NCP2892 ON Semiconductor, NCP2892 Datasheet - Page 12

• Manufacturer Part Number: NCP2892
• Description: Audio Power Amplifier
• Manufacturer: ON Semiconductor

Detailed Description
until 5.5 V power supply. With less than 1% THD+N, B
version can deliver up to 1.2 W rms output power to an
8.0 W load (V
THD+N, then 1.6 W can be provided using a 5.0 V power
supply.
two identical internal power amplifiers; the first one is
externally configurable with gain−setting resistors R
R
resistors) and the second is internally fixed in an inverting
unity−gain configuration by two resistors of 20 kW. So the
load is driven differentially through OUTA and OUTB
outputs. This configuration eliminates the need for an
output coupling capacitor. The NCP2892A has around
100 W and the NCP2892B has around 10 kW output
impedance in the shutdown mode.
Internal Power Amplifier
were designed to deliver the output power of the
specifications without clipping. The channel resistance
(R
0.6 W when they drive current.
composed of three symmetrical gain stages, first and
medium gain stages are transconductance gain stages to
obtain maximum bandwidth and DC gain.
Turn−On and Turn−Off Transitions
illustrated with plots that show both single ended signals on
the previous page.
transitions, output power in the load must be slowly
established or cut. When logic high is applied to the
shutdown pin, the bypass voltage begins to rise
exponentially and once the output DC level is around the
common
instantaneously. This way to turn−on the device is
optimized in terms of rejection of “pop and click” noises.
by a logic low on the shutdown pin. During the shutdown
mode, amplifier outputs are connected to the ground.
capacitor, it takes 65 ms before the DC output level is tied
to Ground on each output. However, no audio signal will be
provided to the BTL load only 1 ms after the falling edge on
the shutdown pin.
This fast turn on time added to a very low shutdown current
saves battery life and brings flexibility when designing the
audio section of the final application.
differential audio input. In case of a single ended one, there
f
The NCP2892 audio amplifier can operate under 2.6 V
The structure of the NCP2892 is basically composed of
The output PMOS and NMOS transistors of the amplifier
The structure of the internal power amplifier is
A cycle with a turn−on and turn−off transition is
In order to eliminate “pop and click” noises during
The device has the same behavior when it is turned−off
When a shutdown low level is applied, with 1 mF bypass
With 1 mF bypass capacitor, turn on time is set to 90 ms.
NCP2892 is a zero pop noise device when using a
on
(the closed−loop gain is fixed by the ratios of these
) of the NMOS and PMOS transistors does not exceed
mode
p
= 5.0 V). If application allows to reach 10%
voltage,
the
gain
is
APPLICATION INFORMATION
established
NCP2892 Series
http://onsemi.com
in
and
12
− The possible output power is four times larger (the
− Output pins (OUTA and OUTB) are biased at the same
is no audible pop click noise, especially when the input cut
off frequency is higher than 100 Hz.
Shutdown Function
is low. During the shutdown mode, the DC quiescent
current of the circuit does not exceed 100 nA. In this
configuration, the output impedance is 10 kW on each
output.
Current Limit Circuit
1.0 W, V
the load of 500 mA.
load when a short−circuit occurs, the current limit in the
load is fixed to 800 mA. The current in the four output MOS
transistors are real−time controlled, and when one current
exceeds 800 mA, the gate voltage of the MOS transistor is
clipped and no more current can be delivered.
Thermal Overload Protection
temperature exceeds 160°C, and will be switched on again
only when the temperature decreases fewer than 140°C.
external components besides gain−setting resistors, an
input coupling capacitor and a proper bypassing capacitor
in the typical application.
R
configuration.
advantages:
given by
output voltage).
output power, check that the amplifier is not current limited
or clipped.
is 500 mA
P orms
in
The device enters shutdown mode when shutdown signal
The maximum output power of the circuit (Porms =
In order to limit the excessive power dissipation in the
Internal
The NCP2892 is unity−gain stable and requires no
The first amplifier is externally configurable (R
The differential−ended amplifier presents two major
The differential closed loop−gain of the amplifier is
Output power delivered to the load is given by
When choosing gain configuration to obtain the desired
The maximum current which can be delivered to the load
output swing is doubled) as compared to a single−ended
amplifier under the same conditions.
potential V
coupling capacitor required with a single−ended
amplifier configuration.
), while the second is fixed in an inverting unity gain
+
p
A vd
= 5.0 V, R
(Vopeak) 2
I opeak
amplifiers are switched off when the
2 * R L
+
p
/2, this eliminates the need for an output
2 *
+
L
R in
V opeak
R f
(Vopeak is the peak differential
= 8.0 W) requires a peak current in
R L
+
V inrms
V orms
.
.
f
and