参数资料
| 型号： | BD9845FV-E2 |
| 厂商： | Rohm Semiconductor |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 14-SSOP |
| 标准包装： | 1 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 1.5MHz |
| 占空比： | 100% |
| 电源电压： | 3.6 V ~ 35 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 14-LSSOP（0.173"，4.40mm 宽） |
| 包装： | 标准包装 |
| 产品目录页面： | 1373 (CN2011-ZH PDF) |
| 其它名称： | BD9845FV-E2DKR |
BD9845FV
4) Soft start (soft start function)
It is possible to provide SS terminal (13pin) with soft start function by
connecting C SS as shown on the right.
Soft start time TSS is shown by the formula below:
VREF
Technical Note
2uA
Tss
=
Css ?
Vinv
Issso
Css : SS terminal connection capacity
Vinv : Error amplifier reference voltage
(1V typ)
Css
SS
INV
13
1Vtyp.
(Ex) When Css = 0.01 uF
Issso : SS source current (2uA typ)
12
Fig.32
ErrAmp
0.01 × 10 × 1
Tss =
=
-6
2 × 10 -6
5 [msec]
R1
1
VREF
In order to function soft start, time must be set longer enough than
14
DT
start time of power supply and STB.
It is also possible to provide function of soft start by connecting the
resistor (R1/R2) and capacitor (C DT ) to DT terminal (14pin) as shown
on the right.
C DT
R2
Fig.33
5) PWM Comp - DEAD TIME (Pause period adjusting circuit - dead time)
Dead time can be set by applying voltage dividing resistance between VREF and GND to DT terminal.
PWM Comp compares the input dead time voltage (DT terminal voltage) and error voltage from Err Amp (FB terminal
voltage) with triangular wave, and turns off and on the output. When dead time voltage < error voltage, duty of output is
determined by dead time voltage. (When dead time setting is not used, pull up DT terminal to VREF terminal with resistor
approx 10 k ohms.)
Dead time voltage VDT in Fig 32 is shown by the formula below:
VDT ＝ VREF ?
R2
R1 ＋ R2
2.4
2.2
Vt100
Relation between VDT and Duty [See the graph on the right.]
Duty 100% Duty 0%
min typ max min typ max
2
1.8
When f = 100kHz 1.9 2.0
When f = 1.5MHz 1.95 2.1
2.1 1.4 1.5 1.6
2.25 1.35 1.5 1.65
[Unit : V]
1.6
1.4
Vt0
Be careful when oscillation frequency is high, upper/lower limit of triangular
wave (Vt100/Vt0) is shifted by delay time of comparator to directions
expanding amplitude.
1.2
1
6) OCP Comp (overcurrent detection circuit)
This function provides protection by forcibly turning off the output when
abnormal overcurrent flows due to shorting of output, etc. When voltage
between terminal OCP+(8pin)/OCP-(9pin) monitoring the current with
sense resistor exceeds overcurrent detection voltage (50 mV typ), it is
determined as overcurrent condition, and switching operation is stopped
100
Direction
of current VIN
1000
fosc[KHz]
Fig.34
10000
immediately by setting OUT to "H" and DT,SS (and FB) to "L".
It is automatically recovered when voltage between terminal OCP+/OCP-
is below overcurrent detection voltage.
In addition, although hysteresis, etc. are not set here, minimum detection
retention time (1.6ms typ) is set for suppressing the heating of FET, etc.
Sense
resistor
OCP+
OCP-
8
9
OCP Comp
(See the timing chart.)
When the overcurrent detection circuit is not used, short-circuit both
terminal OCP+/OCP- to VCC pin.
50mVtyp.
Fig.35
www.rohm.com
? 2011 ROHM Co., Ltd. All rights reserved.
8/15
2011.08 - Rev.D
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相关代理商/技术参数 |
参数描述 |
|---|---|
| BD9846FV | 制造商:ROHM 制造商全称:Rohm 功能描述:Silicon Monolithic Integrated Circuit |
| BD9846FV-E2 | 功能描述:IC REG CTRLR BUCK PWM 20-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| BD9848FV | 制造商:ROHM 制造商全称:Rohm 功能描述:Silicon Monolithic Integrated Circuit |
| BD9848FV-E2 | 制造商:ROHM Semiconductor 功能描述: |
| BD9850FVM | 制造商:ROHM 制造商全称:Rohm 功能描述:Single-output High-frequency Step-down Switching Regulator(Controller type) |
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