công cụ tìm kiếm bảng dữ liệu linh kiện điện tử |
|
LM4819LD bảng dữ liệu(PDF) 11 Page - Texas Instruments |
|
LM4819LD bảng dữ liệu(HTML) 11 Page - Texas Instruments |
11 / 27 page LM4819, LM4819MBD www.ti.com SNAS133D – FEBRUARY 2001 – REVISED MARCH 2013 load and a 5V supply is approximately 575mW. Substituting this value back into Equation 4 for PDMAX and using θJA = 210°C/W for the DGK0008A package, the maximum ambient temperature is calculated to be 29°C. Using θJA = 170°C/W for the D0008A package, the maximum ambient temperature is 52°C. Refer to the Typical Performance Characteristics curves for power dissipation information for lower output powers and maximum power dissipation for each package at a given ambient temperature. POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. The capacitors connected to the bypass and power supply pins should be placed as close to the LM4819 as possible. The capacitor connected between the bypass pin and ground improves the internal bias voltage's stability, producing improved PSRR. The improvements to PSRR increase as the bypass pin capacitor value increases. Typical applications employ a 5V regulator with 10µF and 0.1µF filter capacitors that aid in supply stability. Their presence, however, does not eliminate the need for bypassing the supply nodes of the LM4819. The selection of bypass capacitor values, especially CB , depends on desired PSRR requirements, click and pop performance as explained in the section, Proper Selection of External Components, as well as system cost and size constraints. SHUTDOWN FUNCTION The voltage applied to the LM4819's SHUTDOWN pin controls the shutdown function. Activate micro-power shutdown by applying VDD to the SHUTDOWN pin. When active, the LM4819's micro-power shutdown feature turns off the amplifier's bias circuitry, reducing the supply current. The logic threshold is typically 1/2VDD. The low 0.7µA typical shutdown current is achieved by applying a voltage that is as near as VDD as possible to the SHUTDOWN pin. A voltage that is less than VDD may increase the shutdown current. Avoid intermittent or unexpected micro-power shutdown by ensuring that the SHUTDOWN pin is not left floating but connected to either VDD or GND. There are a few ways to activate micro-power shutdown. These included using a single-pole, single-throw switch, a microcontroller, or a microprocessor. When using a switch, connect an external 10k Ω to 100kΩ pull-up resistor between the SHUTDOWN pin and VDD. Connect the switch between the SHUTDOWN pin and ground. Select normal amplifier operation by closing the switch. Opening the switch connects the shutdown pin to VDD through the pull-up resistor, activating micro-power shutdown. The switch and resistor ensure that the SHUTDOWN pin will not float. This prevents unwanted state changes. In a system with a microprocessor or a microcontroller, use a digital output to apply the control voltage to the SHUTDOWN pin. Driving the SHUTDOWN pin with active circuitry eliminates the pull-up resistor PROPER SELECTION OF EXTERNAL COMPONENTS Optimizing the LM4819's performance requires properly selecting external components. Though the LM4819 operates well when using external components with wide tolerances, best performance is achieved by optimizing component values. The LM4819 is unity gain stable, giving the designer maximum design flexibility. The gain should be set to no more than a given application requires. This allows the amplifier to achieve minimum THD+N and maximum signal-to-noise ratio. These parameters are compromised as the closed-loop gain increases. However, low gain demands input signals with greater voltage swings to achieve maximum output power. Fortunately, many signal sources such as audio CODECs have outputs of 1VRMS (2.83VP-P). Please refer to the Audio Power Amplifier Design section for more information on selecting the proper gain. Another important consideration is the amplifier's close-loop bandwidth. To a large extent, the bandwidth is dictated by the choice of external components shown in Figure 1. The input coupling capacitor, Ci, forms a first order high pass filter that limits low frequency response. This value should be chosen based on needed frequency response for a few distinct reasons discussed below Input Capacitor Value Selection Amplifying the lowest audio frequencies requires a high value input coupling capacitor (Ci in Figure 1). A high value capacitor can be expensive and may compromise space efficiency in portable designs. In many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 150Hz. Applications using speakers with limited frequency response reap little improvement by using a large input capacitor. Copyright © 2001–2013, Texas Instruments Incorporated Submit Documentation Feedback 11 Product Folder Links: LM4819 LM4819MBD |
Số phần tương tự - LM4819LD |
|
Mô tả tương tự - LM4819LD |
|
|
Link URL |
Chính sách bảo mật |
ALLDATASHEET.VN |
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không? [ DONATE ] |
Alldatasheet là | Quảng cáo | Liên lạc với chúng tôi | Chính sách bảo mật | Trao đổi link | Tìm kiếm theo nhà sản xuất 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 |