BD8643FV-E2 Rohm Semiconductor, BD8643FV-E2 Datasheet - Page 8

• Manufacturer Part Number: BD8643FV-E2
• Description: IC SWITCH REG 3A W/FET 20SSOP
• Manufacturer: Rohm Semiconductor
• Series: -r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of BD8643FV-E2

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1 V ~ 12.6 V
• Current - Output: 3A
• Frequency - Switching: 100kHz ~ 600kHz
• Voltage - Input: 4.5 V ~ 18 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-LSSOP (0.240", 6.10mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

●External parts setting method
BD8643FV
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
1 Output voltage setting method
The output voltage can be arbitrarily set by external resistance.
Please select the constant of R1 and R2 by this expression.
Please select the current that flows to R1 and R2 to become much smaller than output current.
2 Soft start time setting method
BD8643FV can soft start without overshoot because of a charge current to the soft start capacitance (CSS).
The soft start time can be set by connecting soft start capacity (CSS).
When the EN terminal voltage is set VIN_EN or more, the charge to the capacity between SS/DELAY and GND terminal is
begun. The output voltage becomes soft start in proportion to a SS/DELAY terminal voltage rising. When the SS/DELAY
terminal voltage exceeds VSSTH, the output voltage is fixed in a setting value.
Please set soft start time (tss) in 1msec-52.5msec.
Vo
Output setting voltage

(R1
R2

R2)
T
EN terminal
SS terminal
VO
VREF

TW
EN
①
(

50
μ
) s
VENH

0V
0V
0V
V
R1
R2
OST
Vo
I
Fig.16 Output voltage setting circuit
SS
(

(
②
(=50µsec)
0

TW
6 .
4
①
V
μ
EN
A
)
FB

)
Fig.17 Soft start
C
T
SS
②
VO

8/13
VREF=0.8V
(V
V
SSTH
OST(=0.6V[typ])
③
I
SS
③

(

V
OST
4
μ
V
A
SSTH(=1.4V[typ])
)
)

C
SS
35µsec
Min.
TW
Technical Note
50µsec
2010.09 - Rev.A
EN
Typ.
SPEC
75µsec
Max.