BD8646FV

Single-chip Type with Built-in FET type Switching Regulators Flexible Step-down Switching Regulator with Built-in Power MOSFET BD8646FV No.10027EAT44 ●Description The BD8646FV is a synchronous step-down switching regulator that integrates 2 low resistances N-channel MOSFETs. It achieves 2A continuous output current over a wide input supply range. Current mode operation provides fast transient response and easy phase compensation. ●Feature 1) Synchronous rectification with built-in FET type DC/DC converter 2) 2.0A output current 3) Range of operation power-supply voltage 4.5V～18V 4) Reference voltage FB 0.8V±1% 5) Programmable frequency 100kHz～600kHz 6) Over current protection function 7) Thermal shutdown function 8) Under voltage protection 9) Soft start time out function / Soft start delay circuit 10) Programmable OFFLATCH time ●Applications FPD,DVD,HDD Recorder,STB,Amusement,Other ●Absolute maximum rating (Ta=25℃) Parameter Input supply voltage BOOT terminal voltage EN terminal voltage Input terminal voltage SW terminal voltage Output current Power dissipation Operating temperature Storage temperature Symbol VIN VBOOT VEN VINP VSW IOUT Pd Topr Tstg *1 Ratings 20 28 GND-0.3 ～ VIN+0.3 GND-0.3 ～ 7 GND-0.3 ～ VIN+0.3 2.5 1.19*2 -20 ～ 85 -55 ～ 150 Unit V V V V V A W ℃ ℃ *1 VINP Application terminal: SS/DELAY, FB, FC, RT, PSET *2 (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 ●Operating conditions Parameter Input supply voltage Output current * Symbol VIN IOUT Ratings Min. 4.5 Typ. Max. 18.0 2.0 Unit V A This product is not designed for protection against radioactive rays. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 1/13 2010.09 - Rev.A BD8646FV ●Electrical characteristic (Unless otherwise noted Ta=25℃, VIN=12V, VEN = 3V) Parameter VIN supply current (operating) VIN supply current (standby) Reference voltage (VREF) 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 ● ● Technical Note Symbol IQ_active IQ_stby VFB fOSC RHFET RLFET VUVLO ILSW VENH VENL ISSSO VSSFBOST IPSET VPSET Limits Min. 0.792 270 3.8 1.6 2.8 450 3.0 0.8 Typ. 1.5 0.8 0.800 300 120 120 4.0 0 4.0 600 5.0 1.0 Max. 2.5 1.2 0.808 330 170 170 4.2 5 0.4 5.2 750 7.0 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. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 2/13 2010.09 - Rev.A BD8646FV ●Reference data 0.820 0.815 0.810 Technical Note 0.810 VIN=12V VFB and FC [V] 0.805 Ta=25℃ VFB and FC [V] VFBとFC[V] 0.800 0.795 0.790 0.785 0.780 -20 -5 10 25 40 55 70 85 VFBとFC[V] 0.805 0.800 0.795 0.790 4 6 8 10 12 14 16 18 Ta [℃] Fig.1 Reference voltage – temperature characteristic 340 330 320 Fig.2 Reference voltage – VIN characteristic 340 330 VIN[V] VIN=12V fsw[kHz] 320 310 300 290 280 270 2 60 Ta=25℃ fsw[kHz] 310 300 290 280 270 260 -20 -5 10 25 40 55 70 85 4 6 8 10 12 14 16 18 Ta [℃] VIN[V] Fig.3 Frequency – temperature characteristic 5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2 .0 -20 Fig.4 Frequency – VIN characteristic 5.0 4.5 4.0 3.5 VIN=12V Ta=25℃ ISS[μA] ICC[mA] -5 10 25 40 55 70 85 3.0 2.5 2.0 1.5 1.0 0.5 0.0 4 6 8 10 12 14 16 18 Ta [℃] Fig.5 SS/DELAY charge current - temperature characteristic 320 280 240 320 280 VIN[V] Fig.6 Circuit Current – VIN characteristic VIN=12V SW_PGND[mΩ] VIN=12V 240 200 160 120 80 