 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
RT9248 Datasheet(PDF) 9 Page - Richtek Technology Corporation |
|
||||||||||||||||||||||||||||||
RT9248 Datasheet(HTML) 9 Page - Richtek Technology Corporation |
|
|
9 / 14 page  RT9248 Preliminary 9 DS9248-05 March 2007 www.richtek.com DAC Offset Voltage & Droop Tuning The DAC output voltage decreases by VADJ to form the VCORE load droop (see Figure 3). Protection and SS Function The sensing circuit gets by local feedback. RSP = RSN for channel 1 & RSP = 2RSN for channel 2 & 3 (at 3 phase operation) to cancel the voltage drop caused by GM amplifier input bias current. IX is sampled and held just before low side MOSFET turns off (See Figure 2). Therefore, SP S L X R R I I × = Figure 2. Inductor Current and PWM Signal PWM Signal & High Side MOSFET Gate Signal Low Side MOSFET Gate Signal Inductor Current Falling Slope = Vo/L I L I L(AVG) I L(S/H) The DAC offset voltage is set by compensation network & VOSS pin external resistors by . The S/H current signals from power channels are injected to ADJ pin to create droop voltage. ∑ × = X ADJ ADJ I 2 R V 4 R R V 1 1 f VOSS × ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Figure 4. 0A 0V T0,T1 T2 T3,T4 TIME COUNT = 1 COUNT = 2 COUNT = 3 TIME Count = 1 Count = 2 Count = 3 S.S V CORE Overload Applied I LOAD For OVP, the RT9248 detects the VCORE by VDIF pin voltage of the differential amplifier output. Eliminate the delay due to compensation network (compared to sensing FB voltage) for fast and accurate detection. The trip point of OVP is 140% of normal output level. The PWM outputs are pulled low to turn on the low side MOSFET and turn off the high side MOSFET of the synchronous rectifier at OVP. The OVP latch can only be reset by VCC or DVD restart power on reset sequence. The PGOOD detection trip point of VCORE is 92% lower than the normal level. The PGOOD open drain output pulls low when VCORE is lower than the trip point. For VID jumping issue, only power fail conditions (VCC & DVD are lower than trip point or OVP) reset the output low. Soft-start circuit generates a ramp voltage by charging external capacitor with 13 μA current after IC POR acts. The PWM pulse width and VCORE are clamped by the rising ramp to reduce the inrush current and protect the power devices. Over-current protection trip point is set by the resistor RIMAX connected to IMAX pin. OCP is triggered if one channel S/H current signal IX > Controller forces PWM output latched at high impedance to turn off both high and low side MOSFETs in the power stage and initial the hiccup mode protection. The SS pin voltage is pulled low with a 13 μA current after it is less than 90% VCC. The converter restarts after SS pin voltage < 0.2V. Three times of OCP disable the converter and only release the latch by POR acts (see Figure 4). . 4 . 1 R V 6 . 0 IMAX × ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ SP S IN O IN O L(AVG) (S/H) X IN O IN OFF OFF O (AVG) L (S/H) L SP S (S/H) L (S/H) X R R 2L 5uS V V V V I I 200kHz fosc for 5uS V V V T , 2 T L V I I , R R I I × ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ × ⎥⎦ ⎤ ⎢⎣ ⎡ − − − = = × ⎥⎦ ⎤ ⎢⎣ ⎡ − = × − = × = Figure 3. DAC Offset Voltage & Droop Tune Circuit Current Source ∑ + - VOSS VOSS R V 1 I = 2I X1 2I X3 2I X2 FB ADJ V OSS R VOSS R F1 R ADJ V CORE EA V DAC V ADJ VOSS I 4 1 COMP > |
Similar Part No. - RT9248 |
|
Similar Description - RT9248 |
|
|
|
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
