D2-45057_14 Datasheet, PDF (26/31 Pages) Intersil Corporation – Intelligent Digital Amplifier PWM Controller and Audio Processor

D2-45057, D2-45157
Protection
The D2-45057, D2-45157 device includes multiple
protection mechanisms. Output overload and overcurrent
status for each output power stage provides two levels of
monitoring. Temperature monitoring provides two levels
of temperature status. On-chip undervoltage detection is
included for all supply voltages.
Several strategies are provided in the D2-45057,
D2-45157 to prevent damage from the high voltages,
currents, and temperatures present in class-D amplifiers.
This protection is also effective against user-induced
faults such as clipping, output overload, or output shorts,
including both shorted outputs or short-to-ground faults.
Protection includes events such as:
• Output Overcurrent
• Output Short Circuit
• Over-Temperature
• Power Supply Brown-Out
• Shoot-Through Overcurrent
Certain levels of protection are managed using on-chip
hardware. Other protection is integrated into device
firmware, and involves actions to:
• Shut down the outputs for a short circuit,
over-temperature, or undervoltage event.
• Shut down the device if power supply sensors detect
voltages dropping below their design thresholds.
• Providing both indication, and device shutdown if
needed for overload and overcurrent monitors
detection. Dual threshold monitors provide two
levels of high current conditions.
• Chip temperature monitoring provides dual threshold
status of high temperature conditions, providing
both indication, and device shutdown if needed.
Error Reporting
Internal monitoring of system and device operation uses
an I/O pin (nERROR/CFG1) as an output to signal an
external system controller of a channel shutdown error
condition. This output may be used to turn on a simple
indicator.
The error output is also used to signal an external
microcontroller that the I²C bus may be busy. When the
error output is low during system initialization, the I²C
bus is busy as a master device.
This error output is active low and only becomes used as
an error reporting output after the device firmware has
initialized and began running. This same pin is shared as
an input. (Refer to Table 5 on page 24 for further
description on shared-function pins.) During a reset
condition, this pin operates as an input, and is one of two
input pins that are used to define the configuration
mode. A resistor pull-up or pull-down on this pin
establishes this mode input configuration state. After
completion of the initialization sequence, these resistors
do not affect the error output operation.
Short-Circuit and Overcurrent Sensing
Each PWM output FET includes a dual-threshold
overcurrent sensor. Multiple functions occur depending
on detection of overcurrent conditions:
• The lower threshold is used to monitor fault
conditions such as shorts or overloads on the
loudspeaker outputs.
• The higher threshold monitors fault conditions of the
PWM output pin.
• The nERROR output asserts for the channel detecting
the fault.
• For the lower level threshold, nERROR remains
asserted only through the duration of the
overcurrent event.
• For the higher level threshold, the output is shut
down, and its nERROR output is asserted, and these
remain latched until the controller acknowledges the
fault event by turning off the channel’s PWM drive.
(When shutdown, the PWM output pin floats.)
Hysteresis is built into the overcurrent detectors to
suppress PWM switching transient events.
Protection Monitoring and Control
These overcurrent detectors generate either a pulse or
latched logic level (depending on low or high threshold)
upon detection of high current. Detector status is
presented to the nERROR[0:3] pins.
The PROTECT[0:2] pins are used as protection inputs to
the firmware. Firmware action based on these pins’
status depends on the selected output mode
configuration. The nERROR[0:3] output pins and the
PROTECT[0:2] input pins are connected together based
on the particular system and output mode configuration,
as shown in Table 6 on page 25.
Thermal Protection and Monitors
An temperature sensing provides two thresholds of
temperature monitoring.
If the device reaches the lower threshold, a warning
indication is generated, and triggers one level of thermal
protection management.
On-chip hardware thermal protection shuts down the
device upon a high-threshold temperature condition. If
the device reaches the higher threshold, on-chip
hardware latches and shuts down all four output stages.
It also drives all four nERROR0-3 outputs low (active)
providing this shut-down status to the firmware through
their connected PROTECT0-2 inputs.
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FN6785.0
July 29, 2010