LP3954TLSLASHNOPB datasheet(21/58 Pages) TI2

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LP3954

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SNVS340D – JUNE 2005 – REVISED MARCH 2013

AUDIO SYNC ELECTRICAL PARAMETERS

Symbol

Parameter

Test Conditions

Min

Typ

Max

Unit

ZIN

Input Impedance of ASE

250

500

kOhm

AIN

Audio Input Level Range (peak-to-peak)

Gain = 21dB

0.1

Gain = 0 dB

VDDA - 0.1

f3dB

Crossover Frequencies (-3 dB)

Narrow Frequency Response

Low Pass

0.5

Band Pass

1.0 and

1.5

High Pass

2.0

kHz

Wide Frequency Response

Low Pass

1.0

Band Pass

2.0 and

3.0

High Pass

4.0

CONTROL OF AUDIO SYNCHRONIZATION

The following table describes the controls required for audio synchronization.

Audio_sync_CTRL1 (2AH)

Input signal gain control. Range 0...21 dB, step 3 dB:

[000] = 0 dB (default)

[011] = 9 dB

[110] = 18 dB

GAIN_SEL[2:0]

Bits 7-5

[001] = 3 dB

[100] = 12 dB

[111] = 21 dB

[010] = 6 dB

[101] = 15 dB

Synchronization mode selector.

SYNC_MODE

Bit 4

SYNCMODE = 0

→ Amplitude Mode (default)

SYNCMODE = 1

→ Frequency Mode

Automatic Gain Control enable

EN_AGC

Bit 3

1 = enabled

0 = disabled (Gain Select enabled) (default)

Audio synchronization enable

1 = Enabled

EN_SYNC

Bit 2

Note : If AGC is enabled, AGC gain starts from current GAIN_SEL gain value.

0 = Disabled (default)

[00] = Single ended input signal, ASE.

[01] = Temperature measurement

INPUT_SEL[1:0]

Bits 1-0

[10] = Ambient light measurement

[11] = No input (default)

Audio_sync_CTRL2 (2BH)

0 – average disabled (not applicable in audio synchronization mode)

EN_AVG

Bit 4

1 – average enabled (not applicable in audio synchronization mode)

MODE_CTRL[1:0]

Bits 3-2

See below: Mode control

Sets the LEDs light response time to audio input.

[00] = FASTEST (default)

[01] = FAST

SPEED_CTRL[1:0]

Bits 1-0

[10] = MEDIUM

[11] = SLOW

(For SLOW setting in amplitude mode fMAX=3.8Hz,

Frequency mode fMAX=7.6Hz)

MODE CONTROL IN FREQUENCY MODE

Mode control has two setups based on audio synchronization mode select: the frequency mode and the

amplitude mode. During the frequency mode user can select two filter options by MODE_CTRL as shown

below. User can select the filters based on the music type and light effect requirements. In the first mode the

frequency range extends to 8 kHz in the secont to 4 kHz.

The lowpass filter is used for the red, the bandpass filter for the blue and the hipass filter for the green LED.

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