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参数资料
| 型号： | MAX1567ETL+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 29/35页 |
| 文件大小： | 0K |
| 描述： | IC DGTL CAM PWR-SUP 6CH 40TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 应用： | 控制器，数字式相机 |
| 输入电压： | 0.7 V ~ 5.5 V |
| 输出数： | 7 |
| 输出电压： | 1.25 V ~ 5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 40-WFQFN 裸露焊盘 |
| 供应商设备封装： | 40-TQFN-EP（6x6） |
| 包装： | 管件 |
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Six-Channel, High-Efficiency, Digital
Camera Power Supplies
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 )
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 CC to GND:
C P = C OUT x R ESR / R C
If C P is calculated to be <10pF, it can be omitted.
Step-Down Component Selection
This section describes component selection for the
step-down converter, and for the main converter if used
in step-down mode (SUSD = GND).
Step-Down Inductor
The external components required for the step-down
are an inductor, input and output filter capacitors, and
compensation RC network.
The MAX1566/MAX1567 step-down converter provides
best efficiency with continuous inductor current. A rea-
sonable inductor value (L IDEAL ) can be derived from
the following:
L IDEAL = [2(V IN ) x D(1 - D)] / I OUT x f OSC
This 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 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 capaci-
tance may be required to suppress output ripple. Larger
values than L IDEAL can be used to obtain higher output
current, but typically with larger inductor size.
Step-Down Compensation
The relevant characteristics for step-down compensa-
tion are as follows:
? Transconductance (from FB to C C ), gm EA (135μS)
? Step-down slope-compensation pole, P SLOPE = V IN /
( π L)
? Current-sense amplifier transresistance, R CS
(0.6V/A)
? Feedback-regulation voltage, V FB (1.25V)
? Step-down output voltage, V SD , in V
? Output-load equivalent resistance, R LOAD , in ? =
V OUT / I LOAD
The key steps for step-down compensation are
as follows:
1) Set the compensation RC to 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
frequency.
If we assume V IN = 2.5V, V OUT = 1.8V, and I OUT =
350mA, then R LOAD = 5.14 ? .
If we select f OSC = 500kHz and L = 5.6μH.
P SLOPE = V IN / ( π L) = 142kHz, so choose f C = 24kHz
and calculate C C :
C C = (V FB / V OUT )(R LOAD / R CS )(gm / 2 π x f C )
= (1.25 / 1.8)(5.14 / 0.6) x [135μS / (6.28 x 24kHz)]
= 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 0.6V/A, the value of R C
that allows the required load-step swing is as follows:
R C = 0.6 I IND(PK) / 6.75μA
In a step-down DC-to-DC converter, if L IDEAL is used,
output current relates to inductor current by the following:
I IND(PK) = 1.25 I OUT
So for a 250mA output load step with V IN = 2.5V and
V OUT = 1.8V:
R C = (1.25 x 0.6 x 0.25) / 6.75μA = 27.8k ?
Choose 27k ? .
Note that the inductor does somewhat limit the response
in this case since it ramps at (V IN - V OUT ) / 5.6μH, or
(2.5 - 1.8) / 5.6μH = 125mA/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
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1567ETL+ | 功能描述:PMIC 解决方案 6Ch 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 |
| MAX1567ETL+T | 功能描述:PMIC 解决方案 6Ch 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 |
| MAX1567ETL-T | 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 |
| MAX1567EVKIT | 制造商:Maxim Integrated Products 功能描述:6-CHANNEL HIGH EFFICIENCY DIGITAL CAMERA POWE - Bulk |
| MAX1567SUMEVKIT | 制造商:Maxim Integrated Products 功能描述:6-CHANNEL HIGH EFFICIENCY DIGITAL CAMERA POWE - Bulk |
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