Electronic Components Datasheet Search |
|
MAX639EPA Datasheet(PDF) 7 Page - Maxim Integrated Products |
|
MAX639EPA Datasheet(HTML) 7 Page - Maxim Integrated Products |
7 / 13 page 5V/3.3V/3V/Adjustable, High-Efficiency, Low IQ, Step-Down DC-DC Converters _______________________________________________________________________________________ 7 NAME FUNCTION 1 VOUT Sense Input for regulated-output operation. Internally connected to an on-chip voltage divider and to the variable duty-cycle, on-demand oscillator. It must be connected to the external regulated output. 2 LBO Low-Battery Output. An open-drain N-channel MOSFET sinks current when the voltage at LBI drops below 1.28V. 3 LBI Low-Battery Input. When the voltage at LBI drops below 1.28V, LBO sinks current. PIN 4 GND Ground ______________________________________________________________Pin Description 5 LX Drain of a PMOS power switch that has its source connected to V+. LX drives the external inductor, which provides current to the load. 6 V+ Positive Supply-Voltage Input. Should not exceed 11.5V 7 VFB 8 SHDN Dual-Mode Feedback Pin. When VFB is grounded, the internal voltage divider sets the output to 5V (MAX639), 3.3V (MAX640) or 3V (MAX653). For adjustable operation, connect VFB to an external volt- age divider. Shutdown Input — active low. When pulled below 0.8V, the LX power switch stays off, shutting down the regulator. When the shutdown input is above 2V, the regulator stays on. Tie SHDN to V+ if shut- down mode is not used. ____________________Getting Started Designing power supplies with the MAX639/MAX640/ MAX653 is easy. The few required external components are readily available. The most general applications use the following components: (1) Capacitors: For the input and output filter capaci- tors, try using electrolytics in the 100µF range, or use low-ESR capacitors to minimize output ripple. Capacitor values are not critical. (2) Diode: Use the popular 1N5817 or equivalent Schottky diode. (3) Inductor: For the highest output current, choose a 100µH inductor with an incremental saturation cur- rent rating of at least 600mA. To obtain the highest efficiencies and smallest size, refer to the Inductor Selection section. _______________Detailed Description Figure 1 shows a simplified, step-down DC-DC con- verter. When the switch is closed, a voltage equal to (V+ - VOUT) is applied to the inductor. The current through the inductor ramps up, storing energy in the inductor’s magnetic field. This same current also flows into the output filter capacitor and load. When the switch opens, the current continues to flow through the inductor in the same direction, but must also flow through the diode. The inductor alone supplies current to the load when the switch is open. This current decays to zero as the energy stored in the inductor’s magnetic field is transferred to the output filter capacitor and the load. V+ VL L VOUT COUT IL Figure 1. Simplified Step-Down Converter SWITCH OFF 0V SWITCH ON 0A SWITCH OFF SWITCH ON IL AT 200mA/div VL AT 5V/div Figure 2. Simplified Step-Down Converter Operation |
Similar Part No. - MAX639EPA |
|
Similar Description - MAX639EPA |
|
|
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 |