參數(shù)資料
型號(hào)： S-8520
廠商： Seiko Instruments Inc.
英文描述： PWM Control Step-Down Switching Regulator-Controller(PWM 控制，步降開(kāi)關(guān)穩(wěn)壓器-控制器)
中文描述： PWM控制降壓型開(kāi)關(guān)穩(wěn)壓控制器（脈寬調(diào)制控制，步降開(kāi)關(guān)穩(wěn)壓器-控制器）
文件頁(yè)數(shù)： 8/30頁(yè)
文件大小： 650K
代理商： S-8520
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
Rev.6.1
S-8520/8521 Series
Seiko Instruments Inc.
7
n
Operation:
1. Step-Down DC-DC Converter
1.1 PWM Control (S-8520 Series)
The S-8520 Series consists of DC/DC converters that employ a pulse-width modulation (PWM) system. This series is characterized
by its low current consumption. In conventional PFM system DC/DC converters, pulses are skipped when they are operated with a
low output load current, causing variations in the ripple frequency of the output voltage and an increase in the ripple voltage. Both
of these effects constitute inherent drawbacks to those converters.
In converters of the S-8520 Series, the pulse width varies in a range from 0% to 100%, according to the load current, and yet ripple
voltage produced by the switching can easily be removed through a filter because the switching frequency remains constant.
Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current.
1.2 PWM/PFM-Switched Control (S-8521 Series)
The S-8521 Series consists of DC/DC converters capable of automatically switching the pulse-wide modulation system (PWM) over
to the pulse-frequency modulation system (PFM), and vice versa, according to the load current. This series of converters features
low current consumption.
In a region of high output load currents, the S-8521 Series converters function with PWM control, where the pulse-width duty varies
from 25% to 100%. This function helps keep the ripple power low.
For certain low output load currents, the converters are switched over to PFM control, whereby pulses having their pulse-width duty
fixed at 25% are skipped depending on the quantity of the load current, and are output to a switching transistor. This causes the
oscillation circuit to produce intermittent oscillation. As a result, current consumption is reduced and efficiency losses are prevented
under low loads. Especially for output load currents in the region of 100
m
A, these DC/DC converters can operate at extremely high
efficiency.
2. Power-Off Terminal (ON/OFF Terminal)
This terminal deactivates or activates the step-down operation.When the power-off terminal is set to "L", the Vin voltage appears
through the EXT terminal, prodding the switching transistor to go off. All the internal circuits stop working, and substantial savings
in current consumption are thus achieved.
The power-off terminal is configured as shown in Figure 4. Since pull-up or pull-down is not performed internally, please avoid
operating the terminal in a floating state. Also, try to refrain from applying a voltage of 0.3V to 1.8V to the terminal, lest the current
consumption increase. When this power-off terminal is not used, leave it coupled to the VIN terminal.
3. Soft-Start Function
The S-8520/21 Series comes with a built-in soft-start circuit. This circuit enables the output voltage to rise gradually over the
specified soft-start time, when the power is switched on or when the power-off terminal remains at the "H" level. This prevents the
output voltage from overshooting.
However, the soft-start function of this IC is not able to perfectly prevent a rush current from flowing to the load (see Figure 5). Since
this rush current depends on the input voltage and load conditions, we recommend that you evaluate it by testing performance with
the actual equipment.
Power-Off
Terminal
CR Oscillation
Circuit
Output
Voltage
“H”
Activated
Set
value
“L”
Deactivated
V
SS
Figure 4
ON/OFF
V
IN
V
SS
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參數(shù)描述
S-8520A20MC-AVFT2G 功能描述:DC/DC 開(kāi)關(guān)控制器 Step Down SWR PWM 180kHz 60uA Iq RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
S-8520A21MC-AVG-T2 功能描述:DC/DC 開(kāi)關(guān)控制器 2.1V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
S-8520A21MC-AVGT2G 功能描述:DC/DC 開(kāi)關(guān)控制器 2.1V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
S-8520A25MC-ARK-T2 制造商:SII 制造商全稱(chēng):Seiko Instruments Inc 功能描述:PWM CONTROL & PWM/PFM CONTROL STEP-DOWN SWITCHING REGULATOR-CONTROLLERS
S-8520A25MC-AVK-T2 功能描述:DC/DC 開(kāi)關(guān)控制器 2.5V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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