BD9775FV-E2 Rohm Semiconductor, BD9775FV-E2 Datasheet - Page 22

• Manufacturer Part Number: BD9775FV-E2
• Description: IC REG SW STEP DOWN HE 28-SSOP
• Manufacturer: Rohm Semiconductor
• Type: Step-Down (Buck)r

Specifications of BD9775FV-E2

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Current - Output: 400mA
• Frequency - Switching: 100kHz
• Voltage - Input: 6 ~ 30 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Power - Output: 640mW
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: BD9775FV-E2TR

●SETTING UP INFOMATION (BD9775FV)
・Resistance at FB2-GND setup condition
Short SYNC to VREF if the synchronous rectification function is not needed.
1)Simultaneously OFF Duty of MOSFETs for Synchronous Rectification
The simultaneously OFF duty of both main MOSFET switch and synchronous rectification MOSFET is determined by
resistance (Rsync) between SYNC and GND. See Fig. 4.
In Synchronous Rectification, insert RFB2-GND (RFB2-GND≒3×Rsync) between FB2 and GND, because it is possible to
reduce overshoot(sea fig.2). RFB2-GND decide following formula.
※Rsync(MAX)…MAX dispersion range at Rsync
40
35
30
25
20
15
10
5
0
0
Without Synchronous Rectification（Don’t insert R
20
fosc=100kHz
Δduty=(t1+t2)/t×100 (%)
SYNC
3×Rsync(MAX)
Vsync
40
Threshold Voltage at100%
Rsync (kΩ)
Rsync(MAX)
Rsync
0.4908
Fig.2
SYNC
VREF
-Output Source Current at FB2
2.08
60
+80.7x10
FB2
22/29
Rsync(MIN)…MIN dispersion range at Rsync
FB2-GND
80
T=-40℃
T= 25℃
T=105℃
-6
）
<
R
R
FB2-GND
100
FB2-GND
< R
< 3xRsync(MIN)
FB2-GND
OUT2H
OUT2L
< 3xRsync(MIN)
t1
t
t2