january 2007 rev 1 1/7 AN2474 application note ts4995 1.2w fully differential au dio power amplifier with selectable standby and 6db fixed gain - ev aluation board user guidelines introduction this application note describes the demo ts4995, an evaluation board specifically designed for the ts4995 differential audio amplifier. in this document, you will find: a brief description of the ts4995 differential audio amplifier, a description of the evaluation board, a detailed list of evaluation board components, the layout of the evaluation board. about the ts4995 the ts4995 is fully differential structure power audio amplifier which is capable of delivering 1.2w of continuous rms output power into an 8 load at 5v. due to its differential inputs, it exhibits outstanding noise immunity. an external standby mode control reduces t he supply current to less than 10na. a stby mode pin allows the standby to be active high or low. an internal thermal shutdown protection is also provided, making the de vice capable of sustaining short-circuits. the ts4995 features an internal fixed gain at 6db which reduces the number of external components on the application board, and the flip-chip package with 9 bumps allows maximum space saving. its key features are: differential inputs 90db psrr @ 217hz with grounded inputs operating range from v cc = 2.5v to 5.5v 1.2w rail to rail output power @ v cc =5v, thd+n=1%, f=1khz, with 8 load 6db integrated fixed gain ultra-low consumption in standby mode (10na) selectable standby mode (active low or active high) ultra-fast startup time: 10ms typ. at v cc =3.3v available in 9-bump flip-chip (300mm bump diameter) ultra-low pop & click figure 1 on page 2 shows a typical application for the ts4995 amplifier. for more detailed information about the ts4995, refer to the datasheet. www.st.com
typical application AN2474 2/7 1 typical application figure 1. typical application for the ts4995 audio amplifier p1 vin- p2 vin+ cs 1 1uf vcc cin1 330nf cin2 330nf cbypas s1 1uf stdby / operation vcc stdby mode 2 1 3 2 1 3 + 3 1 8 7 5 4 2 6 vin- vin+ stdby vo - vo + bias stb y byp ass 9 stdby mode gnd vcc ts4995 ts4995 flipchip 8 ohms op ti ona l
AN2474 description of the evaluation board 3/7 2 description of the evaluation board the demo ts4995 is an evaluation board designed to help you evaluate the ts4995 low power differential audio amplifier. this section explains how to evaluate the amplifier in a typical application configuration. using the board, you can: set the amplifier in standby/operation mode, select standby mode (active low or active high), modify the input configuration from capacitor coupled to common mode feedback. the cn4 connector is used to select between standby or operation mode; and the cn5 connector is used for standby to select between active low or active high. for example, in figure 2 , the jumper that connects pin 2 and pin 3 of the cn4 connector puts the device in standby mode, while the jumper that connects pin1 and pin 2 of the cn5 connector determines that the standby is active high. when the amplifier is used in common mode feedback input configuration, the input capacitors are shorted by placing jumpers on connectors cn2 and cn3. figure 2. evaluation board schematic diagram + 5 3 2 13 9 6 4 11 vin- vin+ stby vo- vo+ bias stby bypa ss 8 stby mode gnd vcc ts4995 u1 1 2 jp2 1 2 330nf cin1 1 2 330nf cin2 1 2 1uf cb 1 2 1uf cs 1 2 3 cn4 1 2 3 cn5 cn1 1 2 3 4 jp1 cn2 cn3 vcc vcc vcc
description of the evaluation board AN2474 4/7 figure 3. ts4995 flip-chip adapter table 1. evaluation board bill of materials designation quantity description u1 1 dip14 socket with plugged flipch ip to dip adapter with the ts4995 audio amplifier c1, c2 2 330nf/63v, ceramic capacitors cb, cs 2 1 f/50v, electrolytic capacitor --- 2 jumper, 2.54mm pitch (placed on cn4 and cn5 connectors) cn1, cn2, cn3 1 2 pins header, 2.54mm pitch cn4, cn5 2 3 pins header, 2.54mm pitch jp1 1 4 pins header, 2.54mm pitch jp2 1 2 pins header, 2.54mm pitch
AN2474 evaluation board connectors 5/7 3 evaluation board connectors caution: when you apply the power supply through cn1, do not invert the polarity because it would destroy the amplifier at u1. connector(s) description cn1 power connector (v cc , gnd). power supply voltage from 2.5v to 5.5v. cn2 connector used to short-circuit input capacitor c in 1 by placing jumper on it when the amplifier is used with c ommon mode feedback input. cn3 connector used to short-circuit input capacitor c in 2 by placing jumper on it when the amplifier is used with c ommon mode feedback input. cn4 standby control connector (gnd, standby, v cc ). cn5 standby mode control connector (v cc , standby, gnd). allows you to select standby mode active high or low. jp1 input signal connector (v in- , v in+ , 2 x gnd). jp2 output signal connector (v o- , v o+ ).
evaluation board layout AN2474 6/7 4 evaluation board layout the following schematics show the layers and the top view of the evaluation board. figure 6. top view of evaluation board figure 4. pcb top layer figure 5. pcb bottom layer
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