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参数资料
| 型号： | MAX1917EEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/18页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR SYNC BUCK 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，DDR |
| 输入电压： | 4.5 V ~ 22 V |
| 输出数： | 2 |
| 输出电压： | 0.4 V ~ 5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-QSOP |
| 包装： | 带卷 (TR) |
Tracking, Sinking and Sourcing, Synchronous Buck
Controller for DDR Memory and Termination Supplies
The actual microfarad capacitance value required
relates to the physical size needed to achieve low ESR,
as well as to the chemistry of the capacitor technology.
As a result, the capacitor is usually selected by ESR
and voltage rating rather than by capacitance value
(this is true of tantalums, OS-CONs, POSCAPs, and
other electrolytics).
Input Capacitor Selection
The input capacitor must meet the ripple current
requirement (I RMS ) imposed by the switching currents.
Nontantalum chemistries (ceramic, aluminum, or OS-
CON) are preferred due to their superior surge current
R DRP introduces some power dissipation, which is
given by:
PD(DRP) = R DRP ? I OUT(MAX)2
R DRP should be chosen to handle this power dissipation.
MOSFET Power Dissipation
Worst-case conduction losses occur at the duty-factor
extremes. For the high-side MOSFET, the worst-case
power dissipation due to resistance occurs at minimum
input voltage:
OUT IN OUT )
× ( V ? V
I RMS = I LOAD × ?
?
?
capacity:
? V
? V IN
?
?
?
PD(Q1) = (V OUT / V IN(MIN) ) ? (I LOAD2 ) ? (R DS(ON) )
Generally, a small high-side MOSFET is desired in order
to reduce switching losses at high input voltages.
Setting the Current Limit
The minimum current-limit threshold must be great
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The val-
ley of the inductor current occurs at I LOAD(MAX) minus
half of the ripple current. For example:
I LIMIT(LOW) > I LOAD(MAX) - (LIR / 2) ? I LOAD(MAX)
where I LIMIT(LOW) = minimum current-limit threshold
voltage divided by the R DS(ON) of Q2. For the
MAX1917, the minimum current-limit threshold (100mV
default setting) is 50mV. Use the worst-case maximum
However, the R DS(ON) required to stay within package
power-dissipation limits often limits how small the
MOSFET can be. Again, the optimum occurs when the
switching (AC) losses equal the conduction (R DS(ON) )
losses. Calculating the power dissipation in Q1 due to
switching losses is challenging because it must allow for
difficult-to-quantify factors that influence the turn-on and
turn-off times. These factors include the internal gate
resistance, gate charge, threshold voltage, source
inductance, and PC board layout characteristics. The fol-
lowing switching loss calculation provides only a very
rough estimate and is no substitute for breadboard eval-
uation, preferably including a check using a thermocou-
ple mounted on Q1:
value for R DS(ON) from the MOSFET Q2 data sheet, and
add some margin for the rise in R DS(ON) with tempera-
ture. A good general rule is to allow 0.5% additional
PD ( SWITCHING ) =
C RSS × V IN ( MAX ) 2 × f × I LOAD
I GATE
resistance for each ° C of temperature rise.
When adjusting the current limit, use a 1% tolerance
R ILIM resistor to prevent a significant increase of errors
in the current-limit tolerance.
Setting the Voltage Positioning
The droop resistor, R DRP , in series with the output
inductor before the output capacitor, sets the droop
voltage, V DRP . Choose R DRP such that the output volt-
age at the maximum load current, including ripple, is
just above the lower limit of the output tolerance:
where C RSS is the reverse transfer capacitance of Q1
and I GATE is the peak gate-drive source/sink current.
For the low-side MOSFET, Q2, the worst-case power
dissipation always occurs at maximum input voltage:
PD(Q2) = (1 - V OUT / V IN(MAX) ) ? I LOAD2 ? R DS(ON)
R DRP <
V OUT ( TYP ) ? V OUT ( MIN ) ? V RIPPLE / 2
I OUT ( MAX )
16
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1917EEE-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1917EVKIT | 功能描述:电源管理IC开发工具 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX19191ETI/V+ | 制造商:Maxim Integrated Products 功能描述:ANALOG TO DIGITAL CONVERTER - Rail/Tube |
| MAX19191ETI/V+T | 制造商:Maxim Integrated Products 功能描述:ULTRA-LOW-POWER, 10MSPS, 8-BIT ADC - Tape and Reel |
| MAX19191ETI+ | 制造商:Maxim Integrated Products 功能描述:ANALOG TO DIGITAL CONVERTER - Rail/Tube |
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