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參數(shù)資料
| 型號： | RC5060M |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 模擬信號調(diào)理 |
| 英文描述： | Power Supply Switching Circuit |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO20 |
| 封裝： | SOIC-20 |
| 文件頁數(shù)： | 13/15頁 |
| 文件大?。?/td> | 136K |
| 代理商： | RC5060M |
PRODUCT SPECIFICATION
RC5060
REV. 1.0.2 9/14/01
13
Power Good
The Power Good is an open collector that pulls low if any of
the outputs are less than 80% of nominal.
Over Temperature
The RC5060 is capable of sourcing substantial current, 200mA
minimum to the RAMBUS transistor’s base during S0, 144mA
to the RAMBUS line during S3, and 100mA to SDRAM
during S3. As a result, there can be heavy power dissipation
in the IC. While the RC5060 is designed to accept this power
dissipation, any overloading of outputs can cause excessive
heating. If the RC5060 die temperature exceeds about 150°,
all outputs are shut off. Outputs remain off until the die
temperature returns to its safe area.
Transistor Selection
External transistor selection depends on usage, differing for
the linear regulators and the switches.
The MOSFET switches, Ql, Q3, Q5 and Q6 should be sized
based on regulation requirements and power dissipation.
Since the ATX outputs are ±5%, the outputs driven from
them must be wider. As an example, if we want to hold 3.3V
SDRAM to -10%, we can drop only 5% = 165mV across Q1.
At 4.8A, this means Ql must have a maximum R
DS,on
of
165mV/4.8A = 34m
, including tolerance and self-heating
effects. We thus choose a Fairchild FDS4410Y, which has
20m
maximum R
DS, on
at 4.5V V
GS
at 25°C. We can esti-
mate power dissipation as (4.8A)
2
* 20m
= 460mW, which
should be acceptable for this package. Similar calculations
apply to the other MOSFET switches.
Q4 is a MOSFET functioning as a linear regulator. Since it
delivers only 500mA, it is easy to select a MOSFET, it need
only be able to handle 500mA * (5V±5%–3.3V) = 1W. We
select the Fairchild FDS6630A in an SO-8 package.
Q2 is an NPN bipolar functioning as a linear regulator. As
already discussed, it must have a V
CE,sat
lower than 635mV
at I
E
= 2A and I
B
= 200mA. Its power dissipation can be as
high as (3.3V + 5%–2.5V) * 2A = l.9W.
Alternate for 2.5V Dual
I
nstead of the bipolar transistor shown in Figure 4 for Q2, the
linear pass element for the 2.5V dual for RAMBUS, a MOS-
FET and schottky diode can be used as shown in Figure 8.
Figure 8. 2.5V Dual with MOSFET
The schottky should be chosen to have a low V
f
at the speci-
fied RAMBUS current. The MOSFET’s R
DS,on
must then be
lower than (3.3V—5% -2.5V - V
f
)/I
RAMBUS
including tem-
perature. An additional constraint is that the MOSFET must
have a gate threshold voltage lower than 1.5V. For example, for
2.8A, choose the diode to be an MBR835, and the MOSFET a
Fairchild NDH833N. This same technique can then also be
used for RAMBUS currents higher than can be achieved
with the bipolar transistor.
Output Capacitor Selection
Output capacitor selection depends on whether the line has
overlap time or not.
For both the 5V dual and the 2.5V dual, there is guaranteed
overlap time between when one source is turned on and the
other source turned off. For these outputs, the output capaci-
tor is not needed to hold up the supply, but only for noise
filtering and to respond to transient loading.
The 3.3V dual and 3.3V SDRAM outputs have deadtime
between when one source is turned off and the other source
turned on. During the time when both are off, the output cur-
rent must be supplied by the output capacitor. Mitigating
this, it must be realized that the system will be designed in
such a way that the current has gone to its sleep value before
the transition occurs. For example, the 3.3V dual has a sleep
current of 500mA maximum. Maximum deadtime is 6μsec,
and so charge depletion is 500mA * 6μsec = 3μC. Suppose
that we have a total of 8% drop due to the source tolerance
and the MOSFET drop, and we are trying to hold 10%
regulation. The remaining 2% = 66mV implies a minimum
capacitance of 3μC/66mV = 45μF.
RC5060
16
3.3V Main
2.5V Dual
(RAMBUS)
15
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| RC5060MT | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 SOIC-20 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5061 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:High Performance Programmable Synchronous DC-DC Controller for Multi-Voltage Platforms |
| RC5061M | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 SOIC-20 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5061MT | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 SOIC-20 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5-1/133 | 制造商:ABB Low Voltage Products and Systems 功能描述:A9-A40,SS,RC,50-133V |
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