40 0 VIN_SW[mΩ] 200 160 120 80 40 0 -20 -5 10 25 40 55 70 85 -20 -5 10 25 40 55 70 85 Ta [℃] Fig.7 Hi side FET ON_R - temperature characteristic 320 280 240 Fig.8 Low side FET ON_R - temperature characteristic 320 280 Ta [℃] 200 160 120 80 40 0 4 6 8 10 12 14 16 18 SW_PGND[mΩ] Ta=25℃ 240 200 160 120 80 40 0 4 Ta=25℃ VIN_SW[mΩ] 6 8 10 12 14 16 18 VIN[V] VIN[V] Fig.9 Hi side FET ON_R - VIN characteristic www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. Fig.10 Low side FET ON_R – VIN characteristic 3/13 2010.09 - Rev.A BD8646FV ●Block diagram Technical Note FB 11 FC 12 RT 13 PSET 14 EN 15 NC 16 NC 17 VIN 18 VIN 19 VIN 20 GND 10 SS Softstart/Delay 9 NC OSC CURRENT DET 5V 8 BOOT 7 SW Protect time EN PWM CONTROL 6 SW 5 SW 4 PGND 3 PGND 2 PGND 1 VOUT Fig.11 Block diagram ●Pin assignment No. 1 2 3 4 5 6 7 8 9 10 Symbol PGND PGND PGND SW SW SW BOOT NC SS/DELAY GND Description Power GND terminal Power GND terminal Power GND terminal Switching output terminal Switching output terminal Switching output terminal Boot strap terminal Soft start adjustment capacity connection terminal Signal GND terminal No. 11 12 13 14 15 16 17 18 19 20 Symbol FB FC RT PSET EN NC NC VIN VIN VIN Description Feedback terminal Phase amends terminal Frequency adjustment resistance connection terminal Adjust OFF LATCH time terminal Enable input Power supply input terminal Power supply input terminal Power supply input terminal ●Package outline dimension Product number BD8646 1PIN MARK Lot No. SSOP-B20W (Unit: mm) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 4/13 2010.09 - Rev.A BD8646FV ●Operation description Technical Note 1 Enable control The device can be controlled ON/OFF by EN terminal (15 pin) voltage. An internal circuit starts when VEN reaches 1.4V. 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. VEN EN terminal VENH VENL 0 VSSCLM SS terminal VSSTH VSS 0 VO Output setting voltage 0 tSS Fig.12 ON/OFF transition wave form in EN controlling 2 Soft start time set function As for BD8646FV, output can do soft start without overshoot by charging soft start capacity (CSS) connected between SS/DELAY (9 pin) and GND (10 pin) terminal. Also, soft start time (tss) can be set by setting soft start capacity (CSS) arbitrarily. (Refer to 5-2 soft start time setting method) 3 OSC oscillation frequency setting function The output oscillation frequency can be set by connecting resistance between terminal RT (13 pin) and GND (range = 100kHz – 600kHz) The relation between RT terminal resistance and the oscillation frequency follows Fig.13. 10000 1000 SW[kH z] 100 10 1 10 100 1000 RT[kΩ] Fig.13 Oscillation frequency setting by RT resistance www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 5/13 2010.09 - Rev.A BD8646FV ●Protection function Technical Note Protection circuit is effective for destruction prevention due to accident so that avoid using under continuous protection operation. 1 Low voltage protection function (LVP) The voltage of the terminal FB (11pin) is compared with internal reference voltage VREF. If FB terminal voltage falls below VLVP(= VREF -120mV) and the state continues, output changes to low voltage and the state is fixed. Table 1 output low voltage protection function EN terminal SS terminal >1.4V(typ) 1.4V(typ)