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参数资料
| 型号： | MAX1565ETJ |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | Small, High-Efficiency, Five-Channel Digital Still Camera Power Supply |
| 中文描述： | 3.6 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, QCC32 |
| 封装： | 5 X 5 MM, 0.80 MM HEIGHT, MO-220WHHD-2, TQFN-32 |
| 文件页数： | 18/26页 |
| 文件大小： | 512K |
| 代理商： | MAX1565ETJ |
M
The output capacitor keeps output ripple small and
ensures control-loop stability. The output capacitor
must also have low impedance at the switching fre-
quency. Ceramic, polymer, and tantalum capacitors
are suitable, with ceramic exhibiting the lowest ESR
and high-frequency impedance.
Output ripple with a ceramic output capacitor is
approximately:
V
RIPPLE
= I
L(PEAK)
[1/(2
π
f
OSC
C
OUT
)]
If the capacitor has significant ESR, the output ripple
component due to capacitor ESR is:
V
RIPPLE(ESR)
= I
L(PEAK)
ESR
Output capacitor specifics are also discussed in the
Step-Up Compensation
section and the
Step-Down
Compensation
section.
Step-Up Component Selection
The external components required for the step-up are
an inductor, input and output filter capacitor, and com-
pensation RC. Typically, the inductor is selected to
operate with continuous current for best efficiency. An
exception might be if the step-up ratio, (V
OUT
/V
IN
), is
greater than 1/(1 - D
MAX
), where D
MAX
is the maximum
PWM duty factor of 80%.
When using the step-up channel to boost from a low input
voltage, loaded startup is aided by connecting a
Schottky diode from the battery to OUTSU. See the
Minimum Startup Voltage vs. Load Current graph in the
Typical Operating Characteristics
.
Step-Up Inductor
In most step-up designs, a reasonable inductor value
(L
IDEAL
) can be derived from the following equation,
which sets continuous peak-to-peak inductor current at
one-half the DC inductor current:
L
IDEAL
= [2 V
IN(MAX)
D(1 - D)] / (I
OUT
f
OSC
)
where D is the duty factor given by:
D = 1 - (V
IN
/ V
OUT
)
Given L
IDEAL
, the consistent peak-to-peak inductor cur-
rent is 0.5 I
OUT
/(1 - D). The peak inductor current,
I
IND(PK)
= 1.25 I
OUT
/ (1 - D). Inductance values smaller
than L
IDEAL
can be used to reduce inductor size.
However, if much smaller values are used, the inductor
current rises and a larger output capacitance may 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 chosen to
optimize control-loop stability. In some cases it may help
to readjust the inductor or output capacitor value to get
optimum results. For typical designs, the component
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
(RHPZ) appears in the loop-gain frequency response.
To ensure stability, the control-loop gain should
crossover (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:
1) Transconductance (from FBSU to COMPSU), gm
EA
(135μS)
2) Current-sense amplifier transresistance, R
CS
,
(0.3V/A)
3) Feedback regulation voltage, V
FB
(1.25V)
4) Step-up output voltage, V
SUOUT
, in V
5) Output load equivalent resistance, R
LOAD
,
in
= V
SUOUT
/I
LOAD
The key steps for step-up compensation are:
1)
Place f
C
sufficiently below the RHPZ and calculate C
C
.
2)
Select R
C
based on the allowed load-step tran-
sient. R
C
sets a voltage delta on the COMP pin that
corresponds 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-plane zero fre-
quency (f
RHPZ
) is given by:
f
RHPZ
= V
OUTSU
(1 - D)
2
/ (2
π
L 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 the RHPZ.
For example, if we assume V
IN
= 2V, V
OUT
= 3.35V,
and I
OUT
= 0.5A, then R
LOAD
= 6.7
. If we select
L = 3.3μH then:
f
RHPZ
= 3.35 (2/3.35)
2
/ (2
π
x 4.7 x 10
-6
x 0.5) = 115kHz
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1565ETJ+ | 功能描述:PMIC 解决方案 5Ch Digital Camera Power Supply RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
| MAX1565ETJ+T | 功能描述:PMIC 解决方案 5Ch Digital Camera Power Supply RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
| MAX1565ETJ-T | 功能描述:PMIC 解决方案 5Ch Digital Camera Power Supply RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
| MAX1565EVKIT | 制造商:Maxim Integrated Products 功能描述:SMALL, HIGH-EFFICIENCY, FIVE-CHANNEL DSC - Bulk |
| MAX1566ETL | 功能描述:PMIC 解决方案 RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
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