參數(shù)資料
型號(hào)： DS1244Y
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類(lèi)： Timer or RTC
英文描述： 0 TIMER(S), REAL TIME CLOCK, PDIP28
封裝： 0.740 INCH, PLASTIC, DIP-28
文件頁(yè)數(shù)： 11/21頁(yè)
文件大?。?/td> 1965K
代理商： DS1244Y
MAX17129/MAX17149
Low-Cost, 6-String WLED Drivers with
Quick-PWM Step-Up Converter
19
Applications Information
LED VFB_ Variation
The forward voltage of each white LED may vary up to
25% from part to part and the accumulated voltage dif-
ference in each string equates to additional power loss
within the devices. For the best efficiency, the voltage
difference between strings should be minimized. The
difference between lowest voltage string and highest
voltage string should be less than 8V (typ). Otherwise,
the internal LED short-protection circuit disables the high
FB voltage string.
FB Pin Maximum Voltage
The current through each FB_ pin is controlled only during
the step-up converter’s on-time. During the converter off-
time the current sources are turned off. The output voltage
does not discharge and stays high. The devices disable
the FB current source, which string shorts. In this case,
the step-up converter’s output voltage is always applied
to the disabled FB pin. FB_ pin can withstand 48V.
PCB Layout Guidelines
Careful PCB layout is important for proper operation. Use
the following guidelines for good PCB layout:
1) Minimize the area of high current-switching loop
of the rectifier diode, internal MOSFET, and output
capacitor to avoid excessive switching noise.
2) Connect high-current input and output components
with short and wide connections. The high-current
input loop goes from the positive terminal of the input
capacitor to the inductor, to the internal MOSFET,
then to the input capacitor’s negative terminal. The
high-current output loop is from the positive terminal
of the input capacitor to the inductor, to the rectifier
diode, to the positive terminal of the output capaci-
tors, reconnecting between the output capacitor and
input capacitor ground terminals. Avoid using vias
in the high-current paths. If vias are unavoidable,
use multiple vias in parallel to reduce resistance and
inductance.
3) Create a ground island (PGND) consisting of the
input and output capacitor ground. Connect all
these together with short, wide traces or a small
ground plane. Maximizing the width of the power
ground traces improves efficiency and reduces out-
put-voltage ripple and noise spikes. Create an analog
ground island (GND) consisting of ISET, IN, VCC con-
nections, and the devices’ exposed backside pad.
Connect the GND and PGND islands by connecting
the GND pins directly to the exposed backside pad.
Make no other connections between these separate
ground planes.
4) Place the IN pin and VCC pin bypass capacitors as
close to the device as possible. The ground connec-
tion of the bypass capacitors should be connected
directly to the GND pins with a wide trace.
5) Minimize the size of the LX node while keeping it wide
and short. If possible, avoid running the LX node from
one side of the PCB to the other. Use DC traces as
shield if necessary.
Refer to the MAX17129/MAX17149 evaluation kit for an
example of proper board layout.
相關(guān)PDF資料
PDF描述
DS1245AB-100 128K X 8 NON-VOLATILE SRAM MODULE, 100 ns, DMA32
DS1245Y-120 128K X 8 NON-VOLATILE SRAM MODULE, 120 ns, DMA32
DS1245AB-85 128K X 8 NON-VOLATILE SRAM MODULE, 85 ns, DMA32
DS1245Y-85 128K X 8 NON-VOLATILE SRAM MODULE, 85 ns, DMA32
DS1245Y-70 128K X 8 NON-VOLATILE SRAM MODULE, 70 ns, DMA32
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS1244Y120 制造商:Maxim Integrated Products 功能描述:
DS1244Y-120 制造商:Maxim Integrated Products 功能描述:
DS1244Y-150 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
DS1244Y-200 制造商:DALLAS 制造商全稱(chēng):Dallas Semiconductor 功能描述:256K NV SRAM with Phantom Clock
DS1244Y-70 功能描述:實(shí)時(shí)時(shí)鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線(xiàn)接口:I2C 日期格式:DW:DM:M:Y 時(shí)間格式:HH:MM:SS RTC 存儲(chǔ)容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
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