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參數資料
| 型號： | ADP3155 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 5-Bit Programmable Triple Power Supply Controller for Pentium III Processors |
| 中文描述： | 5位可編程三路電源控制器，用于奔騰III處理器 |
| 文件頁數： | 11/14頁 |
| 文件大小： | 200K |
| 代理商： | ADP3155 |
REV. A
ADP3155
–11–
dc biasing, it is simplest to use two resistors to terminate the g
m
amplifier output, with the lower resistor tied to ground and the
upper resistor to the 12 V supply of the IC. The values of these
resistors can be calculated using:
R
R
V
V
UPPER
C
DIV
OS
=
×
and:
R
R
V
V
V
LOWER
C
OS
–
DIV
OS
=
×
where
V
DIV
is the resistor divider supply voltage (e.g., the rec-
ommended 12 V), and
V
OS
is the offset voltage required on the
amplifier to produce the desired offset at the output. V
OS
is
calculated using Equation 2, where V
OUT(OS)
is the offset from
the nominal VID-programmed value to the center of the speci-
fied regulation window for the output voltage. (Note this may be
either positive or negative.) For clarification, that offset is given
by:
V
V
(
V
VID
OUT OS
HI
LO
(
)
)
–
=
+
1
2
where
V
HI
and
V
LO
are the respective upper and lower limits
allowed for regulation.
Finally, the compensating capacitance is determined from the
equality of the pole frequency of the error amplifier gain and the
zero frequency of the impedance of the output capacitor:
C
C
ESR
Rt
COMP
O
TOTAL
=
×
Trade-Offs Between DC Load Regulation and AC Load
Regulation
Casual observation of the circuit operation—e.g., with a voltmeter
—would make it appear that the dc load regulation appears
to be rather poor compared to a conventional regulator. This
would be especially noticeable under very light or very heavy
loads where the voltage is “positioned” near one of the extremes
of the regulation window rather than near the nominal center
value. It must be noted and understood that this low gain char-
acteristic (i.e., loose dc load regulation) is inherently required to
allow improved transient containment (i.e., to achieve tighter ac
load regulation). That is, the dc load regulation is intentionally
sacrificed (but kept within specification) in order to minimize
the number of capacitors required to contain the load transients
produced by the CPU.
Linear Regulators
The two ADP3155 linear regulators provide a low cost, conve-
nient and versatile solution for generating additional lower sup-
ply rails that can be programmed in the range 1.2 V–5 V. The
maximum output load current is determined by the size and
thermal impedance of the external N-channel power MOSFET
that is placed in series with the supply and controlled by the
ADP3155. The output voltage, V
OLDO1, 2
in Figure 14, is sensed
at the FB pin of the ADP3155 and compared to an internal
1.2 V reference in a negative feedback loop which keeps the
output voltage in regulation. If the load is being reduced or
increased, the FET drive will also be reduced or increased by the
ADP3155 to provide a well regulated
±
1% accurate output
voltage. The output voltage is programmed by adjusting the
value of the external resistor R
PROG
, shown in Figure 15.
Efficiency of the Linear Regulators
The efficiency and corresponding power dissipation of each of
the linear regulators are not determined by the ADP3155.
Rather, these are a function of input and output voltage and
load current. Efficiency is approximated by the formula:
η
= 100%
×
(
V
OUT
4
V
IN
)
The corresponding power dissipation in the MOSFET, together
with any resistance added in series from input to output is given
by:
P
LDO
= (
V
IN(LDO)
–
V
OUT(LDO
)
)
×
I
OUT(LDO)
Minimum power dissipation and maximum efficiency are ac-
complished by choosing the lowest available input voltage that
exceeds the desired output voltage. However, if the chosen
input source is itself generated by a linear regulator, its power
dissipation will be increased in proportion to the additional
current it must now provide. For most PC systems, the lowest
available input source for the linear regulators, which is not
itself generated by a linear regulator, is 3.3 V from the main
power supply.
Assuming that the 3.3 V supply is used to provide input power
for a 1.5 V linear regulator output, the efficiency will inherently
be 1.5 V
4
3.3 V, which is less than 50%. The total current
demand in all of the low voltage power rails (e.g., 1.5 V, 1.8 V
and 2.5 V) can produce unacceptable dissipation and junction
temperatures in the linear regulators. For such systems, Analog
Devices recommends the ADP3156—a switching regulator that
generates one of the lower voltage outputs (e.g., 1.8 V), which can
also be used as a power source to the lower voltage outputs
(e.g., 1.5 V). This results is a highly efficient and reliable power
conversion system that can readily handle the combined loading
specifications for the lower system voltages, with room to spare
for the higher current demands and lower voltages of next gen-
eration PC systems.
Features
Tight DC Regulation Due to 1% Reference and High Gain
Output Voltage Stays Within Specified Limits at Load
Current Step with 30 A/
μ
s Slope
Fast Response to Input Voltage or Load Current Transients
Overcurrent protection may be provided by the addition of an
external NPN transistor and an external resistor R
S2
. The design
specification and procedure is given below.
V
R
Rt
V
V
Rt
1 36
.
k
V
Rt
275
k
R I
OS
C
TOTAL
OUT OS
TOTAL
TOTAL
=
×
+
+
0 8
.
6
–1 7
(
)
(2)
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| ADP3155JRU | 5-Bit Programmable Triple Power Supply Controller for Pentium III Processors |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADP3155JRU | 制造商:AD 制造商全稱:Analog Devices 功能描述:5-Bit Programmable Triple Power Supply Controller for Pentium III Processors |
| ADP3155JRU-REEL | 制造商:Rochester Electronics LLC 功能描述:5-BIT PROGRAMMBLE TRIPLE POWER SUPPLY - Tape and Reel |
| ADP3155JRU-REEL7 | 功能描述:IC PS TRPL PENTIUM III 20-TSSOP RoHS:否 類別:集成電路 (IC) >> 專用 IC 系列:* 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:1 系列:- 類型:調幀器 應用:數據傳輸 安裝類型:表面貼裝 封裝/外殼:400-BBGA 供應商設備封裝:400-PBGA（27x27） 包裝:散裝 |
| ADP3156 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Dual Power Supply Controller for Desktop Systems |
| ADP3156JR-1.5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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