參數(shù)資料
型號(hào)： FAN8048
廠商： FAIRCHILD SEMICONDUCTOR CORP
元件分類： 運(yùn)動(dòng)控制電子
英文描述： 2 DC-DC Converter & 4-CH PWM Motor IC
中文描述： DISK DRIVE MOTOR CONTROLLER, 0.5 A, PDSO48
封裝： 7 X 7 MM, LQFP-48
文件頁(yè)數(shù)： 17/34頁(yè)
文件大?。?/td> 903K
代理商： FAN8048
FAN8048
17
3-8. Buck(Step-down) converter mode (VIN > VSYS)
The step-down converter keeps the average output voltage VSYS lower than DC input voltage VIN all the time. Figure 11-a
shows a conceptual circuit diagram of the step-down converter in case an electrical load is pure resistance. Herein, all switch-
ing devices are supposed to be at ideal conditions and instantaneous output voltage VSYS is dependent on the status of switch-
ing devices. That is, the input/output of the step-down converter is obtained by the following formula according to the Volt-Sec
balance condition and each waveform is shown in Figure.11-b, where D means duty cycle. In this formula, since duty ratio D
is smaller than 1.0, average output voltage VSYS is always displayed in the lower range of the DC input voltage.
where, D is duty cycle.
In practical application circuits, there are several drawbacks as follows:
(1) As most practical circuits are not exposed to pure electrical resistance loads, but to inductive loads and because of the stray
inductive there is the switch would have dissipate the inductive energy and therefore it may be destroyed. .
(2) This is not the case of most application circuit, but when output voltage fluctuates between zero and power voltage VIN, a
low pass filter composed of an inductor and capacitor is required to minimize the output voltage ripple.
Figure 12 shows the operation waveform of internal control voltage VX and VY and output power switching devices in Step-
down converter mode. When the internal control voltage VY is higher than control voltage VX and triangular waveform
V
PCT
, switch D is always turned-on and switch C is always turned-off in step-down converter mode. The switching operation
of switch A is activated by the signal generated by comparison between internal control VX and triangular waveform voltage
V
PCT
. Also, synchronous switch B remains turned-on during synchronous switch B turn-off time. That is, in step-down con-
verter mode, switch A and B always activate in opposite switching operations. The peak-peak ripple voltage (
VSYS) of out-
put voltage is calculated using the following formula:
I
C
C
2
2
Where,
I
L
is the inductor current from Figure11 (b) during turn-off (t
OFF
).
The value of the output capacitor to reduce output voltage ripple is calculated using the following formula.
The average value of the inductor current at boundary between continuos and discontinuous conduction mode is
1
,
peak
L
LB
i
I
=
where,
So to obtain the inductor value using the above formula, the redefined formula is as follows:
]
[
1
D
V
V
V
IN
SYS
×
=
S
ON
T
T
D
=
S
SYS
L
S
S
L
O
O
SYS
T
D
V
C
T
8
T
2
Q
V
)
1
1
1
×
=
×
×
×
=
=
S
SYS
L
L
T
D
V
I
)
1
=
2
)
1
8
S
SYS
SYS
V
S
L
T
D
V
T
C
×
=
)
(
2
2
SYS
IN
S
V
V
L
DT
=
]
[
V
D
V
V
SYS
IN
=
min
,
2
)
1
I
O
S
SYS
T
D
V
L
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
FAN8060 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:1.2MHz, 1A Synchronous Step-Down DC/DC Regulator
FAN8060EMPX 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.2MHz, 1A Sync Step Down DC/DC RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
FAN8082 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 DC Motor Driver RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube
FAN8082D 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 DC Motor Driver Bi Directional RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube
FAN8082DTF 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 DC Motor Driver Bi Directional RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube
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