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EUA4992A Schematic ( PDF Datasheet ) - Eutech Microelectronics

Teilenummer EUA4992A
Beschreibung 2.25W Stereo Audio Power Amplifier
Hersteller Eutech Microelectronics
Logo Eutech Microelectronics Logo 




Gesamt 15 Seiten
EUA4992A Datasheet, Funktion
EUA4992/4992A
2.25W Stereo Audio Power Amplifier
DESCRIPTION
The EUA4992/4992A are dual bridge-connected audio
power amplifiers, capable of delivering 1.25W of
continuous average power to an 8BTL with less than 1%
distortion (THD+N) from a 5.0V power supply, and
540mW to an 8BTL load from a 3.3V power supply.
The EUA4992/4992A provide high quality audio while
requiring few external components and minimal power
consumption. They feature a low-power shutdown mode,
which is achieved by driving the SHUTDOWN pin with
logic low.
The EUA4992/4992A contain circuitry to prevent
from ”pop and click” noise that would otherwise occur
during turn-on and turn-off transitions.
For maximum flexibility, the EUA4992/4992A provide an
externally controlled gain (with resistors), as well as an
externally controlled turn-on and turn-off times (with the
bypass capacitor).
The EUA4992/4992A are available in a 16-pin TQFN
package.
Typical Application Circuit
FEATURES
z Output Power at 10% THD+N, VDD=5V
-- 2.25W/CH (typ) into a 4Load
-- 1.54W/CH (typ) into a 8Load
z Output Power at 1% THD+N, VDD=5V
-- 1.9W/CH (typ) into a 4Load
-- 1.25W/CH (typ) into a 8Load
z Output Power at 1% THD+N, VDD=3.3V
-- 0.75W/CH (typ) into a 4Load
-- 0.54W/CH (typ) into a 8Load
z Shutdown Current 0.06µA (typ)
z Supply Voltage Range 2.5V to 5.5V
z “Click and Pop” Suppression
z Thermal Shutdown Protection Circuitry
z Available in 3mm 3mm TQFN-16 (EUA4992)
and 4mm 4mm TQFN-16 (EUA4992A) Packages
z RoHS compliant and 100% lead(Pb)-free
APPLICATIONS
z Cell Phones
z Portable and Desktop Computers
z Portable Audio System
z Multimedia Monitors
DS4992/4992A Ver1.0 Mar. 2009
Figure 1.
1






EUA4992A Datasheet, Funktion
Typical Operating Characteristics
EUA4992/4992A
Figure2.
Figure3.
Figure4.
Figure5.
Figure6.
DS4992/4992A Ver1.0 Mar. 2009
6
Figure7.

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EUA4992A pdf, datenblatt
EUA4992/4992A
of 1VRMS (2.83VP-P). Please refer to the Audio Power
Amplifier Design section for more information on
selecting the proper gain.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires 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,
however, the speakers used in portable systems, whether
internal or external, have little ability to reproduce signals
below 150Hz. Applications using speakers with this
limited frequency response reap little improvement by
using large input capacitor.
Besides effecting system cost and size, Ci has an affect on
the EUA4992/4992A’s click and pop performance. When
the supply voltage is first applied, a transient (pop) is
created as the charge on the input capacitor changes from
zero to a quiescent state. The magnitude of the pop is
directly proportional to the input capacitor’s size. Higher
value capacitors need more time to reach a quiescent DC
voltage (usually VDD/2) when charged with a fixed current.
The amplifier’s output charges the input capacitor through
the feedback resistor, Rf. Thus, pops can be minimized by
selecting an input capacitor value that is no higher than
necessary to meet the desired -3dB frequency.
A shown in Figure 1, the input resistor (RI) and the input
capacitor, CI produce a -3dB high pass filter cutoff
frequency that is found using Equation (2).
f _3dB
=
1
2πR INCI
(2)
As an example when using a speaker with a low
frequency limit of 150Hz, CI. The 1.0µF CI shown in
Figure 1 allows the EUA4992/4992A to drive high
efficiency, full range speaker whose response extends
below 30Hz.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful
consideration should be paid to value of CB, the capacitor
connected to the BYPASS pin. Since CB determines how
fast the EUA4992/4992A settles to quiescent operation,
its value is critical when minimizing turn-on pops. The
slower the EUA4992/4992A’s outputs ramp to their
quiescent DC voltage (nominally 1/2 VDD), the smaller the
turn-on pop. Choosing CB equal to 1.0µF along with a
small value of Ci (in the range of 0.1µF to 0.39µF),
produces a click-less and pop-less shutdown function. As
discussed above, choosing Ci no larger than necessary for
the desired bandwidth helps minimize clicks and pops.
Optimizing Click and Pop Reduction Performance
The EUA4992/4992A contains circuitry to minimize
turn-on and shutdown transients or "clicks and pop". For
this discussion, turn-on refers to either applying the power
supply voltage or when the shutdown mode is deactivated.
While the power supply is ramping to its final value, the
EUA4992/4992A’s internal amplifiers are configured as
unity gain buffers. An internal current source changes the
voltage of the BYPASS pin in a controlled, linear manner.
Ideally, the input and outputs track the voltage applied to
the BYPASS pin. The gain of the internal amplifiers
remains unity until the voltage on the bypass pin reaches
1/2 VDD. As soon as the voltage on the BYPASS pin is
stable, the device becomes fully operational. Although the
bypass pin current cannot be modified, changing the size
of CB alters the device’s turn-on time and the magnitude
of "clicks and pops". Increasing the value of CB reduces
the magnitude of turn-on pops. However, this presents a
tradeoff: as the size of CB increases, the turn-on time
increases. There is a linear relationship between the size
of CB and the turn-on time.
In order eliminate "clicks and pops", all capacitors must
be discharged before turn-on. Rapidly switching VDD may
not allow the capacitors to fully discharge, which may
cause "clicks and pops".
Audio Power Amplifier Design
Audio Amplifier Design: Driving 1W into an 8Load
The following are the desired operational parameters:
Power Output:
1WRMS
Load Impedance:
8
Input Level:
Input Impedance:
1VRMS
20k
Bandwidth:
100Hz-20 kHz ± 0.25 dB
The design begins by specifying the minimum supply
voltage necessary to obtain the specified output power.
One way to find the minimum supply voltage is to use the
Output Power vs Supply Voltage curve in the Typical
Performance Characteristics section. Another way,
using Equation (4), is to calculate the peak output voltage
necessary to achieve the desired output power for a given
load impedance. To account for the amplifier’s dropout
voltage, two additional voltages, based on the Dropout
Voltage vs Supply Voltage in the Typical Performance
Characteristics curves, must be added to the result
obtained by Equation (3). The result in Equation (4).
( )Vopeak = 2R LPO
(3)
( ( ))VDD VOUTPEAK + VOD TOP + VOD BOT
(4)
The Output Power vs Supply Voltage graph for an 8
load indicates a minimum supply voltage of 4.6V. This is
easily met by the commonly used 5V supply voltage. The
additional voltage creates the benefit of headroom,
allowing the EUA4992/4992A to produce peak output
power in excess of 1W without clipping or other audible
distortion. The choice of supply voltage must also not
create a situation that violates maximum power
dissipation as explained above in the Power Dissipation
section.
DS4992/4992A Ver1.0 Mar. 2009
12

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