LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? description the LX1800 bridges the analog and digital world. the analog interface contains and eight bit adc and 8 bit dac and the digital interface is a serial data smbus interface. the LX1800 works well in a feedback control system such as an lcd backlight system where the analog output of an ambient light sensor such as the lx1972 can be digitized allowing the micro controller to adjust the analog dimming signal accordingly. the LX1800 has an internal bandgap reference and also allows the use of an external reference. the external reference can be used as an analog input for volume control using the dac or to provide wider range for high amplitude analog signals. the 8 pin mlp package is small occupying no more area than a tsot package. important: for the most current data, consult microsemi ?s website: http://www.microsemi.com key features ? 8 bit accuracy ? adc and dac in one package ? fully compliant to standard smbus ? bus controllable sleep mode ? optional external reference applications ? processor controlled dimming ? vid control interface ? digital regulator control ? audio volume control product highlight ccfl to p 3.3v LX1800 scl scd gnd adr aout ain ref vdd brt lx1691 based module lx1972 package order info ld plastic mlp 8-pin t j ( c) rohs compliant / pb-free -40 to +85 LX1800ild note: available in tape & reel. append the letters ?tr? to the part number. (i.e. LX1800ild-tr) l l x x 1 1 8 8 0 0 0 0
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? absolute maximum ratings supply input voltage ........................................................................-0.3v to 7.0v ref, ao, ai, adr, scl, sda........................................................-0.3v to 7.0v operating temperat ure range ..................................................................... 150 c maximum operating junc tion temperat ure ................................................ 150 c storage temperat ure range...........................................................-65 c to 150 c peak package solder reflow temp (40 second 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 . thermal data ld plastic mlpd 8-pin thermal resistance - junction to a mbient , ja 48 c/w junction temperature calculation: t j = t a + (p d x ja ). the ja numbers are guidelines for the thermal performan ce of the device/pc-board system. all of the above assume no ambient airflow. package pin out 1 2 3 4 5 6 7 8 vin adr scl sda ai ref gnd ao connect bottom to power gnd ld p ackage (top view) rohs / pb-free 100% matte tin lead finish functional pin description name description adr smbus address ? the address for the LX1800 is determine d by the sate of this pin. adr = gnd is address 54b, adr = vcc is address 55b. ai analog input ? sampled input for the analog-to-digital converter. ao analog output ? output of digital-to-analog converter. gnd ground ? connect to system ground. ref external voltage reference (optional) ? reference fo r both adc and dac. ref must be less than 80% of vin. scl smbus clock ? connect to smbus clock line sda smbus data ? connect to smbus data line vin power supply ? connect to a 2.7v to 5.5v power source. p p a a c c k k a a g g e e d d a a t t a a
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? electrical characteristics unless otherwise specified, the following specifications apply over the operating ambient temperature -40 c t a 85 c except where otherwise noted and the following test conditions: v cc = 5v, v ref external = 2.500v, control register = 1bh. LX1800 parameter symbol test conditions min typ max units ` power supply operating supply voltage v cc 2.7 5.5 v average supply current i cc dac = ffh; idle adc 100 200 a sleep current i cc control register = 10h 50 a ` dac dac resolution 8 bits dac full-scale output v fs dac = ffh; i ao = 0 10a 2.42 2.50 2.58 v dac zero-scale output v zs dac = 00h; i ao = 0 10a 0 30 mv dac absolute accuracy dac = 00h to ffh -5 0 -5 lsb dac adjacent code error dac = 01h to feh; gbnt -0.5 0 0.5 lsb dac transition delay t td delay from stop transition 1 s ` adc resolvable input range 0 5 v adc mid point output v ai = 1.25v 124 128 132 lsb adc absolute accuracy v ai = 0v to 2.5v -6 0 6 lsb input leakage current i ai v ai = 1.25v -3 0 3 a input capacitance c ai v ai = 1.25v 30 pf acquisition time t aq v ai = 1.25v 100 200 s ` external ref input range v ref 0 5 v input leakage current i