參數(shù)資料
型號： MAX1584-MAX1585
廠商： Maxim Integrated Products, Inc.
英文描述： 5-Channel Slim DSC Power Supplies
中文描述： 5通道電源超薄數(shù)碼相機(jī)
文件頁數(shù)： 20/29頁
文件大小： 632K
代理商： MAX1584-MAX1585
M
I
IND(PK)
= 1.25 x I
OUT
/ (1 - D)
Inductance values smaller than L
IDEAL
can be used to
reduce inductor size; however, if much smaller values are
used, inductor current rises and a larger output capaci-
tance might be required to suppress output ripple.
Step-Up Compensation
The inductor and output capacitor are usually chosen
first in consideration of performance, size, and cost.
The compensation resistor and capacitor are then cho-
sen to optimize control-loop stability. In some cases, it
helps to readjust the inductor or output capacitor value
to get optimum results. For typical designs, the compo-
nent values in the circuit of Figure 1 yield good results.
The step-up converter employs current-mode control,
thereby simplifying the control-loop compensation.
When the converter operates with continuous inductor
current (typically the case), a right-half-plane zero
appears in the loop-gain frequency response. To
ensure stability, the control-loop gain should cross over
(drop below unity gain) at a frequency (f
C
) much less
than that of the right-half-plane zero.
The relevant characteristics for step-up channel com-
pensation are as follows:
Transconductance (from FBSU to CCSU), g
MEA
(135μS)
Current-sense amplifier transresistance, R
CS
(0.3V/A)
Feedback regulation voltage, V
FB
(1.25V)
Step-up output voltage, V
SU
, in V
Output load equivalent resistance, R
LOAD
, in
= V
SUOUT
/ I
LOAD
The key steps for step-up compensation are as follows:
1) Place f
C
sufficiently below the right-half-plane zero
(RHPZ) and calculate C
C
.
2) Select R
C
based on the allowed load-step transient.
R
C
sets a voltage delta on the C
C
pin that corre-
sponds to load-current step.
3) Calculate the output-filter capacitor (C
OUT
) required
to allow the R
C
and C
C
selected.
4) Determine if C
P
is required (if calculated to be >10pF).
For continuous conduction, the right-half-plane zero fre-
quency (f
RHPZ
) is given by the following:
f
RHPZ
= V
SUOUT
(1 - D)
2
/ (2
π
x L x I
LOAD
)
where D = the duty cycle = 1 - (V
IN
/ V
OUT
), L is the
inductor value, and I
LOAD
is the maximum output cur-
rent. Typically, target crossover (f
C
) for 1/6 of the
RHPZ. For example, if we assume f
OSC
= 500kHz, V
IN
= 2.5V, V
OUT
= 5V, and I
OUT
= 0.5A, then R
LOAD
=
10
. If we select L = 4.7μH, then:
f
RHPZ
= 5 (2.5 / 5)
2
/ (2
π
x 4.7 x 10
-6
x 0.5) = 84.65kHz
Choose f
C
= 14kHz. Calculate C
C
:
C
C
= (V
FB
/ V
OUT
)(R
LOAD
/ R
CS
)(g
M
/ 2
π
x f
C
)(1 - D)
= (1.25 / 5)(10 / 0.3) x (135μS / (6.28 x 14kHz) (2/5)
= 6.4nF
Choose 6.8nF.
Now select R
C
so transient-droop requirements are
met. As an example, if 4% transient droop is allowed,
the input to the error amplifier moves 0.04 x 1.25V, or
50mV. The error-amp output drives 50mV x 135μS, or
6.75μA across R
C
to provide transient gain. Since the
current-sense transresistance is 0.3V/A, the value of R
C
that allows the required load step swing is as follows:
R
C
= 0.3 I
IND(PK)
/ 6.75μA
In a step-up DC-DC converter, if L
IDEAL
is used, output
current relates to inductor current by:
I
IND(PK)
= 1.25 x I
OUT
/ (1 - D) = 1.25 x I
OUT
x V
OUT
/
V
IN
So for a 500mA output load step with V
IN
= 2.5V and
V
OUT
= 5V:
R
C
= [1.25(0.3 x 0.5 x 5) / 2)] / 6.75μA = 69.4k
Note that the inductor does not limit the response in this
case since it can ramp at 2.5V / 4.7μH, or 530mA/μs.
The output filter capacitor is then chosen so the C
OUT
R
LOAD
pole cancels the R
C
C
C
zero:
C
OUT
x R
LOAD
= R
C
x C
C
For the example:
C
OUT
= 68k
x 6.8nF / 10
= 46μF
Choose 47μF for C
OUT
. If the available C
OUT
is sub-
stantially different from the calculated value, insert the
available C
OUT
value into the above equation and
recalculate R
C
. Higher substituted C
OUT
values allow a
higher R
C
, which provides higher transient gain and
consequently less transient droop.
If the output filter capacitor has significant ESR, a zero
occurs at the following:
Z
ESR
= 1 / (2
π
x C
OUT
x R
ESR
)
5-Channel Slim DSC Power Supplies
20
______________________________________________________________________________________
相關(guān)PDF資料
PDF描述
MAX1584ETJ 5-Channel Slim DSC Power Supplies
MAX1585ETJ 5-Channel Slim DSC Power Supplies
MAX1586AETM High-Efficiency, Low-IQ PMICs with Dynamic Core for PDAs and Smart Phones
MAX1586 High-Efficiency, Low-IQ PMICs with Dynamic Core for PDAs and Smart Phones
MAX1587 High-Efficiency, Low-IQ PMICs with Dynamic Core for PDAs and Smart Phones
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1585ETJ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 5Ch Slim DSC Power Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1585ETJ+ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 5Ch Slim DSC Power Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1585ETJ+T 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 5Ch Slim DSC Power Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1585ETJ-T 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 5Ch Slim DSC Power Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1585EVKIT 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Evaluation Kit for the MAX1585 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。

采購需求

(若只采購一條型號，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進(jìn)入我的后臺，查看報價

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進(jìn)入我的后臺，查看報價

*型號 *數(shù)量 廠商 批號 封裝
添加更多采購

我的聯(lián)系方式

*
*
*