Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
LM3464 Datasheet(PDF) 7 Page - National Semiconductor (TI) |
|
|
LM3464 Datasheet(HTML) 7 Page - National Semiconductor (TI) |
7 / 14 page Adjusting Frequency Response of the LM3464 Circuit The frequency response of the LM3464 evaluation board can be adjusted by changing the value of the capacitor, C DHC. Higher capacitance of C DHC results in slower frequency re- sponse of the LM3464 driver stage. In order to ensure stable system operation, it is recommended to set the dominant pole of the LM3464 one decade lower than the dominant pole of the AC/DC converter. The default value of the C DHC on the evaluation board is 0.22uF. For applications with slow re- sponse AC/DC power supply (e.g. converters with active PFC), the CDHC value should be increased to make the fre- quency response of the board slower than that of the AC/DC power supply. The cut-off frequency of the LM3464 driver stage is governed by the following equation: (9) Thermal Foldback Control The LM3464 evaluation board features an interface that en- ables thermal foldback control by connecting a NTC thermal sensor to the THM+ and THM- terminals. With the NTC sen- sor attached to the chassis of the LED arrays, the thermal foldback control feature reduces the average LED current and effectively reduces the LED temperature to prevent thermal breakdown of the LEDs. The thermal foldback control reduces the LED currents by means of PWM dimming which the dim- ming frequency is set by the capacitor CTHM following the equation shows below: (10) The default value of the CTHM on the LM3464 evaluation board is 68nF, which set the thermal foldback dimming fre- quency at 258Hz. Thermal foldback control is activated when the voltage at the Thermal pin, V Thermalis between 3.25V and 0.4V as shown in figure 5. Thermal foldback control begins when V Thermal is be- low 3.25V. The LED current will be reduced to zero as V Thermal falls below 0.4V. The average LED current varies ac- cording to the Thermal pin voltage following the equation: (11) 30127113 FIGURE 5. Changes of Average LED Current with Thermal Foldback Control Design Example A NTC thermistor is connected to the THM+ and THM- ter- minals of the LM3464 evaluation board as shown in figure 6 to activate the thermal foldback control function. 7 www.national.com |
Número de pieza similar - LM3464 |
|
Descripción similar - LM3464 |
|
|
Enlace URL |
Política de Privacidad |
ALLDATASHEET.ES |
¿ALLDATASHEET es útil para Ud.? [ DONATE ] |
Todo acerca de Alldatasheet | Publicidad | Contáctenos | Política de Privacidad | Intercambio de Enlaces | Lista de Fabricantes 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 |