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参数资料
| 型号： | MAX16818EVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/25页 |
| 文件大小： | 0K |
| 描述： | KIT EVALUATION FOR MAX16818 |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 电流 - 输出 / 通道： | 1A |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 18V |
| 特点： | 可调光 |
| 输入电压： | 6 ~ 28 V |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX16818 |
1.5MHz, 30A High-Efficiency, LED Driver
with Rapid LED Current Pulsing
? V IN x I OUT x ( t R + t F ) x f SW ?
?
?
? ?
+ ( R DS ( ON ) x I RMS ? HI
? + ( R DS ( ON ) x I RMS ? HI 2 )
?
?
?
I RMS ? HI =
( I VALLEY 2 + I PK 2 + I VALLEY x I PK ) x
Buck Regulator
Estimate the power loss (PD MOS _) caused by the high-side
and low-side MOSFETs using the following equations:
PD MOS ? HI = ( Q G x V DD x f SW ) +
2
2 )
where Q G , R DS(ON) , t R , and t F are the upper-switching
MOSFET’s total gate charge, on-resistance at maximum
operating temperature, rise time, and fall time, respectively.
Boost Regulator
Estimate the power loss (PD MOS _) caused by the MOS-
FET using the following equations:
PD FET = ( Q G x V DD x f SW ) +
? V IN x I OUT x ( t R + t F ) x f SW ?
2
D
3
For a boost regulator in continuous mode, D = V LEDs /
(V IN + V LEDs ), I VALLEY = (I OUT - ? I L / 2) and I PK = (I OUT
+ ? I L / 2).
I RMS ? HI =
( I VALLEY 2 + I PK 2 + I VALLEY x I PK ) x
D
3
The voltage across the MOSFET:
V MOSFET = V LED + V F
where V F is the maximum forward voltage of the diode.
For the buck regulator, D = V LEDs / V IN , I VALLEY =
(I OUT - ? I L / 2) and I PK = (I OUT + ? I L / 2).
PD MOS ? LO = ( Q G x V DD x f SW ) +
The output diode on a boost regulator must be rated to
handle the LED series voltage, V LED . It should also
have fast reverse-recovery characteristics and should
handle the average forward current that is equal to the
( R DS ( ON ) x I RMS ? LO 2 )
I RMS ? LO = ( I VALLEY 2 + I PK 2 + I VALLEY x I PK ) x
(1 ? D)
3
LED current.
Input Capacitors
For buck regulator designs, the discontinuous input
current waveform of the buck converter causes large
For example, from the typical specifications in the
Applications Information section with V OUT = 7.8V, the
high-side and low-side MOSFET RMS currents are
0.77A and 0.63A, respectively, for a 1A buck regulator.
Ensure that the thermal impedance of the MOSFET
package keeps the junction temperature at least +25°C
below the absolute maximum rating. Use the following
equation to calculate the maximum junction tempera-
ture: T J = (PD MOS x θ JA ) + T A , where θ JA and T A are
the junction-to-ambient thermal impedance and ambi-
ent temperature, respectively.
To guarantee that there is no shoot-through from V IN to
PGND, the MAX16818 produces a nonoverlap time of
35ns. During this time, neither high- nor low-side MOS-
FET is conducting, and since the output inductor must
ripple currents in the input capacitor. The switching fre-
quency, peak inductor current, and the allowable peak-
to-peak voltage ripple reflected back to the source
dictate the capacitance requirement. Increasing switch-
ing frequency or paralleling out-of-phase converters
lowers the peak-to-average current ratio, yielding a
lower input capacitance requirement for the same LED
current. The input ripple is comprised of ? V Q (caused
by the capacitor discharge) and ? V ESR (caused by the
ESR of the capacitor). Use low-ESR ceramic capacitors
with high-ripple-current capability at the input. Assume
the contributions from the ESR and capacitor discharge
are equal to 30% and 70%, respectively. Calculate the
input capacitance and ESR required for a specified ripple
using the following equation:
? I OUT +
? ? I L ?
?
2 ?
maintain current flow, the intrinsic body diode of the
low-side MOSFET becomes the conduction path. Since
this diode has a fairly large forward voltage, a Schottky
diode (in parallel to the low-side MOSFET) diverts current
flow from the MOSFET body diode because of its lower
forward voltage, which, in turn, increases efficiency.
ESR IN =
? V ESR
?
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| MAX1681C/D | 功能描述:直流/直流开关转换器 125mA High-Speed Switched-Capacitor Voltage Converters RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1681ESA | 功能描述:直流/直流开关转换器 125mA f-Select Swtcd Voltage Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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