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參數(shù)資料
| 型號(hào)： | SC4624EVB-MLPQ |
| 廠商： | Semtech Corporation |
| 英文描述： | Low Input Voltage, High Efficiency, 4A Integrated FET Synchronous Step down DC/DC Regulator |
| 中文描述： | 低輸入電壓，高效率及4A集成FET的同步降壓直流/直流穩(wěn)壓器 |
| 文件頁數(shù)： | 12/20頁 |
| 文件大?。?/td> | 738K |
| 代理商： | SC4624EVB-MLPQ |
12
2007 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
Operation
Application Information (Cont.)
Switching Frequency Setting
SC4624
5
15
25
35
45
55
65
75
85
95
105
115
125
135
145
200
400
600
800
1000
F
OSC
(kHz)
1200
1400
1600
1800
2000
5VIN
2.5VIN
The operation frequency can be programmed up to 2MHz,
but there is a minimum on-time limitation which is around
110ns. Users should take care of minimum limitation
on the operating duty cycle under high frequency
application.
Synchronization Frequency
Synchronization operation mode is invoked by using an
external clock signal and is activated when the SYNC/EN
is pulled and held above 2V and held below 0.8V. The
range of synchronization frequency is from 200kHz to
2MHz.
A jitter happens when sync pulse clock edge is less than
120ns before the phase switches. It is caused by the
ground bounce of synchronization pulse coupled to PWM
comparator. Users try to avoid this application. (refer to
Figure 9).
Power Good Indicator
The PGOOD pin is an open-drain and incorporated window
comparators output. It’s is necessary that a pull-up
resistor from the PGOOD pin to the input supply for setting
the logic high level of the PGOOD signal. When FB voltage
is within +
10% setting output voltages typical, the output
of power good comparator becomes high impedance after
delay time. The PGOOD signal delay time is around 1024/
F
. In shutdown mode the power good output is actively
pulled low.
For example, 1MHz switching frequency applications, the
PGOOD delay time is around 1ms.
Thermal Shutdown
When the junction temperature rises up around 160°C,
the internal soft start voltage is held low, the internal high
side and low side MOSFETs are turned off and the output
voltage will fall to zero. Once the junction temperature
goes below hysteresis temperature around 10°C, the
regulator will restart. (refer to Figure 8).
Linear Mode Operation (100% duty)
The SC4624 can allows 100% duty cycle operation. The
Vout is,
287
,
'6+
/
,1
287
5
5
9
9
u
where
R
L
: Output inductor DC resistance.
R
: Internal high side P-MOSFET resistance.
(refer to Figure11).
As Vin drops gradually and close to Vout, the buck regulator
will go into 100% duty cycle ratio. A matter needing
attention is internal high side PMOS has minimum off time
limitation and is related to duty cycle rate. T
his condition
makes the working duty cycle perform at randon with the
output ripple increasing and a poor transient response.
Above phenomenon can be improved by larger output
capacitor and smaller output inductor. Users need to
verify whether above application condition has opposite
influence on entire circuit.
Over Current Protection
A over current setting is programmed by an external
resistor (R
). It goes through internal sense resistor and
generates a voltage.
2QVHQVH
5
FF
,
9
9
u
where
I : The current is generated by R
ISET
, and it is amplified
by internal current amplifier.
R
ONSENSE
: Internal sense resistor.
Output inductor current goes through internal high side
P-MOSFET and generate a voltage.
21
'6+
/
,1
5
,
9
9
u
where
I
L
: Output inductor current.
R
DSH(ON)
: High side P-MOSFET conduction resistance.
R
F
Figure 15. Switching Frequency vs. R
FS
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| SC4624EVB-SO | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Low Input Voltage, High Efficiency, 4A Integrated FET Synchronous Step down DC/DC Regulator |
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| SC4624SETRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Low Input Voltage, High Efficiency, 4A Integrated FET Synchronous Step down DC/DC Regulator |
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| SC4626ASKTRT | 功能描述:IC REG BUCK SYNC 1V 1A SOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
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