 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LTC3831 Datasheet(PDF) 11 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LTC3831 Datasheet(HTML) 11 Page - Linear Technology |
|
|
11 / 20 page  11 LTC3831 3831f APPLICATIO S I FOR ATIO decrease in ramp amplitude increases the open-loop gain of the controller feedback loop. As a result, the loop crossover frequency increases and it may cause the feed- back loop to be unstable if the phase margin is insufficient. To overcome this problem, the LTC3831 monitors the peak voltage of the ramp signal and adjust the oscillator charging current to maintain a constant ramp peak. Input Supply Considerations/Charge Pump The LTC3831 requires four supply voltages to operate: VIN for the main power input, PVCC1 and PVCC2 for MOSFET gate drive and a clean, low ripple VCC for the LTC3831 internal circuitry (Figure 5). In many applications, VCC can be powered from VIN through an RC filter. This supply can be as low as 3V. The low quiescent current (typically 800 µA) allows the use of relatively large filter resistors and correspondingly small filter capacitors. 100 Ω and 4.7µF usually provide ad- equate filtering for VCC. For best performance, connect the 4.7 µF bypass capacitor as close to the LTC3831 VCC pin as possible. Gate drive for the top N-channel MOSFET Q1 is supplied from PVCC1. This supply must be above VIN (the main power supply input) by at least one power MOSFET VGS(ON) for efficient operation. An internal level shifter allows PVCC1 to operate at voltages above VCC and VIN, up to 14V maximum. This higher voltage can be supplied with a separate supply, or it can be generated using a charge pump. Gate drive for the bottom MOSFET Q2 is provided through PVCC2. This supply only need to be above the power MOSFET VGS(ON) for efficient operation. PVCC2 can also be driven from the same supply/charge pump for the PVCC1, or it can be connected to a lower supply to improve efficiency. Figure 6 shows a doubling charge pump circuit that can be used to provide 2VIN gate drive for Q1. The charge pump consists of a Schottky diode from VIN to PVCC1 and a 0.1µF capacitor from PVCC1 to the switching node at the drain of Figure 4. External Synchronization Operation SHDN 200kHz FREE RUNNING RAMP SIGNAL TRADITIONAL SYNC METHOD WITH EARLY RAMP TERMINATION LTC3831 KEEPS RAMP AMPLITUDE CONSTANT UNDER SYNC RAMP SIGNAL WITH EXT SYNC RAMP AMPLITUDE ADJUSTED 3831 F04 Figure 5. Supplies Input Figure 6. Doubling Charge Pump 3831 F05 + VCC PVCC2 PVCC1 VIN TG Q1 COUT VOUT Q2 LO BG INTERNAL CIRCUITRY LTC3831 LTC3831 3831 F06a + DZ 12V 1N5242 Q1 LO Q2 COUT VOUT 0.1 µF PVCC2 OPTIONAL USE FOR VIN ≥ 7V MBR0530T1 PVCC1 TG BG VIN |
Similar Part No. - LTC3831 |
|
Similar Description - LTC3831 |
|
|
|
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
