 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LTM4677 Datasheet(PDF) 8 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LTM4677 Datasheet(HTML) 8 Page - Linear Technology |
|
|
8 / 20 page  LTC3870-1 8 38701f For more information www.linear.com/LTC3870-1 operaTion Main Control Loop The LTC3870-1 is a constant frequency, current mode step-down slave controller for parallel operation with the LTC3887-1. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, and turned off when the main current comparator, ICMP, resets the RS latch. The peak inductor current at which ICMP resets the RS latch is controlled by the voltage on the ITH pin, which is tied directly to the corresponding ITH pin of the master controllers (LTC3887-1). When the load current increases, LTC3887-1 master controllers drive and increase the ITH voltage, which in turn causes the peak current in the corresponding slave channels to increase, until the average inductor current matches the new load current. After the top MOSFET has been turned off, the bottom MOSFET is turned on until the beginning of the next cycle in Continuous Conduction Mode (CCM) or until the inductor current starts to reverse, as indicated by the reverse current comparator IREV, in Discontinuous ConductionMode(DCM).LTC3870-1slavecontrollersDO NOT regulate the output voltage but regulate the current in each channel for current sharing with master controllers. Output voltage regulation is achieved through the voltage feedback loops in the master controller. INTVCC/EXTVCC Power PowerformostinternalcircuitryisderivedfromtheINTVCC pin. Normally an internal 5.0V linear regulator supplies INTVCC power from VIN. In high VIN applications, if a high efficiencyexternalvoltagesourceisavailablefortheEXTVCC pin, another internal 5.0V linear regulator is enabled and supplies INTVCC power from EXTVCC. To enable the linear regulator driven by the EXTVCC pin, VIN needs to be higher than 6.5V and EXTVCC pin voltage has to be higher than 4.8V. Do not exceed 14V on the EXTVCC pin. Start-Up and Shutdown (RUN0, RUN1) ThetwochannelsoftheLTC3870-1canindependentlystart up and shut down using the RUN0 and RUN1 pins. Pulling either of these pins below 1.4V shuts down the control circuits for that channel. During shutdown, the PWM pin is in three-state mode. Pulling either of these pins above 2V enables the corresponding channel and internal circuits. During startup, the RUN0/RUN1 pins are actively pulled down until the INTVCC voltage passes the undervoltage lockout threshold of 4V. For multiphase parallel operation, the RUN0/RUN1 pins have to be connected and driven by the RUN pins of the master controller. Do not exceed the Absolute Maximum Rating of 6V on these pins. The start-up of each channel’s output voltage VOUT is controlled and programmed by the master controller. After the RUN pins are released, the master controller drives the output based on the programmed delay time and rise time, and the slave controller LTC3870-1 just follows the master to supply equivalent current to the output during start-up. Light Load Current Operation (Discontinuous Conduction Mode, Continuous Conduction Mode) The LTC3870-1 can be set to operate either in Discontinu- ous Conduction Mode (DCM) or forced Continuous Con- duction Mode (CCM). To select forced Continuous Mode of operation, tie the MODE pin to a DC voltage above 2V (e.g., INTVCC). To select Discontinuous Conduction Mode of operation, tie the MODE pin to a DC voltage below 1.4V (e.g., SGND). In forced continuous operation, the induc- tor current is allowed to reverse at light loads or under large transient conditions. The peak inductor current is determined by the voltage on the ITH pin. In this mode, the efficiency at light loads is lower than in discontinu- ous mode operation. However, continuous mode has the advantages of lower output ripple and less interference with audio circuitry. When the MODE pin is connected to |
Similar Part No. - LTM4677 |
|
Similar Description - LTM4677 |
|
|
|
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
