Rohm BD8643FV Synchronous rectification with built-in fet type dc/dc converter ic Datasheet

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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
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◎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
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◎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
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Appendix-Rev4.0
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