 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
UCC28250 Datasheet(PDF) 13 Page - Texas Instruments |
|
|
||||||||||||||||||||||||||||||
UCC28250 Datasheet(HTML) 13 Page - Texas Instruments |
|
|
13 / 50 page  ( ) d SP SW T 1 T 2 f R 33.2pF - ´ = 0 200 RT Resistor - kW 0 1200 2000 100 OSCILLATOR FREQUENCY vs RT RESISTOR 40 20 120 180 1600 800 400 60 80 140 160 200 600 1000 1400 1800 T D(ps) = 40 ns T D(ps) = 100 ns UCC28250 www.ti.com SLUSA29B – APRIL 2010 – REVISED OCTOBER 2010 RT (Oscillator Frequency Set and Synchronization) (15/2) The UCC28250 oscillator frequency is set by an external resistor connected between the RT pin and ground. Switching frequency selection is a trade-off between efficiency and component size. Based on the selected switching frequency, the programming resistor value can be calculated as: (3) In this equation, fSW is the switching frequency and TD(sp) is the dead time between synchronous rectifier turn-off to primary switch turn-on. TD(sp) is set by an external resistor between the SP pin and ground (refer to the SP pin description). Each output (OUTA, OUTB, SRA, SRB) switches at half the oscillator frequency (fSW = ½ x fOSC). Figure 6 shows the relationship between RT and fOSC at certain TD(sp) and can be used to program oscillator frequency accordingly. Figure 6. Oscillator Frequency FOSC vs External Resistance of RT at TD(ps) = 40 ns and 100 ns The UCC28250 can be synchronized to an external clock by applying an external clock source to the RT pin. Synchronization helps with parallel operation and/or preventing beat frequency noise. The UCC28250 synchronizes its internal oscillator to an external frequency source ranging from 170 kHz to 2.3 MHz, which is equivalent to an 85-kHz to 1.15-MHz switching frequency. The internal oscillator frequency is clamped to 170 kHz during synchronization if the external source frequency drops below 170 kHz. The UCC28250 aligns the turn-on of primary outputs OUTA and OUTB to the falling edge of the synchronizing signal, as shown in Figure 7. If the frequency source is from the gate outputs of another half bridge controller, interleaving can be achieved. The interleaving angle is determined by the frequency source’s duty cycle. When a 50% duty cycle is applied, optimal interleaving is achieved, and EMI filters can be minimized. Copyright © 2010, Texas Instruments Incorporated Submit Documentation Feedback 13 Product Folder Link(s): UCC28250 |
Similar Part No. - UCC28250 |
|
Similar Description - UCC28250 |
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
