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参数资料
| 型号： | MAX1565ETJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/26页 |
| 文件大小： | 0K |
| 描述： | IC DGTL CAM PWR-SUP 5CH 32TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 应用： | 转换器控制器，数字式相机 |
| 输入电压： | 0.7 V ~ 5.5 V |
| 输出数： | 5 |
| 输出电压： | 3.3V，1.25 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
| 包装： | 管件 |
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Choose f C = 20kHz. Calculate C C :
C C = (V FB /V OUT )(R LOAD /R CS )(gm/2 π f C )(1 - D)
= (1.25/3.35)(6.7/0.3) x (135μS/(6.28 x 20kHz)
(2/3.35) = 5.35nF
Choose 6.8nF. Now select R C such that transient droop
requirements are met. For 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 tran-
sient gain. Since the current-sense transresistance is
0.3V/A, the value of R C that allows the required load
step swing:
R C = 0.3 I IND(PK)/ 6.75μA
In a step-up DC-to-DC converter, if L IDEAL is used, out-
put current relates to inductor current by:
I IND(PK) = 1.25 I OUT /(1 - D) = 1.25 I OUT V OUT /V IN
Thus, for a 400mA output load step with V IN = 2V and
V OUT = 3.35V:
R C = [1.25(0.3 x 0.4 x 3.35)/2)]/6.75μA = 37k ?
Note that the inductor does not limit the response in this
case since it can ramp at 2V/3.3μH, or 606mA/μs. The
output filter capacitor is then chosen so that the C OUT
R LOAD pole cancels the R C C C zero:
C OUT R LOAD = R C C C
For example:
C OUT = 37k ? x 6.8nF/6.7 = 37.5μF
Since a reasonable value for C OUT is 47μF rather than
37.5, choose 47μF and rescale RC:
R C = 47μF x 6.7/6.8nF = 46.3k ?
which provides a slightly higher transient gain and con-
sequently less transient droop than previously selected.
If the output filter capacitor has significant ESR, a zero
occurs at:
Z ESR = 1/(2 π C OUT R ESR )
If Z ESR > f C , it can be ignored, as is typically the case
with ceramic output capacitors. If Z ESR is less than f C ,
it should be cancelled with a pole set by capacitor C P
connected from COMPSU to GND:
C P = C OUT R ESR /R C
If C P is calculated to be < 10pF, it can be omitted.
Step-Down Component Selection
Step-Down Inductor
The external components required for the step-down
are an inductor, input and output filter capacitors, and
compensation RC network. The MAX1565 step-down
converter provides best efficiency with continuous
inductor current. A reasonable inductor value (LIDEAL)
can be derived from:
L IDEAL = 2 (V IN ) D (1 - D)/(I OUT f OSC )
which sets the peak-to-peak inductor current at 1/2 the
DC inductor current. D is the duty cycle:
D = V OUT /V IN
Given L IDEAL , the peak-to-peak inductor current varia-
tion is 0.5 I OUT . The absolute peak inductor current is
1.25 I OUT . 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 capacitance may be required to suppress
output ripple.
Larger values than L IDEAL can be used to obtain higher
output current, but with typically larger inductor size.
Step-Down Compensation
The relevant characteristics for step-down compensa-
tion are:
1) Transconductance (from FBSD to COMPSD), gm EA
(135μS)
2) Step-down slope compensation pole, P SLOPE =
V IN / ( π L)
3) Current-sense amplifier transresistance, R CS ,
(0.6V/A)
4) Feedback regulation voltage, V FB (1.25V)
5) Step-down output voltage, V SD , in V
6) Output load equivalent resistance, R LOAD ,
in ? = V OUTSD /I LOAD
The key steps for step-down compensation are:
1) Set the compensation RC zero to cancel the R LOAD
C OUT pole.
2) Set the loop crossover below the lower of 1/5 the
slope compensation pole, or 1/5 the switching fre-
quency.
If we assume V IN = 3.35V, V OUT = 1.5V, and I OUT =
350mA, then R LOAD = 4.3 ? .
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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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