ref -50 0 50 na ` internal ref reference voltage v int 1.96 2.00 2.04 v ` adr high level input voltage v ahl 80 %vcc low level input voltage v all 20 %vcc input leakage current i adr -50 0 50 na ` scl, sda high level input voltage v shl 2.7 < v cc < 5.5v 2.1 v low level input voltage v sll 2.7 < v cc < 5.5v 0.8 v input leakage current i smb -5 0 5 a sda low level output voltage v ol iout = 350a 0.4 v ` smbus smb clock frequency f clk 10 100 khz e e l l e e c c t t r r i i c c a a l l s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? smbus communication format the LX1800 looks for its unique address each time it detects a ?start condition?. if the address does not match, the LX1800 ignores all bus activity until it encounters another ?start condition?. if the address is a match, the LX1800 acknowledges that it ha s detected its address and a w/r bit to either read or write data. if the w/r bit is a ?0?, signifying a ?write command?, the next byte of data sent from the host will be the index. the index points to an internal register in the LX1800 that will be the object of the subsequent data transfers. ther e are four internal registers within the LX1800: the control register, the dac register ,the adc register, and the misc register. in a write command, the LX1800 will acknow ledge the receipt of a valid index. after the index, there may be another byte of data; if so, this byte of data is loaded into the indexed register. the LX1800 will acknowledge receipt of the data byte. if the write command does not contain data, the command line will be terminated by a ?stop condition? received from the host. if for some reason, the data transfer is corrupted prior to ackn owledgement, the LX1800 will not acknowledge receipt of the byte in question and will not take action on the incomplete data. the LX1800 can receive only one data byte in a write command and will ignore all additional bus activity once it has acknowledged receipt of the data byte until the next ?start condition? is detected. receipt of a ?stop co ndition? or ?start condition? will reset the address detection state machine. the LX1800 does not support ?packet error code?. the host can read the contents of the indexed register within the LX1800 using a r ead command line. in this command line the w/r bit is set to ?1?. upon receipt of a read command, the LX1800 will acknowledge that it has detected its address and a valid w/r bit; then it will put a copy of the one byte of data from the indexed register onto the bus. (as explained above, the index may be changed using a write command with or without an additional data byte.) once the LX1800 has pl aced the byte of data on the serial bus, it will ignore all additional bus activity until the next ?start condition? is detected. write format (two optional packet lengths) start address w/r ack data ack stop 0101100b or 0101101b 0 index start address w/r ack data ack data ack stop 0101100b or 0101101b 0 index 1 byte data read command format: start address w/r ack data ack stop 0101100b or 0101101b 1 read indexed register repeated start command format: the LX1800 will support the execution of successive commands that are not separated by ?stop conditions? provided the commands are otherwise formatted as indicated above. g eneral smb us p rotocol s ummary (see smbus specification version 2.0 for more details). start condition: host sends a high-to-low sda transition while scl is high. address: host sends to 0101100 adr=gnd; 0101101 adr = vcc w/r: host sends a ?lo? bit for an instruction with a data write and a ?hi? bit for a data read. acknowledge: LX1800 and host let sda go high while scl is low after data byte transfer indicating next byte may be sent. stop condition: a low-to-high sda transition while scl is high. normal condition: sda transitions only while scl is low. for timing information see smbus specification version 2.0. data is transferred with the msb first. a a p p p p l l i i c c a a t t i i o o n n s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? smbus register map each register has an address which is programmed into the index register. the value in the index register determines which register is accessed on a given read or write operation. control register: address = xxxxxx00b type = read/write default = 10000000 bit assignments: 7 sleep mode 1 = active mode, 0 = sleep mode 6 reference 1 = external, 0 = internal 5 adc start 1 = start a/d; this bit is reset to 0 when conversion complete. 