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LX1792 E

VALUATION 

B

OARD

 

U

SER 

G

UIDE

 

 

 

Copyright © 2002

 

Microsemi

 

Page 3

 

Rev 0.2, 3/4/2002

 

Integrated Products – Power Management

 

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

 

 

F

EATURES AND 

C

IRCUIT 

D

ESCRIPTION

 

 

• 

Fully Assembled Mono Evaluation Board 
with LX1792 Class-D Audio Amplifier  

• 

Supports hearing aid bandwidth (100Hz - 
10kHz)  

• 

Gain set by 2 external resistors  

• 

Three output impedance settings (10

15

, 34

)  

• 

Optimized to drive 200

 speaker load  

  
The LX1792 Evaluation Board allows the user to 
quickly connect and evaluate the LX1792 
Switching Class-D Mono IC.  Banana jacks are 
provided for power supply connections.  A RCA 
jack is supplied to input an audio signal, and a BNC 
connector is provided for a signal generator input.  
A slide switch is provided for easy selection 
between the two inputs.  A ¼" audio jack is 
provided to connect headphones to the amplifier 
output.  A single-ended, low-pass filtered output is 
also available through a BNC connector.  This 
allows the user to connect the LX1792 output to 
either a spectrum analyzer or an oscilloscope.  
Breadboard space is also provided on the evaluation 
board to offer the user the opportunity to attach a 
different filter and/or load.   
  

• 

Banana jacks for power supply connections  

• 

RCA jack for audio input  

• 

BNC jack for signal generator input  

• 

¼" Audio jack for headphone connection  

• 

Single-ended output for measurement and 
analysis  

 
 
The Class-D amplifier generates a Pulse Width 
Modulated output by controlling FETs that are 
connected in a H-Bridge configuration.  The full 
bridge configuration is connected between the 
single supply voltage (VDD) and ground (VSS), 
with the output of the bridge driving a speaker or an 
equivalent load. 
  
Because the FETs have an extremely low "on" 
resistance and an extremely high "off" resistance, 

the majority (95% typical) of the power is delivered 
to the load, making it a highly efficient amplifier. 
  
The only external component required by the 
LX1792 is an input AC coupling capacitor.  The 
evaluation board contains two power supply filter 
capacitors, however, these are not mandatory for 
operation. The output of the LX1792 can be directly 
connected to a speaker.   
  

I

NPUT 

S

ELECT

 

The Evaluation Board provides two input 
connection options: a BNC connector and a RCA 
connector.  The BNC connector should be used 
when inputting a signal from a function generator.  
The RCA connector should be used when inputting 
a signal from an audio source.  A slide switch is 
provided to choose between these two input 
connectors.  
  

G

AIN 

S

ET

 

Gain in the LX1792 amplifier can be set to a 
maximum total gain of 40dB. The preamp gain is 
set by the ratio of the external resistors (R2/R1). 
There is an additional 10dB gain in the H-bridge. 
  

I

MPEDANCE 

S

ELECT

 

Three different output impedances are available 
with the LX1792.  A slide switch allows users to 
choose between an output impedance of 10W, 15W, 
and 34W.  The higher output impedance settings 
reduce current consumption of the LX1792. 
  

O

UTPUT 

S

ELECT

 

The LX1792 evaluation board provides a slide 
switch that allows the user to choose between three 
different output options.  When the switch is in the 
"Headphone" position, the differential output of the 
amplifier is applied directly to the headphone jack.  
If the "Single-Ended" option is chosen, the 
differential output is converted to a single ended 
output with a transformer, and then low-pass 
filtered.  The "Unloaded" option removes the load 
from the amplifier output.  This option can be used 

Obsolete

Summary of Contents for LX1792

Page 1: ...Copyright 2002 Rev 0 3 3 4 2002 LX1792 Eval CLASS D AUDIO AMPLIFIER EVALUATION BOARD USER GUIDE INTEGRATED PRODUCTS Power Management O b s o l e t e...

Page 2: ...ment 11861 Western Avenue Garden Grove CA 92841 714 898 8121 Fax 714 893 2570 TABLE OF CONTENTS LX1792 Evaluation Board Features and Circuit Description 2 Input Select Gain Set Impedance Select Output...

Page 3: ...output of the bridge driving a speaker or an equivalent load Because the FETs have an extremely low on resistance and an extremely high off resistance the majority 95 typical of the power is delivere...

Page 4: ...transformer and then to a first order RC low pass filter with a cutoff frequency of 20kHz This filter removes the 200kHz switching frequency from the signal BREADBOARD The LX1792 gives the user the o...

Page 5: ...elect The Headphone setting will directly connect the differential output of the amplifier to the headphone jack The Single Ended setting will connect the differential amplifier output to a transforme...

Page 6: ...Vin Gain Setting 50mVrms 20dB 25mVrms 26dB 13mVrms 32dB 6mVrms 38dB 12 Audio Source Verify that a low level audio source is being used and set it to the minimum level Start or play audio source and a...

Page 7: ...SCHEMATIC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 C5 C1 C2 J3 J4 Breadboard R3 C6 1 2 3 4 5 6 1 2 3 4 5 6 7 8 1 1 2 2 1 2 3 4 8 7 6 5 1 2 3 4 5 6 1 2 1 2 1 2 3 BNC RCA RCA IN BNC IN Input Select Banana Banan...

Page 8: ...523 31 5486 1010 J1 J5 J6 3 5 DPDT Slide Switch MOUSER 612 EG2201 SW1 1 6 DP3T Slide Switch MOUSER 612 EG2301 SW2 SW3 SW4 3 7 RCA Jack Red MOUSER 161 0096 J2 1 8 Transformer MOUSER 42TL016 T1 1 9 14 P...

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