11/17
TDA7575
Examples of bytes sequence
1
- Turn-On diagnostic - Write operation
2
- Turn-On diagnostic - Read operation
The delay from 1 to 2 can be selected by software, starting from T.B.D. ms
3a
- Turn-On of the power amplifier with mute on, diagnostic defeat.
3b
- Turn-Off of the power amplifier
4
- Offset detection procedure enable
5
- Offset detection procedure stop and reading operation (the results are valid only for the offset detection bits
(D2 of the bytes DB1, DB2, DB3, DB4).
■ The purpose of this test is to check if a D.C. offset (2V typ.) is present on the outputs, produced by input
capacitor with anomalous leackage current or humidity between pins.
■ The delay from 4 to 5 can be selected by software, starting from T.B.D. ms
DIAGNOSTICS FUNCTIONAL DESCRIPTION:
a) TURN-ON DIAGNOSTIC.
It is activated at the turn-on (stand-by out) under I
2
C bus request. Detectable output faults are:
–SHORT TO GND
–SHORT TO Vs
– SHORT ACROSS THE SPEAKER
– OPEN SPEAKER
To verify if any of the above misconnections are in place, a subsonic (inaudible) current pulse (fig. A) is internally
generated, sent through the speaker(s) and sunk back.The Turn On diagnostic status is internally stored until a
successive diagnostic pulse is requested (after a I2C reading).
If the "stand-by out" and "diag. enable" commands are both given through a single programming step, the pulse
takes place first (power stage still in stand-by mode, low, outputs= high impedance).
Start Address byte with D0 = 0 ACK IB1 with D6 = 1 ACK IB2 ACK STOP
Start Address byte with D0 = 1 ACK DB1 ACK DB2 ACK STOP
Start Address byte with D0 = 0 ACK IB1 ACK IB2 ACK STOP
X000XXXX XXX1XX1X
Start Address byte with D0 = 0 ACK IB1 ACK IB2 ACK STOP
X0XXXXXX XXX0XXXX
Start Address byte with D0 = 0 ACK IB1 ACK IB2 ACK STOP
XX1XX1XX XXX1XXXX
Start Address byte with D0 = 1 ACK DB1 ACK DB2 ACK STOP
