NCS603
http://onsemi.com
8
APPLICATION INFORMATION
DESCRIPTION
The NCS603 is a stereo line driver with a NOCAP
architecture. This architecture eliminates the need to use two
large, external capacitors required by conventional audio
line driver applications. The NCS603 is basically composed
of two true ground amplifiers with internal power supply
rail, one UVP−circuit block, and short−circuit protection.
The gain of the NCS603 can be adjusted with two external
resistors.
The NOCAP approach is a patented architecture that
requires only two 1 mF low ESR ceramic capacitors (fly
capacitor and reservoir capacitor). It generates a
symmetrical positive and negative voltage and it allows the
output of the amplifiers to be biased around the ground (True
Ground).
The NCS603 includes a special circuitry for eliminating
any pop and click noise during turn on and turn off time. This
circuitry combined with the true ground output architecture
and a trimmed output offset voltage makes the elimination
of pop and click particularly efficient.
UNDER−VOLTAGE PROTECTION (UVP) PIN
MANAGEMENT
The UVP pin can be used to shut down the audio line
driver by monitoring the board’s main power supply. Then
the line driver can be shut down before upstream devices
disable, contributing this way to eliminate potential source
of pop noise.
The device shuts down when the UVP voltage goes below
1.25 V typically. To monitor the lower main power supply
limit, an external voltage divider constituted with three
resistors, RUP, RDW and RHYS is used (Figure 21).
Resistors values have to be chosen based on the requested
power supply shutdown threshold and hysteresis for a given
application. It is recommended to have RHYS >> RDW //
RUP. RHYS is optional in the case where hysteresis is not
necessary.
UVP
Power Suppp
RUP
RDW
PVDD
RHYS
Vn
I
HYS
On/Off
Figure 21. Voltage Divider Connected to UVP for
Power Supply Monitoring
