 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LTC1703 Datasheet(PDF) 9 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LTC1703 Datasheet(HTML) 9 Page - Linear Technology |
|
|
9 / 36 page  9 LTC1703 1703fa converter, even in cases where the 1-step converter has higher total efficiency than the 2-step system. In a typical microprocessor core supply regulator, for example, the regulator is usually located right next to the CPU. In a 1-step design, all of the power dissipated by the core regulator is right there next to the hot CPU, aggravating thermal management. In a 2-step LTC1703 design, a significant percentage of the power lost in the core regu- lation system happens in the 5V supply, which is usually located away from the CPU. The power lost to heat in the LTC1703 section of the system is relatively low, minimiz- ing the added heat near the CPU. See the Optimizing Performance section for a detailed explanation of how to calculate system efficiency. 2-Phase Operation The LTC1703 dual switching regulator controller also features the considerable benefits of 2-phase operation. Notebook computers, handheld terminals and automotive electronics all benefit from the lower input filtering requirement, reduced electromagnetic interference (EMI) and increased efficiency associated with 2-phase operation. Why the need for 2-phase operation? Up until the LTC1703, constant-frequency dual switching regulators operated both channels in phase (i.e., single-phase operation). This means that both topside MOSFETs turned on at the same time, causing current pulses of up to twice the amplitude of those for one regulator to be drawn from the input capacitor. These large amplitude current pulses increased the total RMS current flowing from the input capacitor, requiring the use of more expensive input capacitors and increasing both EMI and losses in the input capacitor and input power supply. With 2-phase operation, the two channels of the LTC1703 are operated 180 degrees out of phase. This effectively interleaves the current pulses coming from the switches, greatly reducing the overlap time where they add together. The result is a significant reduction in total RMS input current, which in turn allows less expensive input capaci- tors to be used, reduces shielding requirements for EMI and improves real world operating efficiency. Figure 7 shows example waveforms for a single switching regulator channel versus a 2-phase LTC1703 system with both sides switching. A single-phase dual regulator with both sides operating would exhibit double the single side numbers. In this example, 2-phase operation reduced the RMS input current from 9.3ARMS (2 × 4.66ARMS) to 4.8ARMS. While this is an impressive reduction in itself, remember that the power losses are proportional to IRMS2, meaning that the actual power wasted is reduced by a factor of 3.75. The reduced input ripple voltage also means less power is lost in the input power path, which could include batteries, switches, trace/connector resistances and protection circuitry. Improvements in both conducted and radiated EMI also directly accrue as a result of the reduced RMS input current and voltage. Small Footprint The LTC1703 operates at a 550kHz switching frequency, allowing it to use low value inductors without generating excessive ripple currents. Because the inductor stores less energy per cycle, the physical size of the inductor can be reduced without risking core saturation, saving PCB board space. The high operating frequency also means less energy is stored in the output capacitors between cycles, minimizing their required value and size. The remaining components, including the SSOP-28 LTC1703, are tiny, allowing an entire dual-output LTC1703 circuit to be constructed in 1.5in2 of PCB space. Further, this space is generally located right next to the microprocessor or in some similarly congested area, where PCB real estate is at a premium. The fact that the LTC1703 runs off the 5V supply, often available from a power plane, is an added benefit in portable systems —it does not require a dedi- cated supply line running from the battery. Fast Transient Response The LTC1703 uses a fast 25MHz GBW op amp as an error amplifier. This allows the compensation network to be designed with several poles and zeros in a more flexible configuration than with a typical gm feedback amplifier. The high bandwidth of the amplifier, coupled with the high switching frequency and the low values of the external inductor and output capacitor, allow very high loop cross- over frequencies. The low inductor value is the other half APPLICATIO S I FOR ATIO |
Similar Part No. - LTC1703_15 |
|
Similar Description - LTC1703_15 |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
