- 您现在的位置：买卖IC网 > PDF目录224108 > LM3402_07 (National Semiconductor Corporation) 0.5A Constant Current Buck Regulator for Driving High Power LEDs PDF资料下载
参数资料
| 型号： | LM3402_07 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | 0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| 中文描述： | 0.5A的恒流降压稳压器用于驱动高功率LED |
| 文件页数： | 13/24页 |
| 文件大小： | 431K |
| 代理商： | LM3402_07 |
Schottky diode at 350 mA is approximately 0.65V and the
θ
JA is 88°C/W. Power dissipation and temperature rise can be
calculated as:
P
D = 0.065 x 0.65 = 42 mW
T
RISE = 0.042 x 88 = 4°C
C
B AND CF
The bootstrap capacitor C
B should always be a 10 nF ceramic
capacitor with X7R dielectric. A 25V rating is appropriate for
all application circuits. The linear regulator filter capacitor C
F
should always be a 100 nF ceramic capacitor, also with X7R
dielectric and a 25V rating.
EFFICIENCY
To estimate the electrical efficiency of this example the power
dissipation in each current carrying element can be calculated
and summed. Electrical efficiency,
η, should not be confused
with the optical efficacy of the circuit, which depends upon the
LEDs themselves.
Total output power, P
O, is calculated as:
P
O = IF x VO = 0.361 x 49.2 = 17.76W
Conduction loss, P
C, in the internal MOSFET:
P
C = (IF
2
x R
DSON) x D = (0.361
2
x 1.5) x 0.82 = 160 mW
Gate charging and VCC loss, P
G, in the gate drive and linear
regulator:
P
G = (IIN-OP + fSW x QG) x VIN
P
G = (600 x 10
-6
+ 3 x 105 x 3 x 10-9) x 60 = 90 mW
Switching loss, P
S, in the internal MOSFET:
P
S = 0.5 x VIN x IF x (tR + tF) x fSW
P
S = 0.5 x 60 x 0.361 x 40 x 10
-9
x 3 x 105 = 130 mW
AC rms current loss, P
CIN, in the input capacitor:
P
CIN = IIN(rms)
2
x ESR = (0.134)2 x 0.006 = 0.1 mW (negligible)
DCR loss, P
L, in the inductor
P
L = IF
2
x DCR = 0.352 x 1.1 = 135 mW
Recirculating diode loss, P
D = 42 mW
Current Sense Resistor Loss, P
SNS = 69 mW
Electrical efficiency,
η = P
O / (PO + Sum of all loss terms) =
17.76 / (17.76 + 0.62) = 96%
Temperature Rise in the LM3402HV IC is calculated as:
T
LM3402 = (PC + PG + PS) x θJA = (0.16 + 0.084 + 0.13) x 200
= 74.8°C
Layout Considerations
The performance of any switching converter depends as
much upon the layout of the PCB as the component selection.
The following guidelines will help the user design a circuit with
maximum rejection of outside EMI and minimum generation
of unwanted EMI.
COMPACT LAYOUT
Parasitic inductance can be reduced by keeping the power
path components close together and keeping the area of the
loops that high currents travel small. Short, thick traces or
copper pours (shapes) are best. In particular, the switch node
(where L1, D1, and the SW pin connect) should be just large
enough to connect all three components without excessive
heating from the current it carries. The LM3402/02HV oper-
ates in two distinct cycles whose high current paths are shown
in Figure 6:
20192128
FIGURE 6. Buck Converter Current Loops
The dark grey, inner loop represents the high current path
during the MOSFET on-time. The light grey, outer loop rep-
resents the high current path during the off-time.
GROUND PLANE AND SHAPE ROUTING
The diagram of Figure 6 is also useful for analyzing the flow
of continuous current vs. the flow of pulsating currents. The
circuit paths with current flow during both the on-time and off-
time are considered to be continuous current, while those that
carry current during the on-time or off-time only are pulsating
currents. Preference in routing should be given to the pulsat-
ing current paths, as these are the portions of the circuit most
likely to emit EMI. The ground plane of a PCB is a conductor
and return path, and it is susceptible to noise injection just as
any other circuit path. The continuous current paths on the
ground net can be routed on the system ground plane with
www.national.com
20
LM3402/LM3402HV
相关PDF资料 |
PDF描述 |
|---|---|
| LM4681SQ | 10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and I2C/SPI Volume Control |
| LM5009SD | 150 mA, 100V Step-Down Switching Regulator |
| LM5009SDX | 150 mA, 100V Step-Down Switching Regulator |
| LMK02000 | Precision Clock Conditioner with Integrated PLL |
| LMR-01-Z | SPECIAL SWITCH-JOYSTICK SWITCH, SPDT, MOMENTARY, 1A, 14VDC, PANEL MOUNT |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3402EVAL | 功能描述:BOARD EVALUATION FOR LM3402 RoHS:是 类别:编程器，开发系统 >> 评估板 - LED 驱动器 系列:PowerWise® 标准包装:1 系列:PowerWise® 电流 - 输出 / 通道:20mA 输出及类型:1，非隔离 输出电压:17V 特点:可调光 输入电压:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相关产品:LM3508TLX-ND - IC LED DRVR WHT BCKLGT 9USMDLM3508TLDKR-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLCT-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLTR-ND - IC LED DRVR WHT BCKLGT 9MICROSMD |
| LM3402EVAL | 制造商:Texas Instruments 功能描述:EVAL BOARD |
| LM3402EVAL/NOPB | 功能描述:电源管理IC开发工具 LM3402 EVAL BOARD 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 |
| LM3402HV | 制造商:Texas Instruments 功能描述:Buck Regulator ,0.5A ,LED Drivers,MSOP8 |
| LM3402HVEVAL | 功能描述:BOARD EVALUATION FOR LM3402HV RoHS:是 类别:编程器，开发系统 >> 评估板 - LED 驱动器 系列:PowerSmart® 标准包装:1 系列:PowerWise® 电流 - 输出 / 通道:20mA 输出及类型:1，非隔离 输出电压:17V 特点:可调光 输入电压:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相关产品:LM3508TLX-ND - IC LED DRVR WHT BCKLGT 9USMDLM3508TLDKR-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLCT-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLTR-ND - IC LED DRVR WHT BCKLGT 9MICROSMD |
发布紧急采购，3分钟左右您将得到回复。