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參數(shù)資料
| 型號： | MAX1804 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | External Four-Input Feedback Integrator for Power Supplies |
| 中文描述： | 外部四反饋輸入積分器，用于電源控制 |
| 文件頁數(shù)： | 10/11頁 |
| 文件大小： | 570K |
| 代理商： | MAX1804 |
M
External Four-Input Feedback Integrator for
Power Supplies
10
______________________________________________________________________________________
Applications Information
Layout Information
Proper layout is essential due to high current levels and
switching waveforms that generate noise. Place the
regulator
’
s feedback resistors and R
OUT
(from the reg-
ulator feedback point to OUT of MAX1804) close to the
regulator
’
s feedback point to prevent noise pickup
(Figure 5). Minimize leakage of the COMP capacitor and
traces around COMP because they cause IN_ set-point
errors according to the IN_ transconductance. A leakage
of I
COMP
at COMP will result in an error given by:
IN_ error voltage = I
COMP
/ (IN_ transconductance)
For a typical value of IN_ transconductance of 30μS, a
leakage of 0.1μA will result in an IN_ error voltage of
3mV in the set point.
Design Example (Step-Down
Converter Application)
Figure 2 is an example of an application circuit using
the MAX1804 for point-of-load regulation when using a
step-down controller (MAX1653). Use the following
design procedure to optimize the basic schematic.
Begin the design by establishing the following:
Input voltage to the MAX1653 controller (7V to 20V)
Typical output voltage and accuracy of MAX1653
(5V ±5%)
This gives a target of:
V
OUT, min
= 5V - 5% = 4.75V
To minimize power dissipation, set regulator output
V
OUT, R
= 4.8V with MAX1653 feedback resistors.
Choose feedback resistors (R
TOP
and R
BOTTOM
) for
about 25μA current in the resistive divider for noise
immunity.
Therefore:
(R
TOP
+ R
BOTTOM
) = 4.8V / 25μA = 192k
For the MAX1653, the voltage at its feedback point
V
FB
= 2.5V.
Choose R
TOP
= 91k
and therefore, R
BOTTOM
=
100k
.
If the desired adjustment range is +400mV, max OUT
current (MAX1804) is given by:
I
OUT
(MAX) = 0.4V / 91k
= 4.4μA
R
OUT
= V
FB
/ I
OUT
(MAX) = 2.5V / 4.4μA = 562k
To guarantee that the output will not go below the tar-
get of 4.75V, including all error sources, set the
MAX1804 nominal regulation point to 4.85V.
Since:
IN_scale factor = 4 x V
ADJ
, V
ADJ
= 1.2125V
Divide the reference voltage down and bypass as
required if using the MAX1653 reference voltage as
shown in Figure 2. Assuming 0.1% resistor accuracy
and using the MAX1653 reference, the error budget
can be calculated as:
Reference Accuracy
ADJ Divider Accuracy
Scale Factor Error
IN_ Offset Voltage (-15mV)
Total
This gives a worst-case output voltage of 4.73V, which is
below the target of 4.75V. The most-significant error
source is the MAX1653 reference. Therefore, use a better
reference, if available, in the system or increase the VADJ
to increase the worst-case output voltage to 4.75V.
The MAX1653 works well with the MAX1804
’
s GBW
product set at 40kHz, so use a 470pF capacitor on
COMP.
-1.6%
-0.2%
-0.4%
-0.3%
-2.5%
Chip Information
TRANSISTOR COUNT: 636
Figure 5. Proper Layout of Feedback Resistors for Regulator
R
BOTTOM
R
OUT
R
TOP
TO
MAX1804
FB
G
ND
MAX1653
SHORT COMPACT PLACEMENT
OF FEEDBACK RESISTORS
REDUCES NOISE PICKUP
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1804EUB | 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 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1804EUB+ | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Feedback Integrator for Power Supply 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 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1804EUB+T | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Feedback Integrator for Power Supply 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 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1804EUB-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 安裝風格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1805EEE | 制造商:Maxim Integrated Products 功能描述: |
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