ACS422A68TAGZBX8 IDT, ACS422A68TAGZBX8 Datasheet - Page 43

• Manufacturer Part Number: ACS422A68TAGZBX8
• Description: Interface - CODECs
• Manufacturer: IDT

Specifications of ACS422A68TAGZBX8

• Rohs: yes
• Part # Aliases: IDTACS422A68TAGZBX8

ACS422x68
LOW-POWER, HIGH-FIDELITY, INTEGRATED CODEC
©2011 INTEGRATED DEVICE TECHNOLOGY, INC.
3.16. Thermal Shutdown
To avoid overpowering and overheating the codec when the amplifier outputs are driving large currents, the
ACS422x68 incorporates a thermal protection circuit. If enabled, and the device temperature reaches approximately
150°C, the speaker and headphone amplifier outputs will be disabled. Once the device cools, the outputs will be auto-
matically re-enabled.
3.16.1. Algorithm description:
3.16.2. Thermal Trip Points.
There are 2 trip points, “high” and “low”. High indicates a critical overheat requiring a reduction in vol-
ume to avoid damage to the part. Low is set for a slightly lower temperature point, indicating that the
current level is safe but that increased volume would result in a critical overheat condition.
Normally, the overheat bits are polled every 8ms but may be polled at 4ms, 8ms, 16ms, or 32ms by
adjusting the Poll value. Reductions in volume will be allowed to happen at the Poll rate. Increases in
volume are programmable to happen every 1, 2, 4, or 8 Poll cycles and in steps of 0.75dB to 6dB.
This allows a full scale volume increase in a range of 10s of milliseconds to 10s of seconds.
When both overheat bits are 0, the volume is allowed to increment by the IncStep size, unless the
volume has already reached the maximum value allowed. Any subsequent increment will be held off
until the programmed number of polling cycles have occurred.
When the low overheat bit is 1 and the high overheat bit is 0, this indicates that the volume is cur-
rently at a safe point but the temperature is higher than desired and incrementing the volume may
cause severe overheating. The volume is held at the current value.
When the high overheat bit is 1, damage could occur, so the volume setting will be immediately
reduced by the Decrement Step value. As the overheat bits are re-polled, this volume reduction will
continue until the high overheat bit drops to 0 or the volume value reaches the minimum setting. If
the high overheat bit remains 1 even at the minimum setting, then the mute control bit will be
asserted. If the high overheat bit persists even after mute, then the BTL amp will be powered down.
The high and low trip points can be adjusted to suit the needs of a particular system implementation.
There is a “shift” value (TripShift) which sets the low trip point, and there is a “split” value (TripSplit)
that sets how many degrees above the low trip point the high trip point is.
By default:
Therefore:
High Trip Point = 155°C.
Low Trip Point = 140°C.
TripShift = 2 (140 degrees C)
TripSplit = 0 (15 degrees C)
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ACS422X68
V1.6 01/13