ADAU1513ASVZ AD [Analog Devices], ADAU1513ASVZ Datasheet - Page 12

• Manufacturer Part Number: ADAU1513ASVZ
• Description: Class-D Audio Power Stage
• Manufacturer: AD [Analog Devices]

ADAU1513
THEORY OF OPERATION
OVERVIEW
The ADAU1513 is a 2-channel integrated power stage designed
to accept the logic level PWM inputs. The PWM inputs are
amplified, low-pass filtered using a simple passive LC network,
and then can be used to drive the speaker loads. The power
stage has built-in circuits for overtemperature, overcurrent,
short-circuit, and undervoltage protection.
POWER STAGE
The 2-channel ADAU1513 power stage comprises a total of
eight half bridges. Each half bridge is made up of PMOS and
NMOS devices. The gate drive for the respective FETs is
generated internally and does not need a special gate drive
supply or bootstrap capacitor compared to all NMOS stages.
This simplifies the high-side driver design and requires less
external components.
PROTECTION CIRCUITS
The ADAU1513 includes comprehensive protection circuits.
It includes thermal warning, thermal overheat, and overcurrent
or short-circuit protection on the outputs. The ERR and OTW
outputs are open drain, requiring external pull-up resistors.
The outputs are capable of sinking 10 mA. The open-drain
outputs are useful in multichannel applications where more
than one ADAU1513 are used. The error outputs of multiple
ADAU1513s can be OR’ e d to simplify the system design. The
logic outputs of the error flags ease the system design using a
microcontroller.
The power stage does not consist of protection in case PWM
input stays high continuously. In such a case, the output pro-
duces dc and it is possible to damage the speaker. To prevent
this, ensure that the modulator is switching whenever the power
stage is turned on.
THERMAL PROTECTION
Thermal protection in the ADAU1513 is categorized into two
error flags: one as thermal warning and the other as thermal
shutdown. When the device junction temperature reaches near
135°C (±5°C) the ADAU1513 outputs a thermal warning error
flag by pulling OTW (Pin 10) low. This flag can be used by the
microcontroller in the system as an indication to the user or can
be used to lower the input level to the amplifier to prevent the
thermal shutdown. The device continues operation until
shutdown temperature is reached.
When the device junction temperature exceeds 150°C the
device outputs an error flag by pulling the ERR (Pin 9) low. This
error flag is latched. To restore the operation, MUTE (Pin 16)
needs to be toggled to low and then to high again.
OVERCURRENT PROTECTION
The overcurrent protection in the ADAU1513 is set internally at
5 A peak output current. The device protects the output devices
against excessive output current by pulling the ERR (Pin 9) low.
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This error flag is latched type. To restore the normal operation,
MUTE (Pin 16) needs to be toggled to low and then to high
again. The error flag is useful for the microcontroller in the
system to indicate an abnormal operation and to initiate the
audio MUTE sequence. The device senses the short-circuit
condition on the outputs after the LC filter. Typical short-circuit
conditions include shorting of the output load and shorting to
either PVDD or GND.
UNDERVOLTAGE PROTECTION
The ADAU1513 has an undervoltage protection circuit that
senses the undervoltage on PVDD. When the PVDD supply
goes below the operating threshold, the output FETs are turned
to a high-Z condition. Also, the device issues an error flag by
pulling the ERR pin low. This condition is latched. To restore
the operation, MUTE (Pin 16) needs to be toggled to low and
then to high again.
AUTOMATIC RECOVERY FROM PROTECTIONS
In certain applications, it is desired for the amplifier to recover
itself from thermal protection without the need for system
microcontroller intervention.
The ADAU1513 thermal protection circuit issues two error
signals for this purpose: one thermal warning ( OTW ) and the
other thermal shutdown ( ERR ).
With these two error signals, there are two options for using the
protections:
•
•
The following sections provide further details of these two
options.
Option 1: Using OTW
The OTW pin is pulled low when the die temperature reaches
130°C to 135°C This pin can be wired to the MUTE pin using
an RC circuit as shown in Figure 28.
The low logic level on OTW also pulls down the MUTE pin.
The bridge is shut down and, therefore, starts cooling or the
die temperature starts reducing. When it reaches 120°C, the
OTW signal starts going high. While this pin is tied to a
capacitor with a resistor pulled to DVDD, the voltage on this
pin starts rising slowly towards DVDD. When it reaches the
input logic high threshold, MUTE is deasserted and the
Option 1: Using OTW
Option 2: Using ERR
ADAU1513
Figure 28. Option 1 Schematic for Autorecovery
MUTE
OTW
10
15
DVDD
R1
100kΩ
C1
47µF
1N4148
D1
TO MUTE
LOGIC INPUT