Electronic Components Datasheet Search |
|
631Z Datasheet(PDF) 4 Page - Intersil Corporation |
|
631Z Datasheet(HTML) 4 Page - Intersil Corporation |
4 / 8 page 4 FN7370.1 December 21, 2005 Block Diagram Detailed Description The ISL97631 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. It can drive up to 6 LEDs in series or 15 LEDs in parallel/series configuration, with efficiencies of up 85%. The ISL97631 operates from an input voltage of 2.7V to 5.5V and can boost up to 27V. Steady-State Operation The ISL97631 operates with constant frequency PWM. The switching frequency is around 1.35MHz. Depending on the input voltage, inductance, number of LEDs and the LED current, the converter operates in either continuous conduction mode or discontinuous conduction mode. Both are normal. The forward current of the LED is set using the RSET resistor. In steady state mode, this current is given by the equation: Shut-Down When taken low the ENAB pin places the ISL97631 into power down mode. When in power down, the supply current is reduced to less than 1µA. Dimming Control PWM DIMMING The ENAB pin also doubles as a brightness control. There are two different possible dimming control methods. The first dimming method is controlled through the duty-cycle of the ENAB input PWM waveform, which can operate at frequencies up to 1kHz. For frequencies greater than 1kHz, see Analog Dimming. The LEDs operate at either zero or full current. This is the PWM dimming control method. The relationship between the average LED current and the duty-cycle (D) of the ENAB pin’s waveform is as follows: FIGURE 7. ISL97631 BLOCK DIAGRAM FET Driver PWM Logic Controller Current Sense GM Amplifier 1.2MHz Oscillator and Ramp Generator Bandgap Reference Generator 95mV GM Amp Compensation PWM Comparator Vin Enable LX GND FB ISL97631 Vout - FET Driver PWM Logic Controller Current Sense GM Amplifier 1.2MHz Oscillator and Ramp Generator Bandgap Reference Generator 95mV GM Amp Compensation PWM Comparator Vin Enable LX GND FB ISL97631 Vout - 1.35MHz Pin Descriptions PIN NUMBER PIN NAME DESCRIPTION 1 VOUT Output Pin. Connect to the anode of the top LED and the output filter capacitor . 2 GND Ground Pin. Connect to local ground. 3 LX Switching Pin. Connect to inductor. 4 ENAB Enable Pin. Connect to enable signal to turn-on or off the device. 5 FB Feedback Pin. Connect to the cathode of bottom LED and the sense resistor. 6 VIN Input Supply Pin. Connect to the input supply voltage, the inductor and the input supply decoupling capacitor. ILED VFB RSET --------------- = (EQ. 1) average ILED VFB RSET --------------- D ⋅ = (EQ. 2) ISL97631 |
Similar Part No. - 631Z |
|
Similar Description - 631Z |
|
|
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 |