Electronic Components Datasheet Search |
|
MAX8570EUT Datasheet(PDF) 8 Page - Maxim Integrated Products |
|
MAX8570EUT Datasheet(HTML) 8 Page - Maxim Integrated Products |
8 / 10 page High-Efficiency LCD Boost with True Shutdown 8 _______________________________________________________________________________________ Design Procedure Inductor Selection Smaller inductance values typically offer smaller physi- cal size for a given series resistance or saturation cur- rent. Circuits using larger inductance values may provide more output power. The inductor’s saturation current rating should be greater than the peak switch- ing current. Recommended inductor values range from 10µH to 100µH. Selecting the Current Limit The peak LX current limit (ILX(MAX)) required for the application is calculated from the following equation: where POUT(MAX) is the maximum output power required by the load and VBATT(MIN) is the minimum supply voltage used to supply the inductor (this is VCC unless a separate supply is used for the inductor). The IC current limit must be greater than this calculated value. See the Selector Guide on page 1 for selecting the IC with the correct current limit. Diode Selection The high switching frequency of up to 800kHz requires a high-speed rectifier. Schottky diodes are recom- mended due to their low forward-voltage drop. To maintain high efficiency, the average current rating of the diode should be greater than the peak switching current. Choose a reverse breakdown voltage greater than the output voltage. Capacitors Small ceramic surface-mount capacitors with X7R or X5R temperature characteristics are recommended due to their small size, low cost, low equivalent series resistance (ESR), and low equivalent series inductance (ESL). If nonceramic capacitors are used, it is important that they have low ESR to reduce the output ripple volt- age and peak-peak load-transient voltage. For most applications, use a 1µF ceramic capacitor for the output and VCC bypass capacitors. For SW or the inductor supply, a 4.7µF or greater ceramic capacitor is recommended. I P V P V s P L LX MAX OUT MAX BATT MIN OUT MAX BATT MIN OUT MAX () () () () () () .. ≥ ×+ × +µ × 125 1 25 3 2 COMMON APPLICATION FAULTS RESULT WITH COMPETING STEP-UP CONVERTERS RESULT WITH MAX8570 FAMILY OUT to FB resistor missing or disconnected. OUT voltage rises until the output capacitor is destroyed and/or downstream components are damaged. Converter stops switching. Output cap missing and FB floating. OUT voltage rises until the output capacitor is destroyed and/or downstream components are damaged. LX may boost one or two times before the FB voltage exceeds the trip point. In the rare case where the capacitive loading and external loading on OUT is small enough that the energy in one cycle can slew it more than 50V, the internal MOSFET will clamp between 35V and 70V (nondestructively). FB shorted to GND. OUT voltage rises until the output capacitor is destroyed and/or downstream components are damaged. Converter stops switching and OUT is resistively loaded to GND. Diode missing or disconnected. Diode reverse polarity. Inductor energy forces LX node high, possibly damaging the internal switch. OUT is resistively loaded to GND and the converter stops switching. FB node floating. Unpredictable, possibly boosting output voltage beyond acceptable design range. FB node driven above its regulation point, the converter stops switching, and OUT is resistively loaded to GND. OUT shorted to ground. Current ramps up through inductor and diode, generally destroying one of the devices. True off-switch detects short, opens when current reaches pMOS current limit, and restarts soft-start. This protects the inductor and diode. Table 1. Protection Features |
Similar Part No. - MAX8570EUT |
|
Similar Description - MAX8570EUT |
|
|
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 |