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LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
DESCRIPTION
KEY FEATURES
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LED Display Driver: This six channel current sink driver is ideal for controlling brightness and hue of high quality dimmable LED displays. High accuracy, dual mode dimming, and controlled current switching time provides consistent color hue, at brightness ratios of up to 1000:1, and keeps electro magnetic emissions in check. Its wide compliance voltage range combined with 43 volt breakdown capability make the LX1991 ideal for automotive in-dash displays. Precision current control: Precision current mirror circuitry sets all channels to the same current with a single programming input. Sinking current value can be programmed up to 30 mA per channel with a single resistor or potentiometer from ISET+ to ISET-. Channel to channel matching is typically within 1 percent of channel mean at the rated output current. Dual Mode Dimming: Display dimming can be achieved by controlling either current amplitude or duty cycle, and both methods can be employed at the same time.
1000:1 Dimming Range: The DIG_DIM input accepts a TTL or CMOS logic signal that controls duty cycle of the output currents. Independent Channels: The six channels feature independent regulation with respect to output voltage, so one does not affect the others. Any one or more outputs can be left unloaded without affecting current regulation of the other channels. Multiple channels can also be connected together to sink more current in a single load. EMI Control: Rise and fall time of sink currents are precisely controlled by placing a capacitor on the SLOPE_C pin. Special control circuitry maintains symmetrical rise and fall times, preserving the LX1991's ability to provide accurate output current response to very narrow input pulses on the DIG_DIM pin. Power Handling: The LX1991 is supplied in a 4x4 MLPQ package capable of 1.5 watts dissipation. Logic Enable: A separate input puts the LX1991 to sleep at less than 1 uA IDD.
Six precision independent current sink channels Simultaneous Analog and Digital Dimming Modes Precision programming of current rise & fall times 1% band gap reference 40 volt rated output stages 3V / 5V logic input compatible 1.5 watt power dissipation On-chip thermal shutdown 16 Pin 4 x 4 MLPQ Package
BENEFITS
Consistent LED color hue results from high current accuracy 1000:1 dimming ratio with digital dimming Lowered emissions with current slope programming Reduced component count for compact designs Drive up to 108 colored LED's per IC (6 x 18 @ 2.1 volts) Drive up to 60 white or blue LED's per IC (6 x 10 @ 3.8 volts)
IMPORTANT: For the most current data, consult MICROSEMI's website: http://www.microsemi.com
PRODUCT HIGHLIGHT
+36V 5V
LX1991
54 White LED's VF ~3.7V @20mA
SINK1
Bill of Materials
1 1 1 54 57 LX1991 Cap Resistor White LEDs Total Count
SLEW CONTROL PWM SIGNAL
ON
VDD CSLOPE SINK2 DIG_DIM SINK3 SINK4 SINK5 ISET+ SINK6 GND
LX1991
ENA
OFF
1.5K
ISET-
LX1991 LX1991
PACKAGE ORDER INFO
TJ (C) -40 to 85
Copyright (c) 2001 Rev. 1.0, 5/18/2005
MIN VDD 4.5
MAX VDD 5.5V
LQ
Plastic 4x4 MLPQ 16-PIN LX1991ILQ
Page 1
RoHS Compliant / Pb-free Transition DC: 0436
Note: Available in Tape & Reel. Append the letters "TR" to the part number. (i.e. LX1991ILQ-TR)
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
ABSOLUTE MAXIMUM RATINGS Supply Voltage (VDD ) ............................................................................... -0.3v to 6V Analog Output Voltage (SINK1 to SINK6 )............................................... -0.3V to 43V Analog Inputs (ISET).......................................................................-0.3V to VDD +0.5V Digital Inputs (ENABLE, DIG_DIM) ...........................................-0.3V to VDD +0.5V Operating Temperature Range ...................................................................-40C - 85C Storage Temperature Range.....................................................................-65C - 150C Maximum Junction Temperature .......................................................................... 150C Peak Package Solder Reflow Temp. (40 seconds max. exposure) ........... 260C (+0, -5)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of specified terminal.
PACKAGE PIN OUT
CSLOPE ENABLE
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16 DIG _DIM VDD SINK 1 SINK 2 1 2 3 4 5 GND
15
14
13 12 11 10 9 NC ISET SINK 6 GND
6 SINK 3
7 SINK 4
LQ PACKAGE
(Top View)
THERMAL DATA
Plastic 4x4 MLPQ 16-Pin THERMAL RESISTANCE-JUNCTION TO AMBIENT, JC THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA
LQ
2.2C/W 36C/W
MSC 1991 xxxx
LQ PACKAGE MARKING
xxxx Denotes Date Code / Lot Code
Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/ 4 layer pcboard system. All of the above assume no ambient airflow. The JA numbers are to MIL-STD-883D Method 1012.1
RoHS / Pb-free 100% Matte Tin Lead Finish
FUNCTIONAL PIN DESCRIPTION PIN NAME GND VDD SINK1 - SINK6 DIG_DIM Ground Voltage Input, 4.5 to 5.5V input range. VDD is internally switched (see ENABLE) to remove power from chip. Current sink channels one through six. Each output sinks the programmed current from the VLED supply to ground. Compliance voltage is from 1 volt minimum to the VLED supply maximum. A logic input that duty cycle modulates the output currents. All output currents are turned on at the programmed current value when DIG_DIM is high and turned off when it is low. Compatible with both 3V and 5V logic. Chip Enable Input. If logic high, all functions are enabled. If logic low, internal power is disconnected from the VDD pin, disabling all functions. Logic threshold is 1.6 0.8V maximum over supply and temperature range. Maximum current into VDD when ENABLE < 0.4V is 1 A . Current programming resistor pins. Output current in each channel is 24 times the current that flows from ISET+ to ISET- ISET current is 1.26V / RSET. Connect resistor between ISET+ and ISETCurrent rise and fall time programming capacitor. Rise and fall times increase in direct proportion to capacitor value. C = 450A * TR or TF in microseconds, C in picofarads. DESCRIPTION
ISET+ 8 SINK 5
NC
PACKAGE DATA PACKAGE DATA
ENABLE ISET+ ISETCSLOPE
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
RECOMMENDED OPERATING CONDITIONS Parameter
Supply Voltage (VDD) ENABLE Input Voltage DIG_DIM Input Voltage CSLOPE Capacitance Range ISET Voltage RSET Current Programming Resistor Range SINK1 To SINK6 Output Voltage Range 0 1 0.5 3 1.26 40 40* V K V
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Min
4.5 0 0
LX1991 Typ
Max
5.5 VDD VDD
Units
V V V
SINK1 To SINK6 Maximum Output Current 30 mA *At output voltages greater than 5V total power dissipation when using all six outputs at maximum current will exceed power rating of package and ambient of 85C.
SIMPLIFIED BLOCK DIAGRAM
S I N K 1 SINK2 VDD
1:1 Current Mirror
24X 24X
SINK3
24X
DIG_DIM
1.25V REF
Slew Control
GND + ENABLE Bias
2V
24X
24X
24X
BLOCK DIAGRAM BLOCK DIAGRAM
0V
ISET-
ISET+
CSLOPE
SINK6
SINK5
SINK4
Figure 1 - Simplified Block Diagram
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -40C WWW .Microsemi .C OM
Parameter
POWER Power Supply Input Voltage Quiescent current Quiescent current Sleep Current
1
Symbol
Test Conditions
Min
4.5
LX1991 Typ
5 10 3.6 0.08
Max
5.5 16 6 1 2.4 10 1 31.6 21 11 6 2.5 100 100 800 1000
Units
VDD IDD ON IDD OFF IDD_SLEEP VTH_EN IIH ENABLE_ IIL ENABLE SINK 30 SINK 20 SINK 10 VENABLE = VDD VENABLE = 0V VDD = 5V, SINKX = 3V, RSET = 1.02K VDD = 5V, SINKX = 3V, RSET = 1.54K VDD = 5V, SINKX = 3V, RSET = 3.09K VDD = 5V, SINKX = 3V, RSET = 6.19K VDD = 5V, SINKX = 1V to 5V; RSET = 1.54K VDD = 5V, SINKX/ISET ISET = 0A RSET = 1.02K; DIG_DIM 0.8V SINK X = 10mA SINK X = 30mA VISET = Zero Volts; VDD=5V; SINKX = 5V ENA 0.4V, VOUT = 40V VDD = 5V, ENABLE 2.4V; DIG_DIM 2.4V VDD = 5V, ENABLE 2.4V; DIG_DIM 0.8V VDD = 5V, VOUT = 40V, ENABLE 0.4V
V mA mA A V A A mA mA mA mA % ADC ADC mV mV mADC
ENABLE INPUT ENABLE Logic Threshold Input Current Input Current OUTPUT CURRENT SINK X 30mA SINK X 20mA SINK X 10mA 28.4 19 9 4 30 20 10 5 1 24.5 10 10 200 600 50 1 0.8 VDIG_DINM = VDD VDIG_DIM = 0V CSLOPE 20pF CSLOPE 20pF CSLOPE 20pF, DIG_DIM 5uS CSLOPE = 10 nF CSLOPE = 10 nF CSLOPE = 10 nF, TA = 25C RSET+ = 1.50K to ISET1.24 15 15 1.6 50 0.1 340 230 5 22 24 50 1.26 4.5 1.28 29 29 3 2.4 0.8 1.6 4.0 0.4
