supply is turned off without fail when detaching it to G in the inspection process, inspecting, and turning off the power supply. n addition, be give the earth to the assembly process as a static electricity measures, and careful enough when it transports and you preserve it. 8．About each input terminal This IC is a monolithic IC which has a P+ isolations and P substrate to isolate elements each other. This P layer and an N layer in each element form a PN junction to construct various parasitic elements. For instance, the potential difference operates in resistance as shown in the figure below when resistance and the transistor connect it with the terminal and the playground (GND) >(terminal B) joint of PN operates as a parasitic diode in playground (GND) >(terminal A) transistor (NPN). In addition, the NPN transistor of parasitism works with N layer of the element of the above-mentioned parasitic diode and the neighborhood and others in transistor (NPN). A parasitic element in IC composition is inevitably formed because of the potential relation. A parasitic element can operate, the interference with the circuit operation be caused, it malfunction, and, consequently, it cause destruction. Therefore, do not do the usage that a parasitic element operates as a voltage that is lower than the playground (GND;P substrate) is impressed to the input terminal enough. Moreover, do not impress the voltage to the input terminal when you do not impress the power-supply voltage to IC. Give each input terminal to me the voltage below the power-supply voltage or in the guarantee value of an electric characteristic when you similarly impress the power-supply voltage. Example of IC of simple structure 9．Earth wiring pattern If small signal GND and large current GND exist, disperse their pattern. In addition, for voltage change by pattern wiring impedance and large current not to change voltage of small signal GND, each ground terminal of IC must be connected at the one point on the set circuit board. As for GND of external parts, it is similar to the above-mentioned. 10. SW terminal A counter-electromotive force may generate a negative potential at the SW terminal during connection to the particular application. Therefore, it should be inserting a bypass route between SW to GND. 11. About each output terminal We recommend to put Diode for protection purpose in case of output pin connected with large load of impedance or reserve current occurred at initial and output off. 12. Thermal Shut Down Circuit A temperature control is built in the IC to prevent the damage due to overheat. Therefore, the outputs are turned off when the thermal circuit works. 13. Over Output Current Protection SW Output terminal has over current protection circuit of 5A, with prevents IC from being damage by short circuit at over current. However, It is recommend not to use that continuously operates the protection circuit (For instance, always the load that greatly exceeds the output current ability is connected or the output is short-circuited, etc.) in these protection circuits by an effective one to the destruction prevention due to broken accident. REV. A Appendix Notes No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM CO.,LTD. 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