4 adc mode 1 = always on; 0 = turn on as required 3 invert dac mode 1 = normal dac bit polarity; 0 = inverted dac input polarity 2 adc loop back 1 = adc drives dac di rectly; 0 = dac input comes from bus 1 adc continuous 1 = adc continuously converts; 0 = adc on bus command 0 adc clock mode 1 = adc uses scl clock; 0 = adc uses internal clock. dac register: address = xxxxxx01b type = read/write default = 10000000b bit assignments: ffh = full scale (vref); 00h = 0v (normal polarity mode) adc register: address = xxxxxx10b type = read only default = 00000000b bit assignments: ffh = full scale (vref); 00h = 0v misc register: address = xxxxxx11b type = read/write for bits 7:4; read only for bits 3:0 default = 00000101b bit assignments: 7:4 unassigned 3:2 version 01b = version 1 1:0 revision 01b = revision 1 a a p p p p l l i i c c a a t t i i o o n n s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? simplified block diagram scl sda adr vcc gnd ref ain smbus interface uv lockout and control logic command register dac register 8 bit dac internal 2.0v reference 8 bit dac aout adc register figure 1 ? simplified block diagram b b l l o o c c k k d d i i a a g g r r a a m m
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 7 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? application circuits scl scd gnd adr vdd ref ain aout LX1800 ccfl 49.9k 10 f 0.1f 3.3v to p lx1972 lx1691 based module figure 2 ? backlight dimmer with ambient light compensation scl scd gnd adr vdd ref ain aout LX1800 to p analog in 49.9k 49.9k 0.1f analog out 5v 10nf figure 3 ? 1) log or exponential taper using a p lookup table or 2) infinite sample and hold. a a p p p p l l i i c c a a t t i i o o n n s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 8 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? application circuits scl scd gnd adr vdd ref ain aout LX1800 to p audio in 5v 0.1f 100k 2v 1v 0.1f 100k audio out figure 4 ? digital volume control with audio absent detection. theory of operation b asic f unctionality the LX1800 contains an 8 bit dac, an 8 bit adc and a smbus interface which connects the input of the dac and the output of the adc to the smbus host. the LX1800 contains an internal 2v reference and can also be configured to use an external reference. since the 8 bit dac is a multiplying type, th e external reference can be used for an analog input for volume control applications. the adc contains a sample and hold input that stores the analog voltage level while the conversion is being processed. smb us i nterface the LX1800 communicates over the smbus in the slow speed low power level and operates in a ?slave? mode receiving commands and sendi ng and receiving data from the host or bus ?master?. the LX1800 can be configured for one of two addresses, 0101100b when the adr line is grounded and 0101101b when the adr line is connected to vcc. the LX1800 has three intern al registers, the command register, the dac register and the adc register. the cmd register is read/write, th e dac register is write only and the adc register is read only. control of the LX1800 are performed through the cmd register. a a p p p p l l i i c c a a t t i i o o n n s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 9 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? application note l ayout g uidelines the LX1800 is sensitive to noise at the reference pin so this node should be a low impedance path to ground for high frequency noise. as a precaution, the ref node should be routed away from digital switching traces. the vcc pin should be decoupled to ground with a 0.1f ceramic capacitor located in close proximity to the ic. package dimensions ld 8 pin plastic mlp dual exposed pad d e e a a3 a1 e2 d2 b l top bottom side 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. m illimeters i nches dim min max min max a 0.80 1.00 0.0315 0.0394 a1 0 0.05 0 0.0019 a3 0.20 ref 0.0079 ref b 0.25 0.30 0.010 0.0118 d 3.00 bsc 0.1181 bsc d2 1.60 2.50 0.0630 0.0984 e 0.65 bsc 0.0260 bsc e 3.00 bsc 0.1181 bsc e2 1.35 1.75 0.0531 0.0689 l 0.30 0.50 0.0071 0.0197 a a p p p p l l i i c c a a t t i i o o n n s s
LX1800 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 10 copyright ? 2004 rev. 1.0, 2006-01-05 www. microsemi . com smbus to analog interface tm ? 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. n n o o t t e e s s
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