SINK X 5mA SINK 05 2 SINK X Current Matching SINK X_MATCH ISET to SINK X Current Ratio SINK X_RATIO Output Current ISET = 0A SINKSET0 Output Current DIG_DIM 0.8V SINKDIG_DIM0 3 VDROPOUT Dropout Voltage 3 VDROPOUT Dropout Voltage Maximum Output Current, ISET Shorted SINK ISETSC To Gnd. Each Output Output Off State Current SINK X OFF DIG_DIM INPUT DIG_DIM Logic Threshold Input Current, high state Input Current, low state DIG_DIM to SINK X Pulse Response DIG_DIM to SINK X Pulse Response Minimum SINK X Pulse Width CURRENT ON / OFF SLOPE Current On rise time Current On fall time Current on / off delay time RSET PIN Voltage at Pin RSET Pin RSET Max Source Current
1 2
ADC V A A nS nS S Sec Sec
VTH_DD IIH DIG_DIM IIL DIG_DIM TD(ON) TD(OFF) SINK X PWMMIN TRISE TFALL Tdelay VRSET IMAX RSET
ELECTRICALS ELECTRICALS
Sec V mA
At enable voltages greater than 0.4V but less than 0.8V the outputs will remain off but the sleep current may be greater than 1A. SINK X current matching is greatest percentage delta between output currents with respect to the mean, with VSINK X both at 1V and 5V and RSET = 1.54K. 3 Dropout is defined as the SINKX to GND voltage at which the output current sink drops 10% from the nominal value.
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
THEORY OF OPERATION / APPLICATION NOTE FUNCTIONAL DESCRIPTION The LX1991 is designed to drive LED's used in display illumination and signaling applications such as cellular telephones, PDA's automotive dashboard lighting, panel illumination etc. With a single 5V supply, the six independently regulated constant current outputs can drive 6 white LED's (VF < 4.0V), or 12 green or amber LED's (VF < 2.0V each) arranged as 6 parallel x 2 in series. With a separate high voltage LED supply (up to 40V) a large matrix of LED's (>100) can be driven. The LX1991 features resistor settable output current. Connecting a resistor between ISET+ and ISET- pins generates a current that is mirrored into each of the outputs with a gain ratio of about 24. This ratio remains linear for output currents from 3 to 30mA, at output current less than 3mA the ratio increases somewhat. Output current can be varied in an analog fashion by varying RSET resistor, typically this resistor shall be chosen in the range of 1K to 40K. Duty cycle dimming with a fixed current amplitude is accomplished by driving the DIG_DIM input. The switching frequency can exceed 100 KHz, making it practical to use a PWM output channel from popular micro controllers. The upper limit on frequency correlates to the minimum DIG_DIM sink pulse width which is typically about 5S. To use the LX1991 at the maximum usable frequency, or minimum pulse width the CSLOPE pin must be open. The CSLOPE pin allows precise control of the sink current rise and fall time. As the value of the CSLOPE capacitor is increased the slope of the rise and fall time will change correspondingly along with some delay to output. Special control circuitry maintains symmetrical rise and fall times, preserving the LX1991's ability to provide accurate output current response to very narrow input pulses on the DIG_DIM pin. The ENABLE input is TTL compatible with a turn on threshold of about 1.6V with about 150mV of hysteresis. Below 0.8V the chip is disabled and the sink outputs are off. However ENABLE must be driven below 0.4 volts to insure the minimum sleep current from VDD and output off current. All inputs and outputs are ESD and short circuit protected making the LX1991 an exceptionally robust component. The device also includes thermal shutdown however it is not recommended to short the ISET+ and ISET- inputs together while shorting the outputs to 40V as the power dissipation under these conditions is the greatest. APPLICATION NOTES POWER CONSIDERATIONS Each output has an independent current sink, however each must be held above about 600-800mV (typically) to perform properly and maintain the specified current regulation accuracy. The device is designed however to allow one or more of the outputs to be unused (open) without affecting the other channels Or conversely if more than 30mA is needed the outputs can be combined for higher total currents. Package power dissipation can be calculated from the following equation: PD = nxI OUT x VLOAD -VLED n IOUT VLOAD VLED PD = = = = =
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(
)(
)
