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參數(shù)資料
| 型號： | MAX1864 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數(shù)字信號處理 |
| 英文描述： | Fixed-Point Digital Signal Processor 352-FCBGA |
| 中文描述： | 用于xDSL/電纜調(diào)制解調(diào)器的三/五路輸出電源 |
| 文件頁數(shù)： | 18/25頁 |
| 文件大?。?/td> | 384K |
| 代理商： | MAX1864 |
M
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
18
______________________________________________________________________________________
where A
VCS
is the current-sense amplifier
’
s gain (4.9
typ), A
VEA
is the DC gain of the error amplifier (2000
typ), and V
OUT(NOMINAL)
is the output voltage set by
the feedback resistive-divider (internal or external).
Since the output voltage is a function of the load cur-
rent and load resistance, the total DC loop gain
(A
V(DC)
) is approximately:
The compensation capacitor (C
COMP
) creates the dom-
inant pole. Due to the current-mode control scheme,
the output capacitor also creates a pole in the system
that is a function of the load resistance. As the load
resistance increases, the frequency of the output
capacitor
’
s pole decreases. However, the DC loop gain
increases with larger load resistance, so the unity gain
bandwidth remains fixed. Additionally, the compensa-
tion resistor and the output capacitor
’
s ESR both gener-
ate zeros. Therefore, to achieve stable operation, use
the following procedure to properly compensate the
system:
1) First, select the desired crossover frequency. The
crossover frequency must be less than both 1/5th
the switching frequency and 1/3rd the zero frequen-
cy set by the output capacitor
’
s ESR:
2) Next, determine the pole set by the output capacitor
and the load resistor:
3) Determine the compensation resistor required to set
the desired crossover frequency:
where the error amplifier
’
s transconductance (g
m
) is
100μS (see
Electrical Characteristics
).
4) Finally, select the compensation capacitor:
Boost-Supply Diode
A signal diode, such as the 1N4148, works well in most
applications. If the input voltage goes below 6V, use a
small 20mA Schottky diode for slightly improved effi-
ciency and dropout characteristics. Do not use large
power diodes, such as the 1N5817 or 1N4001, since
high junction capacitance can charge up VL to exces-
sive voltages.
Linear Regulator Controllers
Positive Output Voltage Selection
The MAX1864/MAX1865s
’
positive linear regulator out-
put voltages are set by connecting a voltage-divider
from the output to FB_ to GND (Figure 6). Select R4 in
the 5k
to 50k
range. Calculate R3 with the following
equation:
where V
FB
= 1.24V, and V
OUT
may range from 1.24V to
30V.
Negative Output Voltage Selection (MAX1865)
The MAX1865
’
s negative output voltage is set by con-
necting a voltage-divider from the output to FB5 to a
positive voltage reference (Figure 6). Select R6 in the
5k
to 50k
range. Calculate R5 with the following
equation:
where V
REF
is the positive reference voltage used, and
V
OUT
may be set between 0 and -20V.
If the negative regulator is used, the OUT pin must be
connected to a voltage supply between 2V and 5V that
can source at least 25mA. Typically, the OUT pin is
connected to the step-down converter
’
s output.
However, if the step-down converter
’
s output voltage is
set higher than 5V, OUT may be connected to one of
the positive linear regulators with an output voltage
between 2V and 5V.
R
R
V
V
OUT
REF
5
6
=
R
R
V
V
OUT
FB
3
4
1
=
-
C
R
COMP
COMP POLE OUT
≤
1
2
π
(
)
R
g A
COMP
c
POLE OUT
=
×
2000
(
)
(
)
=
=
POLE OUT
OUT LOAD
LOAD MAX
I
C
2
π
OUT OUT
C
(
)
(
)
1
2
π
≤
OUT ESR
SW
5
C
and
1
6
π
V
V
R
)
REF LOAD
OUT NOMINAL
(
DS ON
(
)
≈
×
400
A
I
I
V
V
R
)
A
V DC
(
PEAK
LOAD
REF LOAD VEA
OUT NOMINAL
(
DS ON
(
VCS
)
)
≈
≈
I
V
V
R
)
A
PEAK
OUT REF VEA
OUT NOMINAL
(
DS ON
(
VCS
=
)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX1864-MAX1865 | Fixed-Point Digital Signal Processor 384-FC/CSP |
| MAX1865 | Fixed-Point Digital Signal Processor 352-FCBGA |
| MAX1864UEEE | xDSL/Cable Modem Triple/Quintuple Output Power Supplies |
| MAX1865UEEP | xDSL/Cable Modem Triple/Quintuple Output Power Supplies |
| MAX1865TEEP | xDSL/Cable Modem Triple/Quintuple Output Power Supplies |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1864TEEE | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1864TEEE+ | 功能描述:DC/DC 開關(guān)控制器 xDSL/Cable Modem Triple/Quint Output RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(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 |
| MAX1864TEEE+T | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 xDSL/Cable Modem Triple/Quint Output RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1864TEEE-T | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1864UEEE | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
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