Electronic Components Datasheet Search |
|
MAX6495 Datasheet(PDF) 8 Page - Maxim Integrated Products |
|
MAX6495 Datasheet(HTML) 8 Page - Maxim Integrated Products |
8 / 16 page The gate cycles during overvoltage-limit and overvolt- age-switch modes are quite similar but have distinct characteristics. In overvoltage-switch mode, GATE is enhanced to (VIN + 10V) while the monitored VIN volt- age remains below the overvoltage fault threshold (OVSET < VTH+). When an overvoltage fault occurs (OVSET ≥ VTH+), GATE is pulled one diode drop below OUTFB, turning off the external MOSFET and discon- necting the load from the input. GATE remains low (MOSFET off) as long as the VIN voltage is above the overvoltage fault threshold. As VIN falls back below the overvoltage fault threshold, GATE is again enhanced to (VIN + 10V). In overvoltage-limit mode, GATE is enhanced to (VIN +10V) while the monitored OUTFB voltage remains below the overvoltage fault threshold (OVSET < VTH+). When an overvoltage fault occurs (OVSET ≥ VTH+), GATE is pulled one diode drop below OUTFB until OUTFB drops 5% below the overvoltage fault threshold (MAX6495/MAX6496/MAX6499). GATE is then turned back on until OUTFB reaches the overvoltage fault threshold and GATE is again turned off. GATE cycles in a sawtooth waveform until OUTFB remains below the overvoltage fault threshold and GATE remains con- stantly on (VIN +10V). The overvoltage limiter’s saw- tooth GATE output operates the MOSFET in a switched-linear mode while the input voltage remains above the overvoltage fault threshold. The sawtooth fre- quency depends on the load capacitance, load current, and MOSFET turn-on time (GATE charge current and GATE capacitance). GATE goes high when the following startup conditions are met: VIN is above the UVLO threshold, SHDN is high, an overvoltage fault is not present, and the device is not in thermal shutdown. Undervoltage Monitoring (MAX6499) The MAX6499 includes undervoltage and overvoltage comparators for window detection (see Figures 3 and 12). GATE is enhanced and the n-channel MOSFET is on when the monitored voltage is within the selected “window.” When the monitored voltage falls below the lower limit (VTRIPLOW) or exceeds the upper limit (VTRIPHIGH) of the window, GATE falls to OUTFB turn- ing off the MOSFET. The application in Figure 3 shows the MAX6499 enabling the DC-DC converter when the monitored voltage is in the selected window. The resistor values R1, R2, and R3 can be calculated as follows: where RTOTAL = R1 + R2 + R3. Use the following steps to determine the values for R1, R2, and R3: 1) Choose a value for RTOTAL, the sum of R1, R2, and R3. Because the MAX6499 has very high input impedance, RTOTAL can be up to 5MΩ. 2) Calculate R3 based on RTOTAL and the desired upper trip point: 3) Calculate R2 based on RTOTAL, R3, and the desired lower trip point: 4) Calculate R1 based on RTOTAL, R2, and R3: R1 = RTOTAL – R2 – R3 To improve ESD protection, keep R3 ≥ 1kΩ. R VR V R TH TOTAL TRIPLOW 23 = () × ⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ − − R VR V TH TOTAL TRIPHIGH 3 = × + VV R RR VV R R TRIPLOW TH TOTAL TRIPHIGH TH TOTAL = () + ⎛ ⎝⎜ ⎞ ⎠⎟ = () ⎛ ⎝⎜ ⎞ ⎠⎟ − + 23 3 72V, Overvoltage-Protection Switches/ Limiter Controllers with an External MOSFET 8 _______________________________________________________________________________________ OVSET GND CLEAR GATE OUTFB IN SHDN UVSET R2 VIN R3 R1 MAX6499 DC-DC CONVERTER GND IN OUT Figure 3. MAX6499 Window-Detector Circuit |
Similar Part No. - MAX6495 |
|
Similar Description - MAX6495 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |