Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
LM4863M Datasheet(PDF) 8 Page - National Semiconductor (TI) |
|
|
LM4863M Datasheet(HTML) 8 Page - National Semiconductor (TI) |
8 / 16 page Non-MTE Specific Characteristics (Continued) Application Information EXPOSED-DAP MOUNTING CONSIDERATIONS The exposed-DAP must be connected to ground. The exposed-DAP package of the LM4863MTE requires special attention to thermal design. If thermal design issues are not properly addressed, an LM4863MTE driving 4 Ω will go into thermal shutdown. The exposed-DAP on the bottom of the LM4863MTE should be soldered down to a copper pad on the circuit board. Heat is conducted away from the exposed-DAP by a copper plane. If the copper plane is not on the top surface of the cir- cuit board, 8 to 10 vias of 0.013 inches or smaller in diameter should be used to thermally couple the exposed-DAP to the plane. For good thermal conduction, the vias must be plated-through and solder-filled. The copper plane used to conduct heat away from the exposed-DAP should be as large as pratical. If the plane is on the same side of the circuit board as the exposed-DAP, 2.5in 2 is the minimum for 5V operation into 4 Ω. If the heat sink plane is buried or not on the same side as the exposed- DAP, 5in 2 is the minimum for 5V operation into 4 Ω. If the am- bient temperature is higher than 25˚C, a larger copper plane or forced-air cooling will be required to keep the LM4863MTE junction temperature below the thermal shut- down temperature (150˚C). See the power derating curve for the LM4863MTE for derating information. The LM4863MTE requires forced-air cooling when operating into 3 Ω. With the part attached to 2.5in2 of exposed copper, with a 3 Ω load, and with an ambient temperature of 25˚C, 450 linear-feet per minute kept the part out of thermal shut- down. In higher ambient temperatures, higher airflow rates and/or larger copper areas will be required to keep the part out of thermal shutdown. See DEMOBOARD CIRCUIT LAYOUT for an example of an exposed-DAP TSSOP circuit board layout. 3 Ω &4Ω LAYOUT CONSIDERATIONS With low impedance loads, the output power at the loads is heavily dependent on trace resistance from the output pins of the LM4863. Traces from the output of the LM4863MTE to the load or load connectors should be as wide as practical. Any resistance in the output traces will reduce the power de- livered to the load. For example, with a 4 Ω load and 0.1Ω of trace resistance in each output, output power at the load drops from 2.2W to 2.0W Output power is also dependent on supply regulation. To keep the supply voltage from sagging under full output power conditions, the supply traces should be as wide as practical. BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM4863 has two pairs of opera- tional amplifiers internally, allowing for a few different ampli- fier configurations. The first amplifier’s gain is externally con- figurable, while the second amplifier is internally fixed in a unity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of R f to R i while the second amplifier’s gain is fixed by the two internal 20 k Ω resistors. Figure 1 shows that the output of amplifier one serves as the input to amplifier two which results in both am- plifiers producing signals identical in magnitude, but out of phase 180˚. Consequently, the differential gain for each channel of the IC is A VD = 2 * (Rf/R i) By driving the load differentially through outputs +OutA and −OutA or +OutB and −OutB, an amplifier configuration com- monly referred to as “bridged mode” is established. Bridged mode operation is different from the classical single-ended amplifier configuration where one side of its load is con- nected to ground. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling the output swing for a speci- fied supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions. This increase in attainable output power as- sumes that the amplifier is not current limited or clipped. In order to choose an amplifier’s closed-loop gain without caus- ing excessive clipping, please refer to the Audio Power Am- plifier Design section. A bridge configuration, such as the one used in LM4863, also creates a second advantage over single-ended amplifi- ers. Since the differential outputs, +OutA, −OutA, +OutB, and −OutB, are biased at half-supply, no net DC voltage ex- ists across the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. If an output coupling capacitor is not used in a single-ended configuration, the half-supply bias across the load would result in both in- creased internal IC power dissipation as well as permanent loudspeaker damage. Power Supply Rejection Ratio DS012881-21 Open Loop Frequency Response DS012881-22 Supply Current vs Supply Voltage DS012881-23 www.national.com 8 |
Número de pieza similar - LM4863M |
|
Descripción similar - LM4863M |
|
|
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 |