4-Channel, Automotive Class D Audio Amplifier

21

Table_11._Control_Register_3

Table_12._Control_Register_3_Bit_Description

CTRL3

BIT_#

7

6

5

4

3

2

1

0

NAME

TW

RDET

SDET

DIS

—

HCL

—

LDM

POR

0

0

0

0

0

0

0

0

BIT

BIT_DESCRIPTION

TW

Tweeter-Detect Current Threshold Setting

0 = The current threshold at which OSTAT1.LOAD[3:0] (load indicator bit) asserts is set equal to the shorted-

load current threshold (see the Electrical Characteristics table). Use this setting when running shorted-load

diagnostic.

1 = The current threshold at which OSTAT1.LOAD[3:0] asserts is set equal to the tweeter detect current

threshold. This threshold is approximately 25% of the default value to facilitate tweeter detection. Use this

setting when the running tweeter diagnostic or for detecting the presence of a speaker.

RDET

Open-Load Diagnostic Enable. Upon detecting an open load on any of the outputs, the corresponding

OSTAT1.LDOK[3:0] (load OK indicator bit) asserts. Always perform short-to-ground and short-to-battery

diagnosis before entering RDET mode. If a short-to-battery is detected, do not enter RDET mode. After

performing the short-to-battery test, discharge both outputs by setting CTRL3.DIS to 1 for 200µs, then reset

CTRL3.DIS back to 0. Failure to follow this procedure can result in a loud pop at the speaker.

Because the results are not latched, read LDOK[3:0] before clearing RDET. Wait a minimum of 200µs before

reading these status bits. RDET can only be set after three-stating all four outputs. When performing the

open-load diagnostic, set the CTRL3.SDET (short-to-ground/battery enable) bit to 0.

0 = Disable open-load diagnostic

1 = Enable open-load diagnostic

SDET

Short-to-Ground/Battery Diagnostic Enable. Upon detecting a short-to-ground or battery on any of the outputs,

the corresponding OSTAT2.SBAT[3:0] (short-to-battery) and OSTAT2.SGND[3:0] (short-to-ground) bits assert.

Because the results are not latched, read OSTAT2.SBAT[3:0] and OSTAT2.SGND[3:0] before clearing SDET.

Wait a minimum of 200µs before reading these status bits. Before setting SDET to 1, three-state all four out-

puts and set the CTRL3.DIS (discharge output enable) bit to 1 and then reset back to 0. Before performing

the short-to-ground/battery diagnostic, set the CTRL3.RDET (open-load diagnostic enable) bit to 0. To test for

short-to-ground, set CTRL2.STBY to 0, and to test for short-to-battery, set CTRL2.STBY to 1.

0 = Disable short-to-ground/battery diagnostic

1 = Enable short-to-ground/battery diagnostic

DIS

Discharge Output Enable. Set DIS to 1 to discharge all outputs with 15mA current sources. Use DIS to dis-

charge all outputs before performing the short-to-ground/battery diagnostic (SDET) to avoid a loud pop on

the speaker. DIS can only be set to 1 after three-stating all four outputs.

0 = Output discharge is disabled.

1 = Output discharge is enabled.

HCL

Current-Limit Level. HCL sets the current-limit threshold of the outputs during normal operation.

0 = 7A (typ) current limit

1 = 8.75A (typ) current limit

LDM

Line-Driver Mode. Use LDM to set the load resistance threshold required to assert the OSTAT1.LDOK[3:0]

(load-okay indicator bit). Any load with a resistance greater than the threshold is interpreted as an open

output.