Evaluates: MAX9724A/MAX9724B 19-3203 Rev 0 1/08 MAX9724A Evaluation Kit General Description Features The MAX9724A evaluation kit (EV kit) is a fully assem- No DC-Blocking Output Capacitors Required bled and tested printed-circuit board (PCB) that uses the MAX9724A IC to drive a stereo headphone in 2.7V to 5.5V Operation portable applications. The MAX9724A is a 60mW stereo headphone amplifier with adjustable gain and Adjustable -1.5V/V Gain DirectDrive outputs. Maxims DirectDrive technology eliminates the need for bulky DC-blocking capacitors at 60mW per Channel into a 32 Load the output of the amplifier. The EV kit is configured for a -1.5V/V gain and is 0.02% THD+N designed to operate from a 2.7V to 5.5V DC power sup- ply. The EV kit is capable of delivering up to 60mW per Fully Assembled and Tested channel into a 32 load and achieving 0.02% THD+N. The MAX9724A EV kit can also be used to evaluate the MAX9724B fixed-gain amplifier. Contact Maxim for a free sample of the MAX9724B IC. Ordering Information PART TYPE MAX9724AEVKIT+ EV Kit +Denotes lead-free and RoHS-compliant. Component List DESIGNATION QTY DESCRIPTION DESIGNATION QTY DESCRIPTION 1F 10%, 10V X5R ceramic OUTL, OUTR, 0 Not installed, test points C1, C2, C4 3 capacitors (0603) SGND Murata GRM188R61A105K R1, R3 2 10k 1% resistors (0603) 0.1F 10%, 10V X5R ceramic R2, R4 2 15k 1% resistors (0603) C3 1 capacitor (0402) 60mW, DirectDrive, stereo headphone Murata GRM155R61A104K U1 1 amplifier (12-pin TQFN-EP*) 0.47F 10%, 10V X5R ceramic Maxim MAX9724AETC+ C5, C6 2 capacitors (0603) 1 Shunt (JU1) Murata GRM188R61A474K 1 PCB: MAX9724A Evaluation Kit+ JU1 1 3-pin header *EP = Exposed paddle. OUT 1 Stereo headphone jack (3.5mm) Component Supplier SUPPLIER PHONE WEBSITE Murata Mfg. Co., Ltd. 770-436-1300 www.murata.com Note: Indicate that you are using the MAX9724A when contacting this component supplier. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.MAX9724A Evaluation Kit Test points OUTR, OUTL, and SGND are provided to Quick Start easily measure the output signals. Required Equipment The MAX9724A EV kit can evaluate the fixed-gain Before beginning, the following equipment is needed: MAX9724B IC, also in a 12-pin thin QFN package. The 2.7V to 5.5V, 500mA power supply MAX9724B features a fixed gain of -1.5V/V. See the Evaluating the MAX9724B section for more information. 32 stereo headphones with a 3.5mm plug Audio signal source Shutdown (SHDN) Jumper JU1 controls the shutdown pin (SHDN) of the Procedure MAX9724A that enables and disables the MAX9724A The MAX9724A EV kit is fully assembled and tested. IC. See Table 1 for jumper JU1 configurations. Follow the steps below to verify board operation. Caution: Do not turn on the power supply until all Table 1. Jumper JU1 Shutdown Selection connections are completed. MAX9724A 1) Verify that a shunt is installed on jumper JU1, pins SHUNT POSITION SHDN PIN FUNCTION 2-3 (IC disabled). 1-2 Connected to VDD Enabled 2) Set the power-supply output to 5V. 2-3 Connected to GND Disabled 3) Disable the power-supply output. 4) Connect the power-supply ground to the PGND pad and the power-supply positive output to the VDD pad. Gain Setting The default gain-setting resistors R1R4 configure the gain 5) Verify that the audio source output is disabled. for both the left and right channels to -1.5V/V. The gain 6) Connect the audio source ground, left signal, and right can be changed by replacing these resistors with other signal to the SGND, INL, and INR pads, respectively. surface-mount 0603 resistors. Resistors with a tolerance of 1% or better are recommended for optimum performance. 7) Plug the headphone into the OUT headphone jack. Use Table 2 and the following equation to select new gain- 8) Enable the power-supply output. setting resistors for the corresponding channel. 9) Enable the audio source. Table 2. Gain-Setting Resistors 10)Install a shunt on jumper JU1 across pins 1-2 (IC enabled). CHANNEL RIN RF 11)Verify that the headphones are playing the audio Right R1 R2 source signal. Left R3 R4 Detailed Description RF = -A RIN The MAX9724A EV kit features the MAX9724A IC stereo headphone amplifier. The MAX9724A features adjustable gain and 60mW DirectDrive outputs. where RIN 10k and A is the desired negative gain. DirectDrive generates an internal negative supply Refer to the Output Dynamic Range and Maximum (-VDD) from the positive supply (VDD), thus biasing the Output Swing sections in the MAX9724A/MAX9724B IC amplifier output. Zero-voltage biasing eliminates the data sheet for limitations on setting the gain. need for bulky DC-blocking capacitors at the amplifier Evaluating the MAX9724B output. The MAX9724A operates from a 2.7V to 5.5V The MAX9724A EV kit can evaluate the fixed-gain supply with a low quiescent current of 3.5mA. The MAX9724B IC after performing the following: MAX9724A comes in a 12-pin thin QFN package suit- able for portable applications. 1) Replace U1 with the MAX9724B IC. The EV kits gain for each channel is set to -1.5V/V. The 2) Remove resistors R2 and R4. left- and right-channel gain can be adjusted by modifying 3) Replace resistors R1 and R3 with 0 0603 surface- the ratio of the corresponding gain-setting resistors R1R4. mount resistors. R1 and R2 set the right-channel gain and R3 and R4 set The MAX9724B features a fixed-gain of -1.5V/V. Contact the left-channel gain. The IC delivers up to 60mW per Maxim for a free sample of the MAX9724BETC+. channel into a 32 load while achieving 0.02% THD+N. 2 Evaluates: MAX9724/MAX9724B