Zakładka z wyszukiwarką danych komponentów |
|
LM4953 Arkusz danych(PDF) 9 Page - Texas Instruments |
|
LM4953 Arkusz danych(HTML) 9 Page - Texas Instruments |
9 / 19 page LM4953, LM4953SDBD www.ti.com SNAS299E – SEPTEMBER 2005 – REVISED FEBRUARY 2006 APPLICATION INFORMATION ELIMINATING THE OUTPUT COUPLING CAPACITOR The LM4953 features a low noise inverting charge pump that generates an internal negative supply voltage. This allows the outputs of the LM4953 to be biased about GND instead of a nominal DC voltage, like traditional headphone amplifiers. Because there is no DC component, the large DC blocking capacitors (typically 220µF) are not necessary. The coupling capacitors are replaced by two, small ceramic charge pump capacitors, saving board space and cost. Eliminating the output coupling capacitors also improves low frequency response. In traditional headphone amplifiers, the headphone impedance and the output capacitor form a high pass filter that not only blocks the DC component of the output, but also attenuates low frequencies, impacting the bass response. Because the LM4953 does not require the output coupling capacitors, the low frequency response of the device is not degraded by external components. In addition to eliminating the output coupling capacitors, the ground referenced output nearly doubles the available dynamic range of the LM4953 when compared to a traditional headphone amplifier operating from the same supply voltage. BRIDGE CONFIGURATION EXPLANATION The Audio Amplifier portion of the LM4953has two internal amplifiers allowing different amplifier configurations. The first amplifier’s gain is externally configurable, whereas 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 Rf to Ri while the second amplifier’s gain is fixed by the two internal 20k Ω resistors. Figure 1 shows that the output of amplifier one serves as the input to amplifier two. This results in both amplifiers producing signals identical in magnitude, but out of phase by 180°. Consequently, the differential gain for the Audio Amplifier is AVD = 2 *(Rf/Ri) (1) By driving the load differentially through outputs OUT A and OUT B, an amplifier configuration commonly referred to as “bridged mode” is established. Bridged mode operation is different from the classic single-ended amplifier configuration where one side of the load is connected to ground. A bridge amplifier design has a few distinct advantages over the single-ended configuration. It provides differential drive to the load, thus doubling the output swing for a specified 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 assumes that the amplifier is not current limited or clipped. In order to choose an amplifier’s closed- loop gain without causing excessive clipping, please refer to the Audio Power Amplifier Design section. The bridge configuration also creates a second advantage over single-ended amplifiers. Since the differential outputs, OUT A and OUT B, are biased at half-supply, no net DC voltage exists across the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. Without an output coupling capacitor, the half-supply bias across the load would result in both increased internal IC power dissipation and also possible loudspeaker damage. OUTPUT TRANSIENT ('CLICK AND POPS') ELIMINATED The LM4953 contains advanced circuitry that virtually eliminates output transients ('clicks and pops'). This circuitry prevents all traces of transients when the supply voltage is first applied or when the part resumes operation after coming out of shutdown mode. POWER DISSIPATION Power dissipation is a major concern when using any power amplifier and must be thoroughly understood to ensure a successful design. Equation 2 states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and driving a specified output load. PDMAX = (VDD) 2 / (2π2Z L) (2) Since the LM4953 has two operational amplifiers in one package, the maximum internal power dissipation point is twice that of the number which results from Equation 2. Even with large internal power dissipation, the LM4953 does not require heat sinking over a large range of ambient temperatures. The maximum power dissipation point obtained must not be greater than the power dissipation that results from Equation 3: Copyright © 2005–2006, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: LM4953 LM4953SDBD |
Podobny numer części - LM4953_14 |
|
Podobny opis - LM4953_14 |
|
|
Link URL |
Polityka prywatności |
ALLDATASHEET.PL |
Czy Alldatasheet okazała się pomocna? [ DONATE ] |
O Alldatasheet | Reklama | Kontakt | Polityka prywatności | Linki | Lista producentów 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 |