Electronic Components Datasheet Search |
|
MAX16821A Datasheet(PDF) 8 Page - Maxim Integrated Products |
|
MAX16821A Datasheet(HTML) 8 Page - Maxim Integrated Products |
8 / 24 page High-Power Synchronous HBLED Drivers with Rapid Current Pulsing 8 _______________________________________________________________________________________ Detailed Description The MAX16821A/MAX16821B/MAX16821C are high-per- formance average current-mode PWM controllers for high-power and high-brightness LEDs (HBLEDs). The average current-mode control technique offers inherently stable operation, reduces component derating and size by accurately controlling the inductor current. The devices achieve high efficiency at high currents (up to 30A) with a minimum number of external components. A logic input (MODE) allows the LED driver to switch between buck and boost modes of operation. The MAX16821A/MAX16821B/MAX16821C feature a CLKOUT output 180° out-of-phase with respect to either the high-side or low-side driver, depending on MODE’s logic level. CLKOUT provides the drive for a second out-of-phase LED driver for applications requiring reduced input capacitor ripple current while operating another LED driver. The MAX16821A/MAX16821B/MAX16821C consist of an inner average current regulation loop controlled by an outer loop. The combined action of the inner current loop and outer voltage loop corrects the LED current errors by adjusting the inductor current resulting in a tightly regulated LED current. The differential amplifier (SENSE+ and SENSE- inputs) senses the LED current using a resistor in series with the LEDs and produces an amplified version of the sense voltage at DIFF. The resulting amplified sensed voltage is compared against an internal 0.6V reference at the error amplifier input. Input Voltage The MAX16821A/MAX16821B/MAX16821C operate with a 4.75V to 5.5V input supply range when the inter- nal LDO is disabled (VCC connected to IN) or a 7V to 28V input supply range when the internal LDO is enabled. For a 7V to 28V input voltage range, the inter- nal LDO provides a regulated 5V output with 60mA of sourcing capability. Bypass VCC to SGND with 4.7µF and 0.1µF low-ESR ceramic capacitors. The MAX16821A/MAX16821B/MAX16821C’s VDD input provides supply voltage for the low-side and the high- side MOSFET drivers. Connect VDD to VCC using an R-C filter to isolate the analog circuits from the MOSFET drivers. The internal LDO powers up the MAX16821A/ MAX16821B/MAX16821C. For applications utilizing a 5V input voltage, disable the internal LDO by connect- ing IN and VCC together. The 5V power source must be in the 4.75V to 5.5V range of for proper operation of the MAX16821A/MAX16821B/MAX16821C. Undervoltage Lockout (UVLO) The MAX16821A/MAX16821B/MAX16821C include UVLO and a 2048 clock-cycle power-on-reset circuit. The UVLO rising threshold is set to 4.3V with 200mV hysteresis. Hysteresis at UVLO eliminates chattering during startup. Most of the internal circuitry, including the oscillator, turns on when the input voltage reaches 4V. The MAX16821A/MAX16821B/MAX16821C draw up to 3.5mA of quiescent current before the input voltage reaches the UVLO threshold. Soft-Start The MAX16821A/MAX16821B/MAX16821C include an internal soft-start for a glitch-free rise of the output volt- age. After 2048 power-on-reset clock cycles, a 0.6V reference voltage connected to the positive input of the internal error amplifier ramps up to its final value after 1024 clock cycles. Soft-start reduces inrush current and stress on system components. During soft-start, the LED current will ramp monotonically towards its final value. Internal Oscillator The internal oscillator generates a clock with the fre- quency inversely proportional to the value of RT (see the Typical Operating Circuit). The oscillator frequency is adjustable from 125kHz to 1.5MHz range using a sin- gle resistor connected from RT/SYNC to SGND. The frequency accuracy avoids the overdesign, size, and cost of passive filter components like inductors and capacitors. Use the following equation to calculate the oscillator frequency: For 120k Ω≤ RT ≤ 500kΩ: For 40k Ω≤ RT ≤ 120kΩ: The oscillator also generates a 2VP-P ramp signal for the PWM comparator and a 180° out-of-phase clock signal at CLKOUT to drive a second out-of-phase LED current regulator. f x R Hz SW T . () = 640 10 10 f x R Hz SW T . () = 625 10 10 |
Similar Part No. - MAX16821A |
|
Similar Description - MAX16821A |
|
|
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 |