STA335W datasheet(33/43 Pages) STMICROELECTRONICS

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STA335W

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Writing a single coefficient to RAM

Select the RAM block with register 0x31 bit1, bit0.

Write 6-bits of address to I2C register 0x16.

Write top 8-bits of coefficient in I2C address 0x17.

Write middle 8-bits of coefficient in I2C address 0x18.

Write bottom 8-bits of coefficient in I2C address 0x19.

Write 1 to W1 bit in I2C address 0x26.

5.9.6

Post-scale

The STA335W provides one additional multiplication after the last interpolation stage and

the distortion compensation on each channel. This post-scaling is accomplished by using a

24-bit signed fractional multiplier, with 0x800000 = -1 and 0x7FFFFF = 0.9999998808. The

scale factor for this multiply is loaded into RAM using the same I2C registers as the biquad

coefficients and the bass-management. This post-scale factor can be used in conjunction

with an ADC equipped micro-controller to perform power-supply error correction. All

channels can use the channel-1 post-scale factor by setting the post-scale link bit. By

default, all post-scale factors are set to 0x7FFFFF. When line output is being used,

channel-3 post-scale will affect both channels 3 and 4.

5.9.7

Over-current post-scale

The STA335W provides a simple mechanism for reacting to over-current detection in the

power-block. When the ocwarn input is asserted, the over-current post-scale value is used

in place of the normal post-scale value to provide output attenuation on all channels. The

default setting provides 3 dB of output attenuation when ocwarn is asserted.

The amount of attenuation to be applied in this situation can be adjusted by modifying the

Over-current Post-scale value. As with the normal post-scale, this scaling value is a 24-bit

signed fractional multiplier, with 0x800000 = -1 and 0x7FFFFF = 0.9999998808. By default,

the over-current post-scale factor is set to 0x5A9DF7. Once the over-current attenuation is

applied, it remains until the device is reset.

5.10

Variable max power correction registers (addr 0x27 - 0x28)

Table 48.

RAM block for scaling management

Index (Decimal)

Index (Hex)

Coefficient

Default

Reserved

……

Reserved

0x34

Channel 1 - Post-Scale

C1PstS

0x7FFFFF

0x35

Channel 2 - Post-Scale

C2PstS

0x7FFFFF

0x36

Reserved

0x37

TWARN/OC - Limit

TWOCL

0x5A9DF7

MPCC15

MPCC14

MPCC13

MPCC12

MPCC11

MPCC10

MPCC9

MPCC8

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