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| 型号： | MAX1565ETJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/26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
If we select L = 4.7μH and f OSC = 440kHz, P SLOPE =
V IN /( π L) = 214kHz, so choose f C = 40kHz and calculate C C :
C C = (V FB /V OUT )(R LOAD /R CS )(gm/2 π f C )
= (1.25/1.5)(4.3/0.6) x (135μS/(6.28 x 40kHz)
= 3.2nF
Choose 3.3nF. 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
0.6V/A, the value of R C that allows the required load
step swing:
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:
Auxiliary Controller Component Selection
External MOSFET
All MAX1565 auxiliary controllers drive external logic-
level N-channel MOSFETs. Significant MOSFET selec-
tion parameters are:
1) On-resistance (R DS(ON) )
2) Maximum drain-to-source voltage (VDS(MAX))
3) Total gate charge (Q G )
4) Reverse transfer capacitance (CRSS)
DL_ swings between OUTSU and GND. Use a MOSFET
with on-resistance specified at or below the main output
voltage. The gate charge, Q G , includes all capacitance
associated with charging the gate and helps to predict
MOSFET transition time between on and off states.
MOSFET power dissipation is a combination of
on-resistance and transition losses. The on-resistance
I IND(PK) = 1.25 I OUT
Thus, for a 250mA output load step with V IN = 3.35V
loss is:
P RDSON = D I L2 R DS(ON)
and V OUT = 1.5V:
R C = (1.25 x 0.6 x 0.25)/6.75μA = 27.8k ?
Choose 27k ? . Note that the inductor does not limit the
response in this case since it can ramp at (V IN -
V OUT )/4.7μH, or (3.35 - 1.5)/4.7μH = 394mA/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 = 27k ? x 3.3nF/4.3 = 20.7μF
Choose 22μF. If the output filter capacitor has signifi-
cant 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 COMPSD to GND:
C P = C OUT R ESR /R C
If C P is calculated to be < 10pF, it can be omitted.
where D is the duty cycle, I L is the average inductor
current, and R DS(ON) is MOSFET on-resistance. The
transition loss is approximately:
P TRANS = (V OUT I L f OSC t T )/3
where V OUT is the output voltage, I L is the average
inductor current, f OSC is the switching frequency, and
t T is the transition time. The transition time is approxi-
mately Q G /I G , where Q G is the total gate charge, and
I G is the gate drive current (typically 0.5A). The total
power dissipation in the MOSFET is:
P MOSFET = P RDSON + P TRANS
Diode
For most auxiliary applications, a Schottky diode rectifies
the output voltage. The Schottky diode ’ s low forward volt-
age and fast recovery time provide the best performance
in most applications. Silicon signal diodes (such as
1N4148) are sometimes adequate in low-current
(<10mA) high-voltage (>10V) output circuits where the
output voltage is large compared to the diode forward
voltage.
Auxiliary Compensation
The auxiliary controllers employ voltage-mode control
to regulate their output voltage. Optimum compensa-
tion somewhat depends on whether the design uses
continuous or discontinuous inductor current.
20
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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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