Number of outputs used Current from each output Output Supply Voltage Minimum LED forward voltage Power Dissipated in mW
Care should be exercised not to exceed the power dissipation of the package or the maximum junction temperature of the die. Proper mounting of the package with thermal vias (see PCB Land Guidelines and Thermal Pad Design section) enhances power dissipation capability. As an example to drive 24 white LED's, 4 per channel from a 18V VLED supply @ 25mA per LED string, we will assume the minimum LED forward voltage to be 3.5V with an maximum operating ambient of 50C. PD = (6x25mA)x(18V-(4x3.5V)) = 15x4V = 0.6W This represents a 21.6C temperature rise (36C/W *0.6W) for a die temperature of about 72C, ignoring device drain current power dissipation that only represents about a 3C rise worst case. This is well under the die junction temperature maximum rating of 150C, and within the 85C electrical specifications. DIMMING Dimming can be accomplished both with current amplitude control (changing the RSET resistor value) with a PWM signal (toggling the DIG_DIM input) or both. Current between the ISET+ and ISET- pins may be varied for current amplitude dimming. If a mechanical input is needed, a rheostat in series with a resistor connected from ISET+ to ISET- can be used.: I OUT =Current RatioxISET
APPLICATIONS APPLICATIONS
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
APPLICATION NOTE - CONTINUED The range of the RSET resistor can vary between 1K and 40K Ohms. The resistor in series with the rheostat will set the maximum current and should be a least 1K in value. If a fixed sink current is desired its easy to find the RSET resistor value. As an example, suppose the desired output current is 25mA per sink channel. The RSET resistor can be calculated as follows:
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Typical CSLOPE vs Slope Times
25
Sink Rise/Fall Time (uS)
R SET(K) = Current ratio Output current(mA) x VR SET
20 15 10 5 0 0 2 4 6 8 10
R SET(K) = 24.5
25 x 1.26 = 1.23K
Once the maximum sink current is set the rheostat will increase the RSET value thus dimming the LED by reducing the sinking current. Wide range dimming can be accomplished by using the DIG_DIM input pin to pulse the output sink current. The DIG_DIM pin may be driven with a TTL compatible logic PWM signal to dim the LED's. The recommended PWM frequency for dimming is between 100 Hz and 100 KHz. Below 100 Hz flicker may be observed. Above 100 KHz duty cycle accuracy and minimum pulse width is reduced due to delay times and the current slew rate. To obtain the maximum dim range and still make use of the slope control function ( see CSLOPE pin below) it is advisable to use a lower frequency on the DIG_DIM input. If PWM dimming is used, use of separate power and ground lines directly from the power source point will help to prevent noise generated from the LED current transients from entering video or audio subsystems on the same supply rails. Additional power supply filtering may be needed in PWM dimming applications. Care should be exercised in the PCB layout to prevent coupling from the SINK outputs to the DIG_DIM pin. CSLOPE PIN The CSLOPE pin is available to control the rise and fall times of the SINK outputs during pulse dimming. With the CSLOPE pin open a minimum rise and fall time of about 120 to 200nS will be present on the output waveforms along with a delay time (DIG_DIM to SINKx) of about 200nS. As the CSLOPE capacitor is increases in value so will the corresponding rise and fall times and delay to output. The calculation for the CSLOPE value is approximately 450A * TR or TF in microseconds, C in picofarads. So for a 5uS rise and fall time 0.00045 * 5 = 2250pF or about a typical .0022uF capacitor value. For typical slope rise and fall times see the follow chart
CSLOPE Capacitor (nF)
DRAIN CURRENT
The chart below illustrates the correlation between the IC's drain current and the total sink output current. The drain current will also increase slightly if one or more the SINKx pins are left floating or when the SINK outputs are near dropout, however in both of these circumstances the increased drain current will be small and controlled and is a feature of the design.
