| =|I1 | _0 |
| LXM1598-01 CCFL ( cold cathode flore.scent | ated noi.se. This topology .simultaneou.sly |
| lamp) Inverter Modules are .specifically de- | perform.s three tasks consi.sting ofline volt- |
| signecl for driving LCD back light lamp.s in | age regulation,lamp current regulation, and |
| application.s where dimmability, Ldtrahigh | lamp dimming in a single power .stage |
| efficiency, high light output, low noise | made up of one pair of low lo.s.s FET's. |
| emis.sion.s, reliable fail .safe de.sign, and | The FET'.s clrive an LC resonant circuit that |
| small form factor.s are critical parameter.s. | feed.s the primary of a high voltage tran.s- |
| Both monochrome ancl color di.splay.s are | former with a .sinu.soidal voltage. |
| .supported | Required L and C value.s in the re.sonant |
| The modules convert unregulated DC | circuit are .such that very low loss compo- |
| voltage from the system battery or AC | nents can be u.sed to obtain higher elecfri- |
| adapter directly to high-frequency, high- | cal efficiency than is pos.sible with previ- |
| voltage .sine wave.s required to ignite and | ou.s topologie.s. |
| operate CCFL lamps. The module de.sign | The half bridge LXM1598-01 is optimized |
| i.s ba.secl on a proprietary Linfinity IC that | to efficiently operate with up t0 4 watt |
| provides important new performance ad- | lamp.s over the full 10V t0 14V input volt- |
| vance.s | age range |
| Remarkable improvements in efficiency | The module.s are equipped with a dim- |
| and RF emis.sion.s re.sult from it.s single stage | ming input that permit.s full range bright- |
| re.sonant inverter featuring a patent pend- | ne.ss control from an external potentiom- |
| ing Current Synchronous, Zero Yoltage | eter, and a .sleep inpLit that reduce.s mod- |
| Switching (CS-ZVS.) topology. CS-ZVS pro- | ule power to a few microwatLs in .shut down |
| duce.s nearly pure .sine wave current.s in | mode |
| the lamp enabling maximum light delivery | All modules feature output open and |
| while reducing both conducted and radi- | .short circuit protection. |
| |
Once RSET has been calculated, it may be found that the calcu- lated value does not agree with readily available standard resistors of the chosen tolerance. In order to achieve an RSET value as close as possible to the calculated value, a compound resistor can be constructed by connecting two resistors in series or in parallel. To conserve cost, one moderately precise resistor and one lower precision resistor can be combined. If the mod- erately precise resistor provides most of the necessary resistance, the lower precision resistor can provide a fine adjustment. Con- sider an example where the closest standard l% resistor has only 90% of the value required for RSET. If a 5% series resistor is used for the remainder, then its tolerance only adds 5% of 10% or 0.5% additional error to the combination. Likewise, the l% resistor only contributes 90% of l% or 0.9% error to the combi- nation. These two contributions are additive resulting in a total compound resistor tolerance of l.4%.
BiMOS II devices have much higher data-input rates than the original BiMOS circuits. With a 5 V logic supply, they will typically operate at better than 5 MHz. With a 12 V supply, significantly higher speeds are obtained. The CMOS inputs are compatible with standard CMOS and NMOS logic levels. TTL circuits may require the use of appropriate pull-up resistors. By using the serial data output, the drivers can be cascaded for interface applications requiring additional drive lines.
