参数资料
型号: LM3445TRIACEVAL
厂商: National Semiconductor
文件页数: 16/40页
文件大小: 0K
描述: BOARD EVAL LM3445MM
标准包装: 1
系列: PowerWise®
电流 - 输出 / 通道: 770mA
输出及类型: 1,非隔离
特点: 可调光
输入电压: 8 ~ 12V
已供物品:
已用 IC / 零件: LM3445MM
相关产品: LM3445MMX-ND - IC LED DRIVER TRIAC DIMM 10-MSOP
LM3445MMDKR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP
LM3445MMCT-ND - IC LED DRIVER TRIAC DIMM 10-MSOP
LM3445MMTR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP
SNVS570L – JANUARY 2009 – REVISED MAY 2013
I AVE
I L2 (t)
' i L
I L2-PK
I L2-MIN
t ON
t OFF
t
Figure 22. Inductor Current Waveform in CCM
During the off-period denoted by t OFF , the current through L2 continues to flow through the LEDs via D10.
MASTER/SLAVE OPERATION
Multiple LM3445s can be configured so that large strings of LEDs can be controlled by a single triac dimmer. By
doing so, smooth consistent dimming for multiple LED circuits is achieved.
When the FLTR1 pin is tied above 4.9V (typical), preferably to VCC, the ramp comparator is tri-stated, disabling
the dim decoder. This allows one or more LM3445 devices or PWM LED driver devices (slaves) to be controlled
by a single LM3445 (master) by connecting their DIM pins together.
MASTER/SLAVE CONFIGURATION
TI offers an LM3445 demonstration PCB for customer evaluation through our website. The following description
and theory uses reference designators that follow our evaluation PCB. The LM3445 Master/Slave schematics are
illustrated below ( Figure 23 through Figure 25 ) for clarity. Each board contains a separate circuit for the Master
and Slave function. Both the Master and Slave boards will need to be modified from their original stand alone
function so that they can be coupled together. Only the Master LM3445 requires use of the Master/Slave circuit
for any number of slaves.
MASTER BOARD MODIFICATIONS
?
?
?
Remove R10 and replace with a BAS40 diode
Connect TP18 to TP14 (V CC )
Connect TP17 (gate of Q5) to TP15 (gate of Q2)
SLAVE BOARD(S) MODIFICATIONS
?
?
Remove R11 (disconnects BLDR)
Tie TP14 (FLTR1) to V CC
MASTER/SLAVE(S) INTERCONNECTION
?
?
Connect TP19 of Master to TP10 of Slave (Master VCC Control)
Connect TP6 (DIM pin) of Master to TP6 (DIM pin) of Slave (Master DIM Control)
MASTER/SLAVE THEORY OF OPERATION
By placing two series diodes on the Master VCC circuit one forces the master VCC UVLO to become the
dominant threshold. When Master VCC drops below UVLO, GATE stops switching and the RC timer (>200 μs)
rises above the TL431 threshold (2.5V) which in turn pulls down on the gate of the Slave pass device (Q1).
The valley-fill circuit could consist of one large circuit to power all LM3445 series connected, or each LM3445
circuit could have a separate valley-fill circuit located near the buck converter.
16
Product Folder Links: LM3445
Copyright ? 2009–2013, Texas Instruments Incorporated
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