LX1991 Typical Drain Current Vs Sink Current
200
Total I SINK Current (mA)
150 100 50 0 4 6 8 10 12 14
A APPLICATIONS
Typical Drain Current (mA)
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
ISINK VS VDD AND TEMPERATURE
30.5 30.4 30.3
ISINK VS VDD AND TEMPERATURE
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20.5 20.4 20.3
IOUT Current (mA)
30.2 30.1 30 29.9 29.8 29.7 29.6 29.5 -45 -25 -5
I OUT Current (mA)
VDD=5.5V VDD=5V
20.2 20.1 20 19.9 19.8 19.7 19.6
VDD=5.5V VDD=5V
VDD=4.5V
VDDx=4.5V
1 5
35
55
75
19.5 -45
-25
-5
15
35
55
75
Tem p (C)
Temp (C)
VDD = 5V, RSET = 1.54K
ISINK VS VSINK AND TEMPERATURE
20.4 20.3
SINKX = 3V; RSET = 1.02K
DROPOUT VS TEMPERATURE
800 700
I OUT Current (mA)
20.2 20.1 20 19.9 19.8 19.7 -45
I OUT Current (mA)
SINKx=5V SINKx=3V
600 500 400 300 200
ISINK=30MA
SINKx=1V
ISINK=10MA
-25
-5
15
35
55
75
100 -45
-25
-5
15
35
55
75
Temp (C)
VDD = 5V, RSET = 1.54K
Temp (C)
Load = 10k and 1F Photo Step = Direct Light Input of 14.6W/cm2
CSLOPE = 2500PF RESPONSE
CSLOPE = 470PF RESPONSE
CHARTS CHARTS
VDD=5V ,CSLOPE = 2500pF, Chan 1 = 20Khz DIG_DIM Channel 2 = SINKX = 10mA/DIV, Load = single white LED
VDD=5V, CSLOPE = 470pF, Chan 1 = 100Khz DIG_DIM Channel 2 = SINKX = 10mA/DIV, Load = single white LED per channel
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
MECHANICAL DRAWING
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LQ
16-Pin MLPQ Plastic (4x4mm EP)
D
b
E2 L
Dim A A1 A3 b D E e D2 E2 K L
E
D2
e A1 A3 A
K
MILLIMETERS MIN MAX 0.80 1.00 0 0.05 0.18 0.30 0.23 0.38 4.00 BSC 4.00 BSC 0.65 BSC 2.55 2.80 2.55 2.80 0.20 0.30 0.50
INCHES MIN MAX 0.031 0.039 0 0.002 0.007 0.012 0.009 0.015 0.157 BSC 0.157 BSC 0.026 BSC 0.100 0.110 0.100 0.110 0.008 0.012 0.020
Note:
1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006") on any side. Lead dimension shall not include solder coverage.
LQ
16-Pin PCB Land Guidelines and Thermal Pad Design
1 - 1.2mm 0.05mm minimum 0.5mm
0.15mm minimum gap 2.50mm Maximum
0.15mm minimum 0.37mm Nominal
Package Pad PCB Land Thermal Via
0.3mm Dia.
0.28mm
Pin 1 Indicator (bottom of Package)
Top View
The typical land pattern shown includes thermal vias in the exposed die attach pad for improved thermal performance. Vias should be about 0.3mm in diameter, with the via plated to about 1.0 ounce copper. Vias should be plugged to prevent voids being formed due to capillary action. This can be avoided by tenting the via during the solder mask process. In addition, to reduce solder paste volume on the thermal land, it is recommended that an array of small apertures in the solder mask be used instead of one large aperture, with the goal of 50 - 80% solder paste coverage. Please review IPC / EIA J-Std-001C Section 9.2.6.4 "Bottom Only Termination" for solder joint requirements.
MECHANICALS
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
LX1991
TM (R)
Six Output Programmable LED Current Sink
PRODUCTION DATA SHEET
NOTES
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NOTES NOTES
PRODUCTION DATA - Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not necessarily include testing of all parameters. Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time.
Copyright (c) 2001 Rev. 1.0, 5/18/2005
Microsemi
Integrated Products 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9

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