PA4894 Unisonic Technologies, PA4894 Datasheet - Page 6

• Manufacturer Part Number: PA4894
• Description: 1.8 Watt Differential Audio Power Amplifier With Selectable Shutdown
• Manufacturer: Unisonic Technologies

PA4894
Detailed Description
components R
OUTA and OUTB outputs. This configuration is saving the use of an output coupling capacitor.
power to 4.0Ω load, and when V
Internal Power Amplifier
power of the specifications without clipping. The channel resistance (R
not exceed 0.6Ω when they drive current.
gain stages are transconductance gain stages to obtain maximum bandwidth and DC gain.
Turn-On and Turn-Off Transitions
transitions between turn-on and turn-off conditions. When shutdown mode is over， , the bypass voltage begins to rise
exponentially and once the output DC level is around the common mode voltage, the turn-on mode is over.
SELECT and SD MODE pins, the system enters this mode. During the shutdown mode, amplifier outputs are
connected to the ground to discharge.
Shutdown Function
brings flexibility to the design, as the SD MODE pin must be permanently connected to VP or GND on the PCB. In
many applications, the output of a microcontroller or microprocessor is connected to the SD SELECT pin, so it is not
better to allow this pin float. During the shutdown state, the DC quiescent current has a typical value of 10nA.
Current Limit Circuit
the circuit (P
occurs between both outputs, the current limit in the load is fixed to 800mA for limiting the excessive power
consumption.
The UTC PA4894 includes two power amplifiers internally. Two of them provide a controlled gain with external
The UTC PA4894 is operating on a 2.6V to 5.5V power supply, when V
The internal power amplifier contains output PMOS and NMOS transistors, which is used to deliver the output
The structure of the internal power amplifier is composed of three symmetrical gain stages, first and medium
Output power in the load established must be slowly or cut for minimize the click and pop noise during the
The turn−on time is determined by the following equation (at 25°C):
T
(C
The turned off operation is as the same as the turn-on operation. Through applying a same logic state on the SD
When SD SELECT and SD MODE pins are in the same logic state, the system enters shutdown mode. This
The current limit circuit protects the device from damage from excessive current. The maximum output power of
APPLICATION INFORMATION
ON
BYP
= 0.95×R×C
: bypass capacitor R: internal 150 k resistor with a 25% accuracy)
UNISONIC TECHNOLOGIES CO., LTD
O(RMS)
www.unisonic.com.tw
IN
and R
=1.0W, V
BYP
F
; the gain is calculated by the ratios of the resistors. The load is driven differentially through
P
= 5.0V, R
P
is 5.0V, it delivered 1.0W rms output power to 8.0Ω load.
L
= 8.0Ω) requires a peak current in the load of 500mA. When short-circuit
ON
) of the NMOS and PMOS transistors does
P
is 2.6V it delivers 320mW rms output
CMOS IC
QW-R502-379.A
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